Welcome back, folks. I hope you've had a merry Christmas. Or a merry last few Christmases, for that matter.
So, whatever happened to that weird, radical power trimaran we were working on? The one that filled these pages, oh, seven or eight years ago?

Well, life happened.

Conventional wisdom says that plywood can't take compound curvature. That it can only be bent into conically developable sections.

That's not entirely true. The Starwind 860's amas have a bit of compound curvature, particularly in the forefoot. Here's how we create it.

When your plywood sheets aren't long enough, they must be joined end-to-end.

Butt joints aren't strong enough. Backing blocks can cause problems when you try to bend the panels. CNC-cut puzzle joints work great – if you have a CNC cutter. So the good old scarph (scarf) joint is the standard solution.

Here's how to make one.