4-Ply Underlayment

[Dave Hadfield]

I was in Home Depot yesterday and noticed a new product, 1/4" underlay that is 4 ply instead of the 3 ply they always carried before.

The 3 ply wasn't much good for building since it had a very thick core and 2 extremely thin surface veneers, but going to 4 ply changes the whole picture.

Does anyone know what kind of wood it is (the sticker says only "Brazil") and whether the adhesive is waterproof? I could find no one in the store who knew.

It's CAD $14/sheet -- pretty attractive price.

[John Bell]

For CAD$14 it seems it would be worth buying a sheet and doing some testing with a few wet-dry cycles. If it proves not to be waterproof, you can always use it for jigs and temporary forms.

JB

[rustnrot]

Same stuff just appeared at the local Lowe's. $11 a sheet.

[NormMessinger]

Weelll, as my ole pappy used to say, ya get what you pay for. Four plys, eh. There must be a reason plywood has always had an odd number of plys. On the other hand, $11 !

--Norm

[bud]

It has to have an odd number of plys to keep each ply at right angles to the next. Otherwise, one of the veneer faces will have grain running across the sheet.
I don't trust what they say about the number of plys, there seems to be some leeway, at least in the minds of lumber suppliers, about how plys are counted.

[Bill Perkins]

Norm and Bud ; using the nomenclature of The American Plywood Association : the plywood mentioned has 3 Layers made up from four Plys . The grain of the two center plys run in the same direction ,creating one thickened center layer . This is better than one thick central ply ,which is usually low quality wood for the cheapest panels , called Plyscore around here .

Underlayment grades need to resist denting by spike heels , furniture legs , and such .That made to APA standards has no voids, useing an improved "plugged" C grade ply or better . If the Brazilians are serious about producing acceptable underlayment , the plywood will have no voids , more important in this application than its strength in bending . No great pains may have been taken to produce maximum strength glue bonds .

[ 07-12-2002, 09:48 AM: Message edited by: Bill Perkins ]

[NormMessinger]

Ah, so.... I'm off to Lowes to check it out. Sounds satisfactory for a quick and dirty kid built boat where workmanship is not yet up to $40US a sheet.

--Norm

[Dave Hadfield]

There are definitely 4 layers of wood. I guess the center 2 run in the same direction. Either that or they're skewed a bit.

I'm scarfing together 2 panels right now, to make a sharpie canoe I designed, so we'll see how it works out.

You're right, I should've tried the dishwasher test first, but I was on fire to get started and didn't feel like driving all the way to Toronto for Marine ply, or paying $200 for the wood when I can pay $60.