Well I have tried a lot of the advice given and have ended up just using
a jigsaw with the bosch "clean cut for wood" blades with a 1.4mm tooth
pitch. The results are very good. Well they are easily good enough for
what I am building. There is very little splintering even without any
tape on the 6mm and 12mm ply and the cut is good and straight (or curved
in most cases) if I take my time.

The pack of 5 blades cost more than the jigsaw but the jigsaw only cost
$10. OK it was on special, it should have been $15. But it cuts very
well. With a good saw I would expect even better results. The blades
where $15. I have cut out 8 large panels twice (rough then accurate) for
an 8' dinghy and the blade is still fine and looks as good as the 4
unused ones. I have tried a few other blades and not achieved anywhere
near the same results. I would recommend them as a good buy.

Thanks everyone for the help,

Brian

Brian wrote:
Does anyone have any tips on the best ways to cut marine ply (6, 9 and
12mm)? In particular I want to cut curved 8' boards for a dinghy. So I
guessing that a band saw is a good bet but I don't have one. Are there
any other methods that can produce good results?

Thanks