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Old Sep 25, 2012, 01:45 PM
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Kingsland, Texas USA
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Nick Bo you have anything that shows controls used on these birds.
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Old Sep 25, 2012, 03:16 PM
bat
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cincinnati
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I am really interested in the prospect of an rc condor. In doing research I discovered the king vulture while only having a 6 foot wingspan is closely related to condors in body and wing shape. The broad wings and short tail make for an intimidating design.
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Old Sep 27, 2012, 10:09 AM
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Hi all,

relative newbuilder here needing some advice

Am building the FFF eagle (46") and was wondering what people were using as a wing-brace? I've build wings before with a wooden dowel etc. to strengthen but can't see how i could do it with this wing without the top 2 layers sticking up!

Are you all using flat carbon strips?

Also... how do you get a decent dihedral on the wings whilst still keeping them strong?

The next step is to somehow glue the V-shaped tail feathers?? That's another mystery lol

Thanks for any advice... i'll get there in the end!

Tim
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Old Sep 27, 2012, 02:18 PM
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Tom Frank's Avatar
United States, MA, Walpole
Joined Dec 2003
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Quote:
Originally Posted by acreative View Post
Hi all,

relative newbuilder here needing some advice

Am building the FFF eagle (46") and was wondering what people were using as a wing-brace? I've build wings before with a wooden dowel etc. to strengthen but can't see how i could do it with this wing without the top 2 layers sticking up!

Are you all using flat carbon strips?

Also... how do you get a decent dihedral on the wings whilst still keeping them strong?

The next step is to somehow glue the V-shaped tail feathers?? That's another mystery lol

Thanks for any advice... i'll get there in the end!

Tim
I used my dremel tool to create two span-wise very shallow trenches (e.g. 1mm) in the top and bottom wing surfaces opposite each other. The I used epoxy to glue the wings together with my desired dihedral. Once that was firmly set, I laid a thin layer of 1 hour epoxy in the upper wing trenches, and laid 12K CF ribbon tow strips in the still liquid epoxy, then laid down another thin layer of the same epoxy on the top surface of the CF tow strip, and worked it down into the tow weaving with a flat wood stick so it was essentially flush with the wing surface. Once the CF tow was fully impregnated with epoxy, I let it cure, then repeated the process on the underside of the wings. Once painted, the strips are invisible for all practical purposes.

The eagle flies very slow, so the wing loading is not very severe and the tow strips provide more than adequate strength unless you have more power than needed. The wings have easily survived both slow inside and outside loops, but I seldom do that since it's not meant to be an aerobatic plane. Here's some pics:
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Old Sep 27, 2012, 02:48 PM
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Thanks very much for the advice (great looking bird!).

That CF Tow looks very useful (hadn't even heard of it! Might have to order some.

Presumably, because yo have it top and bottom the wing won't collapse/unfold once it's all set?

What servos are everyone using? I have some spare 9g servos about, but can get some 5g if necessary?

Is a standard setup ailerons and elevator? Or is there a way to mix in a rudder too? I'm using the V-tail setup.

Thanks again for any help

Tim
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Old Sep 27, 2012, 03:01 PM
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United States, MA, Walpole
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Comments in green below in your post:

Quote:
Originally Posted by acreative View Post
Thanks very much for the advice (great looking bird!).

That CF Tow looks very useful (hadn't even heard of it! Might have to order some.

Presumably, because yo have it top and bottom the wing won't collapse/unfold once it's all set?
Yes, that's correct. The CF tow is very strong in tension, and the foam of the wing keeps the opposite top/bottom strips separated so they act like the flanges on an I-beam.

What servos are everyone using? I have some spare 9g servos about, but can get some 5g if necessary?
9 gm servos are just right, given the size of the ailerons. I did not cut the tip end of my ailerons free! The ailerons actually twist rather than uniformly deflect (I call them "warperons"). The inner end near the body deflects the most, with less and less deflection towards the tip, where they don't deflect at all since the aileron foam is still attached there. It sounds strange, but that's the way the real birds wings shape themselves in flight if you look at pictures, and I wanted to emulate that. I did not use Depron (or similar) stiff foam sheet, but rather the paper-clad foam board you can buy with the paper removed (after soaking in water). This leaves very flexible foam sheet, perfect for this application.

Is a standard setup ailerons and elevator? Or is there a way to mix in a rudder too? I'm using the V-tail setup.
The eagle turns very flat with just aileron action alone, though I also used the V-tail mix in my TX for both rudder and elevator action. Rudder is seldom used because the eagle will yaw, then roll and dive when the tip dihedral turns into the on-coming airstream.

Thanks again for any help

Tim
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Old Sep 27, 2012, 04:04 PM
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Brilliant! Thanks so much for your help... i've got a very clear plan of what to do now (i've had the parts taped up for a few days wondering what to do!!). Time to get started

You've already helped enough... but if you or anyone else has a good photo of the tail servo setup that would be most useful as I know i'll have to deal with that soon!

All the best

Tim
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Old Sep 27, 2012, 04:27 PM
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United States, MA, Walpole
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Quote:
Originally Posted by acreative View Post
Brilliant! Thanks so much for your help... i've got a very clear plan of what to do now (i've had the parts taped up for a few days wondering what to do!!). Time to get started

You've already helped enough... but if you or anyone else has a good photo of the tail servo setup that would be most useful as I know i'll have to deal with that soon!

All the best

Tim
The attached pic shows how I set my V-tail servos (with pushrods crossing to opposite tail surface -not necessary... just easier). And as soon as the video is done being prepared on Vimeo in about 30 minutes, the following will show all the control action:
C:UsersTomDesktopRC StuffEagleEagleControlCheckout (1 min 51 sec)


I show flaperons in the video, but with the bird basically being a flying wing, they have the reverse action of what's expected...plane will dive with flaperons down. I don't use that function now... the bird flies in slow enough without them.
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Old Sep 27, 2012, 04:38 PM
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You're a real credit to this forum Tom, I can't thank you enough

It makes it so much easier for a complete newbie to get first hand advice!

I've built one plane before (the BB J3 Cub) and am totally hooked on building and flying them!

Here's a quick vid on this post of my maiden flight (second takeoff I think) if anyone's interested:

http://www.rcgroups.com/forums/showp...&postcount=270

Cheers

Tim
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Old Sep 27, 2012, 06:37 PM
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I am also making an eagle and thank you Tom Frank for making this very helpful video. awesome community. I will post vids of maiden or first flights when finished. looking forward in flying the eagle...



Quote:
Originally Posted by Tom Frank View Post
The attached pic shows how I set my V-tail servos (with pushrods crossing to opposite tail surface -not necessary... just easier). And as soon as the video is done being prepared on Vimeo in about 30 minutes, the following will show all the control action:
https://vimeo.com/50330729

I show flaperons in the video, but with the bird basically being a flying wing, they have the reverse action of what's expected...plane will dive with flaperons down. I don't use that function now... the bird flies in slow enough without them.
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Old Sep 28, 2012, 09:02 PM
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Kingsland, Texas USA
Joined Aug 2000
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Kestrel flew for the first time today.
Utube Power Kestrel (14 min 0 sec)
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Old Sep 28, 2012, 10:50 PM
Lee
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USA, UT, Orem
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I have several flyers asking about Peregrine kits. At this time we are not cutting the kits but having a good flying bird plane is on my bucket list.

Here is an idea I haven't tried and are untested.

I actually think a peregrine shaped flat foam plane like the FFF Eagle that has plans that are on the Peregrine thread may work if kept light. You could use any silhouette of any bird regardless of the shape of the wing and not have the stall problems that we have with the more complex airfoils and strange angles we have to cut.

Lee
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Old Sep 29, 2012, 01:43 AM
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Kestrel flew for the first time today.
Nice one! Looking pretty good now.

Malcolm
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Old Oct 01, 2012, 09:57 AM
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Joel K. Scholz's Avatar
Kingsland, Texas USA
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Lee, I certainly cannot claim to be an expert in bird plane design, but I have an idea as to why you might be having tip stall problems. I think it is because you are devoting far too much wing surface area to the ailerons. High deflection rates will stall the wingtip and when 30 % or more of the wing is stalled you will tipstall. While the Kestrel is my first devoted bird plane , it does not have a tipstall problem and its wing structure is far less sophisticated than yours. The v-tail is more effective in controlling the kestrel and ailerons are not even really needed. Why not try greatly reducing your aileron size and fly them with significant differential. I hope you do not mind this suggestion, I realize you have far more experience with this type of design than I do. I might add I have found your thread very inspirational and have already begun designing my next attempt. An 82" Osprey.
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Old Oct 01, 2012, 10:44 AM
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Western Europe 52.7 N 8.9 W
Joined Jul 2007
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Quote:
Originally Posted by Lee View Post
I have several flyers asking about Peregrine kits. At this time we are not cutting the kits but having a good flying bird plane is on my bucket list.

Here is an idea I haven't tried and are untested.

I actually think a peregrine shaped flat foam plane like the FFF Eagle that has plans that are on the Peregrine thread may work if kept light. You could use any silhouette of any bird regardless of the shape of the wing and not have the stall problems that we have with the more complex airfoils and strange angles we have to cut.

Lee
Lee, are you talking about somethink like Nick's Bluebird style of aircraft ? ......

I could easily see some effort in making the model more bird like, would be relatively easy, and lots of shapes (bird types) could probably be created without too much effort .... even 'as is' it looks great in the air with the profile looking very Hawk'ish .....

Nick's design is based on a Kfm2 wing and I have to say my 20 or so flights on the version I've recently built has really impressed me ..... I must get a video for it ....

Here's a link to Nick's design .... http://www.rcgroups.com/forums/showp...postcount=4638
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