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Old Mar 13, 2010, 02:39 AM
Slope Drifting?
Lamborghini12345's Avatar
New Zealand
Joined May 2007
508 Posts
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The Effect of tape on LE an TE

Well today I put some reinforcing tape with single direction fibers on the LE and TE of my Glider in a length wise direction. On both they wrapped over about 20mm.

Now I was thinking that this would improve Glide because there would be less resistance between the air being broken at the front and leaving the back instead of the bare EPP.

So I took her out for a spin with the tape adding 4g to the wing and she sank in the wind and couldn't penetrate or Glide well at all. I thought this was due to the windy conditions and went home.

To get rid of weight I removed the TE tape and later went for another spin at the School up the road. It was still sinking at not penetrating well. So I removed the tape on the Polyhedral sections of the wing. Noticeable improvement in Glide, launch and turn. I then removed the middle sections tape and an instant improvement everywhere!

Now I would have though the tape would reduce drag but maybe the bumps from the reinforcing tape messed with the flow of air over the top of the airfoil? Or maybe the difference in surface texture caused uneven flow and drag or downforce?

Can anyone explain it? Is there a simple explanation?
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Old Mar 13, 2010, 09:09 AM
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pyrsly's Avatar
Poland, Śląskie, częstochowski
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I put My money on CG.
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Old Mar 13, 2010, 10:41 AM
turn, turn, turn.
Athol, Massachusetts
Joined Oct 2005
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I've been told that turbulators and other inaccuracies can either help or hurt the performance of some airfoils...depending on the location.

Usually its the luck of the draw.
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Old Mar 13, 2010, 02:29 PM
Slope Drifting?
Lamborghini12345's Avatar
New Zealand
Joined May 2007
508 Posts
The CG was not changed at all or at least not enough to make a huge difference.

Yeah I dont know what it was but it was interesting to find out why.
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Old Mar 13, 2010, 03:08 PM
Herk
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Virginia USA
Joined Jun 2007
1,652 Posts
This is interesting - it sounds somewhat like adding the opposite of turbulators.

Tell us more about this plane, construction materials, span, area, weight, photo perhaps.

You wanted to smooth out the airflow - is the EPP foam leading edge rough? What is the original texture like. What was the texture of the tape like when it was on the wing leading edge? Did adding it to the trailing edge cause a change in camber or cause a warp?

Good puzzle here
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Old Mar 13, 2010, 04:54 PM
Slope Drifting?
Lamborghini12345's Avatar
New Zealand
Joined May 2007
508 Posts
The plane is a converted Fenix 60, High density EPP, 60cm Span, 90sq inch area, 4.5oz/sq.ft wing loading, 90g.

The whole wing was sanded with 1000 grit and is smooth but has small holes between the foam bubbles. The original texture was not as smooth and a little furry. The tape is smooth to feel but had speed bump like bumps in it about .2 of a mm high. The trailing edge had a smoother corners to it as its fairly boxy without the tape on it.

Heres a picture, a bad one but a picture none the less.
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Old Mar 13, 2010, 08:40 PM
Herk
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Virginia USA
Joined Jun 2007
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Based on the numbers you have given here, it appears that this model will have a normal flying speed of less than 15 miles per hour. At that speed this wing will be operating at a Reynolds number of about 45,000. That is well below the critical Reynolds number for most airfoils. For that reason, turbulation should benefit the performance of the wing. Based on the picture, the natural texture of this wing should provide significant turbulation.

If your analysis of the behavior of the plane is correct, I suspect that with the smoothness of the tape on the leading edge, there is less turbulation of the flow over the wing, and so a loss of performance. I don't believe that tape on the trailing edge would have any effect.
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Old Mar 13, 2010, 08:46 PM
Slope Drifting?
Lamborghini12345's Avatar
New Zealand
Joined May 2007
508 Posts
That sounds like a sound analysis of the problem. There wasn't a lot of difference with removing the TE tape as I did it for weight, it was just noticeable though(or at least I think it was).
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