ProPly Boil Test

[Don Maurer]

I picked up a few sheets of ProPly "Premium plywood underlayment" at our local home center to redo by bathroom floor. The stuff is made from baltic birch, 5 relatively even thickness plys in a 1/4" sheet. The literature claims "ProPly is guaranteed to be absolutely free from voids within the core". The home center also claimed it to be made with waterproof adhesives. Looking at the stack in the store, it appeared to be good quality with no obvious voids. Thinking it may make a good boatbuilding material, I took a shim measuring 2 1/4" x 5 7/8" and boiled it for 30 minutes. At the end of that time, I had 5 nice veneers floating in an amber colored broth. Interestingly, the outside and center plys now measured 6 3/8" x 2 1/4". The other two plys measured 5 7/8" x 2 3/8". Also, there was a 1" knot hole at the edge of the center ply. This was not evident prior to boiling. It must have been filled with filler that disolved during the test. My conclusion is that this plywood is not suitable for boatbuilding, but more interesting was the amount of expansion that took place as the plys delaminated.

[Zane Lewis]

Interesting little experiment.
And nice to know before you started building.

Andone boiled any other ply.

[gary porter]

Don, thats some useful info,, Not sure I'd want to use it in a bathroom environment either. I've used a ply they call Baltic Birch here and comes in 5' lengths only, its very nice for building boxes, carving woodcuts etc. but never have used any in boats or a moisture situation. I'd take your test samples back to the dealer so he can be better educated on his products as well. You might try just soaking some pieces in water for a bit but not boiling.
Gary

[Don Maurer]

The results of my boil test on ProPly got me curious, so I decided to boil samples of the boatbuilding plywoods I have used on past projects. The two samples were both BS1088 6mm ply manufactured by Shelman. One sample was Okoume, the other Sapelle. Both are considered top of the line marine ply. I boiled both for one hour. Neither showed any sign of de-lamination. Because the laminations remained intact, they also remained dimensionally stable. I noticed no warping, but the samples were small, so this may be irrelevant. The only change I noticed was a slight discoloration.