Yes You Can Build a Boat #16: Boat Building Adhesives

[@nterry894100]

You have convinced me Jeff. We use both PUR and epoxy in our wood products factory. The PUR we use is from Germany - either Jowat or Purbond (Henkel) are good. I think what you said about flexibility is very important. For building a big strip-plank/epoxy composite boat, one of the things that concerns me is that there needs to be a bit of flexibility in the large monocoque hulls and bridge deck. You do not want anything to crack. The PURs provide this as you say. The PUR also expands very nicely to fill gaps. They other thing is that they are a one-part glue, or at least the ones we use are, and so there is no problem with mixing up batches and, when you rely on workers to do this, you may be putting your life in their hands. From what you have said here, it seems to me that PUR to glue the staves and to laminate them in layers and then a skin of fibreglass-epoxy on the outside and inside of the boat would be an ideal solution unless the outside fibreglass-epoxy skin is going to crack due to some flexing in the entire structure. Do you think that the epoxy can handle the small amount of flex in the structure? I could use carbon fibre cloth if that is going to help, but it is an expensive option that I would prefer to avoid it is unnecessary or not going to help.

[@tjkid07]

Oh yes, epoxy will flex enough. It's pretty rare to see it crack, especially in thinner sections, for example a few layers of fiberglass cloth over wood. By the way, I think Locktite is the Henkel PUR made or repackaged under license

[@nterry894100]

@@tjkid07 Yes, I am not sure which one owns the IP but the Jowat one too is licenced from the original developers. I have used both and they seem to be the same. Thanks for the confirmation about the epoxy.

[@TheBeaker59]

I am definitely an epoxy boat builder as a retired industrial chemist in the coatings and adhesive industry I concur with everything Jeff said here. I have built a Spira design very successfully among many other stitch and tape and ply on frame boats I am a PU fan too though basically use very little only because I have epoxy and trust it so implicitly that I see little reason to use anything else. Polyurethane is actually more water resistant than epoxy its generally harder its also a good filler but when it does it looses strength It is so waterproof it can trap water in the wood. Another advantage of epoxy is all the different grades and manufacturers use the same ingredients from a handful of sources so are remarkably similar in performance a Basic laminating resin is pretty much the same across all suppliers from cheap to expensive that some fumed silica a range of fillers and wood flour is all you need. The West's and other top level suppliers are good for their blends and various products but you can make all the specialty products your self from the above mentioned raw materials. In adhesives the one trend I am not a fan of is Titebond I am seeing that pop up allot and I really think that's a recipe for disaster its not fully water proof or resistant it is biodegradable which means it can rot. Its not alkali resistant, Granted its allot better than its PVA and EVA predecessors but it still has the same problems just slower developing. Save it for furniture and protected outdoor construction which is what its intended for.

[@Dickie2702]

I am a time served wooden boat builder and quite frankly I wouldn't use anything but epoxy. It creates the strongest bond of any adhesive as it will penetrate into the wood fibres better than anything else and it's gap filling properties are second to none. We have messed with all sorts of products over the years but this simple test will put to rest any argument about relative strength. Glue two surfaces together spaced by 0.5mm, two drill bits will suffice. Let it cure and put them on a jig to test the bond strength. Best by far will be laminating epoxy used I this manner. Surfaces should be wet out with un thickened epoxy then bonded with epoxy thickend with silica. Have tried this test with countless products and epoxy wins hands down. Believe me I'd love a non corrosive product that I could use right out of a bottle and cleans up with water, it just doesn't exist in my world.

[@zirconzircon8861]

Thanks for this. Sadly, though, the AeroMarine 400 and all the other links you provided are all currently unavailable.

[@dennisharrington6055]

Thanks. My two lunacies: (1) back yard boat building (I live on the Llano Estacado of New Mexico). All epoxy/thickeners all the time. (2) whirligigs. Gorilla glue for construction, sat. with epoxy before painting. (3) flying. I dust the plane off, vacuum the cabin, clean the windshield, and add oil when necessary. The A&P does EVERYTHING else. OK. So I can’t count.

[@jwnagy]

Excellent video Jeff. Would your boat designs benefit from having filets (like in stich and glue boats)?

[@tjkid07]

Sure, it'll make the glue joint a bit stronger, but unless you are planning on taking it through the grand canyon or something, they're not really required.

[@jeremybates5207]

Thanks, Jeff!

[@mattevans-koch9353]

Thank you Jeff for the information. I do have a question concerning pre-coating the plywood sides and bottom with epoxy before gluing them to the frames. I haven't tried it but have wondered if the epoxy sealing coat would affect the flexibility of the plywood. Take care and have a great week ahead.

[@tjkid07]

It would be stiffer and you may have trouble bending it to fit the curved sections.

[@mattevans-koch9353]

@@tjkid07 That was what I was wondering. Thank you for confirming it.

[@officialWWM]

I'm repairing a 1970 Hartley Vixen. It's a 17 foot boat with a 90hp outboard. One of the planing strikes has delaminates from the hull, I think from bouncing on the trailer rollers. I was going to epoxy it back on then glass over the join. Access is the issue though, it's going to be very difficult to do on the trailer. Do you think I could use a polyurethane instead? It would be a lot easier to get in there with a calking gun!

[@tjkid07]

Possibly, but epoxy is stronger overall, but the polyurethane is more flexible.

[@officialWWM]

Spira Boats thank you for the info. I think I'll see what's available in my part of the world :)

[@robertcain3426]

Just buy laminating epoxy resin and thicken it for glueing with fumed silica. Micro balloons are not recommended for glueing as they make the mixture soft and is, therefore, useful for a fairing compound. Silica or talc (for glue) and micro balloons (for fairing) is all you need.

[@kjkracing1]

Thanks for the info!!

[@bjpollari]

Thanks , Jeff

[@kentonward97]

What about Titebond 3 ? It’s waterproof

[@tjkid07]

I've had several customers use Titebond 3 and they said it was great. For some of the bonds, like frame elements to frame elements, it's perfect, but there's very rarely gaps there. As I describe in the video, it is not waterproofness that is the issue. It's gap filling capability, why I suggest using epoxy or Polyurethane. Does Titebond 3 fill gaps as well? I doubt it. The big questions is, are you a good enough carpenter to make every (mostly curved) joint precise enough to ensure a non-gap filling product is appropriate? Only you can answer that. To be honest, even though I've built a lot of furniture, some structures and many boats, I'm not patient enough to do the carpentry well enough to make it work. You may be, I don't know.

[@kentonward97]

@@tjkid07 thank you for the reply , I was just thinking of using Titebond on the frame but I wouldn’t use it on the plywood to frame glueing as yes I agree epoxy would be best. Thank you for the time to respond.

[@thfi5294]

No, Titebond III is not waterproof, it is water resistant. For that matter, epoxy is not truely waterproof either, it also is water resistant.

[@viti8347]

Jeff - is a "rough sawn" surface better to bond to?

[@tjkid07]

Well it depends on the glue. With epoxy or polyurethane it probably is depending on how rough the rough sawn surface really is. Probably the best for any surface is flat and rough sanded.

[@viti8347]

@@tjkid07 Thanks Jeff

[@Helliconia54]

thank you for using metric. A pleasant change

[@tjkid07]

I'm trying to do that with all of my boat designs and materials, as I have many customers outside the US. I still think in feet and inches and degrees F, but am pretty quick to convert in my head.

[@MK-tu1zh]

I wish this video was around when I started building booth bay. it would have helped. I read all your articles at the time though.

[@MK-tu1zh]

6:54 triggered me... those joints are terrible..

[@thfi5294]

That covered only two adhesives. And I would not use either, not a first choice at any rate.

[@clevelandmortician3887]

Epoxy and 3M 5200 are all you would ever need. What is your first choice??