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Old Mar 14, 2011, 10:43 PM
expert noob
handyfella's Avatar
Joined Feb 2011
108 Posts
Build Log
The "foamyak" My 1st Build finally documented. With Pics and vids and some night fpv!

A few aerobatics here and there testing it's new motor


Did a little Glide testing in last half of this video
foamyak glide stall test (14 min 3 sec)


1st Night flight fpv with tiny dv80 cam

During the glide test, where I cut power at high altitude and see how slowly it will fly without stalling, turns out it won't stall, it just floats down, seriously i could not get this plane to stall and fall out of the sky like most aerobatic planes will, even with the flaps down, where it is just crawling, it will just maintain level forward flight and float down ridiculously slow while being fully controllable.

This is a $ tree foam production completely scratchbuilt by handyfella himself, no plans, all assembled with homemade pushrods, and hot glued together. Just an adjustable cg to get it right and to use different batteries if I want. I move the wing forward a little for the 1800 3s and back a little for the 1000's.

Has taken me a while to finally get around to sorting this plane's cg out and get a suitable power system for it that will do the airframe justice. That turned out to be the motor from the flying wing, which makes this plane pretty fast with an 11x7 and will hover at about 75% throttle with a full battery. Easy flying means battery lasts 12min, lots of rolls and loops and you get 8 minutes.

This was intended to be my trainer plane, very first airframe I've ever built and attempted to fly, and it has taken some abuse with the very best of em. Combined with a few hours of simulator time it has been pretty easy to fly although landing approach is pretty fast, and though it slows down a lot with the flaperons, the do tend to cause a little more roll and yaw than I was ready for, but so far it has worked very well.

It turns out my wing mounting system has pretty much saved it's "tail" several times over. It has 4 breakaway mounts that hold the rubber bands around the fuse. I didn't intend for the mounts to be breakaway, I just wanted to be able to fine tune the cg without adding weight, since this is supposed to be a sporty aerobatic plane, but after extensive crash testing, any amount of twist, like if the wing nails the ground in a banked turn or something, the mounts will just twist against the basswood bracing along the edges of the fuse and snap off due to being superglued on, which has low impact strength, and the holes the tabs stick through are triple thick foamboard, and absorbs all the impact. The durability has blown me away. Also the motor mount doubles as the battery case, so the battery and esc are just behind the motor and the whole power pack slides into the ID of the fuse tube, and then is held in place by one bbq skewer in a cross drilled hole, and this also acts as a breakaway system where in a big impact, the holding pin just shears away and allows the powerpack to just push up into the fuse absorbing even more impact, and usually saving the motor shaft, but rarely saves the prop I'm afraid...

Wing is a sorta kfm3 but top step is centered on the 2nd step and is smoothed with packing tape and a hidden carbon arrow shaft for a spar which makes it really tough and holds up to some pretty high g's. Flight envelope is pretty fast to realllly slow with the flaps on. There is also a basswood spar that runs a good portion of the wingspan, but is not strong enough by itself, so I added an arrow shaft and I definitely think the arrow shaft is strong enough by itself, however two arrows would be lighter than the single basswood spar that is hot glued in the entire way across, which added tons of unneeded weight.

The wheels are a real gem, double thick foamboard disks, a balsa slab either side drilled for the axle, wrapped with weatherstripping, and held on to the umbrella fiberglass rod axle with fuel line. Axle was originally a bbq skewer, but broke every other landing, not so with the fg rod.

auw= 28oz
wing loading= ~7.7oz/ft^2 (including horiz stab)
Root chord=11"
Tip chord=8.5"
WS=48"
spinner to tail= 41"
horiz stab= 17.5" at widest point
vertical stab= 8" above horizontal stab

battery= 1800 3s blue lipo
esc = hobbyking 25-30a ss esc
motor = alpha 450 890kv
prop = 11x7 apc E
servos = dynam 7g $1.60 each (sold in pairs by hobbypartz.com) and work awesome!

Fuse is a 2" square tube made from one 8" wide by 30" sheet of foam, with v notches cut every 2", then glued bulkheads in every 6" before folding it shut and gluing it with hot glue.

Hinges are packing tape. It's a prototype that has been crashed about 7 times, and fixed 7 times.. Hence the added tail length, lengthened ailerons, landing gear was rebuilt about 5 times, and modified the elevator so the sides extend to the forward tip of the stabilizer.







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Last edited by handyfella; Mar 15, 2011 at 12:16 AM.
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Old Mar 15, 2011, 02:03 PM
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Dickeroo's Avatar
Joined Dec 2006
1,180 Posts
Matt... I can't tell you enough how pleased I was to see how well your KFm3 slow speed video came out. You also get excellent control authority even when weather conditions are not ideal. Thanks for posting and may you have many more great flights. You're lucky. You have a terrific plane and a wonderful wife.

Dick
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Old Mar 15, 2011, 02:44 PM
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handyfella's Avatar
Joined Feb 2011
108 Posts
Thanks for the kind words Mr Dickeroo! I am blessed she's a great lady and a real looker too PLUS she came with 10 free acres a lexus and a lifetime supply of all types of ammunition! :-) being from the deep south a hillbilly was a great fit for me anyway and granny sho can put the food out too!

Landings with this plane go much better on smooth surfaces which is why I am tossing it on takeoff. The grass there is deep and causes the plane to just catch and noses the prop into the grass every time. Asphalt parking lots are much better or really well groomed soccer fields.

Theres one point in the video where it almost sits still with flaps and needless to say I was very impressed with the wings performance. After some discussion I think the "stall proofness" isn't the wing but rather the nose heavy cg location...

It's very fun to fly and really responsive.

The intention here was not beauty but rather a steppingstone to flying larger gas powered (not glow) planes.

I have a commercial line stihl 27cc ready to fly and an airframe for it, the $57 nitroplanes low wing trainer which has big wing area so I think it will work well with the heavier motor.

I don't see myself giving up these $1 foam planes any time soon though as it's getting addictive.
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Last edited by handyfella; Mar 16, 2011 at 11:50 AM.
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