Large fin for kayak and SUP

I tried the great design of the itiwit long fin from hungryharris for my Decathlon Itiwit X100 kayak. Because I found some shortcomings in the model I decided to remix it with some minor improvements. I closed a gap at the rear end, made the socket more solid, adjusted the mounting hole for the clip a little bit and added two holes for a cord to attach the locking clip to it.

First I printed the fins in PETG, but it took only a short time before it was broken due to insufficient layer adhesion and mechanical load. Of course I could have printed it with 100% infill, but in doubt I prefer to damage the fin instead of my kayak.

The solution was to print the fins with TPU and 25% infill. They are really light and don't sink if dropped in water or become loose. Furthermore, TPU has an excellent layer adhesion unlike PETG or PLA. This is very important as the lateral forces are mainly acting on the few layers between socket and fin. Whenever you feel the fins scraping against the ground in shallow water, don't worry. This will not damage the fins or the boat's mounts. The TPU fins are very flexible and do not break when in contact with the ground.

The large fins have proven themselves in the water. The kayak has a significant improvement in straight-line stability compared to the small factory fins.