Any R/C aviators? I need some info. - Page 3

mikester · 08-28-2007, 03:05 PM

Rob; what about a delta wing design - it adds to wing area significantly while reducing the complexity of a multi wing design.

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Mikester,

Delta wings have traditionally been incorporated into lifting bodies that require speed and lift. Look at the XB-70 Valkyrie, SST and NASP. The sacrifice is directional stability. Meaning speed isn't in the design and the width of the wing would require elevons, tabulators to control that we have no computers to control in this project. All we have is 5' x 4'. still not enough wing area. The loading is too high...

What I want everyone to understand is: A certain amount of air traveling over a wing airfoil produces only X amount of lift. Increase the velocity and the lift increases exponentially but so does drag. So we need to get this beast in the air at the velocity we can ultimately accelerate the craft to in 75 feet with all the parameters understood. Thats with 7 pounds of dead load. The airframe mass and power pack, radio, wheels and every other potential thing to come along. My best educated guess will be 12 pounds fully loaded. This can be done. It require allot of wing and thrust. Believe it or not the thrust part is easy with digital MOSFET technology. Brush less motors create a tremendous amount of torque/energy. For 2 pounds in mass I could get 12 pounds of thrust. unbelievable. I have some ideas that I know will work. I thought about it on the way home from work...

Matt, keep in touch..Watch an old movie called "The Spirit of St. Louis" Jimmy Stewart. Similar problem you have...Great movie.

Bob

unimog406 · 08-28-2007, 04:53 PM

tower hobbies, look up the 'zagi'
simplist, yet most effective, I own and fly two
and they are both INDESTRUCTIBLE
literally, should be quite easy to make as well

mikester · 08-28-2007, 10:03 PM

I've seen plenty of small scale flying wings that did not require specific computer controls but again we're looking at a much smaller scale. My question right now is that 7 lbs total weight for the plane or as you said around 12lbs. If it's 12lbs I really question the feasibility of this whole prospect because he is also limited to 40amps max. I've done quite a few smaller electrics and it is quite easy to go over 30 amps with something weighing just over a pound. I have a 21 oz Extra that I do 3D with and I'm pulling over 20 amps with that on a 3 cell lipo (11.1v @ 1320 mah).

I had a 12 lb model that had an 81" wing (vs 60" we're talking here) that I flew with a 1.2 cu inch 4 stroke. Not a small or light model by any means but it was a bit of a floater - it required probably about half of the power it had I suppose. That is still quite a bit more than 40 amps worth.

So a biplane at 60" per wing becomes roughly 120" - that is considerably more wing area (obviously) but I think a tri-plane would be going a bit too far along that path and you're throwing "simple" out the window.

Dutchie · 08-28-2007, 10:32 PM

my parkflyer made of carbon and balsa is pretty lightweight . It weighs just 220 gramms with lipo cells the wingspan is 110 centimeter. I think the servo,s are 4 gramm each

onewhippedpuppy · 08-29-2007, 03:05 AM

Mike, I think Bob is on the right track here. I won't be able to get it done with sheer power due to the 40A limit, 4lb max for a battery, and no LiPo. So, lots of wing area and light wing loading is necessary to get it off of the ground in the required 75 ft. As much as I don't like the extra work associated with 3 wings, I'm starting to think it is necessary.