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Old Dec 21, 2010, 02:19 PM
indoorheli is offline
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2 seconds from crashing
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United States, WA, Seattle
Joined Sep 2007
7,407 Posts
22" 3mm EPPYak55

I purchased a UM-4-site from for $65 which gave me almost everything I needed for this build.
The other stuff needed is:
1 12x36 sheet of 3mm EPP
1 1000mm x 3mm x .5mm carbon flat
2 1mm Carbon Rods
UHU or Welders Glue

I printed out the plans per post #3 in this thread for the 22” span
It was cut almost exactly to plan out of 3mm EPP with the exception of the Keyhole and I did not slice the Fus in half. (I will be posting a plan revision soon as I have to redo them anyhow to do a UV print run)

On the keyhole I had to make it quite a bit smaller since it is out of 3mm EPP and it also needs an area above the elevator for the control horn attachment point for the rudder due to the short servo height the rx has.

After everything was cut out I added UHU to one side of the 3mm flat carbon let it sit for 5 minutes and then attached it to the LE of the wing while the wing laid flat on the table. If you push too hard while doing this with 3mm EPP it can warp the epp so just lightly press it all the way down the wing.

Add a 8-10” section of 1mm carbon rod toward the back of the wing

I then Hinged the Aileron’s with Welders glue – I only used glue in 5 ” spots along each aileron
I also did not add any glue to the wing side connection of the aileron as these small joints can stick a lot easier than the big versions

Next cut out a 3mm by X slot for the wing as in the original build and a 3mm slot for the horizontal Stabilizer (Same relative length and position as the standard Yak)
I then drew a line straight through the middle of the Fus going from nose to tail straight through the two 3mm cuts to help with alignment of the small horizontal bracing later.

Glue the wing as per original assuring it is symetrical with the help of books of supporting each side of the wing and helping keep the fus straight. (I used a piece of carbon to measure from each tip of the wing to the h-stab cutout to assure it is correctly aligned) Let it dry completely and while waiting hinge the elevator with 3 small ” spot glue hinges.

Then mount the H-stab/elevator

Mount the nose pieces which is very easy with the pre-drawn lines.
On the rear the two side fus parts will need to be trimmed a bit to fit as they seemed oddly long for some reason (wasn’t like this on the 32” build)
After it dries attached the rudder with a glue hinge

Cut a hole centered on the cg point the size of the rx through the left side wing. And glue the rx to the fus
Attach the control horns to the tail section and snag the metal rods off the original controls and attach those to lengthened 1mm control rods. Make sure you pick the correct length on the carbon rods before cutting them as you only have a little over an 1/8 of an inch adjustment with the stock metal U bends

Cut down the motor mount excess and make it more like a stick mount
Then cut a hole in the nose to match the cut out and glue it lightly (the lighter the better for crashes as it will come apart rather than tear away)

This first one was really a test so I built it up quick without much artwork or extra support
If you want it exactly like mine it will be an excellent indoor flyer and forgiving but if you demand more out of it you will want to do the following changes:

Add carbon x bracing using the 4-site carbon parts for stop tail twist/ increase rolls and add accuracy to rolls( Pics to follow in a few days with a new one)
Changing position of the rx to be horizontal between the fus (sitting on top of the wing) This will give a cleaner area for the battery below
Adding the counter balance back to the ailerons
Add some SFG’s
Still deciding if I want the flat carbon put into the wing similar to the 32 build

Don’t add the extra carbon bracing if you crash a lot as it will just break over and over again…add it later down the road instead.

Also do not mount the control rod supports so close to the ends of the control rods as i did...i found out later it is hard to take the rx out sinc you loose the end flex of the carbon rod - On the next one i will probably on use one support per ron used in the middle
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Last edited by indoorheli; Dec 21, 2010 at 09:32 PM.
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