I mention this only to make readers awarethat there are certain things that are done inhigh performance large scale aircraft that arecompletely different to what most modellerswill find in their entry level or smaller models.I have heard comments made in passing bysuch ignorant ones, which, if taken seriously bythe uninitiated, would result in some very scaryset ups. It is for this reason that PrecisionAerobatics has sponsored this second part of atwo part series of articles designed to take outsome of the mysteries of what to use, why weuse it and of course, where to get it.

From the outset, let me state that all theequipment shown here is available throughPrecision Aerobatics. Their knowledge and expe-rience has played an integral part in their selec-tion and development of the items they provide.

Servos

There are those who are “hung up” on a cer-tain brand or certain type here. There is, for themost part nothing wrong with this….after all wehave our Holden fans and our Ford fans with lit-tle but sentiment differing the two. If you have aparticular brand that you have confidence in,then by all means, explore their high end servos.There are many options out there for the openminded, and in the end it really comes down to

budget. Either way, there are some “must haves”.The requirements come down to 3 basic

choices…First would be the torque rating. In most

cases the required torque rating will be stipulat-ed by the manufacturer of the model. Usuallythis would range from 11kg/cm to 15kg/cm. Iwould in fact NEVER go less than 11kg regard-less of what is stipulated and don’t be scared togo bigger depending on the type of flying youwish to do. Working a servo at its full capacitycontinuously is going to be hard on it. If indoubt go bigger.

Second would be speed. Again here thereare many various options, but in my opinion thefaster the better. If an advanced style of flying iswhat you are trying to achieve, response speedwill only help. For 3D particularly the speedbecomes imperative. I have seen planes thatseem sluggish and fat, be transformed intosomething far more sprightly and agile by usingfaster servos. I have had some say to me that forthem, speed would be of no benefit as their fin-gers or reaction times are too slow for it to beworth while. This cannot be further from thetruth. If your reaction times are on the slow side,this will only be aggravated by servos with slowreaction times. I would personally put servospeed as second only to torque in order ofimportance. It is not unreasonable to expect lessthan .19 sec/60 degrees speed and I personallyuse nothing slower than .15 sec/60 degrees.

Third would be positioning type. (Analogueor digital). I know some who will never usedigital servos, and some who would never useanalogue. We are of course referring to thepositioning method employed by the servo toaccurately interpret your stick command andgive you a resulting position. This is most feltwhen the command is given to return to centre,and a badly centred servo is certainly noticed,especially if you tend to fly around centre(straight and level) regularly.

Most suppliers, PA included of course, willstock a full range of servos in the high end

brands, and provided the torque and speed areadequate, you couldn’t go wrong choosing yourfavourite. However, you could easily spendmore than the budget allows, so do not hesitateask those at PA about some of the other optionsthat can be easier on the pocket. As an exam-ple, a very good friend of mine who fliesfreestyle at an international level has chosen touse Bluebird 630MGs on his 50cc edge 540. Thisbrand of servo is in my opinion very underrat-ed and while being anything but over pricedoffers very good statistics. The afore mentionedmodel for example gives 15kg/cm torque at .13sec/60deg which is very impressive andalthough analogue, offers centring similar tolow end digitals. This in my opinion is an attrac-tive possibility as the price is around half that ofits digital counterparts.

However, another word of caution; there aresome very cheap servos getting around thatboast some high statistics but simply do notmake the grade or even meet their publishedperformance numbers. There are brands thatcan be trusted for good reason, Futaba, JR,Multiplex and Hitec are all popular choicesamong large scale guys and for good reason.Hitec come with the advantage of being pro-grammable (with a separate programmer) tomatch speed and arc, saving the need for a sep-arate match box, but this is usually only neces-sary on aircraft where there is more than oneservo per control surface.

Linkages & Control ArmsRight, so, we have the servo selected and

installed. Now what? Well, we are setting up ahigh performance aircraft with 3D capabilityright? Step one is to get rid of those 2mmpushrods we’re used to with the Z bend in oneend and the plastic clevis in the other. Here isanother area where we need to step it up anotch or two. Pictured is a set up I put on theEdge 540T using items directly off the PA web-site. These are all high grade items designed totake high loads with protection against vibration

and other forms of failure often found on small-er linkages. Lets look at them piece by piece.

CF Control Horn ExtensionsThese are designed to give more throw to

those surfaces to satisfy the 3D junkies amongus. There are other options available, but thesehave several advantages. First, they will fit anybrand of servo as they are attached to the sup-plied servo arms. Second, being Carbon Fibrethey offer very good resistance to twisting actionimposed by the side loading of the offset balllinks. They are easy to install as per the suppliedinstructions and the only word of caution wouldbe to make certain you attach them to a hornwith the heavy duty boss, not the lighter nylonones that all servo suppliers seem to ‘throw intothe box’ with their high torque servos.

Ball Links, Clevises & Control HornsThere are ball links and there are ball links.

These ones are from Germany and the fit is verysnug with excellent tensional strength andsmooth rotation. They have a nice thick bandthat takes some real effort to remove off the ballwhich prevents any tendency to pop off. Theobvious advantage to using ball links is theirresistance to vibration.

The clevises I used are very nice anodisedalloy with a throughbolt that can be (andshould be) Loctitedinto place. Spring cle-vises or plastic clevisesshould not be usedEVER as they can nei-ther take the vibrationor the loads. The cle-vis bolt’ on the onespictured, screwsthrough the alloy andcaptures the nylon tabon the adjustablehorn. Once fitted andLoctited into placethere should in fact be

no need to ever remove, as adjustment to thecontrol horn length is accomplished by screw-ing the tab in or out (shorter or longer) asrequired. This does assist in getting the geome-try accurate for equalising the throw ofmatched surfaces (i.e. two elevator halves ortwo ailerons) and can be locked up (again withLoctite) to prevent any loosening.

The only thing to be careful of here is thatthe stainless bolt on the horn does actually gothrough a hard point on the surface so that theycan be tightened effectively without crushingthe surface and weakening it in such a crucialspot. Of course this should be the case regard-less or the horn used, but a through bolt controlhorn does become more an integral part of thecontrol surface and has less risk of failure.

Servo Extension Leads

Here there are some things to watch out forthat may not have been an issue on the smallermodels. For example, those high torque servoswill without a doubt require more Amps thanstandards. Not only that, but the measuredlength of the leads will be longer, meaning thatthe quality of wire and plug becomes important.The PA leads are again made in Germany andhave several advantages. Firstly they are light buthave the quality components spoken of alreadyand exhibit very little voltage drop even overlonger distances. Secondly the wires are twistedwhich reduces or eliminates any RF transmission,negating the need for ferrite rings. The plugsconnect with a definite click that feels solid andreassuring; although I still always heat shrink thepermanent connections for added security.

Once the leads are run, they really should bezip tied out of the way to stop them gettingsnagged or worn out on rudder cables etc. If youlook at the picture of the inside of my Edge, youwill notice little plastic cable clips used for thispurpose. These are bought from any electronicsstore and are great for tidying up leads.

Rudder control horn.

Power tray. Note cable tiesreceiving all wiring.

Servo extensionleads.

Power Supply

There are a few possibilities here. Pictured iswhat I would call the bare minimum. It’s a 6VNiMH running through a high current switchharness with two tails. The tails can be runthrough two receivers, both into one receiver,or Y harnessed into a servo lead. There are dif-ferent schools of thought here so, whilst doingmy best not to offend those with other views, Iwill of course promote my own. First….forgethaving two receivers; just buy one good one(we’ll look at that later). Keep it simple, anddon’t load up your plane with gear you don’tneed. Second, just plug both tails straight intoyour receiver. One into the battery receptacle,and one into a spare channel.

In the setup on the Edge 540T I went for aPA2200 mAh LiPo through a regulator. This CFtray is suspended by rubber bands from eachcorner, isolating from vibration, and has theLiPo strapped underneath. The LiPo has aDeans plug connection, but MPX plugs arebecoming very popular and have the benefit ofbeing multi poled for added security. On thisone, I have used a Fromeco regulator, but PAare the sole distributors of Emcotech, and theirmuch acclaimed BIC unit which is by far thebest option I have ever seen.

Emcotech BICThe Emcotec DSPI BIC is an electronic fail-

safe switch, which will take up to two 7.4VLiPos and regulate them individually down to6V via two separate circuits. It has a push but-ton on - off (to switch the unit on or off, holddown the On or Off buttons for 2 seconds) andis loaded with failsafe features. Ultimately itcovers the need of getting safe and reliablepower to the receiver and regulates it to givethe Amps that are required for those high ener-gy manoeuvres. The other very nice feature isthe LCD display that shows all the info youneed about your batteries, including:• The actual voltage of each battery pack• The minimum voltage of each battery since

the last power up (for example: 7.1v, time tocharge up)

• The maximum voltage of each battery sincethe last power up (for example: 8.4v, fullycharged batteries)

• The actual current amps at that moment(showing how much current you're takingwhile on the ground... over 2 Amps you geta warning that you're drawing too muchpower for a plane that is sitting at idle)

• Maximum current draw (in Amps) since lastpower up

• Average current draw (in Amps) since lastpower up

• Consumed mAh since last reset (e.g., sinceyour last charge)

• Runtime in minutes since last reset (e.g.,since your last charge)

These are just a few of its many features, itreally is an amazing device and with a price tagof only $174 it actually represents good value formoney. Also, as with all Emcotec units, thepower from both batteries is used simultaneous-ly, synchronous, not asynchronous like manypower devices. If you need 10 Amps, it's drawing5 Amps synchronously from each pack, not 10Amps from one pack, then the other and back.

ReceiversHere we come to the brains, the epicentre,

the hub……hopefully you get the idea alreadythat this is not the area to go in cheap. My firstradio was a budget brand and it was fine until Igot my first gasser. Then I noticed a lot ofbumps and twitches happening. One day theygot really bad and….well….it cost me a plane. Ihave lost a plane before from the infamous“radio failure”, but let me tell you, nothing isscarier than a big high powered plane that youown and that you can’t control. Anyhow, I gotsome advice and was pointed to the very fine JR9X. It came with a JR10DS PCM receiver that hasbeen faultless in every model it has been in.When I went to get a second one (the invento-ry of gassers was growing), I soon discoveredthat the JR10DS was the finest receiver that JRproduced, and as such was worth what I con-sidered at the time, to be a small fortune.

Pay the extra few bucks. GET A GOODRECEIVER! No point having all the bling andgood gear on your pride and joy if you can’t con-trol it. It is the most crucial item in the set up.

How do you choose a good receiver? Checkout what you are buying, and find out what isthe best in your preferred brand. This is the areawhere I would emphasise you spend as muchas you are able. If you have five models, don’tbuy five cheap receivers, just buy one goodone. It’s not ideal to swap the receiver aroundby any means but its better than having some-thing you don’t trust. There is a difference in the

way they work, and how they select and trans-late a signal, and there is a reason why the moreexpensive ones are more superior. That wasactually the main reason that I set up the Edgewith the carbon fibre tray suspended by rubberbands. The tray had the receiver, the regulator,the battery, and the switch all housed together.This way the entire tray could be taken out andmoved to another model as a complete set up.Again, ideal would be to have a set up for eachplane, but at least this way I could afford thebest gear because I only had to buy it once.

Interference CheckThis is an important step when it comes to

gas powered planes. The CDI units and sparkplugs do give of some RF noise. This is goodreason to keep anything that is plugged into thereceiver as far away from the ignition unit andleads (even ignition battery) as possible. Thencheck your range with the engine turned on andat idle. The best check is to have the transmitteraerial down, and pointing directly at the front ofthe model, while walking away, keeping theengine between the receiver and the transmitter.This is the worst possible scenario and youshould experience lockout at the shortest rangein this position. Make certain that your PCMreceiver is programmed to chop engine to idleand centre all surfaces on lockout. Your rangeshould be a respectable 50 paces.

…..And In ConclusionAs mentioned earlier, there can be a few pit-

falls that newcomers to the 50cc class can fallinto. However the solutions are definitely there,and the possibilities are growing as suppliersand manufacturers are recognising the needsand are filling them with new technology. Thisarticle was prepared mostly with the uninitiatedin mind and in no way is to be viewed as theonly way things are to be done. On the otherhand, safety has to be the priority and thatrequires an informed approach by all who areattempting something new, especially when itcomes to high performance large planes likethose talked about here. For those who aretempted to step up a size or two, don’t feel thatthere is an unattainable amount to learn or com-prehend. There are many more solutions outthere than problems. However do not be afraidto seek advice from those that know. There is alot of experience around these days and mostmodellers I know of are more than willing tohelp. Of course, the guys at Precision Aerobaticsare always able to give advice and can supplyyou with virtually any piece of hardware need-ed to finish that giant scale plane of yours.

All items in reviewed are available fromPrecisionAerobatics.com Tel 02 9558 0443.