slicker centerboard

[DanaDCole]

Many of you may have followed my earlier post where I talked about using formica inside the CB trunk to slicken it up. Others wrote back to say that was a bad idea, etc. I agree, because if anything goes wrong there would be no way to fix it without practically tearing apart the whole boat.

A few posts mentioned adding carbon to the trunk resin, which sounds like a pretty good idea, but again this is messing with the basic structure of the boat. One thing to make sure of at least is that the areas where the blocking will be glued should be masked off so you don't get any carbon there. And then you run into chemical bonding problems because of waiting too long, and so on. So I have decided against this also.

So now my great brainstorm is to add carbon to the final coat of epoxy on the centerboard. This would make it very slick and with the inside of the trunk's epoxy sanded and polished smooth I should get pretty darn good slippage. And, if anything goes wrong, the centerboard can be removed for repair.

I have a nearly full can of carbon left over from some kayak rubbing strips I made and on the can it mentions centerboards as a potential use. So that pretty much settles it for me. Come to think of it I may have some Dynel left over too. I might apply that along with some more epoxy and carbon to the leading edge--if, that is, I can keep it from making the CB too thick to slide into the trunk. This, along with the thickened epoxy strip CLC recommends, should make for a very rugged centerboard. Unless it doesn't.

[Bflat]

I wouldn't apply graphite to the Centerboard without adding it to the Case. If you're going to do one or the other, do the Case. If the Centerboard is made harder than the Case, guess which one would be more likely to wear out first! I'd much rather have the board wear out before the case since it's removable and relatively easily repaired or rebuilt (at least compared to working on the inside of the Centerboard Case; which would be a real puzzle).

Here's how I did it:

1. Glassed the Case sides and filled the weave with the normal epoxy mix as per the manual.
2. Sanded smooth.
3. Masked the areas where the blocking would go so as not to compromise bonding.
4. Applied 2 more coast of epoxy, but with Graphite Powder mixed in.
5. Sanded smooth.
6. Assembled the case as per the manual.

But, like John has stated, glass without graphite is plenty strong. Still, I'm glad I did it since it was so easy and brings me a little "peace of mind." Not counting the cure time it took only minutes to do. Sanding those flat surfaces is some of the easiest sanding of the whole project; much easier than sanding the bilge, for example.

I may end up adding a little graphite (or Teflon, even) to the Centerboard too, but certainly not as much as I did to to the case.

Best of luck,
Bob

[DanaDCole]

Thanks for your comments. There's just one thing I don't follow--I didn't think the graphite powder made the epoxy stronger, just slicker. Maybe it also makes it harder to puncture?

That being said, I think you have a good idea. I have finished three coats on the inside of the trunk and am ready to start sanding. A coat of epoxy-graphite mix would not be that hard to add and should make the trunk pretty impervious to damage, and better lubricated. My intention has always been to mask off the areas where the blocking will be glued.

If any graphite is left, I'll add some to the final coat on the centerboard. There ought to be extremely little friction between centerboard and trunk after that. I still like my idea of some graphite and dynel on the leading edge too.

One question: My understanding is that there is no need for UV protection on the centerboard. The only sunlight it will ever get will go through several feet of water at an angle. If varnish or paint went over the graphite-epoxy, then what would be the point?

[Bflat]

The graphite doesn't make the epoxy "stronger," but it does make it "harder" and more wear resistant than epoxy alone. And, like you said it makes it very slippery.

I don't see any need to paint or varnish the centerboard.

Bob