Boats

Making Scarph Joints in Plywood Panels

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.

Crossbeam bits & pieces

Progress on the Starwind 860 prototype continues. It does seem, however, that I've fallen behind in posting updates about the boat.

The aft crossbeams are nearly done; they still need the fibreglass tape on their outer edges and a final fairing coat before painting.

The front crossbeams now have their upper mid-beam structure installed and are ready to be closed in. That task will probably take place tomorrow.

The Factor Of Ignorance

"Safety factor." It's probably one of the most common, and most misused, terms in engineering.

The "factor of safety" might be better described as a "factor of ignorance". It's a multiplier, applied to loads and/or structural components in a design, to account for things that weren't explicitly taken into account in the design calculations. Those things could include variations in material quality or workmanship, uncertain overload conditions, accidents, and other hard-to-predict conditions that could cause a failure.

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