Bird mouth spar?

[Bob Ketterling]

I was reading an article on the Duckworks site about gluing up spares and they said " The glue is a special Phenolic Resin. Note! NEVER GLUE UP MASTS WITH EPOXY!" My question is why not use epoxy?

[Banjo]

You can use epoxy so long as you protect it from UV, best to paint the mast above the decks.

[Bob Smalser]

That Duckworks article is discussed here:

http://www.woodenboatvb.com/vbulletin/upload/showthread.php?t=74565

[werner]

sometime ago i spoke to a professional spar maker he said not to use epoxy (he uses birds mouth system) . Perhaps the reason is the same why epoxy isn't used to glue up large construction beams under permanent stress ?
[You can use epoxy so long as you protect it from UV, best to paint the mast above the decks.]???
I do not understand how or why a glue joint can or should be protected from UV ? I can not imagine UV light getting into the glue joints, apart from the small visible glue line

[paladin]

My last two sets of spars were glued using epoxy...one set 35 years ago and one set about 20+ years ago. Every five years they were taken to bare wood and inspected, then repainted white. No apparent problems. Both sets were box sections tied together with inner tube clamps while the glue cured. The rudder/centerboard/centerboard case were made for my old Searunner tri using the UF glues and clamps....after nearly 20 years the case split (wood broke, not glue joint) and centerboard broke because a reef was a wee bit harder than the glass encapsulated plywood.

[Todd Bradshaw]

"NEVER GLUE UP MASTS WITH EPOXY!"

Hogwash! Some of the most highly-stressed, over-flexed hollow wooden masts on the planet are iceboat masts and these days almost all of them are glued with epoxy. See for yourself:
http://www.idniyra.org/images/paul_n_jd.jpg

Epoxy has no trouble exceeding the grain strength of the woods used to build masts and once you do that, the glue bond can't get any stronger.

[Pernicious Atavist]

Not that one would use it, but I glued up red oak rails with epoxy and it didn't hold. (I recall this discussion from years back.) I called Gougeon and spoke to their chem guy and he couldn't tell me why the red oak wouldn't well accept the epoxy. I reckon it has to do with oils and such, but I digress from the thread, 'less one wanted to make a mast of red oak....

[Keith Wilson]

I think "never glue up masts with epoxy" is utter nonsense. I've made several, and I know about a lot more, and none of them had had any problems due to the glue. UV exposure isn't a significant problem with a birdsmouth spar because the glue lines are inside the wood and protected. Epoxy softens with heat, but if your mast gets that hot glue failure will be the least of your problems. Just don't paint it flat black. In fact, I think it would be very very difficult if not impossible to get the tight glue lines and high clamping pressure necessary with phenolic resin glue on a birdsmouth spar. Nope - I'd say epoxy would be by far the best bet.

[Tom Robb]

Epoxy...a theological question.
Nothing built by the hand of man will last forever.
The pyramids may come close.

[Keith Wilson]

Nothing built by the hand of man will last forever.
UHMW polyethylene. If you bury it, it's as close to forever as anything gets. Even the continents drift eventually. ;) And with reasonable care, a mast glued with epoxy will last long enough.

[werner]

Why would a professional sparmaker even consider to use anything else than epoxy, surely not because the price difference ,epoxy is perhaps more expensive but much easier to use, faster and will fill large joints no expensive material needed for pressure ,
so why use anything else ?there must be a reason or is this really all about some kind of "religion" or ill advised conservatism .
I am planning to make a mast of almost 40' long 4"7/16 diam at largest to 2 " top .I sure hope I can get this done with epoxy and end up with safe mast

[kc8pql]

That Duckworks article is discussed here:

http://www.woodenboatvb.com/vbulletin/upload/showthread.php?t=74565

Go back and read this thread. The author of the Ducksworks artical really doesn't understand the topic.

[Pernicious Atavist]

"Write it, and they shall believe...." whether or not if it's true, right, factual....