dale Posted August 21, 2009 Posted August 21, 2009 Just got rained out of a trial effort to build a birdsmouth spar (3' long). Seems I just read on a site the other day (can't find it now) that you should NEVER glue a birdsmouth spar with epoxy. That was a new thought to me. What do yo use to glue up a spar? thickened epoxy? gorilla glue? elmers wood glue? or what? Quote
dale Posted August 21, 2009 Author Posted August 21, 2009 I found the site: http://www.duckworksmagazine.com/06/howto/birdsmouth/index.htm Go down about 2/3 the way down. "This is the mast stave scarphs being glued. The glue is a special Phenolic Resin. Note! NEVER GLUE UP MASTS WITH EPOXY!" Quote
PAR Posted August 22, 2009 Posted August 22, 2009 I took a quick look at the article and the guy is kidding himself. First of all, if he didn't use epoxy, there will never be enough clamping pressure for plastic resin or resorcinol adhesive to effectively bond, with just packaging tape. Anyone that thinks this is literally kidding themselves. You need a lot of clamping pressure with both of these adhesives and perfictly matching joints. A close up look at the ends of his spar indicate a good bit of misalignment and fairly thick glue lines. This suggests gap filling and something that nether plastic resign nor resorcinol will do. So again, some one is kidding themselves. Quote
Cricket Posted August 22, 2009 Posted August 22, 2009 Having built a few birdsmouth spars myself, I can't imagine using anything BUT epoxy. I found hose clamps to be a pretty good way to clamp the mess. And it is pretty messy. Jim Luton Quote
Frank Hagan Posted August 22, 2009 Posted August 22, 2009 I agree ... using anything but epoxy is very hard because of the clamping. The bird's mouth joint isn't a really tight fitting joint ... at least mine never were! Epoxy is a gap filling adhesive, and I used epoxy thickened with wood flour to about a peanut butter consistency, and it worked great. Does he give a reason not to use epoxy? The only one I can think of is its tendency to soften at about 140 Quote
dale Posted August 22, 2009 Author Posted August 22, 2009 I think it was the heat that he was concerned about. The guy lives in S. Africa. He apparently has done some significant work having built an 18 meter mast before. Anyway, the rain stopped and I finished. Used gorilla glue (though I will use epoxy if I build the real thing). I had 4 pieces of scraps but one was warped so I made a 6 sided trial. Used 30 and 60 degree cuts. didn't have to reset blade, just turned over the staves. Joints seem pretty tight. Now I'm ready to build a real one! Quote
Hirilonde Posted August 22, 2009 Posted August 22, 2009 It really angers me when people post definitive statements about stuff with no reference to a sound source of fact or even a good logical explanation for the statement. There is so much bad information on the internet because few people take the time to properly research something before acting like experts on a subject. I think I will continue to use epoxy, even for a birdsmouth mast. I think I will continue to visit here as well, where people refrain from insisting on stuff they don't understand and ask questions and start discussions that yield useful information, instead of just proliferating the misstatements. Quote
lbrewer Posted August 22, 2009 Posted August 22, 2009 I wouldn't use anything but epoxy because of clamping limitations. I've built three so far with no problems. Using resorcinol and clamping with packing tape I would expect a failure. Such adhesives, as PAR mentioned, require tight fitting joints and high clamping pressure. Its hard for me to think that epoxy would fail from heat in any reasonable sailing circumstance. In this case I would personally have to defer to my own judgement rather than follow the advice of the author. Larry Quote
Frank Hagan Posted August 22, 2009 Posted August 22, 2009 Gorilla glue expands to fill voids, I think. So it would work, but I've always objected to the glue lines with Gorilla glue. Epoxy has its limitations, but: [quote author=Hirilond Quote
PAR Posted August 23, 2009 Posted August 23, 2009 Over coated with epoxy, your Elmer's and plaster Vacationer might survive fairly well. Quote
ChrisObee Posted August 23, 2009 Posted August 23, 2009 Over coated with epoxy, your Elmer's and plaster Vacationer might survive fairly well. Add chicken wire to the panels for strength. Quote
Konrad Posted August 23, 2009 Posted August 23, 2009 Did I mentioin that the sun rotates around the earth? That's what causes the tides, you know.. Quote
PAR Posted August 23, 2009 Posted August 23, 2009 Everyone knows the sun rotates around the earth and that Neptune breaths the tides in and out . . . Quote
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