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Old 4th June 2008, 10:45 PM   #9
Roger
Dream Team - School Guru
 
Join Date: Aug 2006
Posts: 2,106
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Hi windfrancois,
I think the current wisdom on "surface finishes" for windsurf gear/hi speed sailing dinghys/huge racing yachts is that a polished surface is too smooth and actually cuts down your speed.
Using a "figure 8" pattern with 400 wet/dry abrasive cloth is about the best you can do.
Some folks like a straight pattern in line with the water flow.
The idea is to create a little "tooth" (microscopic maybe, but "tooth" just the same) to hold a boundary layer of water molecules on the surface.
Testing has shown that water has less "friction" on a fully wetted out boundary layer than on a polished surface with no boundary layer or "wet out".
Surface finish can have a positive effect on preventing spin out, but mostly spin out
is due to imperfections in either the foil or the planform of the fin.
Hope this helps,
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