1959 27'constellation inner plywood replacment

3M-101 isn't so much as a bond as it is a sealant. The fasteners do the holding. Yes, 101 or similar polysulfide in the seams.

By encapsulating the plywood (yep, it's just as the word describes) seals it from moisture. This forms a waterproof barrier between the solid wood outer planking and the solid wood structure. I would go to the trouble of sealing the seams in the plywood too, just to anal about it.

Gluing the plywood to the structure, makes the separate elements act as a single (sort of) assembly of parts. Essentially, the outer planking can wiggle around all it wants, because below is a waterproof plywood membrane, separating the vulnerable structure from moisture. There is no 'glass fabric between the layers of planking, just polysulfide.

It's this wiggling around thing, that causes issues in traditional structures and why I prefer a fully encapsulated approuch. You could encapsulate all of the planking, which eliminates the need for caulking and makes the solid wooden pieces dimensionally stable, but at increased cost and effort. I would sheath a fully encapsulated hull.

Log onto Systemthree.com and download their "Epoxy Book" and Westsystem.com to download their "User's Guides" and boatbuilding book (all free). These will offer you an idea of encapsulation, the techniques, methods, materials, tools approaches, etc. This isn't an easy job for the novice, on a boat of this size and complication.

Additionally, for any of the previously mentioned methods to work, the structure has to be sound. Gluing plywood to a rotted and worn out structure is like nailing drywall to termite riddled wall studs. It'll stand for a bit, but don't make long term plans on it's durability. In short, the very last thing in a job like, this is the planking schedule. The first things up, are making the structural elements right again (read tedious and time consuming). This is the butt kicker on most jobs of this scale. The structure may require so much effort and cash, you just peeter out come time to hang planking. So, be careful what you wish for. I know several small shops that wouldn't touch this size project, because they know what it entails and though they have the skills and tools, most owners don't have the resources, for the full monti.

 

Is the inner plywood layer rotted or delaminated?

 

The inner plywood is rotted in the very front of the hull, or should I say that it is missing in a few spots lol.

 

Again, more importantly than the planking, is what it's attached to. The structure is addressed first and the last thing you'll do, before painting is the planking.