Lightweight timber spars as used today for traditional Dutch sailing boats.

Gato are you reading this ? This is a good option for your mini650.

This building method allows you to build hollow tubes of plain timber plancks. It even allows you to make tapered hollow sections. Some builder decide to coat the outside with a layer of glass to increase the stiffness even more.

I think the drawings are selfexplanatory.











My idea is to keep the top and bottom parts flat (only route the little points off) and use the flat surfaces to glue or screw carbon cloth or alu strips too.

The timber properties should be be enough to withstand the loads in the sideways direction.

If you don't to spend much time rounding the sides then you can just route the sharp points of and keep a multi chined pentagonal outer shape. That won't hurt to much at all when hit by your head.

Also if you don't really want a perfectly round section then a good simplifications would be to not to use 8 elements but only 6. Two larger ones on top and 4 on the sides. You would then only have to round the sides a little and leave the rest as it is.

I suspect that this 6 element hollow spar (possibly tapered) could well be just as strong, stiff and light as the earlier (simple) design. It can be homemade realitively easily and cheaply. Ofc ours different cross section profiles can be made by varying the angle under which the elements are glued together.

As I said earlier this setup is used as masts and booms on (small to large) traditional Dutch sailing boats. These spars can take a good loading before failing. And they are surprisingly light.

Wouter