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Old Dec 05, 2010, 05:08 PM
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Nick, Your Polar Duck flies great and the landing looked well controlled. That eye exam was well done. The Stuntcat with canard looked like fun. You are right that there's always another idea out there. It is amazing to me how fast you come up with and incorporate those new ideas.

Too bad about the forced crash, Roger. I had to ditch a 79 inch Cub to avoid a bystander. Please build another one which probably will be even better.
Charles
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Old Dec 06, 2010, 08:27 AM
4.2V of pure Kraut power
bzfrank's Avatar
Germany
Joined Nov 2006
458 Posts
Maybe this is interesting for you too - a fellow modeller built this plane from left over parts. The main wing was from a Vöster Pampa:





Hand launch was a problem. Due to the large 90mm EDF it was almost impossible to grip and due to its location under the wing the plane had the nasty tendency to climb straight up (Even loop around) if too much throttle was applied. When in the air it flew great. One of these days however it crashed too badly on launch...

Frank
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Old Dec 06, 2010, 08:48 AM
What could possibly go wrong?
nickchud's Avatar
Market Harborough
Joined Apr 2006
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Frank - Nice one! I too am a specialist in recycling old parts, usually wings. Really excellent Stars and Stripes. I imagine it goes like a rocket.
Quote:
Hand launch was a problem.
Looks llike a case for a frisbee launch to me.

Charles
Quote:
Your Polar Duck flies great and the landing looked well controlled.
Thanks Charles, but I don't think the video did it justice, too much whizzing about like a flying wing. I've been trying to learn the dark arts of control via throttle and rudder. This model, with a nice big canard, is making it very easy to fly slowly with a high alpha. I just use the ailerons to stay level and the rudder to steer. Not confident enough yet to do that anywhere near the ground.

Cheers

Nick
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Old Dec 06, 2010, 08:50 AM
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bzfrank, Your friend did a beautiful job. It looks well designed with battery access under the canopy? Too bad that he did not have Nickchud's launcher.
It would be a treat to see more of his work.
Charles
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Old Dec 06, 2010, 09:09 AM
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Nickchud
Quote:
I've been trying to learn the dark arts of control via throttle and rudder. This model, with a nice big canard, is making it very easy to fly slowly with a high alpha. I just use the ailerons to stay level and the rudder to steer. Not confident enough yet to do that anywhere near the ground.
Flying with rudder has been neglected with me. One day when testing a Sig trainer for a newbie, the ailerons were ineffective because or their small size and lack of throw and I was forced into rudder control for aileron assist. On landing the left wing dropped and I applied left rudder from lack of practice causing some minor damage. You never know when rudder will be necessary.
Charles
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Old Dec 07, 2010, 01:18 AM
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Quote:
Originally Posted by bzfrank View Post
Maybe this is interesting for you too - a fellow modeller built this plane from left over parts. The main wing was from a Vöster Pampa.

Hand launch was a problem. Due to the large 90mm EDF it was almost impossible to grip and due to its location under the wing the plane had the nasty tendency to climb straight up (Even loop around) if too much throttle was applied. When in the air it flew great. One of these days however it crashed too badly on launch...
Great looking EDF canard! I can understand having a problem with hand launching. Nick's suggestion of bungee launch is a good idea for this style of canard model. Quite often canards can have poor elevator control near the stall speed. Anyway it looks like a nicely proportioned canard model. I hope your friend will be inspired to build another one.
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Old Dec 07, 2010, 05:59 AM
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Depending on the model's size and flying speed, the other common option in cases like this is to hold the model by the top, and throw it underhand.
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Old Dec 07, 2010, 05:08 PM
Survival is Attitude!
Skonkworkstexas's Avatar
Hallsville Texas
Joined Aug 2005
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Rules of thumb needed:

I am curious.
I am considering building a twin-boom canard with single centerline pusher.
It would resemble a P-38 Lightning flying backward.
The reasoning for such a project is for FPV. A twin-boom approach spreads out the places to locate electronics, increasing isolation from RF interference, and a canard seemed a way to decrease wing loading/increase payload, as the horizontal stabilizer is a lifting surface in leu of a straight control surface.
I would consider building out of 3 skysurfer kits, as they are cheap, and made of EPO.
Questions.

Is there a rule of thumb regarding main wing/canard wing area ratio?
Is there a rule of thumb regarding spacing between the two?
Anything else I should consider?
Skonk
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Old Dec 07, 2010, 05:47 PM
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What you're looking for is called "tail volume coefficients", and there are articles in the "Ask Joe and Don" section of our website www.djaerotech.com explaining what they are, how to calculate them and how to use them.

The area ratio between the wing and canard, or the wing and a conventional aft-tail, is pretty meaningless unless you also take the moment arm into account.

As far as payload, in order to get acceptable stall characteristics over the entire operating envelope, a canard layout in the vast majority of cases cannot use the full lifting ability of the wing, and therefore will not be able to carry as much payload as an equally well-designed aft tail. The way to maximize the payload is to use as long a moment arm as possible, with the minimum canard area possible. This also maximizes dynamic stability, which would be extremely important for FPV. This same small-tail-on-a-long-moment-arm approach applies equally well to aft-tailed designs.

The downwash of the canard has a negative effect on the efficiency of the wing, and the lift-making efficiency of the canard itself is also not as good as the wing, which is why making the canard as small as possible and as far away from the wing as possible helps the aircraft's overall efficiency. Conversely, the downwash of the wing on an aft tail helps the tail's efficiency. The net result is that the induced drag "cost" of an upward-lifting canard vs an equally well-designed downward-lifting aft tail ends up being roughly the same for the same amount of static pitch stability. If there is a difference, most of the time it's in favor of the aft tail.

And don't even think of getting me started on the subject of pushers! With extemely few exceptions (almost all of which are driven by issues other than performance, and suffer performance losses in order to deal with that other issue) those should be banned.
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Old Dec 07, 2010, 06:53 PM
4.2V of pure Kraut power
bzfrank's Avatar
Germany
Joined Nov 2006
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Thanks guys! I'll tell him! BTW Bungee launch wasn't considered an option for this plane as the hook would be directly in front of the EDF intake. Any application of power would have caused the bungee rope to be sucked in with all the bad consequences known.

Frank
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Old Dec 07, 2010, 06:55 PM
Survival is Attitude!
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Hallsville Texas
Joined Aug 2005
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If I am reading you right.......Then a conventional setup simular to a P-38 would be superior, possibly scaling simular moments, and ratios to the original.

Hmmmmmmmm...... Well I am a big admirer of Kelly Johnson, hereby my handle Skonkworkstexas!!! A single engine Centerline Tractor maybe in my future. I had picked a large slow two-blade for efficiency. I would still get the triple-fuselage payoff as earlier mentioned....Thanks!
Skonk
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Old Dec 08, 2010, 02:10 AM
What could possibly go wrong?
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Market Harborough
Joined Apr 2006
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Frank
Quote:
BTW Bungee launch wasn't considered an option for this plane as the hook would be directly in front of the EDF intake
What I was thinking of for your plane was a frisbee or discus type throw, holding onto one wing.

How about that?

Nick
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Last edited by nickchud; Dec 08, 2010 at 03:43 AM. Reason: discus not discuss, oops
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Old Dec 08, 2010, 02:44 AM
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^^ Nick, Now I put my glasses on, post #4833 reads frisbee not bungee. Sorry about that!
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Old Dec 08, 2010, 06:21 AM
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United States, OH, Bradford
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Quote:
Originally Posted by Skonkworkstexas View Post
If I am reading you right.......Then a conventional setup simular to a P-38 would be superior, possibly scaling simular moments, and ratios to the original.
Generally yes. Another option would be conventional fuselage with pods or nacelles out on the wings for equipment. Lots of different options.

Quote:
Hmmmmmmmm...... Well I am a big admirer of Kelly Johnson, hereby my handle Skonkworkstexas!!!
Just be careful about trademark issues, L-M and their representative in that area have a history of getting sticky on that, including claiming rights to trademarks they probably don't actually own anymore. There are good reasons why my company will never again even consider producing a model of a L-M aircraft. There are plenty of model subjects from companies who don't behave in such a despicable manner.

Quote:
A single engine Centerline Tractor maybe in my future. I had picked a large slow two-blade for efficiency. I would still get the triple-fuselage payoff as earlier mentioned....Thanks!
Skonk
The layout on the P-38 was a matter of practicality and making best use of the cards he was dealt. He wanted to have the engines and their equipment separate from the cockpit for safety reasons, and needed to keep all the engine-related equipment in-line to minimize drag. By the time he lined up the engines, superchargers, landing gear and radiators, that whole "train" of components stretched almost all the way back to where the tail needed to be. It was simpler and lighter to just extend the nacelles a little further than to make a whole long, relatively empty and useless tail cone on the fuselage in the middle. In the bargain, the stab and wing could help reinforce each other's torsional stiffnesses. That layout also made it easy to put the rudders in the propwash, which helped rudder authority for single-engine operations. It was a perfect example of form following function.
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Last edited by Don Stackhouse; Dec 08, 2010 at 06:29 AM.
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Old Dec 08, 2010, 08:58 AM
4.2V of pure Kraut power
bzfrank's Avatar
Germany
Joined Nov 2006
458 Posts
Quote:
Originally Posted by nickchud View Post
What I was thinking of for your plane was a frisbee or discus type throw, holding onto one wing.
It may have worked, but would have required a modification of the wing. The original wing was build with a very light core covered with 1.5mm balsa (a weak point of the Vöster Pampa - it was a model from the early ages of EDF use and build very light) and would likely have disintegrated on high lateral loads. Some carbon fiber could have changed that easily of course.

Frank
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