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Old Jun 12, 2007, 01:49 PM
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Ocala,Florida
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Charles, would u keep the canard and use elevons to or just omit. I can still leave it off thanks
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Old Jun 12, 2007, 06:11 PM
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Hi Charles, I love the delta shape wing. I want to ask why you choose a flat bottom wing for this design. Do you see any problem with using a symmetric section? I am debating myself at the moment to use a NACA2412 or NACA0012 for the main wing. Mine will be slightly higher aspect ratio and a bit more like a conventional canard than a delta.
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Old Jun 12, 2007, 11:06 PM
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Mustang, Either way I believe that elevons are the best. My two had ailerons and elevator but the elevator was not capable of recovery from a dive. The delta version with elevons which a friend had was a terrific flyer but loved to flat spin with a mind of its own. John 235, If you like slow flying,inside maneuvers and simple construction like I do then the flat bottom wing is good. They also seem to have more lift and do well in thermals. I enjoy the feel of flying symetrical airfoils but felt more comfortable with canard design using the flat bottom type. Best of luck with your designs and please show us some pictures. Charles
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Old Jun 12, 2007, 11:09 PM
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Thanks Charles I will couple the canard with elevons how would be the best way? I'm thinking up elevator on the canard with down on the elevons?like set up a pmix or what?
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Last edited by MustangAce17; Jun 12, 2007 at 11:12 PM. Reason: talking to my gf,quickly posted without detail
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Old Jun 12, 2007, 11:30 PM
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Mustang, The movements you suggest are correct. If anyone can tell me how to make my Airtronics RD 6000 control all surfaces please speak up. I have done V tail and elevons but have never added elevator electronically. Charles
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Old Jun 13, 2007, 12:54 AM
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Thanks Charles your a great help,glad to have you here
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Old Jun 13, 2007, 08:38 AM
Bernoulli+Newton=Lift
magic612's Avatar
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Quote:
Originally Posted by canard addict
Mustang, The movements you suggest are correct. If anyone can tell me how to make my Airtronics RD 6000 control all surfaces please speak up. I have done V tail and elevons but have never added elevator electronically. Charles
Charles, I'm not sure exactly what you're asking...? If you've done elevons, the elevator function is already electronically mixed into the elevon function. What is it that you're looking to do differently? Do you mean adding the canard flaps to move in tandem with the rear wing elevons? If so, that's how I set up the J1-31, and I have a picture that details the linkages necessary.
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Old Jun 13, 2007, 02:17 PM
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Yes Magic, I want to add the canard flaps into the action without linkages. Probably too much to expect from my radio.
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Old Jun 13, 2007, 03:42 PM
Bernoulli+Newton=Lift
magic612's Avatar
Somewhere south of Chicago, IL
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Charles, I think you could accomplish that by using a "Y" connector from channels 1 & 2. Have one set of servos for the back wing, another set for the front. Just remember to have the right rear servo "Y" with the front left one, and vise-versa. That'd do it. But I'm not sure how to have a single elevator servo up front with elevons, or something like that.

Another option is to use flaperons - I did this with another foamie canard. Probably not what you're looking to do, because the elevator function is not mixed with the aileron/flap function on the rear wing. But it allows for some very short landings - crank the flaps down and pull the elevator stick back, and the plane comes in almost harrier-style. It's just a little tricky working the elevator, throttle and flaps simultaneously!!
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Old Jun 13, 2007, 09:16 PM
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There is genius and magic here. Thanks very much, Magic 612!!I am anxious to see it work. I will report back when I can try it. I am wondering if the rear wing could stall with UP reflex applied while the canard wing continues to fly even with DOWN flaps? Should the static margin be increased? Can anyone comment here? Charles
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Old Jun 13, 2007, 10:14 PM
Bernoulli+Newton=Lift
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Well, on my mechanically linked J1-31, the rear wing elevons go up while the front canard flaps go down when I pull the elevator stick back towards me. So that would be what you're referring to, correct?

If so, I can state that I've found it impossible to stall my J1-31 doing that. Granted, it has a significantly larger canard than most canard planes, so there may be wide differences of flight characteristics depending on the design. But I flew the J1-31 with the intention of trying to stall it with full up elevator; couldn't do it. It would just slow down, nose up, and eventually slip to one side or the other, or lose altitude. But it wouldn't stall for anything.

Besides, pulling back hard on the elevator stick (with the linkages done in that configuraton) from a dive is what allowed the J1-31 to *snap* out of the dive so quickly - I think.

If I understand the idea of a canard plane correctly, the idea is that it is inherently far less likely for the rear wing to stall anyway, because the canard will stall first, causing a gentle stall (if any at all) for the whole plane. I may not be remembering that correctly, but I thought that's how they worked (in general).
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Old Jun 14, 2007, 04:00 AM
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Dive recovery of delta canard.

I also like slow flying aircraft with low wing loadings. Back in the days of heavy brushed motors and NiCd batteries, I also used flat bottomed cambered airfoils. With modern equipment I find that symmetric sections give generally enough lift.

I wonder if the problem with the ineffectiveness of the canard elevator when the model is diving might be related to the use of a cambered airfoil section. Although I am not familiar with the 'firebat', I assume this is a low aspect-ratio wing with a cambered airfoil. I have read that most cambered airfoils cause a negative pitching moment, but I don't know if it is large enough to cause the dive recovery problem you found. If you look at some of the airfoils designed for tail-less aircraft some of these feature reflex trailing edges to reduce the negative pitching moment. That is very similar to adding some 'up elevevator' via elevons. I don't have expereince with this type of model, so I am keen to learn from the expereiences of others.
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Old Jun 14, 2007, 07:34 AM
Rhinebeck CD-99,00,01,02
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New Bern, NC
Joined Mar 2001
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John235

"Negative pitching moment in cambered airfoils" You rang a bell with that statement. My Firebat flew great, fast or slow, and the only negative comment I ever had about that model was in a diving fast fly by the nose would drop. I nearly lost the model the first time it happened. Once I was aware of the problem, I was sure to give myself a bit of extra altitude when doing a fast fly by, but it would do it every time. I sold it at NEAT a few years ago. Still wish I had it back. It also had a motor overheating problem what with the motor encased in foam without any air vents, but that was an easy fix. Tom
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Old Jun 14, 2007, 09:07 AM
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Magic612, I feel much better about the elevon-flap control system now. It seems that if the double delta is set up as a canard, the front wing should stall first and if lift is added up front and subtracted at the rear it hopefully will still stall first with the large rear wing? Agree??This may require more thoughts from everyone. John235 and Tom Smith, I agree with all your thoughts and find them interesting. The Firebat had several faults in my opinion: The canard was near the COG, was undercambered,was small and had negative pitching moment.The entire canard moved which could have caused high speed stall. These thoughts came to me with your help. The model needed elevon and canard control. Mine was set up with aileron and canard control. It had a hot Mega and the eight cells were moved forward for balance. At launch with positive trim it zoomed upward to a safe altitude and was trimmed DOWN canard for level cruise. When I turned it back toward me with full throttle, the negative pitching moment took over and it tucked downward like a Wingo, and resembled a rainbow at full throttle into the ground. Had I cut the throttle, the model probably would have recovered.It was a beautiful foam explosion right near my feet. The troops LOVED it! The canard was not capable of controlling UP at speed. This was apparent on my first Firebat with same motor which was launched at neutral trim and turned toward a row of eight foot trees. I applied full UP and it wobbled into them. Two Firebats, two flights. Charles
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Old Jun 14, 2007, 10:31 AM
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Double Delta

Here are shots of my new design which I hope will add thoughts and questions to our discussion. Pardon the fine line pencil. Any thoughts on pusher problems on Deltas? Charles
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