Updated – 3 May 2022

For those lucky to have a CNC machine

This is the way to scarf and cut your plywood.

Andre from Australia is using a CNC router to build this 3.4m long small boat, Noosa, in his workshop in Melbourne. He kindly allowed me to share these pics of his progress.

ply parts cut using CNC. Boat plans CNC

In his workshop, Andre’s using his CNC router to cut the plywood parts of the boat with precision. While it takes a little time to set up, once ready, it only took him 2 hours to cutout the complete boat.

Advantages of CNC

– It’s fast and precise.

– No measuring and marking out before cutting required. This is a big time saving. It eliminates drawing the parallel lines across the plywood, marking out the dots and joining them using a baton. No batons needed, no reading from plans, no lofting, no mistakes.

CNC - finger joint

– Carefully cutting along the lines that you’ve marked out is also eliminated. This is tedious work and requires concentration. The machine does it super accurately and far quicker than you can, resulting in perfectly shaped parts.

– For parts longer than a plywood sheet, no scarfing required. Sheets are normally bonded together before cutting, by grinding a taper on the edges to be joined and bonding them together. It’s a job I never liked… With CNC, it’s not required. The machine cuts finger joints into the parts along the line where they will be joined later.

A big help on large jobs

When I built my cat, a large part of the job is cutting. Slowly and methodically following pencil lines with an electric jigsaw. Pencil lines that took even longer to mark out. Anything that can replace that part of the job is very worthwhile. Cutting intricate shapes in plywood is a time-consuming job and a large part of any build. Even a foam cored or steel boat uses plenty of plywood, for example, in the interior.

You wouldn’t buy a machine just to make a small boat like Noosa, but if you have a machine or have access to one, it’s an interesting alternative. A CNC router is definitely a tool on my list for my next boat build…

CNC cutting boat plywood parts

As with 3D printers, the price trend is down and the performance and variety of brands keeps improving. Kits and plans for making your own router are a great project in themselves. This was rare a few years ago. CNC cutting was expensive, affordable only in the industry and no one would have dreamed of making one themselves.

Model boats

All plans I create these days include CNC files as an option, even for building models. Checkout the nice job Olivier in Tahiti is doing with his CNC router, and 3D printer, building a new model of Geelong.

Pontoon - model plywood boat

Especially with models, 3D printers and CNC machines make creating small intricate parts easy to do and accurate. More on 3D printers, and models, in coming posts…

I hope this gives you some more ideas for building.

More info on CNC routers (Wikipedia).

Happy building,

Tim Weston