Clark-Y Airfoil Ordinates - RC Groups
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Mar 07, 2012, 03:32 PM
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Clark-Y Airfoil Ordinates

Hi all

I understand that using the Ordinates can be found online/in books. But if you have a delta winged RC-aircraft will it be ok to take and use the coordinates for an airfoil from a reputable book/online.

Thank you all

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Mar 07, 2012, 03:54 PM
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Whiskers's Avatar
Mar 07, 2012, 04:13 PM
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I was told that "A delta is a delta. A Clark y is a Clark y! U can't mix the two. U will have to find co ordinates for a delta similar design to yours."
But a delta is a Wing configuration whereas a Clark-Y is an Aerofoil section, two different things... Right?! Confuses me
Mar 07, 2012, 05:33 PM
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Whiskers's Avatar
There is no reason that a Clark-Y airfoil would not work with a delta layout.
Given the usual proviso for a bit of reflex on the control surfaces for longitudinal stability.
How come delta? What has happened to the PBF idea?
Mar 07, 2012, 06:01 PM
Registered User
Well it was decided on by others for a delta configuration. A new design, a new layout, a new everything.
Thanks for the feedback, i have another Q... how can I get the airfoil coordinates for use in my delta design?
Eagerly waiting for your reply my friend
Mar 07, 2012, 06:28 PM
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Whiskers's Avatar
You are on the wrong track with the delta.
You came to us with the problem of being tasked to build a plane with a stupidly heavy motor and a stupidly small wing span.
In other words you have a major wing-area problem.
And now you are giving away about one third of that precious wing area by going for a delta plan-form.
That is unless you are making the delta very long. In which case the Clark-Y will not be suitable.
Mar 08, 2012, 02:26 AM
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slebetman's Avatar
Originally Posted by Whiskers
And now you are giving away about one third of that precious wing area
It's even worse. A pure triangular delta should have only half the area of a square (formula for triangles is 1/2 * width * height). Of course most deltas are not pure so you wouldn't lose that much surface area but you'd definitely lose more than a third.

But I do beg to differ a bit on the suitability of a delta. Deltas are much more stable than planks especially at high speeds so even though you'd basically double the wing loading you may end up improving your chances of success.

Also, even though deltas have significantly less surface area compared to a square they do have significantly larger surface area per wingspan compared to traditional rectangular wings. They can also be built with much less structure (spars etc) compared to rectangular wings.
Mar 08, 2012, 02:37 AM
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slebetman's Avatar
Oh, forgot to comment about the suitability of the airfoil.

Clark-Y generates significant turning moment. For flying wings and deltas this means you need significant reflex (up elevator trim) to counter it. IMHO the Clark-YH is more appropriate due to the built-in reflex. I'd personally recommend using a symmetrical airfoil for deltas. Just pick something reasonable from the NACA series. If you want a good asymmetrical airfoil then I recommend using either MH45 or MH60:
Mar 08, 2012, 07:04 AM
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Whiskers's Avatar
If you look at a delta with reasonably wide tips you'll find my "about one third" is reasonable.
Wing area would do more for them than some fancy dude airfoil.

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