single fin bottom contours

General Discussion
1

i am about to start on a new board. it’s going to be a 6’8" single fin with a round tail. i’m trying to figure out how to do the bottom.i’m thinking single concave under my front foot to flat or vee out the back. one thing i can’t figure out is where the vee or flat should start i.e. how far up from the tail or how far in front of the fin? or maybe a single to double but where would the double start? i may put side fins on it for when it’s bigger. anyways what i’m after is any advice or any general rules of thumb about bottom contours on sinlge fins. i tried the archives but i can’t find a clear answer to where the single concave goes from to flat or vee.

any help would be greatly appreciated

thanks

2

take a look at the Hobie “Deadly Flying Glove”.

go from there…

3

…why put sidefins for when its bigger?!

look at the guns

anyway, I dont know what type of single you want

but I have been got good results in performance single fins (with contemporary outlines and with somewhat retro ones) some with flat bottom and the retro outlines with flat or a bit convex in the first 1/3 then single concave to the tail (modern rails)

4

My experience has been that concave into vee stops water flow - the concave pulls it in and the vee gets in the way of it getting out the back. This is thruster based, because that’s all I surfed in the past 20 years, but I’m confident it applies to single fins, too.