Glen-L.com

Robbins Timber in the UK http://www.robbins.co.uk, a well respected supplier of boatbuilding timber and other materials, has recently been pushing a new adhesive called Balcotan http://www.robbins.co.uk/mar_balcotantech.htm. It's one of those single part polyurethane adhesives that cures in the presence of moisture, and foams to fill gaps when in contact with air.
They are specifically recommending it for boatbuilding and I wonder if anyone has had any direct experience of it, or similar adhesives? I've used products like Gorilla Glue which is basically the same thing and found it to be very good, but I've never really considered it for boatbuilding because a) it's pretty expensive, and b) epoxy is so good I've not really considered alternatives. I wouldn't hesitate to use polyurethane for interior work on boats, but I'm not sure about exterior and constructional work?
The thing with Balcotan is that curing is not temperature dependent, it cures in pretty much the same time whether it's warm or cold, and it's unaffected by humidity in the way that epoxy is. In quantity it's also a bit cheaper than epoxy, not that that's a major consideration in my view but it helps!
With the onset of winter in the Northern Hemisphere those of us working outdoors, or in unheated workshops, are only too aware of the problems of using epoxy in cold temperatures and would welcome a more useable alternative.[url][/url]

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Graham in Shepperton, England

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Hi Graham,

I have also been curious about polyurethane glues and I've done some experimenting with it (stress tests). So far I have not found it to be as strong as epoxy but this was before gorilla glue hit the market and others have claimed it is stronger than previous brands.

I can see why those building in colder climates might be interested, but prudence would require facsimile constructions (out of doors, high moisture, etc) then subjected to real tests of endurance. I'd hate to make a mistake on something like glues.

May spring come soon.

Cheers,

Mark

Graham,

I was wondering about poly glue also,so I used them on my TNT.
So far so good, no failures any where. I used gorilla glue for 99%
of the construction and PL's polyurethane for most of the changes I've
made. Please understand that I abuse this boat. I've gone as far as to
push it with an 85hp Merc (65hp over the boats rating) and before that
with a 35hp I hit a wave so hard I split the #2 frame from side to side.
Still no failures, I'd have to say that's pretty good test.

I saw the pics of your boat it's looking great.

Best Regards,

Steve

In the U.S. there is a new glue called P.L. polyurethane premium construction adhesive- by osi sealants of mentor ohio - website www.stickwithpl.com, they say it is 100% water and weather proof and bonds to wood,metal stone,concrete,vinyl,plastics and foam . Suppose to last as long as the surfaces it joins, is 100% polyurethane and suppose to be safer to use. I read about this months ago on wooden boat forum and got some and experimented with it against epoxy, and in my opinion it is at least as strong as epoxy if not more so, easier to use and cost $2.75 for a 10 oz. tube which works out to about $33. a gallon.I used it to glue my plywood to my forms on my boat and it worked great, slight swelling or foaming action, but nothing like gorrilla glue.It is relatively thin and you could laminate with it.I laminated some plywood with it and it worked great.You can also use it in much cooler and in damper conditions.Epoxy is a good glue, but I am not a fan of it due to the toxicity.15 years ago i got a sample kit of west systems for a stripper, and got 3 drops on my hand that immediately turned to blisters, and scratched the stripper canoe idea.The latest web letter has a guy from florida that can't finish his monte carlo due to epoxy poisoning, what a shame.Some people can't stand to use it, or enjoy working with it, just that simple.

Well the P.l. post was mine, and as others say , the board will take a little getting use to.

I'm thinking I might order some of this Balcotan and use it for glueing my hardwood deck laminate, it's not really structural and won't be subject to much stress, the main requirement is that the glue is waterproof and easy to work with.
I've used 2 part polyurethane adhesives in the past and found them to be extremely strong, better than epoxy in some applications. I'd have no hesitation to use them for structural work in boatbuilding, but I'm still not totally convinced about the single part stuff.
Steve's post about his TNT is encouraging, the first actual "in service" report I've read.

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Graham in Shepperton, England

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I've been talking to a couple of people today who have actually used this polyurethane adhesive, and they both have very good words to say about it.
The first is the owner of one of the props companies at work, eight years ago he built a 16' strip planked canoe from Cedar, working entirely with polyurethane adhesive because he has developed the dreaded epoxy allergy.
The boat is still as good as the day it was made, no joint failures at all, because of his allergy the hull was just varnished, no epoxy encapsulation. Whilst on holidays and at boat rallies the canoe has spent up to a week at a time in the water.
He then put me onto a friend who built his own cold moulded ply cabin cruiser, again using polyurethane exclusively for the same reasons. The cruiser is now 5 years old, spends all its time on the water except for a week each year, and again has no glue problems. Like the canoe it has a painted finish which he admits does require more maintenance, but due to the allergy he had no choice unless he paid someone to glass/epoxy sheath it for him.
On the basis of these and other favourable comments I think I'm going to give it a go at least for my decking, the idea of spending the winter trying to heat a polythene tent, or just not being able to work on the boat until spring is not attractive!

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Graham in Shepperton, England

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I've used the PL Polyurethane adhesive for a few parts on my boat and have been very impressed with the results. I'm by far using mostly epoxy but the tube of PL in the caulking gun is just soooo much easier to use in some cases (rather than measuring, mixing, adding fillers, re-mixing, adding more fillers, wearing all the protective clothing, etc.).

Also, for some of the less-critical joints I'm using "Deckmate" screws from Home Depot. They have the combination Philips/square drive head and are about 10 times easier to drive in than any other screws I've used. They have a special coating that is supposed to be good for boat dock construction and other wet environments. I used some on a deck repair about 4 years ago and just looked at them today. They look great with no apparent corrosion. My only concern would be where I had to grind part of one off like in a butt joint. Anyway, if you're tired of the dreaded "drill skipping" when you drive a screw, give them a try (commercial over).

I had my first experience of using Balcotan polyurethane adhesive today, and I have to say that so far I'm very impressed.
It was easy to use, with the appearance and consistency of honey it spreads easily, open joint time is over an hour so there's absolutely no rush at all!
I used it to apply the first of my 3mm (1/8") thick Mahogany finishing boards around lunchtime, temperature was around 5-6 degrees centigrade and it's now quite hard, enough to remove the clamping screws.
You can see where it's foamed around the edges, not very much as I only applied it to the planking not the ply decking, and it should have risen enough to fill any small voids.
While I was at it I did a few test samples at work too, one I just spread the glue on a scrap of wood and left it open. The glue foamed but nowhere near as much as Gorilla Glue or other polyurethanes I've tried, even the foamed stuff has a bit of strength to it but is apparently easy to sand off when fully cured.

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Graham in Shepperton, England

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Is this the same type of stuff that the building trade use for filling gaps? Comes in an aerosol can and expands like a foam?

No this is very different, it's in the same family of polyurethanes but it doesn't foam up to anything like the same extent. I'm having really good results with it at the moment, for applying this decking it's excellent and I'm trying it for assembling a hatch frame too.

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Graham in Shepperton, England

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This Stuff is very strong. I've used it a couple of times and found that if you laminate Poplar with it you get an interestingly pliable, but very stong material.

Last time, I used it to repair an antique rocking chair. The rockers had worn to the point that one gave out. I created a 1/2" x 1/4" spline for each rocker out of 1/8" strips of Poplar (6 pieces each) and inserted them vertically in the bottom of the rockers so that you can't see them from above.

The rocker that cracked has a little flex (as expected) but it held when I gave it the "Ken Test" (DROPPING my 210lbs on it!)

Haven't tried it in boat building yet but it creates an interesting new material to work with. It's expensive but it's so neat I don't care!

Ken Franks
Calgary, Alberta
CANADA

I might try some of that stuff....working with epoxy when it is -2C outside is a real pain....the tent I built around my boat is not big enough for me to fit inside and walk around...so I have to apply the epoxy, clamp everything up, and then put the tent over it and heat it up overnight...I heat it to about 12C, hopefully the strength of the epoxy bond will be ok...its a pity there isn't some other sort of sheathing material you can use in cold temperatures though..

Well you could use polyester resin instead of epoxy, it's far less temperature dependent, the problem is that it's nowhere near as good!
Although having said that there are plenty of GRP boats that have been around for 20, 30, 40 or more years.

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Graham in Shepperton, England

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Yes and its horrible smelly stuff too....and usually has a colour in it.
I think the best way to go is wait for a reasonably warm day (say 8-10C) and preheat the hull and the epoxy to 25C, do the job as fast as possible and then cover with the tent and heat back up to 15C. It just might work..