Using foam to replace rotten balsa core..?

[ChasB]

Hi. My first post here!

I'm having probs with wet rotten balsa in my grp aft deck. I've posted about it here: http://www.ybw.com/forums/showthread.php?t=214251 The guys who are pros in these matters are adamant that major surgery to the boat is required.

However a couple of others suggested using builders foam, and in the thread Core questions in this forum feetup avocated the use of Gorilla glue which "will react with any residual moisture in the core and turn to a fairly dense, very sticky closed cell urethane foam which hardens into a great core material that is bonded well to both inside and outside laminations". Understandably this solution seems very attractive to me. Since you guys are clearly experts in the matter I wondered what you might have to say on this...

Your feedback would be much appreciated. Cheers!

(I'll now put my flame retardant suit on...)

[Tim]

Can you tell how far out the core damage extends? That's the first and most important step in determining how you should repair the damage. Without knowing this, it's a little premature to guess at means of appropriate repair.

I cannot support the use of canned foam and polyurethane glue as means of core repair. Neither is remotely like the firm, dense, closed-cell structural foams used for core material (i.e. Corecell, Divinycell, Airex, etc), and one should never consider all foams to be remotely equal in intended use. And expanding foams can cause serious damage if inserted into too small a space; the expansion power of some of these is impressive (though this isn't the main reason to avoid them in this case--it's just not at all the right product by any stretch of the imagination).

From looking over the thread from the other forum to which you linked, I'd say you've gotten pretty sound advice from a few of the posters, though they may not be telling you what you want to hear. The best advice rarely gives one the easy way out, unfortunately. That's because there's rarely a good, easy way. There are lots of bad, easy ways. One can choose any advice they like, of course.

With enough detail (and photos) of the damaged area in question, perhaps we can give you some real advice on a good way to proceed, but I must warn you that it may not be what you want to hear! I don't believe in short-cut repairs and don't condone them when suggested by others. Nobody is perfect, but all one can do is the best they can do; anything less isn't worth doing.

Your situation may not be so dire, but I don't have enough information to draw any conclusions or give advice at this point. Any further information you can pass along would be helpful.

[ChasB]

Cheers Tim. Thanks for the trouble.

Will be on the boat later drilling holes Hopefully it won't be too bad, whatever that means. Anything looks bad at this stage...

Will report back later.

[Quetzalsailor]

Perhaps you can work, at least investigate, from underneath. This may ease aesthetic issues at the cost of extra pain and inconvenience. Lots of posts on this subject on this site.