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Foamboard Shrike

Techno

Sunny Day Park Flyer
#1
Hello. I'm building a Shrike from out of an free-bee issue of Flying Models Magazine but out of foam.
So far the scaling up from an Ultra-Micro setup has been great. However, I have one Question:

<<<:confused:This is a speed plane, Should I build it with a full airfoil, or would a flat foil work?:confused:>>>

My electronics are as follows:
1800KV Brushless Outrunner
20A ESC
3x9g servos
900mAH 3S lipo
7x5 prop

The concept I have is:
31.5 inches-Wingspan
~21 inches long
Projected 12-15 degree throws.
No expo (cheap old radio).

This is what I have designed so far.
Strike.png

And this is the original:
shrike-180-3.jpg


Original Plans: (I'm using the ones printed in a free magazine, not these)
http://carstensbookstore.com/shrike180.html
 
Last edited:
#3
instead of flat, wouldn't a kfm 4 work? I would think it would be better than a flat wing. should add some lift and strength without adding too much weight or drag.
 

Techno

Sunny Day Park Flyer
#4
I probably will go with a KFM4 but I'm not too great at making KF airfoils, I always make the step too big. The original stuff said the step should be as high as about 10% of the chord, but I've never really gotten that to work well
 
#5
I probably will go with a KFM4 but I'm not too great at making KF airfoils, I always make the step too big. The original stuff said the step should be as high as about 10% of the chord, but I've never really gotten that to work well
eh, when I make a "step" I just make it 1 layer of foam board high. soo, 1 piece for the full wing, one folded over for the step on top and 1 for the step on bottom. so, basically your leading edge will be 3 times that of the trailing, and each of the steps will be 50% of cord. (talking about length, not height of step)
gluing the layers that way adds lots of strength to the wing.
I tried a kfm 3 once where I made the first step higher by having it sit angled up on the next step, but that left a gap under it and lowered the strength of the wing.
Any step is better than no step :)

another option is the main wing out of DTFB and the step out of dow foam. it can be shaped and sanded for a fairly clean and smooth edge. of have seen some nice flying wings made that way. This gives you a .5 inch tall step. (could be less if you wanted to sand down the trailing edge of the dow foam)

I have been trying out more combos of DTFB and Dow foam. They each have their own advantages. some combos of them work well, better than just full DTFB.
 

Techno

Sunny Day Park Flyer
#6
I probably will fold another piece of foam over and under the wing, I was just going to put thicker foam on both sides, but this looks much better, Thanks for the suggestion!
 

Techno

Sunny Day Park Flyer
#7
Update 2

I just finished my second concept.
I added a KFM4, A dowel strut, and a lot more color!
Shrike V2.png
Next, I start building!:D
 

AndyKunz

Junior Member
#8
How's your Shrike coming along?

I've built this plane in 4 sizes so far, and all fly great. The only recommendation I'd make is to fatten the airfoil and blunt the leading edge a bit. You really want that to prevent sudden departures due to the sharp LE.

Andy
 
#9
Can you post some plans because the link you posted doesn't work.. I was also wondering if I could use one aileron servo instead of two..
 

Techno

Sunny Day Park Flyer
#10
Wow, TBH I'm surprised this thread resurfaced on the New Posts section. anyway BIG NEWS. I ACTUALLY BUILT IT. FYI, the color thing definitely won't work, that Update 2 thing is practically useless. Concerning posting plans, I don't really do PDFs, I prefer to tell you how to find it in the google sketchup warehouse so you guys can see all the dimensions and stuff for yourselves. (I'm lazy/busy) Personally, I wouldn't use only 1 aileron servo for reliability, but yes, you can bend some coat hangars/control rods and do that. I think I'll be tending to the thread a lot more in the future.