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... The end
grain isolates moisture instead of wicking it the full length of the structure. Maxprop wrote: That was the theory behind end-grain balsa, but ultimately it didn't work. Eventually the wood will tranfer water a great distance between lamina. Yes, but "eventually" Mt Everest will be reduced to beach sand, too. The progression of rot is much much slower with end grain core than encapsulated plywood. I would not call that failure, myself. As for plywood "core" what's the point? Why not get plywood that's strong enough in the first place, instead of adding a skin of something that is heavier & not as resilient & will trap water in the wood? Actually, the one exception is the upper face of a deck. Fiberglass is a lot more abrasion resistant than wood, and makes a great deck surface. It's probably not a lot more abrasion resistant than dry teak, Guess it depends on how you define "a lot" and what kind of abrasion you expose it to. Fiberglass will basically have almost no wear at all from foot traffic. Teak will... I know this for a fact, having just removed a 20 year old teak deck. BTW this teak deck was screwed into balsa core, which had a dessert-plate sized spots of rot. If it had been plywood, it would all have gone to mush. .... which makes the best non-skid of all IMO. Disagree, but then that's based on personal experience rather than heeding the opinions of others. Heresy! .... For those boats with ply decks, many manufacturers covered the decks with canvas and later Dynel or fiberglass. I've read the Dynel is supposed to be better, not used it myself. .... Look at an Ericson and you will see core with a flat taper or bevel in the decks. Some eras of C&C did this as well, but they also put in plywood or milled PVC blanks in place too for some models in some eras. So did some other builders. The older Pacific Seacrafts, sure. The last ones I looked at (2003 & 2004 models) they had deliberately built the boat with glued-in molding & fabric liners so that you could not see or access any part of the structure. Frustrating... and suspicious IMHO. I should have asked first... you know Pacific Seacraft was bought up by a conglomerate? Personally I think they're playing the sausage game. Nothing stays good for long. But many builders just toss the core in the mold and slap cloth over it. Those same builders never anticipated being in business years later when those cores were soaking wet, either. They might not have thought it made that much difference, and couldn't afford the labor to do it right anyway. Maxprop wrote: Damned if I can recall what manufacturer did this, but I recall seeing a boat on which all thru-bolts were first drilled oversize, then filled with solid resin--epoxy, I presume--and then redrilled to the proper, smaller diameter. The problem with this method of repair is that you're cutting away the strength memeber... the skin. But the epoxy filler is stronger in compression than the core, so that's good. You're cutting away such a small diameter of the skin that I think the result is negligible, especially if the unit of hardware being installed is quite a bit larger. That's a good point. If the hardware is a lot larger, or has at least 3 mounting holes, it's probably just fine. I was thinking of single bolt stuff. I also drill out areas and fill with epoxy to mount small stuff with self-tapping screws. No, but freeze-thaw cycles will still cause progressive delamination if any water gets into it. And Airex is also weak in compression, thru-bolts will crush it and cause leaks. It's surprisingly stiff and rigid. I installed a sheet stopper on the cabin roof, and I was preparing to route out some of the Airex and replace it with epoxy and West System's colloidal filler, but the local glass man told me it wouldn't be necessary with Airex. I couldn't detect any undue compression when I tightened the fasteners. Of course I bedded them and the stopper in polysulfide caulk, tightened only slightly until the caulk had a chance to set up slightly, then tightened it further. Interesting to see what the results will be. Airex and Divinycell and Klegecell and there some new German stuff that's supposed to be miraculous but is tediously expensive are all less supject to compression failure, and certainly less prone to rot ![]() to have rigging components thru-bolted to it. It may be that the caulk is resilient enough to keep it watertight anyway, in your application. If you're interested, I can recommend some fairly technical books on composite aircraft construction, which is what I've been studying because there aren't any books on fancy composite boat construction. Same stuff, same issues, though. ..... The real killer of cored structure is lack of maintenance. How long has it been since all deck fittiings were rebedded? Going on 2 1/2 years for me, and I'm thinking about doing it again. But then I was raised in the old school where you do this *every* year. Then there's the school of thought that if you bed everything in polyurethane (3M5200, for example) you'll never have to do it again. That's true, because you'll never be *able* to do it again, and of course it will leak with time. Terrible idea. I used to use 5200 for everything, and then of course had to peel/scrape/wirebrush it off, very tedious. Now I use 4200. And I own stock in 3M..... This turned out to be really long, sorry about that. But it's an important issue. This should have come under the "projects" thread earlier. I think some of us enjoy projects of this nature. And some of us are pedantic enough to want to do it in the best possible technological manner. Most owners are clueless. ("You mean you have to rebed those things? What the hell . . .?") Maybe it is pedantry, but my belief is that it's less work to do things the right way. Especially if you don't want it to fail at an inconvenient time. Another of my theories is that 'if it works, it must have been done right.' I'd like to see some of Frank's work & learn. Fresh Breezes- Doug King |
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