Hi Ray,

Everything holds pretty well the same. If you check the manufacturer’s directions for Urethane and other glues they are very specific about clamping pressure and the allowable width of the glue joint. The specification for clamping pressure is to ensure the narrow glue join as urethane is not gap filling either.

The advantage of my background is covered in the article – I saw the transition of hundreds of boats in my direct experience in racing fleets to epoxy from the non gap filling glues. The change is boat longevity was dramatic and instantaneous.

There are some places where Urethane glues can meet their design criterion – close fits and high clamping pressure – and then they should be as long lived as epoxy.

It is always possible to find some boats glue with non gap filling glues or glass taped using polyester that are “fine” after many years. But in the broader statistical scheme it was a dramatic and sudden change to the characteristics of the boats.

Urethane can be marginally cheaper. But Andy Linn (if you don’t know the name do a google search for a swathe of boat articles and experiences) built two PDRs keeping an accurate cost record and found there wasn’t so much in it. It was largely perception based as epoxy had to be ordered in one lump … but it was easy for people to drop by a hardware and buy yet another bottle of Urethane, modified PVA or other waterproof glue.

The way to think about it .. if building toward the bottom dollar, then every avenue should be exploited. The reason is, if you buy one component at a higher quality level it will be let down by the others. So if you find nice ply it makes sense to spend the bit extra to glue it so there will be zero trouble with that aspect.

I don’t recommend using contact cement like liquid nails in boat building except for holding down carpets. Again … that doesn’t mean that you won’t get away with it. But it doesn’t mean you will get away with it either.

Best wishes
Michael Storer