Single Fin fin box placement

I’ve checked around the site for this info, but it seems most responses involve a tri-fin setup. I’ve made a red and yellow cedar board (8’ X 22.5" X 3"). It’s going to be a single fin and I have a fin box a ordered from Fluid Earth (10" box). I wanted some advice on where to place the fin box, specifically, how far forward of the tail. I was thinking about 8" but wasn’t quite sure. I have a good jig template ready and a plunge router to do the job, but it’s a one time deal so I want to get it right. Any info, experience would be helpful.




C.[img_assist|nid=1061802|title=Old Growth Cedar Board|desc=|link=none|align=right|width=427|height=640]

5"-6" from the tail the further up the looser the further back the more drive.

A2tail is stating the normal fin box setup for single fins. Displacement hulls and some other designs are different but the numbers he gave you are considered the standard when using a 10" box.


As a rule of thumb, you can place the fin you intend on using on the bottom of the board with the base of the fin flush with the bottom of the board on the center stringer line. Don’t include the part that goes down into the box in this alignment, just the part of the fin’s base that matches with the board’s bottom. This gives you a gauge of HOW MUCH tip of the fin will extend past the rail of the board on hypothetical turns. If you opt for 1/3 of the total height of the fin to extend past the rail that is a pretty good estimate at where you might want to position the fin.

Once you do that, you can decide how much box you want forward and behind the base of the fin you choose to use. And as previously stated, forward is looser and back is more drawn out turns. Think of the position of the fin in relation to the nose as “water base” aka wheelbase.

Short wheelbased cars can whip a U turn on narrow streets and so on.

Above all els, have fun!



That makes sense if I’m reading it right.

So I’m basically laying (for lack of a better word) the fin (it’s a 9" fin) parallel to the bottom of the board, not perpendicular, flush with the stringer and the base of the fin that does not go into the box. Move it until appox 1/3 of the fin’s hieght goes past the rail, mark it and give er’.

Sounds good and it seems like it’ll be about 6" from the tail if I go that route. I can always move the fin forward if I want a more ‘loose’ feel.




Cool board.  How much does it weigh?

Thanks…I love the alternating wood look. It weighs about 12-14 pounds right now before the glassing. Should maybe weigh 18 after it’s all done. A little heavy but it’ll glide down the line nice and fast.


C.[img_assist|nid=1061806|title=Cedar Deck|desc=|link=none|align=right|width=427|height=640][img_assist|nid=1061807|title=Cedar Tail|desc=|link=none|align=center|width=427|height=640]

Thanks deadshaper I didn’t know that. I love learning new thingS