Gluing laminated bowsprit

[George Buckwalter]

In the process of rebuilding my laminated sitka spruce bowsprit with 2-8/4 sitka, and the original 3/4" piece of teak that forms the center of a teak platform.

Wondering about what type of adhesive or glue to use and drying time before final shaping andfinishing.

George

[paladin]

CPES the wood,use epoxy adhesive, shape, CPES again, carefully coat with epoxy and either paint or coat with varnish etc of choice....mine is painted and inspected for cracks or fissures regularly....especially around the various fittings.

[JimConlin]

I've not seen any hard data on the strength of CPES when used as an adhesive. The Gougeons did some strength testing on diluted epoxy and found it to be significantly degraded in strength. For use as an adhesive for a wood glue-up,i'd use a full-strength non-diluted epoxy. Others will argue for resorcinol or another tested adhesive.

[Jay Greer]

Having used epoxy for spar layup and seeing it eventually fail, has convinced us to continue using the two glues that have always worked for us and never let go. For spars to be varnished, we rely on Weldowood. For painted spars or if you don't mind a dark glue line, Rescorcinol is stiill the most relyable glue in my opinion.
JMG

[paladin]

I did not intend the CPES to be used as an adhesive...merely a precoating...one time...then my unit is laminated using T-88 adhesive...ain't broke yet...

[JimD]

My bowsprit is laminated with silica thickened epoxy, no cpes. No problems.

[Ken Hutchins]

Laminating 8/4 pieces is not a good plan, you should saw them in half. When laminating the laminations should not be over an inch thick or you will have failures due to the expansion and contraction of the thick pieces, alternate the grain of the parts when assembling. I would use resorcinol glue.

[paladin]

again...I would saw the planks about 1/2 inch thick, then flip every other piece end for end to stabilize the grain.....then quarter sawn will not be as important....

[Andrew S/Y Rocquette]

Rescorcinol - my tuppence worth

[Buddy Sharpton]

I agree the worry here is laminating up those 8/4 pieces. Epoxy has a hard time handling the stress of "holding back" the expansion and shrinking cycles of dimensional
hardwood lumber, much less the bending cyles. My bowsprit at the base is 4" x 2/34", glued with WEST. I saturated the surfaces of the laminations with unthickened epoxy, let it get tacky, and then butterd up the stack with the same epoxy thickened with WEST adhesive fibers to ketchup consistency. Stacked and clamped them under just "snug" pressure as to not squeeze out all the epoxy. But I resawed all my layers to 5/16" thick cutting 3/4" stock end for end on the table saw. That said , my mast is made of almost exactly what you are suggesting, two 1 1/2", and one 3/4" layers of store bought spruce. They have held up nicely for
15 years now. But they are of course softwood. Yours is a mixed composite so I would err on he side of caution. Couldn't hurt.

[Bob Smalser]

When laying up large stock, I find the problem encountered with epoxy is usually the clamping pressure required to pull the stock into a good joint.....often too much for epoxy, thus starving the joint.

Epoxy can't handle any serious clamping pressure to speak of, so large stock or stock or joints that are "out" and need to be pulled in tight with your large Jorgenson's are much better served with resorcinol.

Plastic resin U/F glues like Weldwood...and Polyurethane glues like Gorilla and Elmer's Probond also like a lot of clamping pressure.

Poly's like damp wood, too, if you are steaming your lams....but aren't marine-rated glues and I've only tried them on a few easily-replacable knees and oars to see how they hold up over time.

[ 06-22-2005, 10:14 AM: Message edited by: Bob Smalser ]

[George Buckwalter]

All greatly appreciated advice. I am thinking I will use a combo of resorcinal for the lamination, penetrating expoxy for the thru bolt holes(10) , and epoxy with filler to repair a couple of counter sink shoulders on the teak.

The original structual design of using 2-8/4 spruce boards didn't cause the failure of the sprit. The end of the bowsprit rotted off from the bottom up due to the attachment of the cranse iron, using 6-1/4" thru-bolts and mortised backing plate.(A real nice spot for water to sit and sit and sit.) There was no evidence of any sealant or bedding material used; a small overlooked detail that won't be overlooked again.

Thanks-George

[Andreas Jordahl Rhude]

Ken Hutchins said: "Laminating 8/4 pieces is not a good plan, you should saw them in half. When laminating the laminations should not be over an inch thick or you will have failures due to the expansion and contraction of the thick pieces, alternate the grain of the parts when assembling. I would use resorcinol glue."

I agree with the resorcinol recomondation but totally disagree with his caution of using 8/4 stock. Why not? We use it everyday and for many severe exposure applications. The masts and bow sprit of Old Ironsides are glued laminated timbers using nominal 2 inch laminations. Keels and other members for US Navy 224 ft. MineCounter Measure ships are glued laminated with 2 inch material. We make beams, trusses, and arches for road and pedestrian bridges and use 2 inch laminating stock all the time -- have been for 70 years. Resorcinol is the adheive used.

Mr. Andreas Jordahl Rhude