Model Aircraft Design for High Lift


by sashankhrao
Tags: aircraft, design, lift, model
sashankhrao
sashankhrao is offline
#1
Nov19-08, 01:46 AM
P: 19
Hi,

I need to make changes to an existing design of a model radio controlled aircraft to increase its lift to carry more payload. Pls confirm my ideas and any suggesstions would be really appreciated.

Using wingtips to reduce induced drag and increase lift.
Will a Dihedral affect lift in any way?
Is there any advantage of using a twin vertical stabiliser tail design on lift? what is the advantage of a twin tail over the conventional one?

Also among the wingtips pls suggest which of the below could be best suited for higher lift:
Winglet, Wingtip fence, raked wingtip, blended wingtip.

I would really appreciate any help on the above.

Thanks!
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redargon
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#2
Nov19-08, 03:25 AM
P: 348
this has been discussed before,
http://www.physicsforums.com/showthread.php?t=259012
that might help.

wingtips can reduce drag. I'm not sure how much they're going to help you relative to the size of your model.
can you give us more of an idea about what you mean by twin vertical stabiliser tail. Do you mean a V-tail or one like from an avro lancaster?
Dihedrals make lift generated have vertical and horizontal components, to stabilise an aircraft. It doesn't generate more lift, it actually decreses the "up" component of you lift, ie. this will not help to cary more loads.
what about changing the aerofoil shape and/or making the wings longer/broader?
what about making the aircraft lighter so it can carry more?
FredGarvin
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#3
Nov19-08, 06:51 AM
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Wingtips are the source of most drag. If it weren't for wingtips we could get away with using infinite length wings.

Winglets on the other hand...

redargon
redargon is offline
#4
Nov19-08, 08:55 AM
P: 348

Model Aircraft Design for High Lift


sorry, wrong vocab. Winglets not wingtips. I think the OP is refferring to winglets when they say wingtips.
Topher925
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#5
Nov19-08, 09:11 AM
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P: 1,672
I think the OP is confused on what wingLETS actually do to an aircraft. Winglets can only increase your L/D ratio by decreasing the Drag, not increasing the Lift. However, this can be useful if your planning to achieve more lift by putting a larger power plant on the airplane.

I'm assuming that you want to increase your payload without changing the wing loading or airfoil of the plane. If this is the case your only real options are to increase the angle of attack of the wings and get a more powerful engine. Also, anything you can do to reduce drag is going to help as well.
sashankhrao
sashankhrao is offline
#6
Nov19-08, 09:30 AM
P: 19
Hi,
Thank you very much for your reply. The wing span of our craft is 2.5m just for your reference. The tail is like the one from the avro lancaster. Would winglets be useful for the main wing for our model? I understand that winglets reduce the downwash and hence reduce induced drag. I’m planning to do a CFD analysis to see the flow and compare the difference between using and not using wing tips.

Also we have done some analysis on various aerofoil shapes and chosen the s1223 aerofoil. Any suggestions as to which foil would provide the best lift characteristics? We are also looking at new material to reduce weight. Do you have any suggestions from your side with regard to this? I need to increase the lift without changing the engine.

I really appreciate all the advice.

Thanks!


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