If you want to do the job in one sheet of plywood, the grooves would be cut
with a router. For small grooved like 2mm x 2mm, a small laminate trimmer
would be the ideal tool. Practice a lot at techniques for guiding the tool
before doing the big sheets.
After grooving the ply and securing it to the boat, the panel and its
grooves should be very carefully sealed. I'd recommend WEST epoxy with
their 207 hardener. Warm the ply thoroughly so the epoxy will run and
penetrate all the cut plywood edges. Don't let puddles accumulate in the
grooves. Clean them out with a dry paintbrush or a rag on a putty knife.
Reduce the heat so the epoxy won't out-gas. As the epoxy gels, keep an eye
on it for puddles.
Mask the edges of the grooves and fill the grooves with tinted epoxy or a
polysulfide sealant such as 3M 101 or Life-Calk. Don't use a polyurethane
or silicone sealant . Sand flush and varnish.
Another way to do these decks involves bonding veneer 'planks' to a plywood
substrate. THis is well documented in the Gougeon Brothers book. or on the
WEST Syetem website

"graham" wrote in message
news:1136183897.855581@teuthos...
I am restoring a 15 foot speed boat of maybe 50s vintage.
It has a ply deck that looks like a laid deck and it has rotted.
I am replacing the ply decls but am not sure how the markings were done
to imitate a laid deck.
The grooves seem to be about 2 mm deep and about 2 mm wide and are black
in color.
Can any one assist a novice on how to do a ply deck that looks like a
laid deck ?
Graham A