G’day oneula,
I think the problem is That if it’s too rough them you get air bubbles from the craters in the foam affecting the strength of the glass job. Seems like the optimum binding agent to tie in the inside glass layer between the foma and skin woul be some of foaming epoxy or even something like expanding polyurethane glue like gorilla glue…
Mmm… Not sure how rough is too rough, tho 
I dont think we don’t necessarily need a perfect bond, anyway. Just a bond that is stronger than the EPS should be sufficient. I think that even penetration to a given depth into the EPS is more desirable. So there’s more epoxy in the EPS the closer you get to the surace and less the deeper you go into the EPS. This’d gradually reinforce the EPS depthwise, which should be safer in terms of delams. I thing this depth of the “fingers/hooks” is part of the reason why the unprimed/unspackled boards don’t delam - but they are soaked in epoxy more than needed and thus are rather heavy.
I think if you play the measure game with the interior epoxy lam you’re gonna come up short with air bubbles so your goona want it wetter than usual or your gonna want it smooth as a babies butt using spackle.
U-huh. You may be right. A dry join is a nightmare problem just waiting to bring you grief. That’s why I am wondering how to prime/seal the surface with a very light coat of epoxy. Then play the measure game with the under-skin glass.
But I’m like you thinking that glassing something to spackle isn’t alot of strength if the spackle releases from the foam somehow… With water based spackle this is a strong possibility. EPoxy spackle sound good but how do you prevent soaking the foam too much…
Yeah. So I logically start wondering whether we can get away from spackle entirely.
On the other hand does the Bert method really want the skin to be physically bound and locked in to the foam core? I don’t think so cause you want the deck and bottom to flex and be tightly pinched at the rail…
Like I said above. I don’t think that a perfect bond is necessary. The more I think about it from the different angles the more a carefully measured priming coat of epoxy makes sense to me. It’s certainly the standard kinds of thing to do in non-surfcraft composite/construction areas.
So you light seal the outside into a hard shell and use aliitle more resin on the interrior lam and you should a tough but stiff bond to the foam.
Not quite. I really don’t want to go with stiff. I’d rather have strong a flexible (I see you start commenting on that below). Was more thinking along the lines of sealing the EPS very lightly. There’s going to be some penetration of epoxy into the EPS, but if the epoxy is carefully measured this shouldnt be a huge amount. Then we measure the glass:epoxy out at 1:1, or maybe ever so slightly more epoxy (maybe 1:1.1 or 1:1.05). That’s gonna give us a chemical bond to the priming layer, which has formed a deeper mechanical bond with the EPS than if spackle was there. And because spackle isn’t there (and our priming layer was carefully measured) there shouldn’t be a significant difference compared to a spackled compsand. So I have been wondering how to go about misting the weight of the glass (or 1.5x or 2x the weight) onto the EPS surface.
But deep down I’m leaning to the belief that the binding agent between the skin and the foam needs to be flexible and able to withstand alot of compression and releases with out breaking down. (A Polyethelene/Polyprolpelene layer over EPS seems to be a possible “buffer” solution that could be applied under the final shell to length the life of the EPS core and external hard shell)
Don’t really know You may have a point. It;s something I’ll have to think over. It does seem to me that epoxy should be flexible enough, tho. Whereas spackle or epoxy soaked spackle probably isnt.
It also seems that if you somehow completely seal the foam layer under the exterior wood skin with lots of glass and epoxy, then you can pull the Chris Garrett/Rasta move of only oiling the exterior wood skin as a final coat. It’s be interesting to see how Chris is applying his wood skins so he doesn’t have to glass the exterior side of them and still not have the wood breakdown and the board get water logged.
As someone who has spent a serious amount of time looking for the perfect wood sealant I have a very definite opinion on this Oil, grease, varnish, etc are never, ever going to provide a permanent vapour barrier. Much less a truly water-proof one. That’s why wood boat-builders all moved over to epoxy paints and sealants as soon as they became available. You see, it’s easy enough to come up with something that will penetrate into the surface wood fibers. Most things in a liquid form will do that nicely. But unless that liquid truly sets into a solid (catalyzing) it will NEVER keep all moisture out. The most success I had was by ironing/heat-gunning wax into the surface of wood fibers. The melted wax is a liquid and penetrates, then harden when it dries. Only becoming an issue on really hot days. traditional varnishes, for example, don’t truly catalyze and don’t penetrate the wood surface as well as we might expect. This is easily tested and very well documented. If Garrett/Rasta really are oiling their timber they ARE getting timber penetration over time. Basic fact. It may not be a big deal to them if the sub-surface is properly sealed.
-doug
