Thread: Hello, new GIS build by Simon in ST Pete FL

Hi Rick - Thanks for the kind words. You are welcome to visit anytime, just give me a heads up so we can coordinate as my schedule can be erratic at times. My build is very leisurely as well but I'm planning on stepping it up a couple notches over the next few months. I'd really like to be done before the weather gets real hot again.

The mast staves started out as 1 x 2 (about 3/4 x 1-1/2 actual) lumber. That's just a hair bigger than Mik's specs of 17 x 34mm so I ripped them down to size with very little waste. I'm a bit surprised at how much color variation there is between the staves once they have been epoxy coated. They looked pretty similar when raw. I guess ripping all of the staves out of one giant board would avoid this but that kind of wood is hard to come by and expensive.

I am planning on wrapping a single layer of 2" glass tape, for chafe protection, around the mast base and at the partners. Anyone know if this is adequate? Thanks.

Go round twice at the partner.

MIK

Twice it is. Thank you.

Work on the bulkheads is going well. I am epoxy coating the parts before assembly and masking where the glue joints will be. Is this necessary? The secondary bond between two roughed up epoxy surfaced should be plenty strong, no? Can't tell for sure but from Joost's pictures it looks like he coated everything without masking and then assembled the boat and it has held together. Sure would save some time to not mask, especially the hull sides.

The only highly stressed joints are at the stem and transom, the ones under tension; the bulkhead joints are in compression--they want that contact, the more the merrier.

So if you decide to skip the masking process do it with confidence at the bulkheads but do mask the stem and transom joints.

Here's something I learned building my Goat. I coated the interior after assembly with CPES. I did not pre-coat anything with epoxy except for the centercase and rudder box. While working on the gunwales (with the sides coated with CPES) I occasionally dropped a small dollup of thickened epoxy here and there. When it came time to clean things up the clumps came away clean from the CPES coated sides. Drops of the same stuff that ended up on uncoated plywood (okoume) pulled chunks of wood out. The difference in the bond strength was dramatic.

Howdy,

Just to circumvent some of the discussion ... I don't think CPES is necessary for wood epoxy boatbuilding.

It is interesting that the adhesion is so low for epoxy to unprepared CPES. Generally if epoxy blobs fall onto a clean epoxy surface they will bond pretty well - so it can be safer to dand them off.

This might imply some residue left by the CPES if it is not sanded. Some epoxies that develop waxy amines on the surface can behave similarly.

MIK

I agree with MIK. CPES seems to be what everyone wants. Maybe it is good for timber, but for plywood a lower viscosity epoxy is better because it soaks AND builds up a little. CPES would take forever to build up.

The blobs coming off sounds like the CPES blushes a little bit. I don't like to blush.

Clint

Thanks for the feedback. I have repaired fiberglass boats with epoxy and the bond to properly cleaned and roughed up old glass is massively tenacious which is why I was wondering about the need to mask. Sounds like it's not too big a deal either way as long as no one embarrasses the epoxy. I'm masking the highly loaded bow and transom joints as well as the chine. It's easy enough to do.

I'm building in a friend's garage but this is slow since it's not practical for me to work on the boat in the evenings so in order to speed up the build I brought the components home and am doing the coating outside but letting the epoxy set inside our van to keep bugs and dust out. It's working pretty well.

That is a great shop. Totally mobile. You can go to the seashore to work on your Goat. Or lakeshore.

Clint

I elected not to get into the CPES debate and Mik picked it up. We're in complete agreement in regard to the need for penetrating epoxies (CPES, etc.). Timber and plywood react the same to CEPS type products. They don't (penetrating epoxies) have the peel strength of regular laminating epoxy and are considerably less able to resist moisture vapor ingress into coated wood. For these two reasons, there really isn't a good use for CPES in these type of builds.

Clint, you mean like this?

Originally Posted by SimonLew

Clint, you mean like this?

Haha, love your work Simon

Personally I think CPES is as dumb as a herd of cats.

At least for full epoxy sealed and glued boats.

It is mostly solvent. The idea is to get some type of "extra adhesion" by soaking the epoxy into the ply more.

But the obvious question is ... if we use epoxy as a glue without thinning it ... then why does epoxy used to coat wood need some extra help to stick?

I think it is a holdover from using polyester resin which really doesn't stick reliably to wood, so many will thin the first coat so it soaks in a bit more - but I don't think they add any where the amount of thinners that are added to CPES or the OZ/NZ Everdure.

Then the data shows it doesn't prevent moisture getting in.

To be fair I did once make these sorts of comments with some people on the Woodenboat forum and a couple of them had a good place to use it.

They are doing trad boatbuilding where the water has to get into the to make it swell so the joints become tight. So they use it in that circumstance. The purpose is that a lot of wood available today is not properly dried and can crack or check as you spend the time building the rest of the boat. The CPES can reduce the amount the timber dries as well as making sure that it dries in a more even way rather than dry out thoroughly along the corners and ends and so crack.

Does that fit in your experience Paul (PAR)? Others?

MIK