To Mike Borgelt, Anthony Smith or anyone else who knows.
I am really confused about this drag thing so please stay with
me on this whilst I explain.
My confusion surrounds the speed range at which defects in
the BOTTOM surface of the wing effect the performance most. Do
defects (read extra drag) on the bottom surface of the wing hurt the
low speed performance most or the high speed performance most?
(As I understand it the top side produces more drag than the bottom
side, three times as much at 40 kts, two times at 50 kts and 1.5 times
at high speeds.)
Mike Borgelt said;
> "the bubble is usually smaller on the top surface because to
>get one you need a favourable pressure gradient for laminar flow and
>low Reynolds numbers. This occurs on the lower surface at low
>speeds/high angle of attack. On the top surface the low angle of
>attack case occurs at higher speeds where the Reynolds numbers
>are higher and hence the bubble doesn't form or is small."
Does this mean;
1. That anything that prematurely triggers a bubble on the top
surface will be a greater drag penalty than something that prematurely
triggers a similar bubble on the bottom surface?
2. That anything that prematurely triggers a bubble on the top
surface will effect the high speed performance more than the low
speed performance. (Because on the top surface the low angle of
attack case occurs at higher speeds where the Reynolds numbers are
higher and hence the bubble doesn't normally form or is small.)
3. That anything that prematurely triggers a bubble on the
bottom surface will effect the low speed performance more than the
high speed performance ( Because a favourable pressure gradient
exists for laminar flow and low Reynolds numbers at low speeds/high
angle of attack.)
I am completely confused !!
PS 1. I am very interested in this stuff and really appreciate the
benefit of your knowledge.
PS 2. Anyone who is bored by this stuff is welcome to hit the delete
key at anytime.
Regards
Andrew Wright (VH GAM)
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