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Red Tailed Hawk glider

earthsciteach

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#1
Here's one of the many projects I've been contemplating/building for a while. I am making a Red Tailed Hawk glider with the intention of getting video of the hawks that nest on my school grounds. I figure they will be at least curious, aggressive at best. The picture shows the rough cut outs for the wings, tail and body. For dimensions, I used the wingspan of a small adult. Then, after looking at pictures of red tailed hawks online, I scaled the remaining dimensions based on body proportions. Given that birds can almost infinitely change the shape of their wings, I imagine that balancing the cg while maintaining scale dimensions will be quite a challenge. Also, I'm still not sure how I want to launch it. If I can get the stability worked out, I could tow it up behind my Super Cub. A high start is another option. Doubt DLG would work well. It will be a 2 channel (rudder and elevator). Another challenge is going to be protecting attacking hawks from the electronics and control rods. I want to eliminate anything that could injure them. One idea is to directly attach elevator and rudder to the servo arms. The battery and esc will have to be well contained from their talons. Due to the compound wing curvature, I'm thinking of going with a KF airfoil. If anyone has a better idea, I'd appreciate your input!
 

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teflyer

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#2
Looks nice!
Yeah, a DLG would not be that great of an idea for the purpose. In my opinion, a hight start would be the best. Towing would probably work too, but there is always the chance the hawk would attack the tow plane. If you are going to use the KF airfoil, I would use either the KFm2 or the KFm3. Personally, I prefer the KFm2 just because I have had a much better success rate with a KFm2. For CG, just make a slot for the battery way up in the front to balance. Also, is there dihedral in the wing?
 

earthsciteach

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#3
A red tail's wing is flat when soaring. But, with a 2 channel, it will need a bit of dihedral. I hope to minimize the dihedral as much as possible.
 

teflyer

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#4
What you can do instead of rudder elevator is the use of elevons. That way all you need is about 5 degrees of dihedral so that the wing is relatively stable.
 

colorex

Rotor Riot!
Mentor
#5
Excellent idea, you're the best science teacher I never had!

You will need very good artwork on it. I don't think the hawk will mind the dihedral. But you really need to make a bright glassy eye, as that is quite significant from an animal's viewpoint in determining live or real. Doves for example, will not get scared by moving humans unless the humans look towards the doves.

Good luck, I really want to see this go through.

You're the best science teacher!
 

teflyer

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#6
That's a cool little fact! So that sort of explains why birds never seen to be afraid of cars until the car is about three feet away.
 

earthsciteach

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#8
No worries. I have an art teacher in my building who is incredibly talented and just happens to be addicted to RC planes, too. He and his wife just had a baby (yesterday!), so when he's back at school, I'll have him airbrush an amazing paint job on this thing!

The Alula looks like a very quality glider and is the inspiration for this one. I'm having a lot of fun with this!
 

earthsciteach

Moderator
Moderator
#11
Taking your advice, Tex and going with the KFM3. Funny thing about these KF airfoils. I knew the concept was familiar to me from back in the '80's. As I was looking up the KFM3, I realized where it came from - I owned the book, "The Ultimate Paper Airplane," when I was in school. Funny how things come back around!
 

teflyer

Full Circle
#12
ok, cool! just do the steps on 50% and 75% of the wing without elevons if you are doing elevons. From what I have been experimenting with, with a wing with the steps at 50% and 75%, it seems that a lot of the air is directed down at the back of the wings. With a flying wing, that is not very good. WIth the wing I was experimenting with, the KFm3 type would be fine for half a second and then nose down drastically and seemed to fly a lot better upside down than right side up. I am thinking that this occurs because of the redirecting of air from the airfoil. With the KFm2, I had a lot more success with a pretty good glide. If you are doing just rudder and elevator, add a little bit more foam at the end of the wings when doing the KFm3
 
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earthsciteach

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Moderator
#14
Interesting testing, Tex. Thanks for the info. I'm planning on elevator and rudder. A red-tailed's tail has a pretty broad surface area when soaring. According to the info, the KF-3 has a pretty wide range of CG. I'll need that with this bird.
 

colorex

Rotor Riot!
Mentor
#15
Teacher (So, what's your name again), Are you able to sand the foam you'll use? If so then sand the edges round to improve airflow. Oh well, I assume that's kind of obvious.
 

earthsciteach

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#16
The name's Patrick, Andre. The wings are triple layered foam board. LE is 1.5 cm thick, so there is plenty of room for sanding. I am going to round them off. She's coming together nicely. I'll try to tack her together to get a pic or two.
 

colorex

Rotor Riot!
Mentor
#17
The name's Patrick, Andre. The wings are triple layered foam board. LE is 1.5 cm thick, so there is plenty of room for sanding. I am going to round them off. She's coming together nicely. I'll try to tack her together to get a pic or two.
Wow, 1.5cm is quite thick! Do you plan to sand it into a slight airfoil (thinner towards the back)? Or just curved?

You said that you wanted to put direct linkages for the control surfaces. While being a good idea, don't you think it can throw off your CG too much?

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Just came across a wild thought: Birds fly bank'n'yank, they don't use rudder... So I fly like a bird!
 

colorex

Rotor Riot!
Mentor
#19
Oh, KFM! I must have missed that part.

But I sincerely think it will fly better with elevons than elevator/rudder. Just split that tail.