The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.
When I bought my Catalina 25 2+ years ago, the original rudder was split down the leading edge and the previous owner was using a kick-back rudder in it's place. Earlier this year, I built a rudder from scratch matching the original rudder's shape. I applied the first coat of gelcoat but no barrier coat. I had friends coming for a weekend sail so I put it on the boat with the intention of bringing it back home to finish it with a layer of gelcoat and a couple barrier coats. One thing lead to another and instead of just the weekend, it stayed on the boat in the water for 7 months. Every time I'd sail over the summer I'd think, "I need to take that home and finish it" but I didn't. Don't judge me.
When I took it off and pressure washed it last weekend, I wasn't very surprised to see all the tiny blisters. I thought I'd post this as an educational piece to show everyone what happens to an unprotected fiberglass material (polyester resin) after being in the water for awhile. It simply illustrated that fiberglass is not waterproof and barrier coats are really important if you leave your boat in the water. Click to View Full Sized Image
I'll sand it all down, apply fairing, barrier, gelcoat, and anti-fouling and it will be ready for winter sailing.
Some people recommend drying blisters for as much as 6 months. I don't think that's necessary. 30 days might not be necessary either, but after you've done that much work, it's probably worthwhile to protect your work. Any moisture in there will be there forever after you barrier coat it.
Steve Milby J/24 "Captiva Wind" previously C&C 35, Cal 25, C25 TR/FK, C22 Past Commodore
Thanks. I wasn't sure what the original rudder's core was made of so I used two sheets of 3/4" plywood glued together. I wanted to err on the side of too much strength rather than risk it cracking if I'm caught out in a storm. The top to bottom shape was easy. I just traced it. The tricky part was the "wing" shape of the bottom half of the rudder. I traced it as well while realizing that it was slightly deformed from absorbing so much moisture.
I found some rudder cross-section drawings on-line so I had a pretty good idea of the different widths from front to back. I used a belt sander to get the rough shape and used the plywood layers as a guide.
After some hand sanding of the edges, I applied several layers of fiberglass.
I finished with a layer of gelcoat but realized that it wasn't all smooth (my haste to get it done) so I sanded down the obvious spots. That is why the original photo shows several spots where you can see the fiberglass through the gelcoat. What is that old saying, "If you don't do it right the first time, you'll get an opportunity to redo it later".
Notice: The advice given on this site is based upon individual or quoted experience, yours may differ. The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.