posts: 156161
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| post_id | thread_id | thread_title | post_number | author_username | post_date | post_date_iso | post_body |
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| 156161 | 6778 | Shaper thread (show us what you are shaping) | 52 | dingpatch | Sep 8, 2019 | 2019-09-08T18:36:31-0400 | Driftwood brings forth a very relevant point, , , , In my beginning fin making days I always had "trouble" using poly on various woods. Not all woods but, mostly the ones that you'd say are "the best looking", etc. Glass this morning, looks OK this afternoon but, tomorrow morning, , , , What The Heck !!! They would look like they were delaminating here-and-there. Did some internet research that led me to boat builder forums. One guy was asking about using poly on some marine ply in his old wooden ski boat. The one notable reply simply said "NO", about a hundred times, in bold 20 point!!! Another guy responded with "the only thing poly resin sticks to is poly resin". Further research revealed that it was a matter of chemistry. It is/was not a matter of the wood having too much oil/sap in it. The problem is that the chemistry of the wood has a lot of phenols in it; the stuff that gives your smoking wood its smell and flavor, , , ,. And, it is not just a simple matter of the poly resin not "sticking"; the chemistries of the poly and the woods just plain HATE EACH OTHER. I ended up stripping the glass off of a fin about two days after I glassed it. Underneath the cloth was a layer of "goo" that would make duct tape seem slippery! This is why, way-back-in-the-old-days, glassers hated to glass elaborate wooden tail blocks. I now put a sealing coat of epoxy on the fins, and then 60 grit it, prior to poly glassing. |