I got home yesterday from work and had a look at the fin I'd been working on the last time I was home. I'm trying to condense a 38cm fin into a shorter one, with the same overall area, that will perform just as well as the larger one but for shallow water with weed that anchors itself to the seabed. Ended up being 27cm and can't remember the area right now!
I guess the beer goggles had let me settle for a second rate job. The fin was crooked on the trailing edge and in frustration I'd let it go until a later date.
So with renewed vigour (and the inspiration that only comes from alcoholic ginger beer) I set about fixing the issue. Put the fin on a flat surface and ran a straight edge around it marking high and low spots. Sorted them out with the bench top sander and realised a low spot towards the base. Kind of flat really, with the ratio around 5%. I'd set the ratio for 7% for this fin and hope like hell my research had paid off. I use the term research loosely as inspiration can come from many places. Copy from one book and it's called plagiarism, copy from two or more books and it's called research, go figure!
I digress, filled the hole with carbon, sand it down, paint a layer of graphite infused epoxy and Robert's your Mother's brother!
There's lot's of ways of getting to the same desired result, this is just mine. And hopefully with the longer chord I can get away with 7%.
They're done, was hoping for a westerly so I can come to Australind. Kill two birds etc. 
pepe nice job on benders fins have you thought of using a wheel, just chop up some of your off cuts and wheel it in, you can get a small wide wheel , just keep adding chop until the hole is level , also a good way to use off cuts
But seriously, I've tried a number of different ways and this is the method that works for me.
If the box is going to be black, I'll use carbon to line the mould. If it's white, I'll use open weave glass. Then I'll fill the mould with epoxy resin with a bit of powdered glass up to about 2mm from the top of the mould edge. When that's gone off and shrunk, leaving a concave in the top, I'll top it up so the level is spot on. There's probably a right way and a wrong way, this is just mine.
The downside is sometimes it can be brittle, but I've had no complaints so far.
A number of hours later. Mind you I do a two week on two off roster, so I have time to spend on my obsession. Hobby, depending on your viewpoint!
