Ok, so marking out fins and placing my dots on a twin fin fish using futures plugs … looking at the keels (the modern type where the back/base of the fin lifts away from the board) how does the rear of the fin relate to the fin dot ???
Rear edge of the fin should be the rear dot or rear end of your pencil line. But very often when the blank is glassed at a Pro Glass Shop an installer assumes that the rear dot is the rear of the fin box or plug. If you do your own install you can compensate for this. A lot of fins are foiled or templated in such away that they hang beyond a Futures, FCSII or Fusion box. For FCS plugs, the Install Kit comes with a plastic template that can be used for a precise marking and install based on the trailing edge. The proper method for marking a blank is to put the dot at the rear edge of the fin you plan to use. Keeping in mind that this will change if you change fins. When I used to use FCS Plugs, I would make a 4 or 4 1/2” straight pencil line. This would insure that the two plugs are aligned on install. I still use a penciled line. Too many things can happen at the glass shop. Had an installer put the Futures boxes behind the dot instead of in front once. That was a real “cluster fk”. Use a straight edge against the back edge of the fin to determine where the back edge of the fin would be if it were not “lifted up”.
The dots are where you want the futures fin Tab routed. If using a single foil twin keel the rear dot will indicate the rear inside (stringer side) of the fin tab. You must account for the extended base of the keel fin. For example if you wanted the rear of your keel fin at 6 1/2’ from the tail and the fin hung
1 1/2 inches past the fin tab you’d make your dot at 8."
If you use the FCS plastic marker it’s pretty easy to get the rear of the slot in the plug where you want it. Which if compensated for puts the rear edge of the fin you plan to use where you want it.
For years the width of a Stock/production FCS fin base was 4 or 4 1/2”. That was the basis measurement for marking fins and lots of shapers still use it. With of course some adjustment and compensation.
Thanks guys… heres a pic of keel fin that lifts away from the bottom of the board at the red mark.
Where would fin dot be in relation to either the red dot or the yellow dot?