Hot Glue and Canoe

[catsittingstill]

So...

I don't remember if I mentioned it, but a while back I came across this page explaining how to use hot glue instead of staples, clamps, or fishing line to secure planks to the forms while the carpenters glue holding the strips to each other dried. 

I was a little dubious; despite the assurances that it worked, the method struck me as running the horrible risk of gluing the forms permanently to the inside of the hull. However, staples leave holes in the strips that the epoxy fills and makes watertight while simultaneously making sure they will be visible forever.  Clamps don't do a good job of securing the hull to the forms, so that the hull comes out with some distortions.  Fishing line is kind of slow.  Perhaps hot glue would be a way around these disadvantages.

So I shelled out 20$ to get a pound of the special sticks of hot glue, and a cheap hot glue gun.  They came on Thursday.  I had to go to Maryville to cut planks, so I stuffed the box in my pack in case Martin wanted to try it out.  Thursday and Friday were busy and it didn't happen.  Today I spent the morning mining Arkonor in Eve (long story) then went to get back to fixing the forms to the strongback.  Looking at the dozens of screws in the forms already up, screws necessary to secure the fishing line if I went with that method again, it occurred to me that it would be smart to test the hot-glue method now, rather than put more screws in to hold fishing line, only to take the screws out again if I decided to use hot glue.

So I cut a bunch of short strips, put a piece of scrap plywood in the vise, figured out how to work the hot glue gun (first tool I've bought in a long time that didn't have any instructions) and started gluing up.  White glue between the strips, a bloop of hot glue on the edge of the plywood, stick the strips onto the plywood, add a couple of beads of hot glue across the top of the strip-strip joint, count sixty seconds, and release.

It works.  I glued up six or so strips, then tried a few glued to two scraps of plywood, so I could have the strips meet the plywood at an angle rather than in a T.  This is because at the bow and stern of the boat the strips will meet the plywood forms at an angle, and I needed to be sure the hot glue would still hold (white glue, for instance, wouldn't hold worth a damn here because there's no surface-surface contact to speak of.)

And it works at an angle too.  I left everything to cure 30 minutes (so the white glue between the strips would cure), then undid the vise, put the strips in the vise, and whapped the plywood with a mallet to see if the hot glue would indeed fail under sheer stress, and it obligingly does.  I was afraid the hot glue would rip chunks out of the strips when it came away, but it takes only a few small splinters.  It's slightly worse than duct tape, but only slightly, and I don't think it will be an issue, because all the divots will be on the inside of the boat, where they won't affect the shape that touches the water.

Upshot: I will be trying hot glue with this boat.  Plywood form edges get no duct tape.  I will have to be careful not to put too much white glue between strips; I don't want the boat gluing itself to the forms with white glue, as this does not have the obliging failure characteristics of hot glue.  I took the screws out of the faces of the forms, since I won't be using fishing line and they would just get in the way.   Putting the rest of the stations on the strongback should go faster without having to do the extra screws.

Martin says I'm his R&D department.

Comments

[nojay.livejournal.com]

Try using a hot-air gun to melt the glue when you want it to free up before resorting to a mallet. It's not exactly canoe-building but I use a hot-air gun to melt book glue when I'm debinding and rebinding books. The glue should soften and melt long before the wood would scorch from the heat.

[catsittingstill.livejournal.com]

I will bear in mind your suggestion about the hot air gun. However I would have to buy one--I don't have one now.

And I just bought an angle grinder, so I'm feeling kind of poor.

[jerusha.livejournal.com]

You may want to experiment (on scrap wood, natch) with a hair dryer, if you have one. (If you don't, it's completely understandable - we have one only because we needed it to shrink the winter-proofing plastic across the windows in our last apartment)

[catsittingstill.livejournal.com]

As it happens, I have one. I almost never use it, but it would be available for experimentation.

Actually, logically, by the time I remove the stations it will probably be getting close to summer--I could wheel the whole thing out into the sun and leave it for an hour and warm it up that way.

[tfabris.livejournal.com]

So what happens if the hotglued canoe sits in the sun on a hot day?

I once used hot glue to fasten something in my car interior. It came unfastened the first time I parked the car in direct sunlight.

[catsittingstill.livejournal.com]

The hot glue is temporary, like a clamp. It holds all the strips in the right bend and twist while the carpenters glue between them dries. The hot glue all gets removed once the last strip is glued into the hull.

[tfabris.livejournal.com]

OH!!! I get it now!

That's *brilliant*.

[catsittingstill.livejournal.com]

I thought it was very clever when I read about it. Well, I thought it would be very clever if it turned out to work.

Which it seriously looks like it will. I will be keeping the internets posted as I work with it.

[boywizard.livejournal.com]

Are you actually using white glue (like Elmer's?) to bond your strips (as described in last paragraph), or carpenter's glue (as mentioned in the reply to tfabris)? I realize that the wood is (theoretically) sealed between two layers of epoxy, but I am a belt and suspenders kind of guy, and would prefer to employ something with at least a modicum of water resistance, like Titebond III or Gorilla Glue, just in case. Still, your boats are still afloat, so what works, works, I guess.

Thanks for your kind offer to transport some wood for me. I live in Marion, Ohio, and the only cons I generally get to any more are Marcon, Context, and OVFF, all in Columbus, so you would be looking at a rather lengthy drive with twenty-foot boards strapped to your roof. I'll do some further research when the time comes to start my next project (after I get the Shark in the water), and if I can't come up with anything suitable locally, perhaps we can work something out.

Exactly what kind of 'special' hot glue are you using? I have a hot glue gun, and I'm interested in trying this approach. Do you think it will be able to hold the strips in places where they are significantly twisted, as at the stem and stern?

[catsittingstill.livejournal.com]

Regarding the elmers/titebond, on the one hand I understand the desire for security. On the other hand, the epoxy really does permeate everything. And cleanup is so much easier if the glue isn't waterproof. Every drip you can get off with a wet paper towel is a drip you don't have to sweat in the sun sanding off.

I don't seek out elmers--I buy my glue at the hardware store, in the carpenters section. So I suppose it's carpenters glue. That probably sounds hideously slapdash, but there it is. On the other hand I make no attempt to seek out glues specialized for outdoor use.

As for transporting wood, well, I go to OVFF regularly, as you know, and Marcon sometimes. And I pretty much always drive. The 20 foot boards would be a bit of a pain but I could allow some extra time. Maybe I'll think of some wood available where you are and not here and we can swap :-) We boatbuilders need to work together.

The special hot glue is from Hot Stick Adhesives LLC (www.hot-stick.com) and is HS-300. Actually the packing slip says "HS-300-716x10 but I think the extra is just the dimensions of the stick, which will vary according to what size of glue gun you want to feed it into.

The web page I learned about it from is here:http://www.laughingloon.com/shoptips2.html Note that the name of the company has changed twice since that page was written :-)

For the stem and stern, where the last stations are parallel to the keel instead of perpendicular, I will not be using hot glue because I don't think I would be able to apply shear force to break the station loose. Beads of hot glue across the strip-strip joint will still work, and aside from that, I intend to go with the method I used last time--screws through the strips into the plywood station. Possibly augmented with bar clamps.

For places where the strips twist a lot but the stations are still perpendicular to the keel I may end up buying a heat gun--strips bent and twisted while heated tend to stay that way when the heat is removed. The tricky part is that I'll have to twist the strip to match what is needed without getting the heat too close to the hot glue holding previous strips.

[boywizard.livejournal.com]

A heat gun sounds like a really good idea - I should have thought of it myself. I've had a Thermostrip 3200 gun for years (125 to 1000 degrees, two fan settings), and it has served me well for many tasks (great for encouraging a fire in the wood stove), but I don't know if they are still available. Any good brand should serve (Makita, DeWalt, etc.) I'd stay away from the really cheap ones. Mine was eighty dollars fifteen or twenty years ago.

Thanks for pointing out the hot-stick and laughingloon sites; I've book-marked them for later reference. Which glue gun did you get?

[catsittingstill.livejournal.com]

I got the cheapie--the 5$ one. Since I didn't know for sure if I was even going to end up using it, spending the extra 13$ on the next step up made me nervous.