Fixing rotted balsa end grain in deck

[Frank Hagan]

Anyone have experience fixing rotted balsa end grain core material?  There's a Potter owner who is planning to drill holes every few inches and pour in thinned epoxy as a way of fixing the problem.  I'm not sure this is the solution, and I thought some of our more experienced members might know a way to fix this kind of problem.  His plan is at http://bbs.trailersailor....tter/index.cgi/read/55039 and he is seeking as much free advice as possible!

[Charlie Jones]

I've been watching the thread Frank. Ray and others have pretty well covered it. I didn't see any need to add more.

But it never hurts to get more thoughts. Hey, I don't know it all, that's for sure.

[Frank Hagan]

I only saw his thread in the Potter board over there, so didn't know if you guys had chimed in on it yet.  I'll have to start reading the main forum over there again when things settle down ... any day now, any day now ....

[Oyster]

I was in a new 19 about a month ago. It seems to be so open, that a repair could be done and hidden from the outside, messing up the finish coat. This is if the owner plans on keeping the boat. I would emagine that there is several sections that are worse than others, and he could maybe get the worse out from an opening in the underside of the deck, if accessible. in the worse areas There are ways that you can acheive a finish for the overhead, without working completely overhead by fabricating panels, and do the finish work off the boat, and just use decrative mouldings to cover the cut sections. I would also think that doing this in stages would not render the boat useless, either.

[PAR]

The usually repair is to drill holes (typically 1/8" on 2" centers) and fill with neat epoxy. Do not use thinned epoxy, CPES or other reformulated thinned epoxy. You're just waiting time and money.

For the repair to work the core has to be able to return to it's original or better compression strength and (most importantly) it has to be very well bonded to the inner and outer skins, without prospect of sheering. The use of thinned epoxy will guarantee it will sheer it's skins and delaminate in the future.

As Ray mentioned the core has to be below 15%, which can take several months, depending on conditions. The rotted areas of core must be removed (no Get-Rot doesn't fix the rotten wood, nor does CPES), the whole of all contact and bond areas cleaned, then abated. Then you can apply good quality laminating epoxy.

If just drilling holes and not exposing the core (harder, takes longer and you have hundreds of holes to repair), then mix milled fibers and silica at 50/50 to inject into the holes.

It's usually more cost effective to cut off one of the skins over (or under) the affected area, remove the soaked and rotten core, clean, abate and bond in a new core, then bond the old skin back down. A lot less patching to do and the work can be done very quickly.

[Hirilondë]

The subject of wet coring comes up a lot in http://www.plasticclassicforum.com/ .  Do a search there and you will find numerous threads on the subject.  I suggest paying particular attention to comments made by "Tim". the forum administrator and a professional fiberglass boat renovator.

It's usually more cost effective to cut off one of the skins over (or under) the affected area, remove the soaked and rotten core, clean, abate and bond in a new core, then bond the old skin back down. A lot less patching to do and the work can be done very quickly.

In a nutshell that is by far the best way.  Anything else is just a quick fix and prone to failure, if it even does anything at all.  Moisture trapped in the core will virtually never dry out.  And even if it did, you will never rebond the core to the skins effectively. 

"Nothing is more permanent than a temporary fix".