effects of moving center fin of thruster froward

hey guys I am marking out some fins for a board i am working on. I was thinking of setting the center fin of the thruster at around 5 to 5- 5 1/2 up from the tail instead of the normal 3 3/4 to 4 inchs up that i doing the side fins at 12 1/4 up from the tail.

 the tail of the board is 16inch at the one foot mark. (see the photo) what affects would this have on the way the board surfs

the reason for this is that the board deck shape does not allow me to get my tail pad as far back on the tail as i would have liked and i want to get my foot well over the fin cluster

what you thoughts


the closer to the tail you have the fin, the longer the board rides, on one of my high performance longboards, I had the side fins at 12-1/2", made me stand so far back on the tail that I didn’t have enough rail in the water in turns, re-routed the boxes at 14-1/2’", what a difference, then I started with the center fin.

I’d take a sharpy with me to the beach along with my center fins, ride with the fin in one position, mark it then come in for a change up, no matter how much I moved it around, I always came back to the one sweet spot for that board where it all came together and that was side fins 14-1/2" and center at about 7-1/2" to 8 ’ up from tail.

My single fins are about the same, I don’t like a fin hanging over the end of the tail

thanks jim for the imput. i should have said that i am using fin plugs with fcs pg-7 fins and the boards 6ft long 22 wide with a strong vee in the tail

cheers antony

In the domain I play in (kneeboards) there are guys who have their centre fins way up (front lining up with the rear or the side fins).  Obviously their boards lack drive but do pivot quite well.  This is particularly effective for getting the board vertical (but it’s an optical illusion - basically they are pivoting vertical and letting the wave pass under them).

The general rule of thumb has been 1/2 the distance of the side fins from the tail, so settings of 18’ for sides and 9" for rear are common, and I think that’s what Jim saw in his post above.

If you use FCS plugs just try it out. Install 3 or 4 center plugs and play around which works best for your surfing.