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Bobcat 50 Ideal Airfoil

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Bobcat 50 Ideal Airfoil

Old 08-03-2008, 12:42 PM
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tizer33
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Default Bobcat 50 Ideal Airfoil

Hi i wanted to ask if you were to build a bobcat style plane what would you use for the airfoil?
Would you use foam or built up wing?
I have the basic Profili program but am swamped by the choices.
The existing wing has a root chord of 470mm, Tip chord 180mm, step back on tip rib is 420mm and the span is 560mm
The naca airfoil 2410 which modified to a 1.5% chord is the closest i found to existing rib.
What would you use i would like to make new wings as the old ones are no more
Thanks
Tim.
Old 08-03-2008, 01:00 PM
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stuartrobm
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Default RE: Bobcat 50 Ideal Airfoil

Hi Tim,
I am not familiar with the bobcat, however, if the naca 2410 is very close and the original flew okay then I would probably go with that.
Good luck.
Stuart
Old 08-03-2008, 01:25 PM
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Default RE: Bobcat 50 Ideal Airfoil

It fly very well.... straight into the ground!
I only broke the wings though, it pushed the gear and half the ribs up through the sheeting
heres the plane though http://www.nitroplanes.com/newsibo5051a.html
Old 08-03-2008, 05:13 PM
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Default RE: Bobcat 50 Ideal Airfoil


ORIGINAL: tizer33
......
The naca airfoil 2410 which modified to a 1.5% chord ......
I'm not sure what you mean about a 1.5% chord. 1.5% of what? I'm assuming this is a typo or misunderstanding?

For high speed planes a simple and thin symetrical airfoil is best. It's the fastest and it'll still fly well. For something like the Bobcat you linked to I'd suggest a NACA 0008 or so. This is a simple symetrical section with 8% thickness. If this results in a wing that is thicker than the stock one you broke then choose a thinner last number but keep the first three 0's. A 2410 is thicker than you want and would have more camber than you need. The camber and thickness will hold back the high speed aspects of the plane.

Another option would be the Selig 8020 symetrical airfoil and thin the profile at the root using the "Process" option in Profili to reduce the thickness both top and bottom equally until you have the same thickness of airfoil as the original.

Sheeted foam or built up and sheeted. Either is an option and it's up to you and what you are most comfy working with. But either way I would not suggest you leave any of the wing open bay with covering over it. This is a high speed model and it'll benifit from a really smooth and rigid airfoil surface. And that means no covering over open structure areas on the wing.
Old 08-04-2008, 12:48 PM
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Default RE: Bobcat 50 Ideal Airfoil

Thanks for the reply the 1.5% came from a slider adjustment in profili it said 2% camber @ 40% chord i changed this to 1.5% and the airfoil fitted my wing better. The thickest part of the airfoil is 46mm which is 10% of a 470mm chord if i go smaller it wont match up too the root built on the plane
The only thing that worries me is i dont have a symmetrical airfoil to start with does a symmetrical airfoil produce similar lift?
I only have a OS55 pushing it along so no turbine speeds here maybe 100mph if im lucky, im more after good all round flight performance which probably comes from the airfoil you suggested
Thanks im a total newb to airfoil shapes
Tim.
Old 08-04-2008, 03:19 PM
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Default RE: Bobcat 50 Ideal Airfoil


ORIGINAL: tizer33

The only thing that worries me is i dont have a symmetrical airfoil to start with does a symmetrical airfoil produce similar lift?
When you are changing the airfoil on an existing design, the angle of incidence may not work with the new airfoil. When an aircraft is designed and developed, most everything that matters is adjusted to the wing. So if you change that wing you change the way the airplane "fits" it's new wing.

Cambered airfoils often work at AOA that are quite different than symmetrical airfoils AOAs. And the AOI you're working with, since it was setup for a cambered airfoil wing, is probably not going to match the AOI that the AOA of the symmetrical wing would have given you.

Your question might be better stated as, will a symmetrical wing work well in a fuselage root slot that was setup for the AOI of a cambered wing. And the answer is probably not.
Old 08-04-2008, 04:31 PM
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Default RE: Bobcat 50 Ideal Airfoil

thanks you have been a great help i shall copy the wing exactly
now foam or built up ribs hmmm...
Tim.

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