single fin question

I’ve been asked to make a surfboard for my little sisters birthday. I’ve decided to use this opportunity to experiment a little bit.

She’s a total beginner so I’m thinking of making a 7’0" * 20 3/4" egg shaped board with a pin / rounded pin tail. I plan install a fin box for a large single fin (7")

Question -

Can anybody advice me on how far forward I should install the fin box. I want a 50:50 compromise between drive and manoeverability.

What type of bottom contours work good with a large single fin.

Any advice would be really appreciated


Hey Brain,

I think you’ve make a good choice on the outline shape and width as long at it will float her real well.

I think a full Bahne Box that starts about 4.0" from the tail ought to work pretty well. That’ll give you plenty of room to dial the single in. A 7.0" to 7.75" fin has a nice generous tip will give the board a little more lateral stability while she’s learning to stand up. You can always move the fin forward to make the board turn more easily.

My thoughts on the shape are these: Keep it simple. Flat bottom to about 2.5 feet from the tail and then introduce a very subtle vee that gradually increases into the tail but don’t make it very steep at all or the board will want to run too deep in the tail. Make the rocker moderate and continous. it will turn more easily as a result. The rails should be about 60/40 and not too boxy. Make the board about 2.75" - 3.0" thick and keep some thinkness in the tail. I would keep the lines of the tail full as well and make it about 14.5" wide.

I commend you on the project. Your little sister is gonna love it.

Mahalo, Rich

Hey Rich, what would happen if you made this same board, but put a very light single conave in at the point where you suggested starting the vee (~2.5 ft from tail)? If you did this, where would you turn that concave into a vee to exit the tail (anterior or posterior to the fin box?)?

I’m actually finishing up a similar board (my first), and was thinking about this very subject. Any thoughts would be cool.


Hey Matt,

If you put a single concave in the last couple feet or so of the board. It’ll make it ride much higher in the water. It’ll be slippery and won’t hold in the wave face as well. It’ll also may rail transition much, much different. I hope some pro shaper like Jim the Genius shows up here. Someone with vast experience as a shaper could sum up what’ll happen in very few words much better than I. My thought was to keep it traditional and simple because it’ll be much more user friendly.

Mahalo, Rich

Cool. I agree with the KISS philosophy for sure, so I’m gonna Vee it up like you mentioned. I’m curious however, 'cause it seems as though I’ve been reading a bit about single-concave bottomed single-fins recently…

Thanks for the reply,



A mild double concave would be fine. It’d give the board more lift in the turns. I have a longboard that’s shaped that way and it works really well both as a single and with rail fins. We’ll just have to hope for some input from the experts on some details of the way a single concave will act.

Happy Shaping, Rich

make the board with as much room to stand as possibble…hard to give measurements when don’t know the size and ability…fin box…4-5" up from tail…my fin is usually a hand spread from the tail…thats to the back of the fin when its in

Hmmm… (insert sound of ears perking up). If you were to throw a little D.C. into this theoretical board, where would you start/end it? Is it important to always exit with a vee? Do you transition from the D.C. to the vee at the fin box?

These questions are probably such old hat for most folks that they are sick of answering them. I really appreciate your input for this reason.


Hey Halcyon

Thanks for all the advice. She really light so a 7’0" * 20 3/4 will float her real good. I agree with the choice of Vee over Concave. I’ll be postign a couple of pics in about 2 weeks

Thanks again