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Old Feb 24, 2013, 02:45 PM
Whisper Model Aircraft
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Greensburg, PA
Joined Feb 2008
558 Posts
Build Log
Supra X or Super Supra Assembly

Introducing a full build log for a whisper model aircraft kit.

The Eastern Soaring League and lots of others around the world have found that the Molded Supra by Vladimir Models/Kennedy Composites is an excellent all around TD and F3J contest design, I own one and learned pretty much all my contest soaring skills flying it. But building is part of my thing so I started asking about bagging wings and molding fuselages (thanks Anker!) which ultimately lead to the Supra X 4m. You can find other threads of the Super Supra I created which finally got me to the Supra X 4m, you'll see in this build log.

There have been many significant changes from the Super Supra design and construction and most important the move from a "tipper" full flying horizontal stab to the current "articulated" horizontal stabilizer used on a few of the lastest Euro-Moldies recently. (I want to thank Phillip Kolb, Larry Jolly, JoJo and GordySoar for their input on this topic!)

The tipper stab uses a V-mount which I found expensive and fragile, so it didn't take too much to inspire me to try the old style articulated stab and elevator. It wasn't a good option in the past due to a bunch of factors, including weight, incidence consideration, and stab airfoil. Those factors have been overcome by brains in the hobby far greater than mine (again thanks guys!), so I went full speed ahead on designing a pylon for the new stab which you'll see later in this build.

The Super Supra (3.8m) and Supra X (4.0m) are bagged models designed for thermal duration/F3J task soaring. The original Drela Supra airfoils were used with the cords enlarged 10%, the spans were increased for each versions. The supra x has an ag35 center panel which was used in the bubble dancer. The thicker center panel allows for a stronger spar and somewhat better slow speed range. The center panel has 5 degrees of dihedral along with each joiner. The supra x has faced wingtips.

For the center panel spar a semi molded spar cap (built from 9oz uni carbon), a full length carbon tube, and epoxy cotton filler for a shear web. The tips are stressed skin with 4oz uni carbon. 1.7oz Kevlar is used all around with .7oz fiberglass for a smooth finish. The paint is klasskote and sprayed to a thickness requested. For this build I used a very light opaque coat.

The fuse is a molded, one-piece pressure bladder construction. The nose is built from s-glass and Kevlar making it 2.4 friendly. The tail and pylon area are constructed from 5oz carbon, uni and more s-glass. The boom uses high modulus uni carbon, 3k fabric on the bias, and bias spread tow fabric.

Either a full flying stab or the articulating stab/elevator can be used, both have a disser (carbon strip X-ing to decrease weight/waste/cost) construction.

The Articulated stab/elevator has very good effectiveness and comes with a very light molded pylon. The full flying tipper horizontal stab needs a Supra V-mount which can be purchased from Kennedy Composites.

The rudder is a simply bagged Kevlar with some uni-carbon to stiffen it and to proved a sort of spar to 'tie' it to the tail boom or a tube which then will allow you to slip it off the boom for transport/storage. (the tube is made by the builder from carbon weave sock, sort of like Chinese Handcuff, by slipping it over the tail boom rear, wetting it with resin then pulling it off once it has hardened - more on it later in the build thread).

All foam cores are CNC cut from 25psi foam.

Average weight breakdown:

Super Supra: 67oz Auw
Supra X: 71oz Auw

Completed fuse: 20oz
Empty fuse: 6.5oz

3.8m wing 42oz
4.0m wing 43oz

Stab for v-mount 37grams
Elevator horizontal with hinge 49grams
Rudder 29grams
Joiners 2oz

William Lipscomb
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Old Feb 24, 2013, 06:29 PM
Skye Malcolm
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Upper Arlington, OH
Joined Mar 2009
594 Posts
Awesome

Subscribed!
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Old Feb 24, 2013, 06:30 PM
Whisper Model Aircraft
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Greensburg, PA
Joined Feb 2008
558 Posts
Pylon mounting blocks

So lets get started!

First thing is cleaning up and shaping the saddle. Using permagrit, sandpaper, and some alcohol to clean up any area that needs a structural bond is important. I use West Systems and 403 filler which is cotton fiber that adds much strength to glue.
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Old Feb 25, 2013, 08:49 AM
Whisper Model Aircraft
heliwill10's Avatar
Greensburg, PA
Joined Feb 2008
558 Posts
Rear Bolt Hole and Wing Alignment

The rear bolt hole should be drilled about 4.5" back from the main bolt. Double check that your going to end up drilling down into your ply blocks in pylon.

Remember you have a spar to miss and a wire channel that's going to need room later.

I taped some winch line to my boom and adjusted the wing until I had the proper alignment. Having a helper to hold down the wing before drilling will make things easier.

Drill a pilot hole through the wing and fuse at the same time. Then go back and install the blind nut and open up the wing hole for the bolt.
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Old Feb 25, 2013, 08:50 AM
Whisper Model Aircraft
heliwill10's Avatar
Greensburg, PA
Joined Feb 2008
558 Posts
Wing Saddle Install

The saddle comes after the wing bolts are installed. This way we can adjust the fore/aft position of the saddle as necessary.

Its important to have filler between the wing and saddle. Creating this custom bed insures with each bolt down the tail will be aligned. Use some spray glue and wax paper on the wing, slop on the bondo then bolt down the wing.

Some filler and sanding is going to be needed for a good fillet. Sometimes its necessary to use a little balsa to cut down on the bondo.
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Old Feb 25, 2013, 09:44 AM
Malta & Newport
United States, RI, Newport
Joined May 2010
86 Posts
Super Supra pylon

This is the wing mount I made for the same plane and wing, The ply is split down the middle to take the wing dihedral and the crease was then filled with epoxy. The wing is mounted just forward enough so that there was no gap between the upturned leading edge and the saddle. The ply was faired into the carbon saddle with the usual mix of 410 and epoxy, faired and sprayed black. Other wise the rest is just as Will describes.
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Old Feb 26, 2013, 10:38 AM
Whisper Model Aircraft
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Greensburg, PA
Joined Feb 2008
558 Posts
Building Tube for Removable Rudder

The credit for this idea belongs to Alex Hall.

Using some biaxial sleeve and some plant tie a simple tube can be made to allow the rudder slip on and off.

I used 1/2" carbon sleeve from soller: http://www.solarcomposites.com/compo...20sleeves.html

The green string is from home depot. The plant tie is a real improvement from using vcr tape.
http://www.homedepot.com/buy/gardene...l#.UR-quxG9KSM

Its important to use one layer of freezer paper between the boom and the layup. Otherwise removing the sleeve will be nearly be impossible.

Two layers of sleeve will add the thickenss required for bolting down the rudder.
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Old Feb 26, 2013, 10:54 AM
Whisper Model Aircraft
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Greensburg, PA
Joined Feb 2008
558 Posts
Rudder Mounting

Two long screws attach the rudder and keep the alignment. Use some balsa inside the boom where the bolts will pass to provide a little more strength.

For the rudder pushrod exit point I'd recommend using some bias sock for reinforcement.
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Old Feb 26, 2013, 03:34 PM
Malta & Newport
United States, RI, Newport
Joined May 2010
86 Posts
Removable vertical and rudder.

This is my take on the removable tail, however using the same idea that is used by Vladimir and his designs.
Using the boom as a mould, I used 1/2" diameter carbon sock around it, making sure there was enough release compound and wax. After removal, this was attached to the fin with quick curing epoxy adhesive, having made sure there was the same radius on the bottom of the fin to increase adhesive contact area. Once this cured, I faired in the joint between the fin and the tube and followed it by some medium thickness uni carbon, which wraps around the tube and up the side of the fin, slow laminating epoxy was used for this. After final curing, most of the tube was cut away leaving a ring about 1/2" in width beneath the leading edge and about 3/4" beneath the hinge line. The fin was plumbed up with the main wing and horizontal stab and then a 1/8" dia hole was drilled in the after most ring and through the fuselage boom to accept a removable carbon dowel, which is just held in place with tape during flight. If one finds the wall thickness of the boom to be too thin, a slight coating of epoxy adhesive with beef it up and when cured just re drill. The attached photos show the completed set up minus detail sanding and final coat of finishing epoxy.
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Old Feb 26, 2013, 04:56 PM
Whisper Model Aircraft
heliwill10's Avatar
Greensburg, PA
Joined Feb 2008
558 Posts
Articulated Stab

The camber should be very close with the molded pylon. When aligning the stab some 5 min epoxy and tape will be enough to tack everything in place.

After your happy with the alignment use some laminating epoxy and uni carbon to secure everything.

Clearance: Since your rudder might be off for this step make sure you leave room. Also your going to need room for pushrod travel.

Etched Teflon (pushrods) can be found here: (I also try to keep some in stock) It will adhere will CA.
http://www.tailboom.com/teflon.php

Carbon pushrods are found here. Again, I also keep some in stock. Use .06 for the elevator and .07 for the rudder in 96" length.
http://www.acpsales.com/Solid-Rods.html

Control Horn Note: The elevator control horn requires an offset from the centerline of the pylon. Mine is offset from the centerline about 1/2" to allow enough room for the bend and wrap that attach the carbon rod to the music wire clevis. More on this later...
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Old Feb 27, 2013, 06:39 AM
Malta & Newport
United States, RI, Newport
Joined May 2010
86 Posts
V Tail

Using a mount purchased from Barry Kennedy, one of the most noticeable issues is the difference in boom diameter, with the Super Supra being about 5/8" in dia whilst the Supra being nearer 7/8".
The first thing to do was the removal of the top part of the circular bridge, making sure that the lower part forms a continuous inner curve with the sides. Next was applying judicious heat with a film shrinking gun while at the same time, ever so gently, closing the lower part of the circle in a vise. Enough heat must be applied so the resin in the carbon becomes soft enough to bend and not break. The bending won't happen all at once so it must be allowed to cool just a bit, then reapply heat, soften and then tighten the vise a shade more.
The pushrods where internally passed, their exits where elongated to allow a fair curve for the outer casing, and then glued to the boom and the exits faired with epoxy. The boom and mount were abraded and cleaned, the area masked, and mount aligned and glued with enough epoxy adhesive to cover the mating surfaces. Once this cured, a mixture of resin and 406 was applied to the exterior joints and especially where the bridge once was, fillets were applied and gently smoothed out with a slightly wetted finger.

The exit hole for the rudder pushrod was reinforced as this exits just forward of the vert. fin and is in the thinnest part of the boom. The teflon tube, guiding the pushrod, exits the boom for about 10mm, this was filleted with some 5min epoxy and smoothed over before it cured using a wet finger. Upon curing this was lightly abraded, as well as the surrounding boom, and carbon tow was wrapped around the exit hole. To keep the tow from unravelling a touch of thin ca was applied to one end, well clear of the wraps. Four wraps was sufficient to cover the teflon tubing ending just a bit forward of it, the tail end of the tow was also tacked with ca, again clear of the main wraps. I highlight the importance of keeping the ca away from the wraps as the next step involves coating the bulk of the wraps with laminating epoxy, soaking it very well, before blotting off the excess with kitchen paper and the epoxy will not adhere to the ca. Once all cured, a light sanding will remove the loose ends and smooth off the tow.
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Old Mar 01, 2013, 08:43 AM
Whisper Model Aircraft
heliwill10's Avatar
Greensburg, PA
Joined Feb 2008
558 Posts
Servo Tray

Keep the servo opening small! Also, keep some material above the canopy lip otherwise the canopy fit will be difficult. You can see I opened up the canopy about centered in molded lip.

The nose compartment has square sides which allows for many different servo installations. If your planing to nose over hard it helps to add stringers and ply enforcements as below. Adding these ply inserts will do more benefit than adding more weight to the layup.

I've done installs with servos flat, in line, and now on the 45. Having them on the 45 allows for more room for the receiver and battery to slip forward. Take your pick!
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Old Mar 04, 2013, 11:54 AM
Whisper Model Aircraft
heliwill10's Avatar
Greensburg, PA
Joined Feb 2008
558 Posts
Pushrod Install

Two options for linkages, internal or external. Both have their advantages, use whichever you prefer.

Links for pushrod material:
http://www.tailboom.com/teflon.php
http://www.acpsales.com/Solid-Rods.html

A few notes, some repeated:
The control horn needs to be offset from the center as it will interfere with the pylon exit.
With an internal install you can squeeze some thin CA in from the aft of the boom to attach the teflon.
The control horns were cut from G10 fiberboard.

Build log continues on next page.
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