R/C Soaring Digest - Nov 2012

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SoaringDigest

Radi C ntr lled

November 2012 Vol. 29, No. 11


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2 R/C Soaring Digest

November 2012

Vol. 29, No. 11

C O N T

E N T S

Front cover: James Mercado builds line tension prior tolaunching his Xplorer 4000. Photo taken at the 2012 WorldSoaring Masters, held at the AMA ying site in Muncie Indiana,

by Mark Nankivil. Coverage of the event by Mike Reagan withmore photos from Mark begins on page 63.Canon EOS Rebel T3i, ISO 100, 1/250 sec., f13.0, 36.0 mm

World Soaring Masters 2012 63Event coverage with text by Mike Reagan and photos by

Mark Nankivil.

Scenes from F3J Samba Cup 2012 94 A photo essay by Martin Pilny .

Inexpensive Model Storage 108 A reclaimed styrofoam box gets a new life.

A Stuart Bradley creation.

3 RC Soaring Digest Editorial

4 F5J Aircraft DesignMarc Pujol details the initial concept and evolution of hisGenoma2 with text and numerous illustrations.

40 Toba F3B/F3F from RCRCM and OleRC.comReviewed by Andy Page.

60 KST DS125MG servoBill and Bunny Kuhlman review this metal gear, thin wing,digital servo from KST and OleRC.com.

Back cover: An Enjoy3 passes in front of the partial moon.Photo taken by Martin Pilney at the F3JSamba Cup 2012. More of Martin's photos from this event canbe seen starting on page 94.Nikon D300, ISO 200, 1/1250 sec., f5.6, 200mm


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R/C Soaring Digest

November 2012Volume 29 Number 11

Managing Editors, Publishers B2 Kuhlman

Contact [email protected]://www.rcsoaringdigest.comYahoo! group: RCSoaringDigest

R/C Soaring Digest (RCSD ) is a reader-written monthlypublication for the R/C sailplane enthusiast and has beenpublished since January 1984. It is dedicated to sharing

technical and educational information. All material contributedmust be original and not infringe upon the copyrights of others.It is the policy of RCSD to provide accurate information. Please

let us know of any error that signicantly affects the meaningof a story. Because we encourage new ideas, the content of

each article is the opinion of the author and may not necessarilyreect those of RCSD . We encourage anyone who wishes to

obtain additional information to contact the author.

———Copyright © 2012 R/C Soaring Digest

Published by B2Streamlines P.O. Box 975, Olalla WA 98359

All rights reserved

———

RC Soaring Digest is published using Adobe InDesign CS6

In the Air

Another huge issue of RCSD! 110 pages!

Marc Pujol continues from where he left off in the Octoberissue ("F5J Altitude," p. 10) with a complete examination of hisGenoma2 airframe, from initial concept through its evolution to anextremely well behaved contest entry.

RCSD was contacted by OleRC.com earlier this year and giventhe opportunity to review the Toba F3B/F3F sailplane and theKST DS125MG servo. Fellow Seattle Area Soaring Societymember Andy Page volunteered to review the Toba, while we

handled the KST servo. Our sincere thanks to OleRC.com forproviding the review samples and particularly to Mei who handleda number of concerns quickly and professionally.

Mark Nankivil was CD for the World Soaring Masters once againthis year and he managed to forward nearly 2.5GB, more than350 images, to RCSD. As you can imagine, going through thiscollection and choosing which to use was definitely a long-termproject. MIke Reagan's write-up on the WSM event first appearedon the RCSE, and is reproduced here with his permission.

Martin Pilny usually photographs F3B events, but he did attendthe F3J Samba Cup 2012 near the village of Sebranice, CzechRepublic, where Samba Models (home of the Pike series) islocated. His photographs are filled with color and superbly portaythe "flavor" of the event.

And Stuart Bradley sent a few photos of his model storage unit, areclaimed styrofoam box. We couldn't resist sharing it with RCSD readers.

Thanks again to everyone who contributed to this issue!

Time to build another sailplane!

http://www.rcsoaringdigest.com/http://www.b2streamlines.com/http://www.b2streamlines.com/http://www.rcsoaringdigest.com/


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How to structure a rational 3Regulation analysis 3The plane and its trigger elements 5 Altitude gain in lift 7Thermal searching 12Return to the land eld 13Landing 13Classication of trigger plane element 13

After the Pasmespumas and the Genoma, here is my new F5J plane: The Genoma² 17The GENOMA² construction 21Tail and n 21Wing 24Fuselage 27How does Genoma family is ying? 28The Genoma² in its rst TD F5J contest 34Conclusion 36

F5J discipline (also called ALES) appeared in January 2012.This is the rst time for electric glider categories where thepropulsion set is not so important. This is a revolution. Thisis the end for all such very expensive gliders full of carbontechnologies that allow them to be very light and highlyresistant.

So, for the rst time, a standard glider can have “similar”chances against more optimized planes. Of course, similardoesn’t mean equal. There are still some differences betweenthem. But strategies are of far more importance especiallyduring a y-off where the conditions are usually moredemanding.

This paper is written to provide you with a rationale that mayconduct you into the selection of your next F5J plane. Ofcourse, you can apply it to any other discipline with a littleadaptation.

F5JAIRCRAFT

DESIGNMarc Pujol, [email protected]

Initial concept and evolution of the Genoma 2


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At the end, I will provide you with theresult of my own rationale and delivera full glider denition set - a glider that

appears to be optimum and far cheaperthan any commercial design set, a glideryou can build either with foam andcomposite materials, epoxy and baggingor with structural techniques as I did.

How to structure a rationale

The rationale has three steps:

• Regulation analysis and classicationof points that appears important to win.

• Identication of the trigger elements ofa plane and their classication in relationto the regulation and air conditions.

• Denition of the plane that meets suchtrigger classication.

Regulation analysis

The F5J regulation is quite simple:

4 meter maximum for the wing span,

electric propulsion, 30 seconds to climbup to 200m altitude, and a penalty of0.5 point per meter gained with thepropulsion on.

You have to perform a ten minute ightthat includes the altitude gain with themotor and a precision landing (1m 10points).

Figure 1: This is the ancestor (2008/2009) of the Genoma: The “Pamespumas,” an F3B

plane from my friend P. Medard (PAtrick + MEdard + PUjol + MArc= Pasmespumas)

that I have transformed to experiment with yawing stability. This was a rst revolution

for me. But not the last one!


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Of course there are additionalrequirements, but these are the majors.

First of all, what appears important is

the advantage to cut the motor at lowaltitude. If you switch it off at 100mand all the other yers at 200m, that isa 50 point difference if you made thesame ight length. (If all the competitorsare making 10.00 minute ights and50 point landings, the rst yer gets1000 points and the second 550 / 600· 1000 = 917. That is 83 points less).

In F3J, competitors are ghting for 5to 10 points... Imagine what 83 pointsper ight is... F5J is the rst time wherethe objective is not to be at the highestaltitude possible, nor to do it in theshortest time possible. We then haveto think differently. I will say “opposite.”Instead of trying to launch high, we haveto try to launch low. The plane mustthen have the ability to y at low altitude,

circling in the very small thermals youcan encounter at such altitude.

Instead of being in a hurry, let’s taketime to go up and use the 30 secondsto reach the altitude and the locationyou think is good for thermaling. Youcan go 400m away (or even more) at theminimum altitude required to take thelift (for sure, you expect it is there). As

a consequence, if you want to increase

your chances, your plane must be quitebig in order to be seen perfectly far awayand must be very easy to y.

For sure, F5J gliders must be differentfrom any other disciplines.

This 30 second rule is the triggerrule of the discipline. It reinforces thestrategy aspect and the pilot ability tosuccessfully realize it.

Exit powerful motors, hello light weightpropulsion set.

So let’s be very open in our mind andchoices.

This very rst analysis reminds us thatthe ight has several phases and thateach of them does not have the sameinuence on the nal result. Determiningwhich phase is important and which oneis less or not important at all is a rstmandatory step in the design of a newplane.

I have then split the F5J TD ight into vephases.

1. Altitude gain with propulsion2. Thermal search3. Altitude gain circling in thermal4. Return to the landing eld5. Landing

In order to classify them, I propose toyou the following method:

Compare each of them with the othersand give 1, 2 or 3 points to the one thatis more important. For example, Phase

2 (thermal searching) is much moreimportant than Phase 1 (altitude gain withpropulsion). It takes a 3 rating.

My personal rationale provides thetabular result shown in Table 1 at the topof the adjacent page.

Of course, your understandings may leadto different notations. And this makes thediversity of our world.

If we count points and crosses, thatprovides the results shown in Table 2 onthe opposite page.

It is difcult to trigger “Thermal search”and “Altitude gain in lift.” Both phasesare quite equal. It is like chicken and egg.Which is rst? It’s up to you to choose.My rationale is that the 30 seconds toclimb is also a time to go into the lift (or

close to it). So “thermal search” might beless important than “altitude gain in lift.”

Of course you do not have to sacrice alanding for an additional few seconds ofight. But the place of this phase meansthat you must nd a thermal, take the lift,and go back rst. Landing is in addition.


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Table 1: The author’s personal rationale

Is more important

than

Altitude gain with

motor

Thermal search Altitude gain in lift Return to landing

eld

Landing

Altitude gain withmotor

Thermal search X (3) X (1) X (1)

Altitude gain in lift X (3) X (1) X (1) X (1)

Return to landingeld

X (3) X (1)

Landing X (3)

Table 2: Results of evaluation of the author’s personal rationale

Altitude gain in lift 4 crosses6 points

Weight = 24

Thermal search 3 crosses5 points

Weight = 15

Return to the landing eld 2 crosses4 points

Weight = 8

Landing 1 cross3 points

Weight = 3

Altitude gain with motor 0 crosses0 points

Weight = 0


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So our plane must be able rst to nd and take a thermal.Second, it must have the ability to return home even fardownwind, and then it must have the ability to land precisely.

Each phase requires a specic ability that corresponds to aspecic plane parameter. So let’s dene the trigger elements ofthe plane.

Of course a ight occurs in a specic air condition. This mustbe dened rst:

• Speed of wind • Density of thermals in the eld. Are they numerous, fare away

from the landing zone, upwind, downwind… • Thermal characteristics (force, size, catching altitude)

• Turbulence of the air • Altitude of the eld,• Humidity, • Ground and air temperature, sun • …

In the design process, the plane will have to take into accountall those elements.

The plane and its trigger elements

A plane is the result of alchemy. It is a complex balancebetween several parameters more or less independent, more orless against or in favors the others.

That’s why it is important to have a clear view of theirinuences. (See Figure 2)

We will dene the plane thanks to physical parameters andaerodynamic parameters.

Figure 2: Plane creation: A complex alchemy.

Physical parameters are dened by:

• Span • Chords and associated distribution • Wing surface • Aspect ratio • Fuselage length • Fuselage maximum front surface • Tail surface (if any) • Fin surface (if any) • Rudder, ap, aileron, elevator sizes


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• Weight of all elements and associated location in space andinertia

• Prole(s) data (Camber, thickness and position in chord of

such…). • Tail volume • Center of gravity • …

Aerodynamic characteristics are the consequences of suchphysical denitions on plane behavior:

• Gliding ratio and speed associated • Minimum sinking rate and speed associated • Speed polar (Vz/Vx)

• Yawing, rolling, pitching moment • Yawing, rolling pitching dynamic behavior (frequencies and

damping factors) • …

Some of such parameters are real parameters, others are theconsequence of a conjunction of them and should be rejected.We then need to have a clear picture and analyze everything.

So let’s look at the physical parameters that allow the accurateaerodynamic characteristic behaviors that comply with our

classication and air conditions.In reality, we will do the reverse:

For each ight phase, we have to determine and optimize theaerodynamic characteristic that fullls our classication andnd the associated physical characteristics that comply with it.

Altitude gain in lift

In order to optimize altitude gain in a thermal, we must rststudy the thermals - their size, location, altitude...

In Western Europe, most of the thermals are quite narrow at lowaltitude. Let’s say that typically, the lifting air has a diameter of20m at 50m altitude. This will then be a reference for our planedesign.

Their location and density in the eld depends upon the elditself - humidity, temperature difference, sun… Nothing to sayfor the plane except that in some cases you might require goingfar away to nd them (so big plane, easy to y). (See Figure 3)

Figure 3: A thermal can be modeled with few sinus functions.

Realistic? Let say this is not so stupid. That’s a start of the

understanding.


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Knowing the thermals, then comes thestrategy to circle and take the lift.

There are roughly three strategies:

(1) Make a circle, estimate the center ofthe lift and make the next circle aroundthe estimated center…

(2) Increase circling radius when the liftappears slow, relax the circling radiuswhen the lift increases in intensity.

(3) Cross the lift, make a quarter turnaround the lift, cross it again, estimate

the lift in size and center and then circle.Studies have been made for drones inorder to optimize their ight duration.Different software has been tested tond the better strategy. To this end,this depends upon the turbulencerate. Strategy (1) may be a bit easier inturbulent air.

But what about our planes? Nothing and

lots of things.First of all, you need to circle and thenhave the ability to continue circling. Buthow tight?

Knowing the size of the thermals andtheir intensities, we can compute thesinking rate of a plane circling and thenpredict if the plane is going up or down.This allows predicting the best bankangle to take the lift. This shows us that it

Figure 4: The model of a lif t is useful to estimate the optimum circling radius. For small

lift, the bank is more or less at 45°. Quite tight isn’t it?


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is required to circle at high angle (more orless 45° in our reference case). Our planemust then have the ability to circle with

a small radius in a very easy way. (SeeFigure 4)

Of course, in order to take low intensitythermals, the sinking rate of the planemust be minimum (advantage to bigplanes and light planes).

Circling ability and minimum sinking rate,that’s two important aspects.

The circling ability is, at rst, a matter of:

• Wing loading. It must be as reduced aspossible

• Cz. It must be as high as possible• Cz3 /CX². This demands high lift and

low drag. Some thin airfoils wouldpotentially be required then.

Despite what is usually believed, circlingability is not a matter of wing span.

Make few calculations and you will seethat if you can reduce the circling radiusby a few percent, the climbing rate isincreased much more. Circling ability isthen the very important characteristic ofthe F5J category.

To nally convince you, we had twocompetitions this year where the rstor the second place was taken by amotorized F3K plane or an Easy Glider.

Figure 5: The higher the aspect ratio, the higher the wing loading. It’s not for nothingthat birds like eagles have quite low aspect ratio. And it is also not for nothing that sea

gulls have a higher one. They do not y the same air.


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They where competing against fullcarbon 4m planes with good pilots...What were the differences between

them: Ability in circling tight! This is alsoconrmed byfull size glider experienceswhere for example, a Pioneer (full metalvery rustic plane, but very agile thanksto a long fuselage and which ies at lowspeed) was compared to a Bocian (SZDplane with a 30% better gliding ratio andspeed). The rst one was said as havingbetter thermal ability without doubt.

Of course, we need to y in the wind.We then can dene a wing loading rangethat will have to be obtained to cover thatcomplete wind condition range. Let’ssay that standard wing loading (for thecomplete plane) should be between 20and 30 g/dm².

Since there is a direct link betweenaspect ratio and wing weight, the aspectratio should be as high as possible

to obtain the minimum wing load (i.e.the 20 g/dm²). It is then a matter ofconstruction techniques and propulsionequipment weight and no more a matterof aerodynamics. (See Figure 5)

If you have studied thermals, you mustknow that at low altitude they are quitesmall. Circling may then be most of thetime at high angle of bank. This can be

Figure 6: Blue and red curves are longitude and latitude. The plane is going straight.

Light brown shows the altitude, the pink one is the speed and the green one is the

yawing. As you see, even if the pilot tries to ight straight, the reality is a bit different.

It is the conjunction of Dutch roll and phungoïde movement. All such movement

(minimum V +/- 1m/s and yawing +/- 3 degrees) are very difcult to be seen without

measurement devices.


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feasible if, and only if, the yawing stability is optimum. In orderto illustrate this, I will say that the plane must y like an F3Kone. As a consequence, the fuselage should be accurately

long and the n surface also accurately calculated. Here, it is amatter of dynamic behavior and no more a static one. Refer toRCSD late 2011 for a better understanding.

I can say, without much pretention, that actual F3J planesare not optimum in that concern (except for the SUPRA in itsoriginal conguration (1.4kg)). The fuselage should be longerand n surface increased.

Once again, it is not sufcient to have a very good wing tomake a good plane. If the plane doesn’t have accurate dynamic

behavior, the wing can not express its best. And the pilot cannot place the plane in a very easy manner at the right time inthe right position at the right speed. (See Figure 6)

Tight circling and long fuselage have consequences on n apsize: When turning, the radius describes by the wing is not thesame than the one on the n. This means that the natural effectof a n during circling is to go against the turn. In order to havea turn without skid, it is required to have the n in the directionof the turn. And the longer the fuselage is, the more important

the action on the n is. Of course, in reality, due to bank angle,the action is on both n and tail. But the rationale remains. (SeeFigure 7)

As a consequence, for a long fuselage, the rudder shouldrepresent 50% of the chord or even more. 60% should bepreferred.

Circling requires also good low speed behavior. That meansthat the plane must have a speed range at low sink rate as largeas possible. If you compare the Pike Perfect to the Supra, the

Pike appears better in this area (and worse in others of course).

Figure 7: When turning, the tail describes a trajectory with

a radius equal to “R0” but at a distance equal to “A + R0”.

For long fuselage “A” is not neglectable (up to 20 cm). As a

consequence, the n provides a torque in the opposite way of

the turn. This requires n action as if it was fully twisted from

5° to 13°. For sure, the ap should be quite important for a 4m span glider.


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Figure 8: Trying to nd the best speed that optimised up wind or downwind conditions, the McCready analysis shows us a range of

speed between 6 to 15 m/s.

This is fundamental. I made speed measurements and it is verydifcult to y at a xed speed even with the speed informationin my eyes (I have a Xerivision system for my experiments). Evenin a straight line, the plane’s speed is varying from +/- 1m/s.This means that the minimum plane speed is much closer to thestall if the pilot expects to y at Vzmin. If the plane speed rangearound Vzmin is not “very large,” it is absolutely impossible to

y at Vzmin. The plane has a good chance of stalling, especiallyduring circling.

And the more the aps are deected (in a positive way), theshorter this range is. So caution with ap during circling.

As a consequence, the F5J plane will have proles with a bitmore camber than for F3J. Flaps should be used for transition

or speed reduction (circling in the core of the lift if stable).


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Thermal searching

Despite the pilot ability to read the air and the ground, the planemust be able to reach the thermal prior to being too low in

altitude.

This means best gliding ratio and good ability to signal airmovement (so reduced inertia for the whole plane).

As the number of days without wind are quite reduced(especially in my living area), the plane must have the ability tohave good gliding ratio between 7 to 15 m/s as it can be foundplaying with McCready approach taking into account sinking airand upwind ight.

So proles and aspect ratio should be optimized for such a kind

of speed range.

In F5J there is no requirement to have a plane that has goodbehavior at high speed. 100 km/h (28 m/s) or higher is only forfun. So keep it for F3J and other disciplines. (See Figure 8)

Of course, in order to have good ability in circling and goodgliding ratio in the wind, aps are required for high windconditions.

The best possible gliding ratio is an alchemy that integratesprole drag at a dened lift, induced drag, Reynolds number,stability...

As a consequence, the prole thickness should be optimizedaccording to its camber, (this means try to reduce it in therespect of critical Re), and aspect ratio maximized. Both shouldintegrate the weight prediction for a dened load resistance.

For sure, the wing span is an important factor. 4 m span allowsbest gliding ratio. And since the wing span is limited, be surethat winglets will appear in the next generation of plane.

As written, it is alchemy…

Return to the landing eld

Return to the land eld is not only a matter of best gliding ratio.The question is should the plane capable to return ight after

climbing in a thermal? After climbing, the plane should be far away downwind at areached altitude. Should it come back safely? (See Figure 9)

This is then a matter of climb angle (a mix of climbing rate anddeviation to follow the thermal movement) and angle of descentupwind. The quicker the climb and the better the gliding ratioare, the higher is the chance to return home.

The ability to take the lift gets once again its importance with allthe consequences on plane denition.

Figure 9: Return to the landing eld


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Landing

Landing means reach the spot everytimes. Despite the pilot agility, the plane

must have specic requirements:

• Stop quickly when landing. In ordernot to destroy the propulsion unit, Iwould recommend not to land as F3Jplanes. Since it is not possible to afxany stop feature, the only remainingsolution is a tail that continues underthe fuselage like for the AVA / BubbleDancer, F3K planes…

• Have good maneuverability and goodstability in order to pass throughground turbulence and reach the spot.Maneuverability and passing throughturbulence without any affect arequite opposite. Since there are greatadvantages for all the other phases tohave very low inertia, the plane shouldhave very good maneuverability as

compensation.Here, it is a matter of rolling rate, brakingefciency, descent angle at a xedspeed. Consequences are on inertia, apand aileron sizing, inertia (constructionissues are once again important…) andalso high dihedral in order that wing tipsdo not touch the ground prior landing...

Classication of trigger plane element

Let’s take all of the plane parameters andestimate their consequences (in terms

of advantage / disadvantage) for the veight phases.

Of course, for F5J, the rst phase(reaching altitude) could be forgiven sinceit has no inuence on the plane. Butthis is not the case for most of the othergliding categories.

This provides the following table for themajors. But you can complete it by any

parameters you want. (See Table 3)

As you can see, there are threecategories of parameters:

• The very important ones. In this rstcategory are found two dynamicstability parameters (on pitchingaxis) and only one static parameter(wing span). This means that despitewhat was usually admitted, the most

important thing is to have a very stableand well balanced plane.

• The important ones. Quite close to therst category in terms of importance,are found other dynamic parameterssuch as yawing, inertia. Then arecoming what we can call the “standardplane parameters” (fuselage length,mass, prole curvature...). Once again

we have to point out the very highimportance of the dynamic behaviorfor a F5J plane. This is not the only

category that may have similarclassication. But very few planes arestudied in this way. AVL and XFLR5are here to improve our design.

• The others. It is quite surprising to seeparameters like drag, gliding ratio,aspect ratio... at the bottom of theclassication. Is it so surprising? Lookat an eagle and look at a sea gull.

Two birds, two types of ights, twoadaptations to an environment. Sodon’t be so surprised.

After the Pasmespumas and the

Genoma, here is my new F5J plane:

The Genoma²

After a rst trial with a modied F3B (witha very long fuselage for good yawingstability) which shows the interest of

yawing stability calculation, I developeda series of proles specically for theF3J category. The idea was to promotespeed (and then small airfoil curvatureand very low thickness), high aspectratio (to compensate the lower airfoillift by reducing the induced drag andlift). The objective was to be better thanthe Supra in speed and transition. Weconstructed it in a few exemples. I put all


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Table 3: Aircraft parameters and consequences for ve ight phases


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of the information for the construction ona 200 illustrated pages (French languageactually only, sorry). For those interested

see the website for more details. We measuredits performance and I have to confessthat this is quite a satisfaction to obtaina plane that corresponds exactly to thecalculation. I wanted it, I obtained it, andI love it. This plane is the best plane Ihave ever piloted. (I have constructedmore than 100 planes.) (See Figure 10)

Then came the F5J category and Irestart from scratch my studies takinginto account new considerations suchas minimum weight for a dened aspectratio and G load, minimum circlingdiameter...

This conducts me to the GENOMA².

It is similar to the Genoma, but quitedifferent for some aspects:

• Less aspect ratio to reach the 20g/dm²wing load,

• higher camber for the proles for lowerminimum speed,

• lower minimum wing load, • more span (4m) to be at the maximum

of the F5J regulation, • a new series of proles taking

information from the Pike perfect, theSupra, the AVA...

Figure 10: The GENOMA as dened in 2010. It ies like a F3K plane with a 3.65 m span.


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• a new n and tail to adjust dynamicbehavior.

The objective was:

• To improve speed range at low sinkrate in order to avoid stall duringcircling. In this respect, the Pikeperfect was taken as a reference.

• To improve Gliding ratio betweenminimum sink and 15 m/s. The Suprais taken as the reference for thisaspect.

• To improve low speed.

• To have the same or even betteryawing and pitching stability than theGenoma.

This provides me with the planformshown in Figure 12 (next page), with anassociated prole series (icons and linkson next page).

The length of the fuselage is the sameas for the Genoma for transportation

reasons, 2.2m long, that’s for me nearlythe maximum. Otherwise it is difcultto store it at home or in the car withoutrisk of damage... And I don’t want yet tomake a fuselage in two pieces.

Dimensions are:

• Fuselage from nose to leading edge:53 cm. Don’t think this is too much.When using a 105g / 700W geared

Figure 11: Comparison polars


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Genoma2 Airfoil Series

Genoma F5J 1:

Genoma F5J 2:

Genoma F5J 3:

Genoma F5J SAUMON:

Figure 12: Genoma 2 (2012)


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motor and a 1300mA/h 3S Li-Pobattery (or even a 2200mA/h 3S Li-Po), this is not too much. This is just

sufcient for the very long rear leverarm.

• Fuselage from wing leading edge tothe end (n trailing edge): 166 cm

• Max section dimension of the fuselage:6*4 cm

• Wing area: 85.56 dm² • Root chord: 26 cm • Aspect ratio: 18.7. • Max diameter of the boom = 34mm. Of

course you can reduce this diameter inorder to be lighter. But caution with thefuselage exibility...

Wing data and proles:

• Root: Dihedral = 3° - Chord = 26cm -Thickness = 7.8% - Camber = 2.9%

• Root + 50cm: Dihedral = 3° - Chord =25cm - Thickness = 7.5%; Camber = 2.7%

• Root + 100cm: Dihedral = 7° - Chord =

24cm - Thickness = 7.5%; Camber =2.7%.

• Root + 169cm: Dihedral = 7° - Chord =16cm - Thickness = 7.3%; Camber = 2.6%

• Root + 190cm: Dihedral = 7° - Chord =110cm - Thickness = 6.8%; Camber =2.4%

• Root + 200cm: Chord = 5cm - Thickness =6.8%; Camber = 2.4%

Flaps are 30% of the chord from theroot until 15 cm prior to the tip. Thenthe aileron is gradually reduced down to

20%. Flap and aileron are “on the sameline” looking at the plane from the top.

Tail:

• Surface = 6.8 dm² (8% of wingsurface). But look at the comfortabletail volume.

• Tail leading edge distance from wingleading edge = 1315 mm

• Root chord = 12cm

• Aspect ratio = 8.4 • Tail volume = 0.47 • Prole = HT-13

Fin:

• Surface = 7.4 dm² • Fin leading edge distance from wing

leading edge = 1500 mm • Root chord = 18.5cm • Height = 55cm (including 11 cm under

the boom) • Prole = HT-13 • 50% of the surface makes the rudder.

This is a minimum. You can go upto 60% without a problem but withbenets.

The GENOMA² construction

There are 20 moulds made for theGenoma. We planned initially 21, but

nally limited the number... Quite a lotI know. That’s why the Genoma wasstarted in a club. One guy is doing this,

the other one that…We then succeed without much difcultyto create these moulds in less than 6months. And in one year of construction,the Genoma was ying. Of course, forthe Genoma² I reuse all of the moulds,even if the proles are a bit different.The D-box is quite exible so there is noadaptation problem.

For details, look at the 200 pages (inFrench, sorry, but with lots of photos)written at www.xerivision.com (this is notmy website). (See Figure 13)

Tail and n

The spar of the n and the sub-n isrealized with a carbon rod 3*0.8 mm onupper and lower side. The spar caps aremade with balsa. After it has been glued

together (Cyano), a Kevlar shing wire isrolled around. Then balsa prole leadingand trailing pieces are glued. The trailingedge is made with a carbon rod 3*0.8mm and the trailing edge is coveredwith a small sheet of carbon (cut from aunidirectional 80g/m² carbon layer).

The leading pieces are glued every 1.5cmand the trailing pieces can be gluedevery 4.5 cm. (See Figure 14)


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Figure 13: The Genoma² prior to recieving its composite D-boxes. This is quite long

to proceed but not very difcult at all. Nothing requires many tools (We used a CNC

machine for cutting the proles, you can do without).

Figure 14: Stabilizer (L) and vertical n

and rudder (R) drawings.


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November 2012 23

The D-Box is made with a sheet of Kevlar (60g/dm²).

Do not forget the D-box for the rudder. It has a very importantrole. 1.5cm large is sufcient.

The secret of the D-Box is in the glue to assemble it. Thereis always too much glue! If you count at the end, this gluerepresents up to 25% of the total weight. Far too much for a solittle resistance. Try to reach 10 to 15% and you will be a king.

(See Figures 16 and 17a and 17b)

Wing

The wing is a tail that is a bit bigger. That’s all… But thetechniques used are identical. (See Figures 18 and 19)

The spar is made with two layers of carbon sheet 15*1mm atthe root. Then after 500mm, only one layer remains. The sparis also tapered down to 2mm at the tip.

Leading prole pieces are glued (Cyano) every 2cm and thetrailing edges every 4cm.

Figure 15a and 15b: How to mould the D-boxes? Easy. On a

positive mould. Not much science behind this. For the wing,

two layers of Kevlar of 60g/dm² is fairly sufcient (the wing can

support all aerobatic maneuvers). For tails and n, a 60g/dm²

kevlar is OK.


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Figure 16: Tail and n. Making them lighter and stronger is

difcult but possible. There are too many wood sticks in the n.

We can suppress 2/3 of them for the rudder. But this was for

the look!

Figure 17a: Vertical

n and rudder and

horizontal stabilizer

mounted to fuselage

before covering.

Figure 17b: Vertical n

and rudder and hori-

zontal stabilizer mount-

ed to fuselage after

covering.


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November 2012 25

Figure 18: Wing plan


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Figure 19: All balsa wood pieces have been realized on a CNC

machine. Of course, on request, les can be provided.

Figure 20: How to mould the ap and aileron D-boxes — on a

window! Do not forget to “wax” it.


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November 2012 27

Above, Figure 21: Few detail of the wing to fuselage assembly

system.

Upper right, Figure 22: General view of the wing. The leading

edge is covered with paper for protection reason. It will be re-

placed by molded D-box.

Lower right, Figure 23: View of D-box mold under process. On

top, you can see the D-box bagged, in the center the D-box

results and in the bottom of the picture the D-box mold.


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The leading edge D-box is made with2*60g/dm² Kevlar layers. This is enoughfor F5J. The standard 165 g/dm² Kevlar-carbon layer is too much / too heavy forthis category.

The ap and aileron D-boxes are cutfrom a 60g/dm² Kevlar layer that wasmoulded on a window… (See Figure 20)

Nothing difcult. Everybody can do itwith a bit of experience or in a club. It isonly a bit long. (The wing requires moreor less 30 hours of work if you have the

D-box moulds and the wing ribs alreadyprogrammed for the CNC milling!)

But the result is... Magic! (See Figures 21,22 and 23)

Fuselage

The Genoma² fuselage is the same as theGenoma.

Total length: 2.2m

Nose to Leading edge distance =530mm. This is not too much. I stronglyrecommend not to shorten the nose.

Other dimension: Maximum larger =40mm, Maximum high = 60mm. Enoughplace to x everything you want in termsof propulsion, batteries, servos... Thefuselage section is neither round norrectangular. We prefer an ovoid sectionas you can see in the pictures.

Wing incidence is 4°, so that the planeies with a horizontal boom.

This is the ying attitude the Genomafamily has. And the fuselage of course

Figure 24: A view of the fuselage to better appreciate the design. Figure 25: The details on how to x the tail. Very

similar as the Supra / Bubble Dancer... Except that

here, everything is inside the boom. Everything is

made with very rustic moulds (and easy to be made).

Nothing difcult!


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November 2012 29

remains in this position with ap putdown or up.

This horizontal attitude is for me quite

important to manage ight when theplane is very far away.

Note: I usually play with the plane ying600m away (in our eld this is wherethermals are).

I confess that most of the F3x planesdo not have such incidence. But theirdesigns are based on speed. Remember,F5J is not F3J.

The boom is horizontal and the nose hasa 2.5° pitch starting at the wing leadingedge. (See Figure 24 and 25)

How does Genoma family y?

The Genoma (First) is quite magic. Youplay with it like with a F3K plane.

Of course because of the wing span, itis a bit different. The rolling rate is lower,

the gliding ratio is far better, but you dowhat you want when you want in a verysmall volume. I’m not a great pilot evenafter I playing with gliders for 40 years,but I still started to circle at 20 m altitudeduring the second ight.

The next thing to be noticed is that it isvery easy to y. For the last two years itis the plane I use for teaching new pilots.The trainees also learn how to land with

it. I use an “Easy Glider” at the very

end of my teaching lessons in order fortrainees to know how to play with theirown future plane! (See Figure 26)

Easy to y means also easy to circle atlow altitude. As an example, I circle 10minutes between 20 and 50 m altitudeas if it was a normal ight. Thermal liftwas ridiculous, small, but of coursequite frequent. And this ight was made

without any difculties. I didn’t feel

uncomfortable at all during the ightnor exhausted after the ight even if theplane was 100 to 200m away from thelanding zone. (See Figure 27)

One of my favorite ways to y in athermal is to play with the “hand brake”when turning (like with the car): Whencircling in the downwind branch, therudder is put at its maximum. The

Figure 26: One of my trainees with the Genoma after his ying lesson. They learn

everything with it.


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Figure 27: The proof that the Genoma can y at very low altitude. And “No fear, no

fun” is not my motto.

ailerons are in the opposite direction soas to maintain a at attitude. The planeis turning on its wing root, like a car with

the hand brake. A bit of pitch when beingupwind, then aileron order to restart theturn...

When done in the very core of the lift,the plane has a “vertical” trajectory...Interesting, no?

Another renement I’m using now is thefourth axe management. I play with thecamber of the wing all along the ight.

Instead of using pitching throttle (leftstick), I prefer to use the camber oneplaced on the right stick. The speedvariation is as with the left stick but theplane fuselage remains horizontal. Thisis marvelous during circling. You “push”when you are going upwind, and pullwhen going downwind. The pitching axisis used to maintain the circling radiusand the camber one manage the ight

speed. The plane then circles in a verysmooth and regular circle without havingmuch pitching order to be provided. And the fuselage remains in the sameposition (horizontal) which is once againfundamental to better feel the thermal.If you had used the pitch, the fuselageattitude would have changed due to yourpitching action… (See Figure 28)


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November 2012 31

Figure 28: The Genoma in ight. The fuselage doesn’t appear so long does it?


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In terms of yawing behavior, measuresand computation are very close. Again,“Magic”! (See Figure 29)

What about Genoma² ightThe new Genoma² is as expected fromcalculation.

It ies as its older brother:

• It is a F3K plane but with 4m span.This means that the way to y it similar toany F3K plane with of course more inertia(more time to roll).

• It has this ability to circle very shortly. And in this respect this open new wayof ying; On top of the standard “gentlecircling” way of ying with very smoothactions on the sticks that you need tomaster for TD ight, the Genoma familyallows to have a more aggressive wayof ying without much difculty. Thisis quite useful at low altitude when thethermals are narrow and not very regular.

Here, the yawing stability behavior is areal advantage compare to any otherplanes.

• It is a full aerobatic plane. Loop, roll,invert ight, chandelle are easy. The rstones (1 loop + 1 roll + 1 chandelle) weremade starting at less than 50m altitude…and of course nished by a landing closeto the pilot.

Figure 29: Comparison of different planes in yawing. The Genoma (in light blue) is far

better than any other planes (Supra original in yellow, Pike Perfect in purple, F3B plane

in dark blue) which provides it with very good circling ability. The Genoma² is of course as its older brother.


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November 2012 33

Figure 30: First ight of the Genoma (First version) was in January 2010. Since that time, this 1.9kg plane ies every week without

trouble. It even succeeds to ying three minutes alone (without any control due to an electrical problem) and crash in a eld after a

50m dive without any destruction. So light and so resistant!


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• Stalling is difcult with a radio mix“Elevator” -> “Camber.” In such conditionthe stall is a 5m loss of altitude with

recovery after. And if you insist, it startsfor another cycle of stall/lost of altitude/ recover. Then the only way to escape isto use the buttery airbrakes.

On top of this abilities are:

• The potential wing load range of 19to 35g/dm² which is optimum to anyight condition. As a consequence, thecircling radius (minimum 6m compared

to the 10m for the Genoma) and theminimum speed and sinking rate areimproved.

• The sub-n acts as a stopper duringlanding. The grass “sliding” is only50cm. That’s better than the 2m to3m for the rst version. I wonderedwhether the fuselage and sub-nattachment will be strong enough.For “standard” and “nearly standard”landing (that’s what I made actually),nothing adverse happens.

As already expressed, it is very difcultto measure minimum sinking rate or bestgliding ratio. It depends so much on airconditions that you can say one thingand it’s contrary. I then will not providevalues that don’t mean anything. Just tosay that with 30km/h wind, the Genoma²

Figure 31: The man is 1.93m long. Quite a plane, no? The Genoma² weighs 1.6-1.7kg.

It is 300g lighter than the Genoma for greater span and surface... The Genoma² is also

able to make the barrel rollss in circles or any other aerobatic maneuver.


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November 2012 35

without ballast stays in the sky with a“standard” sinking rate (as for any otherplanes for such wind that obliges to

y at best gliding ratio and not at bestsinking rate). Of course, with such wind,it is recommended to have 500g to 800gballast for better penetration / glidingratio. In this case Genoma and Genoma²are quite equivalent. Differences couldnot be measured for me.

The Genoma² in its rst TD F5J contest

After only two ights in 30 to 40 km/h

wind, I made an F5J contest. The planehad never been ballasted, circling hadnot been tested, ap compensationwas not well triggered, airbrakes andprecision landing never tested.

Because F5J is a new discipline, only fewcontests occur in my area. I had then toparticipate.

I also have to state that I’ve only made

competitions two times in my life. Therst one was in 1980 (I nished last) andthe second in 1982 (I nished third butwe were only three competitors and Icrashed my plane on the rst ight). So,in reality I consider that it was my realrst Thermal Duration (TD) contest.

Because of the pressure and the veryfew number of ights with the Genoma²I wanted to start with the Genoma. But

Figure 32: The Genoma² (facing the camera) and the Genoma ready for ight.


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then the rst failure occurs during aight test: a ap servo failed. ThanksMister Murphy! I then have to y with the

Genoma² which you will recall had onlytwo ights since new... Not a good wayto start a TD contest.

Other competitors had madecompetitions for years (F3J, otherTD types...). Gliders used were PikePerfect, Maxa, AVA, Shadow, Electra,Graphit, Alfa club and homemade planesincluding the Genoma².

Conditions were good with low wind(10 to 25km/h wind) which obliged thelightest planes (Maxa and Genoma²)to ballast a bit when the wind went up(+ 250g). The AVA didn’t have ballastcapability which was a disadvantage insome ights. All other planes had wingloadings between 27 and 35g/dm² anddidn’t require ballasting.

I was then quite impressed and anxious

for the rst run.

I then ew and discovered that the planeis very good, and even without thermals,did equal with the others. My rst landingwas not so good because I didn’t knowhow the plane reacted or how to land ona spot...

Then all the other seven ights proved tome the following:

Figure 33: Genoma² for its rst ight. Except few adjustments, it ies perfectly

and I found immediately comfortable. It is even better in circling ability due to the possible low wing load (19g/dm² without ballast). Of course things needs adjustment

(compensation, trim…).


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November 2012 37

1) The Genoma is better than any othersin circling. It ies like an F3K plane andof course can also y like an F3J plane.

This ability to circle in an aggressive wayin a very low volume is a real and majoradvantage for a TD competition. Andthen, my analysis in this respect is reallyvalid. With thermals, the plane alwayswent over the others or at the samealtitude. The Genoma² opens a new ightenvelope compared to existing 3m to 4mspan gliders. And I’m not an expert inthermal hunting!!!

2) Transition: The plane is as good asthe others. I didn’t play much with apduring transition because of the apcompensation adjustment was notcorrect. But I’ve never been trappeddownwind as the AVAs were. What Ican say is that the higher camber ofthe Genoma² wing indicates you needto play with the aps if you want to be

as good as a Maxa for example. Andof course, a full moulded wing made inaccurate moulds are always better thana handmade one. But once again, thecosts are very different and for the price,the Genoma² is really good.

3) I discovered how to land after the TDcontest when I offered other competitorsto y the Genoma². It is nally verysimple. Plane has to transit back to the

spot in order that it reaches a 2m altitude5m in front of the spot. Then full brake.The plane stops in the air, pitches and

falls like a parachute at low and constantspeed. It remains agile on all axes andyou can adjust the spot. At the very end,pull on the elevator stick and the planelands at. The under n and the lowspeed immediately stop the plane. As theEnglish say “it’s a piece of cake” if youhave a few practice sessions.

4) Concerning the sinking rate, it is asgood as any others. With real mouldedwing it will be a must for sure!

So my landing was not good at all. Twooutside, one at 1.2m, the others between3 meters and 5 meters.

I knew I obtained 1000 points for onerun. I miss another one for a stupidmisunderstanding with my caller (Ithought that only two minutes remainedand exited the thermal — I was 100m

over all the others — and start myapproach back... When I reach 180maltitude (50 m lower than others), Idiscover that 5 minutes of the ightremains... And no more thermals exceptvery narrow ones... So I get an 8 min 40second ight.

And nally, I nish the contest in thirdposition... Good for a start isn’t it?

So despite the inability of the pilot tomanage the sticks correctly, the planehas real potential.

ConclusionYawing stability is fundamental for ourplanes. This was not calculated in thepast due to lack of knowledge and tools.But thanks to M. Drela and A. Deperrois,this is no more the case. This could beapplied to all our disciplines. Aerobaticplanes and F3K already do it. For thosewho play other games, you can also

apply the yawing stability calculationprinciples. As an example, I made aracing plane with good results. (SeeFigure 34)

Making our own model is still possible forF5J planes. It’s not a matter of expertisebut only a matter of time to construct it.This means that this discipline has roomfor experimentation and that you are notobliged to spend $1000 to $2000 to get a

single plane.

The cost of the Genoma is about $400without equipment. And if you make itin a club, this cost of course could godown.

Yes, this is quite more expensive thanmaking an F3K plane, and then we needto make calculations to predict the resultprior to launching the building phase. But


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Figure 34: A small racer (1m span, 300w only) where the fuselage length is longer

than the span. Despite the fact that this conguration disturbs our minds, it is not so

unusual for real racing planes. The fuselage increase allows us to reduce n and tail

dimensions (and then drag) and to increase the stability. Flight is like an arrow —”on a

rail.”

the ying envelop of a 4m span plane isalso far more extended!

The Genoma² has been created

taking into account 40 years of glidingcalculation experiences, 100 planesconstructed (most of them werehomemade) with about 25 years forelectric TD planes including some forduration records. The Genoma familyhas already made one to one TD ightswith good results. The rst competitionresult is also quite encouraging. Youmay say that this could come from the

pilot itself. But my experiences (andespecially my rst competition) show methat it is mainly due to the plane itself,and especially to the yawing stability. Ofcourse this doesn’t mean that it is thebest plane.

If you are satised with a dened wing(even I think that the Genoma² is moreaccurate for F5J, I will never say that

actual F3J wings are not good for F5Jcategory), you can then improve yourplane by redesigning a fuselage and a nand rudder for accurate yawing stabilitybehavior. This is then far cheaper thancreating a new plane. And tools like AVL or XFLR5 are here to guide us. Thiswill force the builder to propose realgood planes and not planes that have


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November 2012 39

In a future issue of RC Soaring Digest...

Walk-around: Tony Condon’s Niedrauer NG-1

Jerome Niedrauer built this glider in the early 1970s with the goal of reducingdrag and increasing the performance of a stock BG-12. It is now owned by TonyCondon who says, “The NG-1 is the latest addition to the Condon family glidereet and is an interesting collection of Briegleb BG-12 and custom made gliderparts. Most people can’t gureout what it is at rst glance, and the best short

answer I have heard to describe it is simply “Experimental.”

commercial interests and fashion behindthem.

For those who want to have an up to date

F5J plane, the Genoma² is the one youexpected. You can then either:

• Copy the Genoma² with the same orsimilar standard construction (woodand D-box),

• Or use the Supra published buildingtechniques and construct yourGenoma²; this will of course workperfectly,

• Or make some moulds with a CNCmachine.

If you make moulds (be sure that it isreally feasible for a non professional guyto have a plane as light as the publishedversion), I of course encourage you to doso. Only advise me in order to see howI can get one of those wings. Thanks inadvance.

We have seen that wing loading is verylinked to aspect ratio. This means thatif you do not want to have a plane at20g/dm² without ballast but somethingmore closed to 25 to 30 g/dm². You canplay with this parameter. One possiblesolution is then the Genoma rstgeneration.

So let’s y F5J!


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from RCRCM and OleRC.com

Review

Andy Page,


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November 2012 41

From designer/pilot Carlos Pisarello of Argentina comes the Toba, a new modelfor F3B multi task soaring, F3F sloperacing, and electric assist soaring. Builtby RCRCM in China, the Toba is anaffordable sailplane. But make no mistake,it is also a well built model and that makes

it a great value. Tobas were own by theChinese team at the 2011 F3B WorldChampionships in China. Wing layupoptions are carbon D-tube and full carbon.The review model, supplied by OleRC in Hong Kong, isthe full carbon version.

What you get

In addition to the airframe, RCRCM supply

machined plywood servo frames for apand aileron servos, servo covers, ap hornfairings, a ballast tube (for F3F fuselageonly), a servo tray, wire harness withMultiplex-style 6-pin connectors, carbontube pushrods, clevises, wing pushrods,and a towhook.

The frames are sized for MKS DS6125servos but with small modications canbe made to work with any thin wing servo.This is a nice accessory not often includedand the use of wood makes them easilymodiable for versatility.

Oddly, the towhook comes unassembledand with quite a loose t of the unthreadedsteel hook in the aluminum plate. Isubstituted one of the readily availableunits from Kennedy Composites.

Specications and Weights

From the manufacturer’s website:

Wing span: 3085mm

Length: 1456mm

Wing airfoil: RCRCM2010-8 Wing area: 58dm2

Tail airfoil: RCRCM2010-10

Flying weight: 2000-2100g

Review model component weights in grams:

Left Wing: 747

RIght Wing: 745

Left Tail: 50

Right Tail: 50

F3B Fuselage with nose and tail cones: 208

F3F Fuselage with nose and tail cones: 215

Wing Joiner: 104

Ballast Tube: 25

Servo Tray: 14

Wire Harness: 79

Servo Frames (4): 16

Servo Covers / Pushrod Fairings (6 pcs): 9

Tail Joiners (2): 6

Carbon Tube Pushrods (2): 31 (when cut to required length)

The total F3B airframe weight without hardware or radio gearcomes to 1910 grams, or about 67 ounces.

For those of you who wonder about such things as weight

distribution, the wing panel CG (nished with servos, covers, and

wiring) is at about 40% of the half span.


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First impressions

Like anyone else, I could not resistputting the parts together for the rsttime immediately after unpacking andwas pleased to note that both the designand execution of this sailplane are welldone. All of the joiners t precisely right

out of the box - a good sign.

While these are purpose built tools forserious competition, it isn’t all aboutmechanics and performance. We likegood looking airplanes too and theToba does not disappoint with its veryattractive lines. All the molding is verycrisp and smooth. The graphics andcolors are striking and not just the same

old thing.Breaking it down again I moved on to acloser inspection. The molding qualityis very good with clean and smoothedges. There is some visible telegraphingof fabric weave and spar edges on thewing panels but nothing unusual orconcerning.

The elevators and ailerons stop short of

the tips, leaving a small vulnerable areathat could be easily damaged. In factone of the tail tips was slightly crackedalready. A drop of thin CA xed that. Careduring transportation and handling willbe needed to keep these intact.

Available space for aileron servos is tight.This is a thin wing, measured at 8% atthe root. If using the supplied covers,

Complete

contents laid out

for inspection.

Right out of the

box. What a great

looking sailplane!


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November 2012 43

Above: Flap wiper and pushrod fairing recess.

Above right: Top hinged aileron wiper. Lower skin

recessed for servo cover with integrated pushrod fairing.

Right: One of the smoothest molded leading edges I’ve

seen. No ridges, no pits.

Below: Wing root. Middle pocket is for ballast.


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any of the typical aileron servos will t.

But if you wish to substitute at coversyou have very little space to work with.The inside height of the bay is about15/32" at the forward edge and only5/16" at the aft edge. Space is of coursemore generous in the ap servo bay,with 13/32" of height at the aft edge. Airtronics 94761’s t nicely there.

Unlike most composite sailplanes these

days the ailerons are top hinged andintended to be driven with an externallinkage. It may be possible to run thelinkage inside but I used the stock setupand covers. Flaps are bottom hinged.The wipers are some of the best I’veseen with very tight tolerances to the skinwith no interference. Hinge movement isvery good with plenty of range of motionand no binding at all.

Two fuselages were supplied with the

review package, for F3B and F3F. TheF3B fuselage is very small in crosssection and sets the wing at a positiveangle of incidence. The F3F fuselageappears to have zero-zero incidencesettings and is sized about 1/10" tallerand wider in order to accommodatethe ballast tube. Only one servo trayand harness were supplied. We did notbuild out the F3F fuselage as of the timeof publication, though other than thedifferences noted above it is identical.

The large cross section carbon wing joiner is typical for a two piece wing. It’shollow, with two spaces on each endthat can be used for ballast. It may nothave much practical effect but the depthof the cavities on the subject joiner varyby about an inch left to right. Additional

ballast cavities are molded into the wing

roots. It should be possible to tailor theballast to load it up without changing theCG. By my rough calculation there is alittle less than 9 cubic inches of volumetotal in all cavities which would give amaximum possible capacity of about 43ounces of brass or 59 ounces of lead.Tailoring for CG will likely reduce themaximum possible weight.

The wing skins are not pre-cut for appushrod exits or for horn installation.Supplied horns are glass and seemrather small for secure attachment.Two of them were lost in shipment,however, so I had no choice but tofabricate new ones. The hardware waspackaged in thin, fragile plastic bagswhich had broken open, and the box wasconstructed so that small parts could

Supplied ap and aileron horns. Two of these escaped during

shipping. Probably would work just ne, but I elected to make

the replacements a bit larger for more substantial attachment.

Final parts ready for installation.


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November 2012 45

easily escape. Those lost horns mightbe doing endless speed runs across thePacic in the belly of a 747.

The removable nosecone is glass butthere are four strips of approximately 1/4"wide carbon running through the nose ofthe fuselage itself. About 4" forward of

the aft end of the nosecone the fuselagetransitions to all carbon. The nose isopen on the bottom rather than the top,keeping the pushrods clear of the wing joiner and your antennae on the best sideof the mass of tightly packed radio gear.

The Build

First the ap pushrod exit was createdby using a straight Dremel bit to cut theupper skin. The skin is molded with arecess for the pushrod fairing so thereis no guesswork here, just cut it backleaving a small ledge for the fairing.

Next, deect the ap all the way downand relieve the auxiliary/shear spar usinga small Dremel sanding drum. The samedrum works nicely for relieving the ap

wiper.Since I wanted to make the ap horn abit longer than stock for the strongestpossible connection, I opted to rst testt a pattern cut from 1/64" ply beforecutting the circuit board stock.

First I cut a squarish opening in the apshear web using a #11 blade. A couple ofeyeballed trials using scissors to cut the

Now, all you seasoned experts out there already know this, butit might be worth mentioning some tools that are handy for anymolded sailplane project that might not be in the typical modelairplane shop.

• Rifer les are great for precise access in tight spaces, useful

here for roughing up the inside of the nose for gluing in the tray.They’re also indispensible for shaping details in composite repairssuch as around wing root llets.

• Chainsaw les, in several small round sizes, are cheap andreadily available at any hardware store. Their sharp, ne teethhappen to cut our materials very well. I reach for these moreoften than any other type of round le. They can do very preciseshaping of balsa, plywood, composites, and of course metals. Ifyou cut the smooth end off with a cutoff wheel you have cutting

teeth right at the end where you often need them. • Woodworking chisels and a small ush-cutting Japanese sawmake quick work of precise trimming of wood parts, especiallyplywood. I used them to enlarge the openings in the thickplywood tray.

This is the only source I could nd that has a photo of theJapanese saw. It’s in the UK: .This is te same saw from a US source: .

Look for a specialty woodworking store in your area and you’llnd many things well suited for model airplane use that you justwon’t nd at hobby shops. For example, the best old schoolhardware and hand tool store in Seattle and possibly anywhere isHarwick’s in the University District. There’s not much on their siteyet but there is an incredible selection in the store: .


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Opening the upper skin for ap pushrods. Auxiliary/shear spar cleared for pushrod. Flap shear web

opened for control horn.

Making a template for the ap control horns. Checking for clearance and range of motion.


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November 2012 47

ply and I had the right shape to t insidethe ap and contact both the upper andlower skins. Tracing that wedge shape tofresh ply stock I added the horn as a bestguess. After a little trimming to makesure it t under the fairing and wouldprovide the required range of motion, it

was done. Make sure it doesn’t hit thelower skin when deected for up aperonmovement. The nal template is shown inthe photos.

The circuit board stock was cut roughlyto shape with a Dremel cutoff wheel thennished with a disc sander and les.

Aileron horns were done similarly but didnot need the leg to t into the surface.

They are just a standard triangular shape.Thickened epoxy holds them all in.

The remainder of the wing work willbe familiar to anyone who has done amolded model.

Servo frames are glued in with thickenedepoxy, with the servo mounted in theframe after rst wrapping with Saranwrap. Be sure to tighten the screws just

as you will when securing the servos foright, do not weight them down duringcuring, and allow plenty of time for cure.I like to do this step rst so they can curefor a few days while I do the rest of thebuild. A little care during this step willeliminate any telegraphing of the framefootprint through the skin.

Flap pushrod installed. These are Sullivan clevises and 2-56

threaded rods rather than the supplied hardware.

Flap horn installed.


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Aileron horn installation. Lower skin and wiper relieved for clevis

using sanding drum. Shimmed wire ensures the same geometry

for equal movement of both ailerons.

Aileron horn installed.

Airtronics 94761 ap servo in frame being glued in place. Servo

is screwed in tightly, protected by Saran wrap.

Clip a short servo extension and attach it to music wire with

heat shrink tubing for an effective tool for shing wire harnesses

through wings.


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Multiplex 6-pin connector. You may wish to pot this into the

wing. I chose to leave it loose. There is just enough length in the

wire harness to allow disassembly without yanking on the wires.

A little alcohol on a glove allows neat smoothing and shaping

of thickened epoxy, here to rm up and protect the wires where

they’ll be handled during assembly/disassembly.

Twisting the knife: the easy way to drill holes incomposite skins.

Drill a few more holes then clear it out with a chainsaw le.

A at le cleans it up the rest of the way.


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Laying out radio gear. Space is very tight so plan ahead for clevis clearance and nose weight.

Fuselage connectors can be glued against molded recesses in the wing root.


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November 2012 51

There really is nothing to do on the tailsunless your horns need to be reglued.One of mine was not very secure andpulled loose. It was roughened witha diamond le and reinstalled withthickened epoxy. Be sure to give thema good test and correct the glue joint

if you’re at all in doubt. You do have torelieve the tailcone for the elevator hornsusing a small sanding drum.

The supplied fuselage tray is widerthan the F3B fuselage so that it can beused with either version. I used a pieceof sheet balsa tted to the nose as atemplate to reduce the amount of trialtrimming of the 1/4" ply tray.

No guidance is provided for locating it.Beware that you may need to leave morespace up front for balance weight thanyou think! At the location shown, my trayleft just enough space to balance themodel at a neutral CG, and that is witha four cell battery pack (Elite 1500mahNiMH).

Put the tray as far back as you can,allowing just enough room to workwith the aft servo pushrod. The servoopenings are slightly smaller than neededfor the Airtronics 94809 but there issufcient material to t two of them.

Height and width inside the noseconeare very limited so plan carefully. I left just a little space at the ‘bottom’ of theservos and put them on the centerline,

resulting in near zero clearance betweenthe clevises and the nosecone.

If using the stock pushrods you willneed to support them midway down thetailboom. I used a block of stiff foamrubber cut roughly to the fuselage crosssection shape and about an inch long.

Holes are easily drilled in it by twistinga metal tube with a rough sawn end byhand.

You could shove the foam block downthe boom with a stick and hope theholes stay properly placed and sizedto avoid binding the pushrods, but Iadded aluminum tubes (from the stockused to drill the holes) to the foam, then

used the pushrods themselves to guidethe assembly into place. The tubesare longer than the foam to help avoidgetting epoxy on the pushrods duringassembly and added less than a gram.

One O-ring CA’d to one pushrodprovides a stop for pushing it into place.Just make sure the O-ring is placed soas to not contact the tube during normaloperation.

After masking the accessible area insidethe nose I smeared some 5-minute onthe foam and in it went. The result isfrictionless movement with no slop dueto buckling of the bendy pushrods andvery little added weight. All this is bestdone before adding anything else to thefuselage.

My calculations show a possible savingof just about one ounce overall bychanging to .07" carbon pushrods inteon tubes, taking into considerationthe reduction in noseweight as well aspushrod weight.

Although you could use the supplied

pushrod hardware, I substituted Sullivan2-56 clevises and threaded rod. I nd theSullivan clevises just t better and staytighter on threaded rod than other brandsof metal clevises. The popular Hayesplastic clevises may not t in some of thetight spaces on this model.

After rst ights I usually put a drop ofblack CA on the threads to lock them in

place.

Initial Setup

I eyeballed the CG to a point about4" from the wing LE. RTF weight withstock build and this CG is 88.5 Oz. Notethat this is the full carbon version. It isnot known how much weight can besaved with the D-tube layup. My initial

control surface throws were as follows,measured at surface roots:

Elevator 1/2" up and down.Rudder 1/2" left and right. Aileron 3/4" up , 1/2" down.Flaperon, 25% of aileron movement.Flaps, about 60-70 degrees max forlanding mode.


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Launch ap, a conservative 1/2". It willneed more to pull hard.

Float, Cruise, and Reex set to thestandard “little bit down, at on the lowersurface, and a little bit up.” Lackingpublished settings, these will work andthings will sort themselves out during the

rst few outings.

Flying the Toba

Before we did the range check I hadbeen somewhat concerned about thecarbon strips and tightly packed gear inthe nose. This proved to be unfoundedthough because we had no issues withrange using an Airtronics 92104 receiverwhich did its job awlessly as always.

After a quick jog to see how the modelfelt with some airspeed I did a few handtosses. Elevator setting was spot onand the throws felt ne. So up the lineit went, tracking straight and behavingas it should. The full carbon wing is verystiff, giving a precise feel to the handling.Subsequent ights showed the CG to be

neutral. Actual measurement puts this at4 1/8" from the wing LE, or 105mm.

The obligatory pre-maiden photo. Andy

with the newly nished Toba. Notice

the slim nose, typical of modern F3B

machines.


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November 2012 53

TOBA DETAILS


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With the model pointed away from meI rolled it back and forth a few timesquickly to see how the nose tracked – theold roll-around-a-point exercise.

With the above settings and about 40%rudder mixed to aileron input the Tobatracked straight with no adverse yaw.

Roll rate was crisp, just how I like it.

Running through a few quick tests Ithen checked out the handling, stallcharacteristics, and pushed the limits alittle to see how it responded.

I h ith th CG I t l t


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November 2012 55

I was happy with the CG so I set elevatortrim for oat and cruise modes thenplayed around with stalls. The Toba hada lower stall speed than expected andshowed no bad habits.

Next was to see how it reacted to a bitof abuse. Starting from a moderately fast

speed I cranked it up hard into a steepturn. Toba was right at home, retainingenergy nicely through several revolutions.Forcing a high speed stall in that attitudeagain showed the forgiving handlingqualities. The recovery was immediateupon proper pilot input.

Setting up for a landing, I pulled aps tocheck the elevator compensation mix.

I’d programmed in a guess which was anearly linear curve with moderate downelevator travel, and that proved to be agood place to start. As expected, theaps are very effective with about 60-70degrees of maximum travel. That is morethan enough.

This is a much heavier model than I amused to, with a wing loading of 14 oz/ ft2, yet it oats and goes up in lighter liftthan I expected. The crisp handling andwide speed envelope should be an assetfor the task soaring it is designed for aswell as make for a fun sailplane for big airdays at the thermal eld or slope.


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Conclusion

The Toba was one of the most trouble free,

straightforward molded sailplane builds I’ve

done. There is nothing tricky or complicated

about the build and nothing signicant needsto be reworked, though you may choose to use

lighter pushrods or your own control horns.

This is a lot of sailplane for the money and I

look forward to ying it more!

Resources:

OleRC:

Toba:

Airtronics:

Pushrods, towhook, etc.:


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The KST DS125MG is a thin, metal gear, digital servo. It isdesigned and congured to be used to drive ailerons and apson 2-servo, 4-servo or 6-servo wings.

During our evaluation, many comparisons were made with theHitec HS-5125MG, a similarly sized servo with which we areextremely familiar, having used them extensively over the lastfew years.

Our sample was provided by OleRC in Hong Kong and arrived in the usual retail cardstockbox and was enclosed in a bubble packet. Included with theservo were three plastic servo arms, a blue anodized aluminumarm, three mounting screws and the servo arm set-screw asshown in the title photo.

The body of the DS125MG is primarily machined aluminum.There is a molded plastic portion which sits at the base of thegear train. The case itself is very reminiscent of those produced

DS125MG servoKST

by Volz for model aircraft use - the at sides of the motor areush with the case surface.

All of the gears in this servo are metal. There is no play in thelinkage and the sound in operation reects the sturdiness withwhich this servo is built. Operation is extremely smooth and themeasured travel with signals from 1.00μsec to 2.00μsec wasslightly more than 90 degrees.

In our testing, centering was consistently right on with no load,and deviations of about 1/8th inch were measured with a loadof 48oz.in. (It should be noted that the nylon control armsdeect substantially under this load as well.) With a 5-cell NiMHpack, current draw is approximately 230mA with a load of24oz.in, and 850mA with a load of 48oz.in. The maximummeasured current draw, 1.2A, occurred under full stallconditions.

Because the DS125MG is slightly taller than the HiTECHS-5125MG and like servos, it may not be able to be used as

a direct replacement in most installations. For new installs,wood frames need to be made slightly longer because ofthe placement of the two “ear” holes. The KST DS125MG is3gm/0.12oz heavier than the HS-5125 but is rated at about50% more torque, so will be an advantageous choice in someapplications.

Sources:

OleRC: KST:

Bill & Bunny Kuhlman, [email protected]


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November 2012 61

KST DS125MG HiTEC HS-5125MG

KST DS125MG HiTEC HS-5125MG

Dimensions

W x T x H

30mm x 10mm x35.5mm

1.185" x 0.395" x 1.414"

30mm x 10mm x 34mm

1.185" x 0.395" x 1.332"

Rated torque 4.8 Kg.cm, 66.66 oz.in@ 4.8v

5.80 Kg.cm, 80.55 oz.in@ 6.0v

3.0 Kg.cm, 41.7 oz.in @4.8V

3.5 Kg.cm, 48.6 oz.in @6.0V

Operating speed 0.15 sec/60° @ 4.8V

0.12 sec/60° @ 6.0V

0.17 sec/60° @ 4.8V

0.13 sec/60° @ 6.0V

Case material Machined aluminum andmolded plastic

Molded plastic

Weight 27g, 0.95oz 24g, 0.84oz

Bearings Dual ball bearing Dual ball bearing

Gear material Bronze and steel with

steel output shaft

Nylon, steel and bronze

with steel output shaft

Retail price $45.00 $50.00


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SSSOOOAAARRRFFFEEESSSTTT 222000111333222333///222444 FFFeeebbbr r r uuuaaar r r yyy 222000111333 aaattt MMMaaatttaaammmaaatttaaa

OOf f f f iicciiaall EEnnttr r yy FFoor r mm** Entries Must be received by 20-02-2013

Two Payment Options :

1. Snail-mail - with Cheque made out to AucklandSoar Inc. to:

Soarfest36 Ripon Cres Meadowbank Auckland 1072

Email Aneil Patel (doing Matrix) at : [email protected]

Ted Bealing at : [email protected] once the entry is in the mail.

2. Pay online to the cl ub bank account National Bank, Onehunga. A/C No 06 0209 0085092 00

Email Aneil Patel at : [email protected] or Ted Bealingat : [email protected]

once the payment has been made.

Name : ____________________________________________

NZMAA Number :________________

Frequency 1 : _______________ Frequency 2 : _______________

Open (Entry Fee $20.00) Sportsman (FREE Entry fee)

Saturday Night BBQ (Details T.B.A)

All entries MUST BE RECEIVED and FEE/S PAID by 20 February 2013Email entries accepted up until 8 pm on the 20th February – NO Later.

Entries only accepted on the field if there are no frequency clashes and an available slot is left in the matrix

Please also provide an Alternative FrequencyIf you cannot change frequencies – you May Not be able to fly.

Event to be a Hybrid of Premier Duration/F3J.

By entering this contest I agree to abide by the Rules and Regulations as set out by AucklandSoar Inc, theContest Director or the Contest Protest Committee.

I agree to and accept the above conditions.

________________________________________

(Signature)


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November 2012 63

Wo r ld Soa r ing Ma

s t e r s 2 0 1 2

T e x t b y M i k e R

e a g a n, m d r e a g a n 1 @ g m

a i l. c o m

P h o t o s b y M a

r k N a n k i v i l, n

a n k i v i l @ c o v a d. c o m

Hey guys, I thought you might like a little


64/110


Hey guys, I thought you might like a littlereport on this years masters. If you werenot there you missed one of the bestcontests in a long time. I have been to allfour of the Muncie based Masters andown in the yoffs twice, which means Ihave own 58 rounds, which gives me a

great perspective from which to observethe competition. This also means I havebeen burned and done a little burningmyself.

Every kind of condition existed this yearfrom dead calm to 30+ mph winds,rain, cold, you name it. This was a realtest of man and machine. Aspires werethe plane of choice and in the wind gotgreat launches and penetrated well.

However, the few times the wind was notblowing put them at a big disadvantageagainst the light weight Maxas and superlight Explorers. Being at the optimumballasted weight was crucial to doing wellin every round. Being too heavy meantthat getting that great save or climbingwith the group was almost impossible.Being too light meant you could climb

out only to get way down wind with noway to get back!

Having a good caller was also critical,made even harder because of the shorttime between groups, and the randomorder made sure you had to get someonedifferent to call almost every round.

Trying to follow other planes down windled to many land-outs in the beans

(zero) and planes landing miles away as over the beans, no hope, a puff came my plane to go y and when I turned on


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November 2012 65

( ) p g ypilots pushed the limits of their visibilityand underestimated the wind and theirplanes ability to get back, which wasnecessary many times to get that max.

I ew twice WELL past my comfort zone,but did get my time! Many low saves

were made throughout the contest, nevergive up was the order of the day.

Ben Clerx and Jim Fricky made greatsaves during the nals, but the best savewas done by Joe. 20 ft. high downwind

, p , pthrough. Zero gain the rst few turns butslowly developed into great lift, climbingout to the clouds.

I was timing another ier in this groupwho made his time easily hooking upright after launch. As Joe said, you must

have screwed up to be in that position inthe rst place. It is much more fun whenyou make those low saves, though!

The iers helping each other wasamazing. On one of my rounds I grabbed

y p g ymy transmitter I got the blank screen ofdeath, done, after all that expense andeffort. The Horizon boys soon foundout and diagnosed the problem as adead battery. Before I knew what washappening I had a new battery and was

up in the next ight group ready to rockand roll! I cannot thank these guy enoughfor their amazing help and willingness tohelp a guy when he’s down.

On Saturday, trying to nish the lastregular rounds, the wind was blowingso hard that the contest was called forsafety reasons. These guys were stillying and making maxes! Think aboutthat next time you complain about a little

breeze! My group was next up. I switchedto my Aspire with the full 32oz of ballast,but was pushed till the next morning.

This worked out great for me as myMaxa is made for super light morningair. I pushed out early as far forward andsouth as possible as the rst group haddone well out in that same spot. I stayedas long as possible and slowly drifted

back. Others in the group were alreadystarting to land. Now I was out in front ofthe winches and starting to feel bumpsof the very rst early morning thermals.Two different circles showed zero gain,but the third showed promise. Workingas delicately as possible, I began to driftback over the landing area at about 50ft.It was at this point that I realized I was

the only one still in the air. I was literally


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y ycircling over the guys in my group thatwere putting their planes away.

Getting burned was just part of the gameand it happened to almost every pilot;I think only two did not feel the pain. Inanother group I was rst to launch and

the wind was well over 25. With thismuch wind my ight was pretty muchdecided within a minute of launch.

The problem was the last to launchwas 90 seconds after me. Skip had thishappen to him only it was 2 minutes afterhe launched that the last pilot, after aline break, nally got in the air. Next yearthis will be addressed with staggeredlaunches as was done in the nals.

This is a very intense contest. Not for thefaint of heart. You can come to learn, itmay be painful, but you will learn! Bringtwo planes that are tried and true andwon’t blow-up with full ballast launchingin 30 mph wind. If you want to play, theMasters will be up next year to start thestagger every other year with the WorldChamps.

Congrats to Joe, ying Maxas, for hiswell deserved win. He came all the wayfrom New Zealand and his winningsalmost payed for his trip!

See you next

Documents

R/C Soaring Digest - Nov 2012