Hull vibration from fiberglass fin

I curved the front edge over the fin a lot,and the rear less so, and sharpened the edges. It improved a lot, but still makes a quieter tone starting just below skiing speed.
Tomorrow I will make it shallower by an inch or more, which will hopefully quiet it completely.

The boat was built in 1986. The story from the original owner is that he bought it at the Toronto Boat Show (which is in January). He put it in the water early summer and the fin ripped off during the first turn, opening a large hole, so he drove it up on the beach. Apparently the company he bought it from had gone out of business and the remains bought by another. They looked at the boat and cleared it to be a hull meant only to take to shows, way too light and never intended to float. So they rebuilt it, doubling the thickness of the fiberglass, and he has been skiing behind it until 3 years ago when I bought it from him.
I completely redid the floor and transom, not trying to make a work of art of it, but to make a solid reliable ski boat.

 

JPage:

This is the second CA 18 Hydrodyne on the website in less than a year so please start a new thread about your tracking fin issues and I am sure that you will get a response (by me as well:~). I want to know more about your boat build (as do others).

Kevin-

 

When working on your fin, you'll likely have better luck eliminating noise/singing if you leave the trailing edge squared off rather than filing it to a sharp point (keep the leading edge sharp though). The same is true for props - if you look at your blades, the leading edge is sharp with the trailing edge squared off. If you ever have a repaired prop sing at idle speeds, it's usually because the shop filed the trailing edge to a point, and filing it square will eliminate the singing.