Thanks, Howard, That's about what I was looking for. Did you repair your deck from the top down or the bottom up, like I am? Tom B On Mon, Apr 14, 2014 at 2:34 PM, Howard Audsley <haudsley@tranquility.net>wrote:
Tom:
You may want to reconsider the balsa option. I wouldn't be too quick to eliminate it. The reason you have what you have is the bolt holes that pass through it were likely not sealed on the inside. What was protecting the balsa was nothing more than the bedding compound the fixture was resting upon. Over time, that hardens, cracks, etc and water manages to weep past it, then through the bolt holes and into the balsa. Yes, balsa is more likely to soak up water and rot, but even with foam, the water will still be there doing damage (and adding weight) unless you completely seal the hole.
The way to seal the hole is to enlarge the bolt hole from the inside (larger hole inside on bottom of cabin top). Then tape off the inside bottom hole, and backfill the bolt hole with slightly thickened epoxy. What you are essentially doing is pouring an epoxy compression bushing between the outer and inner sandwich layers, which not only seals the hole, but any water that gets past the bedding compound enters the bolt hole.......and drips straight on through to the inside of the cabin. It never reaches the balsa, which can't get wet if it is fully encapsulated with no chance of exposure. Balsa is relatively low tech, but still one of the best, and least expensive choices for glass sandwich core. Also, with the epoxy bushing into place, you can crank your bolts down without having to worry about compressing the inner core.
To those wondering how to tell if your balsa core is wet, take a good sized plastic handled screwdriver, use the handle end and gently tap/rap the outside. If the core remains solid and dry, you get a solid ring/ping. If the core is wet and rotten, it is a dull thud/thunk. If you are trying to sound it out, keep moving around in a grid pattern and map it out. Start near the bolt holes and work your way out.
And whatever you do, make sure you use epoxy resin to make your repairs. Do not use a polyester. It was right to build the boat with, but not to repair it with.
I would also double/triple check the thickness of the core. I had to redo my chain plate backing. That was half inch as I recall. Didn't think so until I got into making the repair. Had to buy core materials twice.
On Apr 14, 2014, at 2:07 PM, Thomas Buzzi wrote:
Hi All, Between availability and the small amount needed and the desire to not use balsa again I am ordering a sheet of diviney foam, scored on a scrim. The repair will take about four square feet above my v-berth in the M 17. Has anybody used this particular product? I am looking for personal knowledge hints on problems I might encounter with this stuff. I have read all the literature on installing it. Fair winds, Tom B M-17, #258, 77'