Hi fin 66.
The whistling is most likey caused by a thin area just in front of the trailing edge of the fin.
Sometimes there are some little "hollow areas" in the last 2" before the trailing edge.
To check for this, try to find a hardened and ground dowel pin (3/8"-1/2" x approx 2' long). Roll the dowel pn down foil just in front of the trailing edge of the fin and look for any hollow areas.
(You can also use a precision straight edge, but the dowel pin is cheaper and more accurate for this testing).
If you find any hollows, then Mark H.'s suggestion is right on.
You need to carefully straighten the profile of your fin so it is perfectly flat from the high point of the foil back to the trailing edge.
This is best accompished with a sanding block and wet/dry abrasive paper.
If you don't find any hollows, what usually works is to take a sanding block with some fine grit wet/dry abrasive cloth.
Place the sanding block perpendicular to the fore/aft axis of the fin (square to the trailing edge of the fin) and sand a tiny "flat" all the way down the trailing edge.
Then turn the sanding block and go down the squared off trailing edge at a 45 deg. angle on each side of the trailing edge to slightly break the sharp edges between the flat and the foil.
Also, if you have a Drake fin with the "Drake" logo near the rear edge, get some 400 grit
wet/dry abrasive paper and rub off any high spots on the logo.
I've found several of the 2008 Drake fins where the logo is very slightly raised and it needs to be smoothed out to blend with the rest of the foil.
Use a sanding block if you have one, and lots of water.
Hope this helps,
Last edited by Roger; 6th July 2008 at 10:57 AM.