Plywood Delamination/older boats

[geoleo]

I have been messing around past 15 years restoring older boats. Many of them have been plagued by partial and total delamination of the plywood used to build them. There has also been a lot of veneer delaminating from the plywood. It is a real pain. Many of the builders used very cheap plywood like 3 ply for 5/8 thickness with cheaper woods in the middle layer. Sometimes the entire glue used just "gives up" at once, leaving a twisted useless mass of crap. I have tried repairing non-structural plywood by many methods, peeling, injecting screwing and various combinations -also adding layers of new good stuff on top . Some of the worst old plywood has been found on Gulfstars, Ft Myers Shipbuilders, Marine Traders, Fuji. Good stuff on Island Packets.

[Tillsbury]

Surely it’s never worthwhile to repair a boat that contains something other than real marine ply?

[HellBentSailing]

This is a common problem even on smaller boats. I had to scrape out and replace the entire companionway bulkhead on my 79' Ranger. Rest of the boat was extremely well built but the entire bulkhead was completely delaminated. I was able to just peel layers away by hand. As it was structural I ended up ripping the whole thing out and bonding in a replacement made of proper marine ply. Luckily that's the only piece of ply not encapsulated by fibreglass but I can't imagine what it's like on a much larger boat.