Rudder delam: why not closed cell spray foam?

[Tetepare]

Our rudder has areas of delamination from freezing. The boat has always been in fresh water, and any water that drains out of the rudder is clear, so no rust.

The best and most expensive route is a new rudder. Second best and second most expensive is the bifurcate the rudder and refill. Big job.

Most sources suggest drilling voids and filling with epoxy. Like this one https://www.epoxyworks.com/index.php/rudder-repair/

However, isn't that going to add weight? And, what assurance is there that the epoxy goes where it's supposed to?

In our case, the void is not between the shell and the foam core, in some cases it's somewhere in the core. That could be a lot of epoxy, with no guarantee the epoxy goes where it's supposed to.

It strikes me that since the core is closed cell foam, a closed cell spray foam would somewhat match the original material, and readily fill the voids. However, I can't find much on this approach, and I wonder why.

Any insights on using closed cell spray foam?

Thanks.

[tkeithlu]

I doubt that you are talking about enough weight to throw off your balance, independent of how you solve the problem.

If you don't want to split it, consider drilling 1/4" or so hole in the top, several in the bottom, and after it appears to drain, shoot some compressed air in the top with your air gun. Then, you could simply seal it up so water doesn't get in again. If you prefer, yeah, squirt some foam in at the top and then at the bottom, or fill with epoxy. You won't be able to fill it - you're just gluing the sides together.

The important part is the attachment of the rudder to the rudder post. That's structural, probably with straps welded to the post and extending aft in the fiberglass of the rudder. What happens in the foam core isn't going to influence that.

Good luck with it.

[Mike OReilly]

I make no claim that this is the best, or even right solution, but it's what I did a few years ago when I discovered our rudder had water intrusion.

In the fall, when I pulled the boat, I drilled a few 1/4" holes and let the water drain and dry over winter. Then in the spring I blew it out with a hair dryer, and then injected some closed-cell foam. I filled from the bottom holes until it came out to the ones above.

Caution... the foam expands, so you don't want to give it space to grow. The risk is it could expand and crack the rudder.

Once the foam had cured, I glassed over the holes.

I did this six or seven years ago. So far, it's been fine.