View Full Version : Strip Building

Big Red
10-11-2004, 07:40 AM
Whats the opinion on Poly Urethane glue for stripping WRC? 13 foot dinghy, 1/2" x 1 1/2" strips. I will glass the outside, but what about the inside? Necessary or just epoxy would be ok?

Thanks for opinions.

Bob Perkins
10-11-2004, 08:05 AM
Big Red,

If you are talking about a glue like Gorilla glue - That stuff that foams up w/moisture - I wouldn't use it. It would be a pain to work with in a strip built boat.

When I strip built my canoe, I used this powdered glue that mixed with water - when dry, it is waterproof (according to some gvt standard printed on the can) It was very easy to work with.

Epoxy would work too..

I like to work neat - so I wipe up the drips as best as possible as I go - the foamy glue will not allow that.

My Thoughts,

10-11-2004, 08:41 AM
GG would be my last choice for reasons stated above. Ya can't go wrong with epoxy especially if you do not bevel the edges of the strips to get a tight fit. Seems to me the hull should be glassed on both sides but opinions seem to be all over the map on that. Oughtred specified glassing his Farne Islander (1-3/4" x 5/8" WRC strips) on the outside. I asked him if it should also be glassed inside. He replied that he consulted local builders who advised it would hurt to glass the center 2/3. I did it all, one layer of glass inside and out with an extra layer outside below the water line. We call them wooden boats but they are composite boats (the best of both worlds, eh Cleek). Don't be half way about it. Glass the inside too.

Bob Smalser
10-11-2004, 09:50 AM
I use poly regularly on WRC in other outdoor applications and like it. The only glue I know of that likes green wood. One advantage is that it's easier to scrape if you scrape within 8 or so hours. It doesn't sand as well as epoxy or UF resin once fully cured, however.

It's a great application in situations where you have too much clamping pressure for epoxy and have no resorcinol handy, as like resorcinol, I don't think you can clamp it too tight.

It's not rated for below-waterline use, however...and hasn't stood the test of time. But neither is UF resin rated for below the waterline, and on balance, poly is a much more waterproof glue between the two.

Personally, I'd use epoxy...the most flexible of glues. No personal experience with how flexible poly is, although I haven't had a glue joint fail with it except the ones I experimented with in a driving rain on sopping wet cedar. UF resin is not what I'd call a flexible glue in comparison to aliphatics, let alone epoxy and I suspect it's a lot less flexible than poly.

But there appears to be no shortage of home builders out there using poly for your application without complaint....at least yet.

I use resin in preference to aliphatics for general gluing, and probably have used at least a 55 gal drum of it over the decades. I've had a number of neglected outdoor glue joints with it fail....and I'm never sure if it's from water or seasonal expansion. If you use it, keep it well sealed.

[ 10-11-2004, 11:28 AM: Message edited by: Bob Smalser ]

captain's gig
10-11-2004, 11:23 AM
lets take the opposite tack (he he) for a moment, tell us why you do not want to use ordinry carpenters yellow glue.


[ 10-11-2004, 12:24 PM: Message edited by: captain's gig ]

Bob Smalser
10-11-2004, 02:15 PM
Originally posted by captain's gig:
lets take the opposite tack (he he) for a moment, tell us why you do not want to use ordinary carpenters yellow glue.

1) Totally impossible to glue over in a repair without letting in new wood.

2) Sands like chewing gum.

3) Doesn't take stain and ya can't dye it.

4) Freezes in the shop overnight in winter.

5) Likes to creep in hard glueups.

6) No more water resistant than resin.

7) Totally impossible to glue over in a repair without letting in new wood, giving any knowledgeable grandkids another reason to cuss your work some day after you are gone.

Hasn't been a bottle of it in my shop for 25+ years.

Did I say it's totally impossible to glue over in a repair without letting in new wood? Did I say I used to conserve/restore antique furniture as a sideline which greatly expanded my 4-letter vocabulary over previous, destructive repairs?

You've heard this before, eh? Well, it's worth saying again.

[ 10-11-2004, 07:50 PM: Message edited by: Bob Smalser ]

Dave Gray
10-11-2004, 02:44 PM
Well, at least your name would be remembered, if not quite in the manner you would want! :D

On a more serious note, Bob, what would you recommend for gluing two slabs of maple together? I'm interested since I have a coffee table project in my future and I have always used yellow glue on furniture projects....

Don't mean to hijack the thread, apologies if I have

Big Red
10-11-2004, 04:27 PM
I have used the PU before, I was thinking it could make quite a mess of the hull oozing out between the strips. I haven't built with strips before. I don't know anything really about UF glue. Is that a choice I should explore?

I would like to use epoxy, but I am thinking a 1 part glue would make life a lot easier. Whats this powdered glue you mentioned Bob? I have heard of waterproof PVA glues now available. Any feelings on those?

Edited to add: The first Bob :D

[ 10-11-2004, 05:31 PM: Message edited by: Big Red ]

10-11-2004, 04:51 PM
The first question is what stiffness the hull's planking needs to have.

In heavy strip plank construction, where there is substantial internal framing to support teh hull, I have no experience or opinion.

In a strip canoe, as there is no internal framing, the structure needs glass skins in both sides of the planking. If the planking is to be glassed on both sides, it's encapsulated and the glue between the strips only needs to hold the strips together while they are faired and sheathed. After sheathing, the glue serves no structural purpose. For light strip composite construction, I like yellow glue. It's easy to apply and sets quickly which matters if i'm trying to avoid staples and applying only one pair of strips in a cycle. I prefer to let the glue bead out of the joints and scrape it off later than to wipe the glue into every pore of the planking. If the joints are cove&bead, they're tight and the lousy sanding properties of the yellow glue aren't a problem.

For heavier strip composite work like your dinghy, I'd lean toward filled epoxy.

Carl Simmons
10-11-2004, 05:03 PM
As John pointed out, strip built construction only uses the wood for the shape. The fiberglass gives it the strenght. Since I wasn't beveling my
strips I used the PU glue so that when it expanded it would fill the voids. Worked well and
since it was encapsulated in fiberglass, below the waterline concerns wasn't an issue.


Kev Smyth
10-11-2004, 05:17 PM
I would use the new Titebond "waterproof" glue from a bottle. When the glass and epoxy go on the glue becomes irrelevant, and the epoxy will find its way into the gaps on the outer surface on the hull if the strips weren't beveled.

With glass on both sides of the wood, the strength of the wood is much higher than required. Remember, true glass boats are now built with foam for the cores, and the foam is much, much weaker than WRC in all regards.

Dave Gray
10-11-2004, 05:19 PM
Ted Moores in his strip kayaking book recommends against the waterproof glues, but I disremember why just now as i'm at work and the book isn't handy.

Bob Smalser
10-11-2004, 06:41 PM
Epoxy and fabric gonna protect that glue joint forever?

Think ahead several decades to when one careless grandchild holes or scuffs thru the goo and fabric in a few spots then leaves it out in the rain for a couple-five years.

Of all the boats that happens to, I'd like to think mine would be one selected for restoration long after all the others go to the burn pile.

The powdered glue is urea formaldehyde "plastic resin" made by DAP and others available from Jamestown Distributors, Ace Hardware and others. Powder mixed with water. Powder shelf life one year, but doesn't mix well when it goes bad. Also the cheapest glue out there when you are using a lot of glue....I've laminated maple and other hardwoods with it successfully for decades.

[ 10-11-2004, 07:47 PM: Message edited by: Bob Smalser ]

captain's gig
10-11-2004, 06:49 PM
Urea Formaldehyde Resin Glue

"..it is the traditional boat building glue and my first choice for gluing strips because it is easy to work with and inexpensive".

Ted Moores and Merilyn Mohr


[ 10-11-2004, 07:50 PM: Message edited by: captain's gig ]

10-11-2004, 07:42 PM
Ya'all are pushing your favorite glue but without qualifications. No single glue will work in all givens circumstance. Specifically I see a lot of good stuff recomended that requires a tight fitting joint and proper clamp pressure. We're talking strip planked here, remember.

Bob Smalser
10-11-2004, 07:52 PM
Bob, join the list. My recommendation is unchanged...epoxy.

Big Red
10-11-2004, 09:59 PM
Well, I still wanna use a one part glue. Cause I'm a lazy git, but have a look at this thread : Cracked Planking (http://media5.hypernet.com/ubb/ultimatebb.php?ubb=get_topic;f=1;t=010371)

Obviously this is something to be avoided :eek: But it might say more about the lack of frames than the glue. But I think epoxy will be chosen, whether I like it or not ;)

10-12-2004, 06:31 AM
The glue is irrelevant after the hole is in the glass to the wood as the glass will fail due to the swelling of the wood. Use carpenters glue. If you do not like the yellow lines, they do make a dark colored glue I used on my redwood and cedar strip canoe. Also you do not need gloves for the gluing and cleanup is with water. And the strength of the PU glue is much lessened without tight joints. Many people think poorly of PU glues because they use them like epoxy and are afraid to starve the joint. You need pressure for PU glues to work best. Just my 2 cents - maybe it was 4.