"1/2 A" & "1/8 A" airplanes These are the small ones...more popular now than ever.

my 1/2a biplane

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Old 03-25-2003, 01:40 AM
  #1
gusman
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Here is my 1/2a biplane so far. this my first scatch built airplane. It's got a 22" wingspan with a fully symmetrical airfoil. It is 4 channels and i plan to put ailerons on the bottom wing only. I have no idea what the weight will be, but i want to be able to hover and do pretty good aerobatics, so what size engine should it be and what kind, cox??? i want throttle. My last question is do i need another spar behind the last spar and the trailing edge?
Thanks
gus
wups forgot to ask if i need wing incidence?
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Old 03-25-2003, 01:42 AM
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here's my plans or design or whatever ya wanna call it
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Old 03-25-2003, 02:04 AM
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your spars probably adequate if you put in 1/16" vertical shear webs on main spar. Hover? well it will have unlimited vertical w/074 below 19 oz., but not true hoverability. will prop hang, but you would need 12-13 oz. to hover with authority and be able to pull out. hard to acheive. incidence helps. on staggered wings, it helps to have a little positive incidence on the forward wing so it stalls first. otherwise you wind up in a tail heavy condition! if you measure and make forward wing 1/16" higher at leading edge than rearward wing, that should do.

have you entered the design contest? your plane looks like a likely candidate, if it is not too late to enter!
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Old 03-25-2003, 02:14 AM
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thanks for the tips. I think the top wing will be farther forward, but i just drew my plan like that because of the clancy stagger bee with the top wing back. they say then the bottom wing will stall first and you will be flying on the higher wing. but i dont' know yet. any other tips would be apreciated
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Old 03-25-2003, 02:44 AM
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Those are some thick wings! With airfoils that thick you'll have very soft stalls, so that shouldn't be a problem. It is a lot of wing for a little motor to pull though the sky though. I'm guessing 2" thick x 44", that makes a plane with a frontal area of about 90 sq in., you asking a lot from a little motor. I'm not an expert, I play one on the Internet though, but I'd say most 1/2a's are closer to 18~20 sq in frontal area. It should turn on a Canadian dime and give you $.09US in change, won't be fast though. Neat plane.
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Old 03-25-2003, 02:56 AM
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with a mere 22" wingspan I would think a .049 NORVEL would be the ticket however as WildFred has mentioned the .074 would make the "fun Factor" go way UP!!!!!!

looks great so far!

design contest mabey?




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Old 03-25-2003, 06:42 AM
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Quote:
Originally posted by gusman
...i plan to put ailerons on the bottom wing only
...they say then the bottom wing will stall first and you will be flying on the higher wing. but i dont' know yet. any other tips would be apreciated
I built a 20" span bipe with ailerons on the bottom wing only. Whtn the bottom wing stalls and it is flying on the wing without ailerons, things can get pretty hairy.

I only have 1 other bipe with ailerons on the bottom wing only, but it is a Sopwith Pup and it flies well on rudder. I won't build another bipe without ailerons on both wings unless it can fly on rudder control.


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Old 03-26-2003, 08:08 PM
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thanks everybody, i didn't even think of not having control when the wing with the ailerons stalls. should i put a servo for each wing or two in the bottom wing and connect the ailerons with pushrods? about the design contest, i'm not even sure it's gonna fly considering this is my first scatch built plane. maybe. one more question, what is the best covering for small planes like this that isn't 5 bucks for a two square foot sheet. thanks
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Old 03-26-2003, 09:13 PM
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I've done bipes with push rods between ailerons, one servo on each wing and one servo per aileron. I just go with whatever seems to be the easiest for that particular plane.

I use Ultracote for all my small stuff, just because I'm familiar with it.

If you make sure your balance is correct, it'll fly. Are the wings swept?

Here's a diagram illustrating how to calculate the CG of a bipe where 1 wing is swept and the other is straight. Just replace the .3 in the formula with whatever balance point you wish to use. For example if you want to balance at 25%, then use .25.

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Old 03-31-2003, 05:13 PM
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A word about incidence. I'm not an expert on bi-planes, however I've been doing a lot of research before building my Smith Miniplane. All the self proclaimed experts say to set the top wing at -1 degrees and the bottom at 0. What this will do is on a landing, if the bottom wing stalls, the top wing would still be flying and it basically acts as a monoplane. With those thick airfoils you might not have this problem. L.O.L.
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Old 03-31-2003, 07:48 PM
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Your little bipe looks a lot like a little thing that I designed using a wing from a Tiny on the bottom and a slightly extended version on the top. I think that incidences were either 0 of -1 on the top. 26" top wing and 24" bottom, 9" chord that makes for a whole lot of wing for a 16 oz plane. There was so much drag that the .061 had a hard time with anything vertical, and whatever speed I could gather was soon lost to drag. Real fun, had 2"full-span ailerons on both wings. Check my photo gallery for the pics and I think that I have plans on my website. http://www.aft-cg.freewebspace.com/photo3.html
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Old 04-01-2003, 01:16 AM
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thanks everybody for your tips. i find that you people are much more willing to help me and give me tips on the 1/2a thing. anyway- about the thickness of the wings, i got the airfoil off the fun fly forum so hopefully it will fly like one of those. but i guess it's too late now anyway unless i build new wings. but thanks again everybody.
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