kaitak744
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Need Help Building A Plane

Sun Sep 03, 2006 5:28 am

For a science project, I am in an event where I am supposed to make a plane with a wing span of 50cm, maximum wing chord of 7cm, maximum stabilizer span of 30cm, and maximum stabilizer chord of 4.5cm. It will be powered by a single propeller which is turned by a rubber band (which is winded before flight). The objective is to have it fly for the longest possible time (before any part of the plane touches the ground). Now, does anyone have any design recommendations?

So far, I was thinking of 787 style wings with raked wingtips, but I don't know if that will be so good for a plane going this slow.

Thanks in advance for the help.
 
doug_or
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RE: Need Help Building A Plane

Sun Sep 03, 2006 9:23 am

simplfy. On a plane of that size going for endurance, you'll probably want simple wings. Either rectangular or tapered (as on a Cessna). Sweep will do nothing for you in the speed range you're going for.
When in doubt, one B pump off
 
kaitak744
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RE: Need Help Building A Plane

Sun Sep 03, 2006 11:45 am

I see. Now, I can play around with the design quite a bit. (I am making if from scratch) So, do you recommend perhaps an aft loaded wing? Fixed flaps?
 
lowrider
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RE: Need Help Building A Plane

Sun Sep 03, 2006 12:08 pm

I would keep the wing as clean, simple, and light as possible. Look to sailplanes for examples. I would also consider a canard configuration.
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Fly2HMO
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RE: Need Help Building A Plane

Mon Sep 04, 2006 10:07 am

Just buy one of those guillows kts and claim it as your own Big grin

But seriously, they make good planes, you could probably grab a kit and easily modify it to your likings.
 
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Starlionblue
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RE: Need Help Building A Plane

Mon Sep 04, 2006 10:23 am

I will agree with previous posters. A straight, simple wing can be made light and efficient. If you look at real world endurance designs like Proteus, Voyager and Virgin Global Challenger they all have long straight wings.

For stability, a slight dihedral should work. Something like the wing of the Kyosho Stratus http://www.kyosho.co.jp/web/products...rs/stratus1600/stratus1600-e.html. or Kyosho Ciero http://www.kyosho.co.jp/web/products...liders/ciero2000/ciero2000-e.html. My old Stratus was an extremely good glider with the engine off.

A foldable prop may be a good option to reduce wind resistance once the power has been extracted from the rubber band. You will find such props in most R/C motor gliders.

Proteus has an interesting planform but I don't know how hard a canard configuration is to get right.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
kaitak744
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RE: Need Help Building A Plane

Mon Sep 04, 2006 11:39 am

Oh, I forgot to mention a few things, sorry. The plane can't be a pre-built kit. I need to make it from scratch. This does however give me alot of design flexibility. Also, I have a prop which is about 18cm in diameter and 1.5 cm in chord. Sounds good enough for a plan this size right?

By the way, Doug_OR, Lowrider, FLY2HMO, and Starlionblue, thank you very much for your help so far.
 
bri2k1
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RE: Need Help Building A Plane

Mon Sep 04, 2006 4:17 pm

Quoting Kaitak744 (Reply 6):
I need to make it from scratch

The idea here is for you to experiment and learn about various airfoils. Asking others for any help diminishes the benefit of your own trial and error. You said this is for a science project; inot a competition, so why don't you learn what you can while you're at it?
Position and hold
 
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Starlionblue
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RE: Need Help Building A Plane

Mon Sep 04, 2006 8:56 pm

Try something weird, like a disc shaped planform. Big grin
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
jamesbuk
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RE: Need Help Building A Plane

Mon Sep 04, 2006 9:10 pm

Could you just do a flying wing, no fuselage with the prop on the front (or if your adventourous on the back)

Rgds --James--
You cant have your cake and eat it... What the hells the point in having it then!!!
 
doug_or
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RE: Need Help Building A Plane

Tue Sep 05, 2006 12:50 am

Quoting Starlionblue (Reply 8):
Try something weird, like a disc shaped planform.

Chord MIGHT be a problem there  Smile

Quoting Jamesbuk (Reply 9):
Could you just do a flying wing, no fuselage with the prop on the front (or if your adventourous on the back)

Very hard to balance out for a free flight model I would think

You haven't mentioned materials, are you doing a balsa and tissue construction? Are there any restrictions on materials used?
When in doubt, one B pump off
 
dw747400
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RE: Need Help Building A Plane

Tue Sep 05, 2006 1:31 am

I judge a similiar competion for the AIAA in Baltimore every year (electric power however, and larger--up to 95cm span), and there are two design concepts that always come out ahead. The first (and best) is a large blasa wing structure covered by thin clear membrane, and most people following this concept seem to use a twin boom tail configuration connecting to a single horizontal tail (because in this competion the planes are theatherd, you can get away without a vertical tail if you balance the aircraft well.) The wing is generally a thick cross section and massive area, most probably exceeding the dimensions you need to stay within.

The second, slightly less effective design might be more practical for you. It uses a straight, foam wing. Generally it is a higher aspect ratio than the balsa designs, and seems to work well.
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meister808
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RE: Need Help Building A Plane

Tue Sep 05, 2006 2:36 am

All I can suggest is to make everything as adjustable as possible. Mount each wing and each stabilizer so that the angle of incidence with the fuselage can be adjusted as much as possible. When making airfoils, they aren't going to be perfect, so making things adjustable allows for you to decrease the lift being made by your slightly more efficient right wing so that there isn't a constant left roll.

Aside from that, I'd just say experiment a lot, make a lot of different stuff and try it all out. I once had to design a plane with max wingspan of 11" to fly in a 24 mph wind-tunnel. I think we worked on that thing for a total of about 300 hours, and we eventually had about 10 fuselage designs and about 20 sets of wings, all interchangable, to work with. We kept trying stuff to see how it would work, and we eventually honed it down to a combination of 3 sets of wings on one fuselage that worked out well.

-Meister
Twin Cessna 812 Victor, Minneapolis Center, we observe your operation in the immediate vicinity of extreme precipitation
 
lowrider
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RE: Need Help Building A Plane

Tue Sep 05, 2006 12:28 pm

Here are some folks that do something that sounds similar to your project. The goal is to make the model fly as long as possible, in confined space. They do some amazing things with lightweight materials. They are fragile and will only work indoors. Maybe it will help.

http://www.indoorduration.com/IndoorDurationFrame.htmerw
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wingscrubber
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RE: Need Help Building A Plane

Wed Sep 06, 2006 9:07 am

STRAIGHT wings! NACA 4412 aerofoil section!
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