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Old Jan 14, 2011, 11:06 AM
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Don Stackhouse
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Note, Nick and Charles have been experimenting with what amounts to a tailless delta arrangement, where much, if not most, of their elevator authority comes from someplace other than the canard. Their canards are undersize enough that they are not a main determinant of pitch stability, which is part of what keeps them out of trouble. They are also trying to deliberately flat-spin their planes, which means they are deliberately stalling the wing. You could do that here as well, but that would require downsizing the canard and using elevons on the wings for much of your elevator authority. Even so, if you have elevators on the canard, you could still have some "interesting" stall characteristics.
Don, I take your comments as a touch of approval and it has, coming from you, put my spirits on cloud nine. Nick must also feel proud of his creation.
That Traplet machine put the cap onto a super start to my day. The color scheme looks like a maroon version sitting on top of the white one. I want that model in my hands with canard elevator control!!! Maybe a twin Delta Duck will be possible.
Charles
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Old Jan 14, 2011, 11:24 AM
More Motors, More Fun... :-)
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Phoenix, AZ
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Link to Contra

Quote:
Originally Posted by nickchud View Post
Don

Twin props sounds like an interesting idea. Remember this one, unearthed by Dereck early last year and published in QEFI magazine

Plans are available from Traplet.
The link to the plans are here
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Old Jan 14, 2011, 02:36 PM
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Originally Posted by nickchud View Post
...On the other hand, the Starships all work perfectly well, including gentle loops and they don't have any pitch control except for the canard out in front. My Polar Duck has a tractor prop mounted on a rear pylon and it gets all its pitch authority from the canard at the front.
But it doesn't have the canard sitting in the middle of the propwash, right behind the propeller.

Quote:
...I don't think my little extra panel behind the prop makes much difference at all...
It compensates for the nose-down effect of the high thrust line. Remember how you had trouble keeping the nose up on takeoff until you added it?
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Old Jan 14, 2011, 04:01 PM
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Nick then Don
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...I don't think my little extra panel behind the prop makes much difference at all...

It compensates for the nose-down effect of the high thrust line. Remember how you had trouble keeping the nose up on takeoff until you added it?
At full speed Nick's comment may be true but on take off, Don nailed it on page 318, post 4765. Nick verified it in post 4767. The discussion around those pages regarding the Polar Duck was outstanding and just illustrates how great things can be achieved with various inputs.
Charles
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Old Jan 14, 2011, 06:49 PM
who has rabbit ears down
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Hi Gang! I see others are at least interested in the Contra! I'm planning that one about 5 birds away from present builds.- 'ceptenfer's no contra rotationals.
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Old Jan 15, 2011, 04:02 AM
What could possibly go wrong?
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Hi Johnny! How are those present builds coming on?

Don and Charles... fair enough, I stand corrected.

Tony, I think the simplest arrangement, tractor or pusher, usually has the thrust, wing and canard all in the same plane. Tractor works perfectly well for the LongEZ and Starship. you can keep the noise and vibration down if the prop has a reasonable clearance behind the wing, specially around the circumference.

I like my pylon approach because it's easier for belly landings. But then you have to make allowance for the rotational effect. That's when some kind of horizontal (minus a few degrees) surface in the prop-wash is useful, though I'm still not convinced it needs to have any control panel in it.

Must rush, sorry not to have thought it all out more carefully!

cheers

Nick
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Old Jan 15, 2011, 09:30 AM
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That Contra is beautiful, and it makes a lot of sense because you get those motors right near the CG.
RE
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Old Jan 15, 2011, 09:36 AM
RC did this to me
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Originally Posted by nioa View Post
The link to the plans are here
sweet!!
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Old Jan 15, 2011, 10:34 AM
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Nickchud
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Don and Charles... fair enough, I stand corrected.
You are a great sport, Nick. After thinking back through our discussions on your Polar Duck I am wondering how or if it may be improved. I feel that the rear stabilizer needs to be at 90 degrees to the prop to avoid any rotation with increasing rpm unless the elevator calls for it. Secondly, it seems that you may have excessive climb at full throttle. This is based on your comments on reducing the canard size, not moving the CG rearward, adding down trim with speed and moving the canard out of prop blast.
Here are a few things to consider to reduce high speed climb: Reduce the down thrust to rotate the nose more downward. If the horizontal stab is at 90 degrees to the prop, it will now have less tendency to lower the rear end with speed. Change the high lift canard to symmetrical with only one degree of incidence.
Balance the model's fuselage level on the calculated CG. These are just ideas to kick around.
Charles
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Old Jan 15, 2011, 11:24 AM
What could possibly go wrong?
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This is what I've been playing with since I got home... Mine is the mini Polaris, ws is 22", AUW is 10oz with 800mAHr battery. She flies and lands well even in winds of 10 to 13mph. You have to stay awake, it's very nippy!

I bought the kit see how the pylon approach works. They use 2deg of down thrust for the motor and the same for the tail plane. It works a treat, I have to say. The only noticeable pitch surprises come when you cut the motor completely and the drag from the prop causes a pitch up.

What is now going through my mind is to scale it up to 44" ws and add small, all moving canards, like the Eurofighter we saw at Stone Mountain Park when I was there with Charles. I'll change the airfoil from flat board to something symetrical and 10-12% thick. What I would hope to see then is good slow-fly, high alpha stuff.

What could go wrong?
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Old Jan 15, 2011, 11:26 AM
who has rabbit ears down
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Hi Gang! The builds are "ahead of schedule" as per the last couple years! here's a preview,
as I did some leapfrogging at Crimson for the guys.
http://www.rcgroups.com/forums/showp...&postcount=178
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Old Jan 15, 2011, 11:27 AM
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Thank you Guys

I have modified my original design. I hope it will reduce some issues a little.
Quote:
In addition, your swept wing and canard certainly look very cool, but the sweep is unnecessary at the speeds this aircraft will be flying, and creates other problems of its own.
I have reduced the wing sweep a little.
Quote:
Not have enough elevator authority to flare for touchdown on landing. At full power it might act like vectored-thrust, with so much elevator authority that you can flip the plane around completely backwards in flight.
Not good at all to me. so I'll change it to a pusher, I think I'll have problems with the weight distribution but I'll try to build the wing light
Quote:
would help some of these issues would of course be a pusher prop (I can't believe I just said that!!).
Quote:
a pusher arrangement causes significant efficiency losses for the prop, among other things, such as vibration, vibrational stresses, higher and more annoying noise
I'll have to live with that.
Quote:
safety issues on launch
I didn't want to do it but if possible I will add landing gear. Its embarrassing question but I have never designed a landing gear before. Is it possible to design a landing gear which handles grass and tracked true without a rudder or steering?

Tony
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Old Jan 16, 2011, 01:34 PM
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Nickchud
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What is now going through my mind is to scale it up to 44" ws and add small, all moving canards, like the Eurofighter we saw at Stone Mountain Park when I was there with Charles. I'll change the airfoil from flat board to something symetrical and 10-12% thick. What I would hope to see then is good slow-fly, high alpha stuff.
That sounds exciting, Nick. The Eurofighter and other jets with canards just reinforce my strong feelings that the canard wing has a needed place in aircraft. Properly used, I believe that it not only aids in steering but adds safety. Disadvantages are added costs and pilot visability along with others which Don can name.
On the Polaris, my worry is about the distance from the canard's lift to the CG. Elevons are a must have to assure nose up control. I am happy that you are interested in the Eurofighter style.
Charles
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Old Jan 16, 2011, 01:50 PM
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Don
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would help some of these issues would of course be a pusher prop (I can't believe I just said that!!).
Tony, It seems that Don likes the power up front better.

A tricycle LG would work well with nose steering. My D Squared canard build log shows how a torsion main gear is built into the wing. Just go to post #1 here, last paragraph and find what page the build starts on.

Quote:
In addition, your swept wing and canard certainly look very cool, but the sweep is unnecessary at the speeds this aircraft will be flying, and creates other problems of its own.
Does the sweep here refer to the canard?

Charles
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Old Jan 16, 2011, 03:14 PM
What could possibly go wrong?
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Hi Charles
Quote:
Elevons are a must have to assure nose up control
My plan for the enlarged Polaris would be to keep the elevators and ailerons just as they are, but add the canard for maneuverability. The length of the plane would be 60" v a span of 44".

I'm trying to think what our experts would say about that and have a nagging feeling that it might be "so what?". To which I might say: if the span and length are doubled, the wing area will quadruple. So will the control surface areas, but not their moments. Rolling and pitching will be more sluggish. We all know that small fast planes can be hard to manage, while bigger ones respond more more gently. I don't know if that justifies adding some pitch control at the front, but it feels like a good idea. The addition of an airfoil instead of flat board wings should give it better low speed handling.

It's a bit of a long term plan, this one. There are lots of other jobs in the pipeline first. Wait till you see my 3-plane formation, presently under construction.

And anyway, I'm finding Tony's plan much more interesting. I vote for a pusher, but I might propose that the TE between the two fins is kept square, not swept. This will keep the prop circumference further away from the wing. I know from trial and error that this would reduce the noise.

cheers

Nick
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