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From: ccrosby@mweb.co.za
Date: Wed 13 Nov 2002 - 06:10:47 GMT
Ted Rogers sed:
> Aerodynamic drag is equal to 1/2(density of fluid) x Velocity^2 x Area x
> Coefficient of Drag.
--- snip ---
Just something to consider, in the range of Reynolds numbers we are dealing with
(Re-number is a convenient way of expressing the relative significance of viscous and
momentum effects), the Coefficient of drag is far from constant. In fact, it is quite
inaccurate to assume that drag is proportional to V^2 if you are dealing with cylindrical
shapes under these conditions.
--- snip ---
> But the biggest drag reduction we can probably make without rotating masts
> is to get away from round masts
--- snip ---
> a "D" shape is the best compromise, as the sharp rear corner trips
> the flow before it gets too big a vortex going.
Only of you can make that D shape rotate to align (more or less) with the breeze. Anyone
feel up to making that work with a multi-spreader masthead spinnaker rig?
Just another observation, I was looking at some photos of Aussie NS14's (for some other
purpose), and it is striking how small their jibs are in relation to the mainsails (AFAIK
they can also distribute sail area between main and jib as they wish), presumably because
the rotating wing masts that they use makes the mainsail more efficient than it would be
if set behind a circular section mast.
Charles
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