View Full Version : glue for mast

03-19-2002, 09:28 PM
I'm laminating new blanks for 2 unsupported masts of about 11.5 and 7ft. Should I use a glue that retains some flexibility, do I need to use a marine glue and do I need to dowel the joins. I built a temporary rig for my Macgreggor for the summer and now I want to do a propper job on the permanent one.

03-19-2002, 11:23 PM
Please humor me if I'm having just another blinding flash of the obvious, but I glue virtually everything with epoxy, its strong and flexible. Also, any glued joint is only as strong as the weakest link in the chain, which is usually the wood, not the glue. Dowels, or any method of through fastening will prevent a joint from shearing apart.

J. Dillon
03-19-2002, 11:33 PM
I used a plastic resin glue made by DAP on my 17' un supported mast. A powder you mix with water. Just the glue and no dowels. It has stood up now for 6 years no problems. I apply several coats of varnish each season and by now it must have thirty coats. If you use a resorcinol glue it will show a glue line.


03-20-2002, 04:37 PM
Thanks all, I should have looked at past posts before opening my electronic mouth, but sometimes at the crunch one has self-doubts [/LIST]

03-21-2002, 03:24 AM
suggest using resorcinol glue. no fasteneings or other would be required and the glue won't break down in the sun as epoxy will.

Ian G Wright
03-21-2002, 03:59 AM
Resorcinol glue would be my choice.
Don't get trapped by the idea that epoxy is 'the answer' to all gluing questions, it isn't, though some folk would try to convince you otherwise.


Scott Rosen
03-21-2002, 09:35 AM
Resorcinal is the best, but it requires clean, well-fitting joints and is temperature sensitive. Epoxy is much more forgiving.

Billy Bones
03-21-2002, 10:20 AM
The glue debate is endless so I won't add anything to it here.

However, don't add the dowels. The glue is strongest in shear (as in laminations) and is much stronger than the wood. If you dowel the thing, you'll be adding spots of irregular grain orientation. (and a cross-grain dowel wouldn't do much good, would it?) Hence, you'll have weak spots which will focus local stresses and cause failure.

A friend made a serpentine tiller out of mahogany and oak laminations for a 35' sail boat. He didn't know/trust the epoxy so he drilled holes across the laminations at various spots and bedded big dowels in it. In addition to looking absurd, it failed catastrophically at two of the dowels during a hurricane-induced grounding.

Class, repeat after me: Either you trust epoxy or you don't.

Dave Fleming
03-21-2002, 10:23 AM
Built some Redwood Benches for the Sonoma Cheese Factory in, where else, Sonoma, CA.. That was in the early 1970's. Was up there in Novemeber last and they are still there. 7/24/365, heat of summer, wet of winter, no delamination no finish aka varnish or oil since I made them. Built 10 masts out of Sitka Spruce for Lightnings in the late 1970's.
No failures from glue but several did suffer damage from sailing and handling.
The glue.....Weldwood Plastic Resin. Light beige powder mixed with H2O till smooth and creamy. Plenty of clamping pressure and 24 hours in clamps with temp over 65 degrees
Ya folla? ;)

03-21-2002, 10:28 AM
any thoughts on titebond II for this application?

03-21-2002, 10:39 AM

I've made 2 spars so far. The first was a mast glued up with tite-bond II and the second was the sprit glued up with thickned epoxy.

I've not had any problems with either. The glue lines are more visable on the epoxy glued sprit, but both look fine.


03-21-2002, 11:11 AM
That question was in my mind as well, Jake. I would think for as casual use as the masts I build get, it would be satisfactory as would Gorilla glue, et.al. GG would give a much better open time which might be a problem with Titebond II. Resourcinal would be the ultimate, of course, IF one can get good joints and clamp tightly in a proper enviornment.


03-21-2002, 11:31 AM
The spars on my old boat and the centerboard were done with resorcinol and they is still good. Ain't broke yet..... :D

Frank Wentzel
03-21-2002, 12:42 PM
I agree that all of the mentioned adhesives would probably do the job if the stock preparation, fit, temperature, and clamping requirements for each are met. However, as Scott Rosen observes, epoxy is the most forgiving of all the various adhesives. If you believe you can adequately control all the above parameters on an 11 foot mast, use any of the listed adhesives, though resorcinol would be the best. If you have any question about your ability to control the all of the various parameters simultaneously, you might be best to "stick" (sorry! :rolleyes: )with epoxy.

/// Frank ///

03-21-2002, 03:38 PM
Right. Resorcinol if you don't mind the visible glue line, Weldwood resin if you do. Years ago at Richmond Boat Works we built a 50' box section mast, using resorcinol, and shipped it to Ecuador. Some years later I found myself in Guayaquil, and located the mast, on a cutter. It was very sound, in the humid tropics not far south of the Equator. Other masts, glued with Weldwood, have stood up well over the years.

Dave Fleming
03-21-2002, 03:49 PM
Bayboat, Resorcinol got a bad name early on because most folks did not.
A: read the instructions
B: didn't follow the instructions regarding pressure and temp.
Saw some really bad failures. it took awhile for folks to catch on and bye that time Epoxies were on the horizon.
Best work I ever saw with RR was from the old Marinette Marine minesweepers.
Laminated frames, IIRC OAK, done on a big ironworkers platen type table and pneumatic clamps and heat cure. I also believe some of the reproductions done in recent years have had frames laminated with it in some furniture factory in the Southeast USA..
Least that is what I recall seeing when they were building the California down here in San Diego at Spanish Landing.
But I could be and have been wrong before :D

[ 03-21-2002, 03:51 PM: Message edited by: Dave Fleming ]

03-21-2002, 05:00 PM
Why not use the more user friendly Resorsonol Aerodux 500?It can be used as low as 45 deg. F and with 20 % fillers added can be gap filling to 1/16 inch and requires only close contact not high pressure.Thats the way I'm going when building my future masts....Jim

Bob Cleek
03-21-2002, 05:57 PM
Yep, I keep hearing good things about Aerodux 500's gap filling properties. Worth a try. Nothing wrong with epoxy, but use the slowest hardener you can find to maximize working time. (West's Tropical hardner is my favorite.)

Funny mast gluing thing happened to me on the way to the forum...

I had a boom that was starting to delaminate. (40 years old or so) It was glued with God-knows-what, but probably some kind of powdered monkey-dung. Anyhow, I split the whole thing apart with wedges carefully... cleaned up the faying surfaces and reglued with epoxy thickened with colloidal silica. When I split her apart, there was one section that was holding very well, so I left it alone. Now this boom always had a bend it it to one side... sort of like some guys have a... well, anyway, I wanted it straight so when I reglued it I clamped it down on a big length of 12" I beam to get a true line. It worked great for about four years, but now, wood having a mind of its own, the old glued seam that I left alone took the stress of holding the reglued boom straight and popped, leaving a 16" x 5' seam I'm going to have to fill with epoxy. (No way am I going to try to take the whole thing apart now that I've epoxied most of it.) Clamping the popped seam puts the kink back in the damn thing! Moral of the story is, 1) don't mix adhesive systems in the same damn spar, and 2) epoxy is stronger than dried monkey-dung, or just about anything else.

03-21-2002, 07:06 PM
I've grown rather fond of Aerodux 500 and found I like the glue line and it doesn't react with people unable to be near epoxy (a couple of guys working for me) It'll survive the boiling test so we can park our wooden boats over active underwater volcano's without worry.

Bill Perkins
03-21-2002, 08:44 PM
I think The Chemist ( where is that lurking oracle ? ), or someone else once mentioned that the boiling test is a type of accelerated weathering simulation .It's not always practical to wait for prolonged tests in the natural envirnment , but it's understood that you're not going to " boil your boat ".