Rudder Rebuild Questions


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Blogs Author

During haul out, I noticed a quarter size hole in luffalee’s rudder apx. 2” behind rudder post on the top edge. There was a small amount of rust stained water just below the surface of the hole, so I drilled some exploratory holes around the area. Of course, the rudder was wet and there was standing water in the leading and trailing top corners. The center and bottom of the rudder seemed dry, but I wasn’t excited about having standing water in the rudder, so I had the boat lifted and took the rudder home to explore.

My initial idea was to cut open the areas where the standing water was, remove and replace saturated foam, and reuse the removed skin. However, when I applied air to the hole at the bottom of the rudder a small amount of water came out so I decided to open the whole thing. Surprisingly, the skin was extremely well bonded to the foam core and it took almost 30 minutes of careful prying to get it off. The problem was immediately clear, there were large voids in the top corners of the rudder so when the rudder was holed (could have happened when my motor fell of the back and was hanging on by the battery cable, but that’s a whole different story) water filled up the void. On the positive side, the rudder post and structure looks reusable and 90% of the foam is in great shape.

I have a few questions on the rebuild.

  1. I’ve heard 16 – 20 lb foam is ideal for this process, but the foam used seems to be much less dense. Possibly 4-8 lb. I’m thinking it would be best to use the same density foam. Anyone have any ideas on what Ericson / Foss used in the original?
  2. I can find the foam on, but shipping is expensive and they seem to take a while to fill orders. Does anyone know where I can get foam in the Seattle Everett area?
  3. Should I reuse the old skin, bonded with thickened epoxy, and taped with tapered seems or reskin the rudder with 1708 biaxial and epoxy? I have access to a vacuum pump to ensure good adhesion, but I’m a little concerned about the strength of a taped seem.
  4. The rudder post and joint is in great shape and I can’t see any sign of leaking or stress cracking. However, I know this is the source of most leaks so should I break a good seal and re-build it or keep a good thing going?


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Innocent Bystander
At this point I would get a quote for a Foss replacement and consider that in your decision.

I see complications from:
* adhering new foam to wet/damp foam
* adhering epoxy to wet/damp foam - I tried doing this for years on a failing rudder, it really doesn't work
* getting a good foil shape out of the result
* getting sound structural strength out of the result - the sides of the rudder will not be of similar strength/stiffness

Given the time necessary for the repair plus the emotional cost of wondering about these things every time the rudder is stressed, the Foss replacement may not be such a bad deal.

This was my calculus a couple of years ago and I don't regret the decision.


Member III
Blogs Author
Follow up

I finally got a quote from Foss of $1,200 including shipping to Everett, WA which isn't bad, but I decided to continuing rebuilding my rudder. I'm a little nervous over the timing, but I'm really having fun doing the work my self. I've been off following this guide:

To answer my own questions:
1.) I ended up going with 8 lb foam which turned out to be really close to the original.
2.) Fiberglass supply has everything I needed, is located in Burlington, and ships out of the same FedEx I get my deliveries from. It's actually cheaper to ship it then drive.
3.) I'm going to keep the rudder post seal in tact. The water intrusion was obviously from the hole, so no need to disrupt a good thing
4.) I decided to reskin the section I removed with 3 layers of 1708. I'm thinking it's going to be about the same fairing the seems as the whole side, so I decided to do everything and have more control over getting rid of the voids.

Here's a pic after the last of the 3 foam pours. I'm planning on shaping the foam and laying the glass tomorrow, fairing and painting the first coat of barrier coat on Saturday, second coat on Sunday, then bottom painting Monday and Tuesday, and splashing on Thursday...fingers crossed