Evo Construction - Preparation

LAY OUT THE MAIN WING SHAPE

Preparation

Cut out all of the Mugi Evo components as listed on the plans page. You can use the checklist to ensure that you have everything ready to begin building.

Lay the main wing shape of your Evo on a flat surface or building board. You may find that marking construction lines on the wing will help with alignment and accuracy during the build. For example, the centre-line of the aircraft is shown marked above. Make any marks on the inside of your wing to avoid having to clean off surplus ink later.

When you're ready to begin, move on to the next step and fit the nose doubler.

Evo Construction - Nose Doubler

NOSE DOUBLER

Installing the Nose Doubler

The nose doubler is an important component in the Mugi Evo as it lends strength and rigidity to the front of the aircraft where the heaviest items of flight gear, such as batteries, will be later mounted. The doubler is a diamond shape so that no hard line is created at the rear of the doubler which would encourage a crease to form.

The nose doubler should be placed about 8mm back from the nose; when correctly placed there should be a gap of around 5mm between the doubler and the wing score line.

Glue the nose doubler in place with Evostik, following the instructions on the tube, and press down firmly using a flat implement such as a heavy book. A good bond is essential as a good deal of the Evo's nose strength will be built in here.

Evo Construction - Servo Preparation

INSERT THE SERVO CABLE TIES

Pushrod Exit Slots

The pushrod exit slots marked in the Evo plans are designed to accomodate a 2mm size pushrod and are for use with a ball joint at the elevon end. As marked, the pushrods are coupled to the elevons at near half span and so eliminate control surface flutter at high flight speeds.

Servo Mounting Straps

We recommend using 4.5mm wide cable ties to hold your servos in place. These are very strong and their width ensures that forces are spread over a large area to discourage tearing of the twinwall material.

Using a screwdriver or a similar instrument of about 3mm diameter, make holes through your twinwall sheet at the points marked as servo mounting holes on the Evo plan. Please note that these holes are correctly placed for the use of standard 9g micro servos and Mugi pushrod kits available from us. Note the orientation of the servo cable ties - so located that when tightened, the free end will point towards the rear of the aircraft.

If you are using different servos and/or pushrods from our standard then you'll have to use trial and error to find the correct placing for your servos.

Check the Servo Horns

At this stage it's a very good idea to make sure that the holes in your servo horns will fit the pushrod connectors you are using. With Mugi pushrod kits and micro servos you will most likely have to make the holes a little larger. This is easily done by carefully rotating a scalpel or sharp blade in the hole, constantly checking for fit until the connector will go through the hole without jamming.

Evo Construction - Servo Fitting

STRAP DOWN THE SERVOS

Add the Servos

Place your servos on the wing so that the cable ties will grip the servo just below their mounting lugs, as shown. A drop of glue or a piece of double sided tape under each servo will ensure that they will never slip out of their mounts.

Tighten the cable ties down around the servos as practically tight as you can manage. The free ends of the ties should be left free, not cut off.

Locating the cable tie holes

For a guide to where to make holes for your cable ties, either place the servo so that the horn lies on the servo line (see "Plans"), or follow these instructions:

Measure 150mm back from the nose of the sheet and then measure 60mm out either side of the centreline - make small holes here

Measure 170mm back from the nose of the sheet and then measure 70mm out either side of the centreline - make small holes here.

You now have holes through which to put the cable ties that put the servos in the correct alignment - presuming you're using ball-joint connectors at the elevons.

Evo Construction - Optional Carbon Spar

ADDING AN OPTIONAL 6x4x450mm CARBON TUBE SPAR

Why is it optional?

If you are planning to fly your Evo extremely fast, for example with a 'hot' brushless motor and Lipoly cells, then you will need to add a carbon reinforcement to the Evo wing.At extremely high speeds, the spar will prevent the airframe from deforming.

For Evo gliders and standard speed 400 aircraft this spar is not required.

However, if you are planning to upgrade your Evo powerplant in the future then it may be worth adding a spar now. Also, the spar is reusable and can be transferred into your next airframe.

Fitting the Spar

The spar is a carbon tube outside diameter 6mm, inside diameter 4mm and length 450mm. It weighs nominally 18g. This tube is available from Mugi.It should be placed half way between the trailing edge of your Evo and the servos. You can fix the spar in place by using self-adhesive tape.

Evo Construction - Gluing

APPLY GLUE TO THE TRAILING EDGE

Getting the glue in the correct place

Your wing is now ready to fold and glue. Test fold the wing and make a mental note of where the glue should go on each surface - if the two wing halves overlap in the centre of the wing during this test fold then you may need to trim a small amount off them until they meet perfectly. When folded over, the wing should create a section with about a 25mm height at the highest point.

Remember that in the centre of the wing, the corners folded in will need the glue to follow the final 'M' shape of the trailing edge.

Apply the Evostik as per the instructions to both surfaces to be glued. Plenty glue is better than too little!. The bond made when folding the wing comes under quite a lot of pressure during flight and so should be as strong as possible.

You need a glue width of about 25mm to ensure a good and solid bond.

Evo Construction - Pushrod Fitting

FITTING THE PUSHRODS

Pushrod materials

The material you choose for your pushrods should be a thin, lightweight and rigid material. Suitable materials are bamboo, hardwood dowel or 2mm carbon rod.We find the 2mm carbon rod is superior in use as most connection hardware such as clevises and threaded adjusters will fit directly onto the end of the 2mm rod. The carbon also offers very high stiffness and is very durable. Our Mugi Evo kits include carbon pushrods and we also stock full pushrod sets (including clevises and adjustable ball joints and horns).

Fitting the pushrods

Lift the two wing halves to near vertical position above the building board. You can now thread the pushrods through the exit slots from the outside of the wing and clip the clevis at the servo end into place on the servo horn.

The servo horns will twist slightly as you do this, and the pushrods will bend to accommodate the angles but they should not break. Now use a couple of books, or a helper to hold the wings in this position while you get a one metre ruler ready to clamp down the trailing edge of the wing.

Evo Construction - Wing Folding

INITIAL FOLD ALIGNMENT

Folding Your Wing

This is the critical moment of your Evo build. The wing folding creates your wing section and so accuracy is essential. If you've cut a very accurate base shape for your Evo then you should have no problems with alignment and final wing shape. If you haven't already done so, try a test fold of the wing to see how the two halves meet in the centre. Be careful not to let the two glued surfaces contact each other or they'll grab and you'll have to peel them apart!

If you're happy to go ahead with the folding and gluing then read on.

Initial Fold Alignment and Initial 'Grab'

Take your aluminium ruler, or whatever you're using, and then, as shown below use it to bring both sides of your wing down equally. As you do this the wing will start to adopt a curved section. About 140mm or so back from the nose will be the highest point of your wing. As you bring the two sides down, adjust the position of the trailing edge fore and aft so that this highest point will be about 25mm.

When you are satisfied that your wing has the correct form then you should press down firmly all the way along your ruler, moving it forward slightly to ensure that the glue around the silencer area is grabbing. With the glue initially grabbed you can now move on to the wing clamping.

Evo Construction - Wing Clamping

FIRMLY CLAMP THE WING

Clamping the Wing

Clamping the trailing edge as the glue dries greatly increases the strength of the bond between your two wing surfaces. With as many clamps as you have, ensure that the trailing edge is firmly held together across the full span. A second shorter ruler, placed ahead of the main one in the centre of the wing, may help to ensure a good bond around the silencer cut-out area.

No Clamps?

Simply spread your body weight along the full width of the ruler as best you can using your forearms. With elbows at the wingtips and palms in the centre of the wing you should be able to body-clamp the glue joint quite successfully. If your arms start to get tired, resting your head on your hands in the wing centre might look very ungainly but will do the job nicely.

Evo Construction - Silencer Cut-Out

TRIM THE SILENCER AND TRAILING EDGES

Trim the Silencer Shape

The silencer 'M' shape at the rear of the Mugi Evo removes an amount of material near to the pusher prop and a great deal of the noise associated with models like this is reduced. Another benefit of the silencer is that the material removed from the rear of the aircraft,makes it slightly easier to balance. The 'M' shaped silencer is also the trademark shape of the Evo.

Trailing edges

At this stage of the build, the trailing edges of your airframe will be somewhat untidy and the top and bottom wing surfaces will not line up . This is normal and occurs as a result of the top surface travelling a greater distance than the bottom in the process of forming the wing section. The trailing edges should be trimmed to a straight line as shown in the diagram above.

 

Evo Construction - Exo-Doubler

1. MARK TOP

2. MARK UNDERSIDE

3. GLUE

EXO-DOUBLER  

Fitting the Exo-Doubler

The Exo-Doubler is an essential component in the Mugi Evo. The doubler featured has a total wrap-around shape and improves greatly in strength on earlier versions.

The exo doubler cut as per the Evo plans should be folded along the central flute. To make this fold simply crease the material along the intact flute - do not cut out any material as you will weaken the structure.Score fold along the diagonal lines and your doubler will be ready to fit.

The fitting technique described below refers to the images lower down this page. Once again, clicking a thumbnail image will enlarge it into the main image.

Mark the Fit

Dry fit your doubler to become acquainted with how it fits the nose of your Mugi. The doubler should meet the leading edge of the wing on both sides and drape over the nose of your aircraft. When you've found the best fitting position, hold the doubler in place and mark the location on the nose of the Mugi with a ballpen as shown below.

Glue Topside

Check that in this position, when wrapped around the nose, the doubler meets in the middle of the underside of the Mugi. If so, and you're satisfied with the fit, apply glue within the boundaries of your pen lines and then stick the doubler to your wing. If the doubler overlaps, trim to fit. If the doubler does not meet, either adjust the position or forget about it and live with the gap.

Glue Bottomside

Turn your Mugi over and glue the doubler to the bottom of the wing. Hold it firmly in place while it dries and then, to finish off, tape from the nose the rear of the doubler along the join between the two sides. This should help to keep dirt and moisture out of the twinwall during landings.

Evo Construction - Underbelly Doubler

UNDERBELLY DOUBLER

The underbelly doubler

We now have in place the spine piece which has its flutes oriented so to provide the best rigidity across the span of the aircraft. Heavy crashes, nose first, will create large forces that will try to crumple the Evo from tail to nose. The underbelly doubler is a very useful way of vastly increasing the plane's strength in this direction.

Since the measurements in the plans for this piece are 'nominal', you'll need to put the piece into place without glue and then trim the width at the nose - to match the exo doubler - and at the tail for overall length.

When the piece is trimmed correctly, glue it to the underside of the Evo and then, if desired, tape over the join where the underbelly doubler meets the exo-doubler.

Evo Construction - Access Hatch / Spine Piece

1. CUT AND HINGE

2. GLUE IN PLACE

3. CUTOUT HATCH

ACCESS HATCH AND SPINE  

The access hatch and spine piece

An access hatch atop your mugi will allow easy access to your radio gear and also make swapping flight batteries a very quick task. The Mugi Evo is designed for an eight-cell standard battery pack or high performance Lipoly pack, some of which tend to be quite large, making this feature practically essential.

The hatch is built into the 'spine' of the aircraft. The spine is a strengthening piece that runs down the back of the airframe with its flute direction spanwise to provide the greatest rigidity against the in-flight forces that would try to fold the Evo wing in half.

Fitting the hatch

You should have now cut out the hatch/spine piece according to the instructions on the plans page. Lay the spine in place from the rear of your exo doubler down the top of the airframe. At this time you can trim the spine to fit widthwise with your exo doubler and also for length so that it does not extend beyond the rearmost point of the Evo's tail.

Mark the position of the piece lightly on the top of your airframe and then apply the contact adhesive - be sure not to glue the hinged hatch panels! When the glue is ready to bond, firmly stick the spine in place (as in diagram 2 above) and then open the hatch to reveal the wing below.

You can now cut out the wing material directly below the hatch to grant access to the inside of your aircraft (as diagram 3 above).

For flight, the hatch can be taped down for security before launch. Tape is a cheap and painless solution to preventing the hatch from opening in flight.

Evo Construction - Fin Mounting

FIN MOUNTING

Locating the fins

With a pen, lightly draw a line from the top of the silencer cutout along the flute toward the front of the Mugi aircraft. Repeat this for both left and right wings of your Evo. These will be the lines on which the fins will sit.

INSERT DOWEL INTO FIN

Mounting rods

Take a 2mm dowel or barbeque skewer and cut it to about 80mm length. Insert one end into a flute near the front of each of your two fins as shown above. These mounting rods will add a great deal of rigidity to the fins when they are mounted on the model and can also allow quick removal of the fins for transport or replacement.

PUSH DOWEL THROUGH WING

Attach the fin to the Evo wing

Mounting the fin onto the Evo wing is very simple. Mark the position on the fin location line where the dowel will need to go and then firmly push the dowel through the top surface of your wing. If your dowel is not sharpened then use a screwdrive to make the dowel holes.

The fin should be mounted at an angle of 30-45 degrees from the vertical to suit your tastes. The two fins should be angled away from each other. Angling them towards each other is found to impair the top speed of the Evo - perhaps due to turbulence in the line of the motor.

FRONT VIEW X-SECTION OF THE FIN MOUNT

Additional security

As shown in the diagram above, using 25mm wide self-adhesive tape, tape the bottom edge of the fins to the top surface of the wing. Without tape, at high speeds the fins have been known to depart and control is adversely affected.

Evo Construction - Connecting Pushrods

CONNECTING PUSHRODS

Connecting pushrods

The best performing pushrod-to-horn connection for use on the Mugi Evo is a ball joint type connector. The elevon horns should be around 20mm in height. Beginners should use the topmost hole on the servo horn, though more confident or advanced pilots may enjoy the extra manouvrability offered by going down one hole.

Connect the elevon horn to your pushrod using whichever hardware you've chosen and then bring the elevon and horn together with the rear of the elevon raised about 10mm as shown in the diagram below.

Rotate the elevon horn slightly so that the horn and pushrod are aligned all the way to the servo arm. While maintaining the 10mm 'up elevon', mark the position of the elevon bolt holes on your elevons. Now attach the horn for real and secure it in place with the nuts and bolts provided - adding a smear of glue to the threads of the bolts to ensure long term security.

Why the 10mm 'up elevon'?

The Mugi Evo, being a delta aircraft requires a constant amount of up elevator in order to fly straight and level. This amount of built-in up elevator is often referred to as 'reflex'.10mm is not guaranteed to give you straight and level flight from your first launch, however. There will be lots of factors that determine the flight of your aircraft, such as motor thrustline, exact wing section etc. You will usually need to 'trim' the model in the first few flights. This can be achieved using the trims on your transmitter during flight, then more permanently set using the adjustments offered by your pushrod connection hardware.

 

Evo Construction - Radio Gear

RADIO GEAR LAYOUT

Radio Locations

When locating your radio gear inside your Mugi Evo it's a good idea to place the more delicate items behind the heavier and less vulnerable ones. The battery needs to go in the nose, usually about as far forwards as you can push it without distorting the airframe. Behind this we sit the receiver. The receiver antenna can be routed down one wing to the pushrod exit slots and can then be threaded down a flute in the material to the trailing edge and thereafter into the breeze. This keeps the antenna in a fairly straightish line.

If you hate trailing aerials, and you tend to keep at short range, you could thread the antenna from the trailing edge down one of the flutes on the bottom surface to the wingtip. This is not recommended practice but may suit you if you know your receiver will not suffer adversely from doing so.

The Electronic Speed Controller (ESC) for use in the electric powered version of the Evo can site somewhere between the receiver and the motor. We find that motor wires long enough to reach the hatch allow very convenient access and do not suffer any adverse effects such as interference etc.

Mounting Your Radio Gear

Keeping it simple, we use self-adhesive hook and loop fastener to secure the radio gear in place. A lightweight micro receiver will not move in normal flight when attached in this way. It's worth considering wrapping your receiver in foam, or placing foam ahead of it in your aircraft just in case you make an unplanned vertical arrival.

In practice, your main electric flight battery pack or glider receiver pack can also be held in the nose with the hook and loop. You will find that as you push the battery into the nose, it will become somewhat wedged in place and will not move in normal flight.

If you find that you always run out of one type of hook and loop first, why not put both types onto removable articles such as batteries. That way, you can alternate which fastener you put in your aircraft and even out your usage. You will also be able to 'piggyback' components.

Balancing the Evo

The Mugi Evo should balance at a point 210mm from the nose. With a speed 400, or motor of similar weight, mounted at the rear of the plane, this is usually achieved with a battery pack of 150-160g+ in the nose.

If you are flying the Evo as a glider then the correct balance is usually achieved by placing a receiver battery of around 60g in the nose. This equates to a four cell, 720mAh Nimh battery pack.

Electric Power - Motor Installation

FIT CABLE TIES

INSTALL MOTOR

UNIVERSAL 'CAN' MOTOR MOUNT  

Simple universal motor mount

The simplest way to mount any can shaped motor on your Mugi is with heavy duty cable ties. This solution is extremely strong, quick and easy. The motor sits at the rear of the aircraft in the middle portion of the M shaped silencer cutout. The motor must act in pusher mode.

Making holes for the cable ties

The motor on the Evo is attached by two heavy duty cable ties. 4mm wide cable ties are perfect for this application (these are included in the Mugi Evo kit).

Place the motor in the required position central to the aircraft and as far forward as you can get it without the prop interfering with the trailing edge. In practice it may be necessary to cut the tail point off the silence cutout for extra clearance.

For high torque motors - e.g. brushless motors, a small piece of self adhesive hook and loop fastener between the motor and the aircraft will prevent the motor from rotating in its mount.

With the motor in place, take a pen and mark four dots either side of the motor, the motor's width apart. Two dots should be made as far forward on the motor as possible while still allowing the cable tie to grip the case of the motor. The other two marks should be made near the trailing edge at the rear of the motor. You can then insert the cable ties through the wing as shown in the first diagram above.

Tightening the cable ties

Place the motor in position and then tighten the cable ties as follows:

The front cable tie should be pulled as tight as possible - this will pull the nose of the motor into the wing and create the desired thrustline.

The rear cable tie should be tightened to provide a light grip on the motor - in practice this cable tie merely keeps the alignment of the motor and prevents it from yawing.

Electric Power - Recommended Setups

At Mugi, we are continually experimenting with different electric powerplants on our Mugi Evos and evaluating new motor and battery technologies as they appear. Look out for our power setups in the shop area (expected Autumn 2007).

Non Brushless

Brushed motors represent a cheap way to get airborne with a speed 400 type motor costing around £4. If you have a collection of brushed electronic speed controllers (ESC) and a few old technology batteries kicking around then this is likely to be the instinctive option for powering your Evo. There are a few suggestions to help you maximise the performance of your brushed setup:

Use a 6V Speed 400Lots of motors are the 7.2V type and require more voltage to achieve the same rpm. The 6V types can actually take a vast range of voltages before they burn out - some types are rated for up to 10V on a standard push-on prop.

Use a minimum of 8 cells in a NiCd or NiMh packA 6 cell pack made from these traditional cells only has a voltage of 7.4V which is insufficient for a high performance aircraft. Seven cells offers a little better performance but still rather sluggish and launches are difficult. Move to 8 cells however and the voltage increase to 9.6V means that a 6V speed 400 will give very sprightly performance.

Consider LiPo batteries There have been 'horror stories' about exploding LiPos but the early days of the technology have passed. With a specialised LiPo charger these batteries are very easy to maintain, have an incredible shelf-life when charged and are much more crash resilient than they used to be. The energy by weight makes them incredibly useful for model flying. However, one must note that if using a brushed ESC it must have a LiPo suitable voltage cutout. If unsure, then a LiPo saver device sitting inline (available all over the web) is a good idea.

Our 'ideal' brushed setup:

Speed 400 motor (6V type) 8 cell (9.6V) battery or 3S (11.1V LiPo)

Suitable ESC (capable of handling >18A, to be safe)

Günther push-on prop or our carbon/plastic prop with adapter

You'll get nice speedy flight from this setup and it'll suit the more novice pilot. It's an impressive aircraft on this with great climb and aerobatic performance. Duration will be under ten minutes (more with LiPo). Ultimately though, if you're starting out in the hobby and want to take your first steps in the right direction, then a brushless setup is a better bet.

Brushless Power

Brushless motors are the future. They offer higher efficiency, better power output and are generally more robust than brushed motors of an equivalent size. There are lots of types of brushless motors on the market and the choices can seem bewildering. We recommend a 28mm diameter motor for the Evo. This type of motor shares the same dimensions as the old speed 400 brushed motors but has rewired internals. They are much more expensive but should outlast the brushed equivalent thanks to better power handling and chunkier output shaft. Here are our suggestions:

Choose your kV Brushless motors often quote a kV or rpm/V figure in their specs. This is basically a guide to how fast the motor will try to turn - the higher the number the faster it wants to turn. Sounds great? It is, but a high kV motor on a large propeller will draw much more current than a lower kV motor. It will need a smaller prop turning at more rpm, which reduces the thrust but increases the aircraft's speed. There's obviously going to be an optimum point... We've found that motors between 2000kV and 3000kV are ideal.

Use a 30A brushless ESC With these brushless motors you might draw around 18-20A in flight. A 30A controller gives a nice safety cushion and also allows you to experiment up to these higher currents, perhaps with a larger prop or higher kV motor.

Make sure the LiPo is suitable It's open to discussion but generally brushless motors go hand-in-hand with LiPo batteries. A 3S LiPo kicks out 11.1V and is ideal for the recommended kV motors provided that it's discharge rating is suitable. You'll find that LiPos are sold with a capacity and a discharge specification; e.g. 1800mA 20C.This means that the capacity is 1.8A and that it can give 20 times that amount in terms of amps out (36A). However, it's much better for the battery to stay way below this figure and the 18A in flight that a 2000kV motor gives you is very suitable.

Our 'ideal' brushless setup:

28mm diameter inrunner motor (2000-3000kV) 3S (11.1V LiPo) at least 1500mA and 15-20C

Suitable brushless ESC with LiPo voltage cutouts >30A

Propeller (5x5" CAM to , 4.7x4.7" CAM depending on kV)

With brushless motors such as these there are many parameters determining the overall performance. If you are a beginner then the 2000kV motor is far more suitable than the 3000kV end of the spectrum. Performance with a 2000kV exceeds a brushed setup quite markedly and you will achieve vertical climbs.

Move to 3000kV, however, and we're definitely not in beginner territory. This

will give you an aircraft that is extremely fast, maybe more agile than you are used to and with a climb that will amaze. The power to weight ratio is something like 2:1!

Ultimately, the throttle stick controls the motor and careful use will mean that you can work your way up to flying at 'full beans'.