Finally got around to making some wood fins today. Used blakestah’s template he posted in the fin theory thread and scaled it down to work in a thruster setup. The other one is just a copy of my ol’ reliable stock fin that I usually use. Just needed the practice foiling. It came out pretty good, then I realized when comparing it to the original that I didn’t undersize it a little to account for glassing. Oh well, more practice foiling tomorrow. Still need to cut the tabs out of the straight fin and glass them both. I don’t have resin so it will have to wait until next week as the suppliers aren’t open on Sunday.
Thanks to Bert for posting the fin glassing pics, I picked up alot of good tips that I can hopefully put to good use.
My foiling still needs alot of work so any critiques are welcome. On the straight fin I tried to keep the max thickness at about 25% of the chord and on the curved one I just copied the original as best I could. I’m thinking 2 layers of 6 oz. on each side and I still haven’t totally figured how I’m going to do the plugs.
Lawless not to fowl for your first go when you do thr tag area make the thickness 5.8mm than before you put the 6oz. on put
gun rovings down the tag area into the fin area to give the tag strenght than when you cover it with 6oz. don’t let the resin lay on the tag area as it will be to thick roll it out with a small roller ‘’ gun rove both sides of the tags’'.
Those were interesting projects. But mostly I discovered that chord lengths close to 4.5 inches, maintained over as much of the fin depth as possible, is a key factor in getting a real drivy fin. To do this I made it more raked and started laying my templates up over a grid so I could eyeball the chord length at different depths.
Now, I am moving on to humpback fins (carefully matched for chord lengths). I was all set to use this one next, now I find out I need to add bumps. This is the tenth fin experiment. I could probably do 2 or 3 a week if we had waves - summer doldrums is really slowing it down.
Here’s a humpback fin, sans leading edge bumps, scaled for a thruster fin size. Depth 4.5 inches. Each square in the grid is one inch - the grid is there only for size guidance.
