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Old Jan 25, 2011, 04:08 PM
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Originally Posted by Trevorh View Post
... I wonder whether it might turn out to be easier to mount the whole canard on some sort of ball joint rather than make the forward fins individually moveable? ...
At that point you're starting to deviate from the original design on a pretty fundamental level. You need to ask yourself whether you're building a scale model, or trying to pick up Stanger's work where he left off and develop it to a new, different level.

If the latter, at that point you are most of the way to the method MacCready used on the Gossamer Albatross. On very long-winged, slow-moving aircraft like that, you have to consider not just the mass of the wings that needs to be accelerated when rolling, but also the air surrounding those wings, which has to roll with it. It's similar to the problem that hot air balloon pilots have to deal with, the effect on control response from the approximately two tons of air inside the bag (not to mention the roughly 15 seconds it takes for air heated by a change in the burner setting at the bottom of the bag to rise to the top of the bag, where it can start altering the climb/descent rate).

Rather than fitting the Gossamer Albatross with ailerons, he mounted the canard on a flexible structure, so it could bank without the rest of the plane banking with it. This would tilt the canard lift vector to one side or the other, so that banking the canard resulted in a yaw input to the plane. It was literally being "led around by the nose". Eventually that would interact with the wing dihedral to alter the wing's bank angle, but long before that it would simply force the plane to a new heading, without the need to bank the wing. The side forces developed by the dihedralled shape of the wing plus the side area of the cockpit pod were enough to make the sideways lift to overcome the minuscule centrifugal forces involved in such a slow-speed turn.
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Old Jan 25, 2011, 05:42 PM
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Trevorh
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i) The indoor model was reluctant to turn. Not really surprising since the interplane rudders had very little moment arm. I did set them up with lots of differential so the inboard rudder created more drag which helped a bit. Ideas on a more positive form of directional control would be appreciated.
Trevor, If you increase the span and chord of the canard, it should not be noticeable but it will move the CG forward so that the rear rudders will
have more leverage. You could then add a bit more rearward area to the rudders. Adding some area to the front rudders would also help the turn as the rear of the model moves sideways to start the turn. These increases should balance out the model to appear scale as I see it.
Thanks for your great presentation. I enjoyed the design and building details.
Charles
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Old Jan 25, 2011, 06:04 PM
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Stranger Biplane

Trevorh
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It seemed that the main wheels were lifting off, whilst the nosewheel was still grounded, resulting in the model trying to overtake its own nose. Having retrieved the model, the battery was moved back as far as possible and the foreplane rigging angle increased. Again the model seemed to gather more speed on the ground than I would have expected but, hauling back on the stick, it at last became airborne, and climbed away steadily. Turn response was somewhat delayed but adequate for the spacious Calshot velodrome, given a bit of planning ahead on the part of the pilot, and the model looked quite stately in the air. I was still having to hold in up elevator and I got the distinct impression that the foreplane was still working hard, suggesting that the cg probably ought to go back a bit further still. However, the mission of the evening had been accomplished so an early landing was called and I went home
My original canard experienced this problem and was fixed by adding area to the canard wing. This will cause it to lift first and raise the angle of attack of the rear wings. You may want to add a little positive incidence to the canard and to check that the incidence of the main wings are near zero. The Wright Flier needed two canard wings. Just my opinion.
Charles
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Old Jan 26, 2011, 10:46 AM
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Originally Posted by Don Stackhouse View Post
At that point you're starting to deviate from the original design on a pretty fundamental level.
On the indoor model, I attached the canard by a hinge at the front and arranged a servo to pull the trailing edge down for pitch control. I was thinking of replacing that hinge with a ball joint and using two vertical pushrods on the trailing edge.

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You need to ask yourself whether you're building a scale model, or trying to pick up Stanger's work where he left off and develop it to a new, different level.
I suppose my aim is similar to that of the vintage fraternity who install R/C and electric power into models designed for free flight back in the 1940s and 50s. More a 'tribute' model than a true scale model, I suppose.

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On very long-winged, slow-moving aircraft like that, you have to consider not just the mass of the wings that needs to be accelerated when rolling, but also the air surrounding those wings, which has to roll with it.
Whilst I will want to keep the wing loading down, I don't think it will be in the realms of Gossamer Albatross - it does have to fly outside in the U.K. after all!

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Rather than fitting the Gossamer Albatross with ailerons, he mounted the canard on a flexible structure, so it could bank without the rest of the plane banking with it.
It's good to hear that that control mechanism works. Banking the canard might be easier to arrange than yawing it. I guess either would work.

Charles, thanks for the thoughts on tweaking the areas. With only a few black and white photos to go on, the dimensions of the flying surfaces are largely guesswork anyway. As a free flight model, it would no doubt have been optimised for stability which is not the same as optimising for control.

My initial setting of the cg for the indoor model was based on the position of the mainwheels. From the photos it looks as if Stanger's model was designed to rise off ground. Given that it would have been marginally powered and probably quite heavily loaded, this would be quite a challenge. I assume that Hendon airfield didn't have tarmac runways by then either so I reckoned that, to have any chance of getting airborne, the cg could only have been marginally forward of the main wheels. I now wonder whether in fact the cg might even have been behind the main wheels. There is a rear skid built into the fuselage structure to protect the prop - which itself would have represented several days work to produce. However, none of the photos actually show the model with its nosewheel in the air so maybe the cg was forward a bit.

Of course, if anybody fancies a go at working out the theoretical position. . .
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Old Jan 26, 2011, 01:05 PM
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Trevor, After taking a second reading of your analysis and efforts, it seems that you took a tough situation and made it work as well as possible. stanger's version probably had the CG back near the wing's leading edge. It seems that you moved the wheels and CG forward and had success making it turn in spite of the polyhedral's effect of holding the wings level. Nickchud regards you as a great modeler and so do I.
Charles
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Old Jan 27, 2011, 01:35 AM
What could possibly go wrong?
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You should have a look at Trevor's excellent web site..here.

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Nickchud regards you as a great modeler and so do I.
I certainly do. And he even flies them without crashing too!

Charles, you look as if the maiden for your Delta Duck II will be coming up soon. Good luck!

cheers

Nick
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Old Jan 27, 2011, 04:46 AM
What could possibly go wrong?
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Wot3?

Is this a Wot3, or maybe a triple Wot?

I don't yet have the motors I want to use (waiting for stock) but these are the motors I have around the place and I couldn't resist setting it all up for testing. The lead plane's motor is 2200Kv, which draws about 180watts with a 2 S1P battery and 6x4" prop. The other two motors are identical.

I ran it at full power for about 2 minutes without any problems. There is some flex and bounce in the cf tubes, but they always come back to a straight and square layout. I wonder how much of that I can tolerate? You can see it still needs to be tidied up. - control throws, balance etc.

Weather forecast is not good for the next few days.

All ideas gratefully received, as always!

Nick
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Old Jan 27, 2011, 09:56 AM
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Is this a Wot3, or maybe a triple Wot?


All ideas gratefully received, as always!

Nick
Wot? Wot's a Wot?

Wait for a calm day when there's no-one else at your patch.

Take lots of pictures

Fly it, whatever it's called.

If it flies, stand by for victory parades, scantily clad aeromodelling groupies throwing themselves at you, the usual boring stuff.

If it doesn't, sneak home with remains in car boot, don't mention it again. Possibly build something more conventional, but still sparkling, to make folk forget what you were up to last week/month/whenever.

D
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Old Jan 27, 2011, 10:25 AM
What could possibly go wrong?
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If it doesn't, sneak home with remains in car boot, don't mention it again.
Very good advice Dereck! I shan't forget.

cheers

Nick
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Old Jan 27, 2011, 10:33 AM
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There is some flex and bounce in the cf tubes, but they always come back to a straight and square layout. I wonder how much of that I can tolerate?
Nick, I really do look forward to hearing (and hopefully seeing) how this one goes. For me, the main worry with the flexing of the frame would be if it allowed the lead plane to lose it's positive incidence with respect to the the wing men, which could cause a 'tuck under' problem. I would make sure that you have plenty of down travel on the forward ailerons (elevators), just in case.

Good luck!
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Old Jan 27, 2011, 12:02 PM
What could possibly go wrong?
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I would make sure that you have plenty of down travel on the forward ailerons (elevators),
Thaks Trevor. Something similar crossed my mind. The original ailerons may have been big enough for the individual planes, but they don't look big enough for elevators to me. They're just 20mm TE stock, whilst the chord goes from 160 to 120mm. I increased them to 30mm and I'm wondering if I should do the same with the ailerons on the wing men's planes. They will have some differential, so I think they will effectively just cut the lift on one side or the other, with an increased moment. As long as I get the balance right, laterally, they should be OK as they are. The rudder panels look as if they'll work well. There is a little dihedral in the original planes.

I'll try some fast taxi-ing before I pull the elevator back. Eek!

cheers

Nick
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Old Jan 27, 2011, 04:22 PM
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Trevor's web site

Nickchud
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You should have a look at Trevor's excellent web site..here.
WOW!! Trevor is truly a treasure of the modeling world! I had seen pictures of some of his models without the impressive details.
I love his Stearman which looks just like the one my brother owned and gave me rides in as a kid.
Trevor, why not design a canard for us?
Charles
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Old Jan 27, 2011, 05:42 PM
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Originally Posted by nickchud View Post
There is some flex and bounce in the cf tubes, but they always come back to a straight and square layout. I wonder how much of that I can tolerate? You can see it still needs to be tidied up. - control throws, balance etc.
I'd be worried about the twisting of the rear wing at the centre joint. If there is any kind of flutter problem with the main wing its likely to be a fairly hectic incident. Whatever happens, I'm interested to know the result!!
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Old Jan 28, 2011, 03:01 AM
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Trevor, why not design a canard for us?
Charles, flattery will get you (almost) everywhere, but it would take more than that to get me drawing plans! The Stearman was indeed my own design but it only got published some six years later when Len Whalley insisted that I let him draw it up.

Who knows, maybe if I do get around to the MkII Stanger, one of you Canard CAD wizards might take a fancy to it
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