Wood and aluminum have similar strength to weight ratios. The greater thickness per given weight makes wood stiffer and more damage resistant in smaller scantlings. Aluminum is (with proper corrosion protection) lower maintenance and can be manufactured in longer lengths than are available in clear lumber. Both wood and aluminum can be machined with ordinary tools, but wood is easy to glue; welding aluminum is a specialized trade, the work has to be done in windless conditions so the weld can be bathed in argon gas to prevent corrosion from infecting the weld.
As drawn by James Wharram, MON TIKI has wooden masts. But for the sake of cost and (especially) speed of build, we opted for aluminum masts. A pair of aluminum tubes of the right diameter, wall thickness and length (should have) cost about $200. Add a few hundred dollars for a aircraft-grade welder to braze on the bits and pieces and we (should have) had a couple of masts for under $1000.
In fact, 33′ aluminum tubes do cost $200 each. But you have to order 12 of them because they’re manufactured in China.
And they need nine weeks lead time.
And there’s a $900 delivery fee.
That’s $3300 before we even get the welder to do his thing!
We sourced 20′ lengths of the right sort of aluminum pipe (by local, I mean manufactured in China at a standard length and stocked locally), but that didn’t come out any better. 20 footers were $500+ each, plus material and welders time to butt them together (and then throw away 15′ of left over tube!)
So back to wood.
We started with about 150 board feet of clear douglas fir.
This was ripped 60mm x 25mm staves. These were scarfed to 33 foot lengths.
The edge of staves were run through the table saw twice to give them a “bird’s mouth” notch.
Now here’s the clever part.
The edge of one stave just sort of snaps into the bird’s mouth of the adjacent stave and *presto*, you have have a 33 foot, hollow octagon.
While the epoxy sets the assembly is held in place by rope (a Spanish windlass generates a lot of clamping power!)
Once the epoxy is set we attacked it with planers, then belt sanders and then finished by hand.
Materials and man-hours together, the cost to make the wooden masts was less than the materials alone for aluminum; and a good chunk of that money when into my crew’s pockets.
Plus there’s knowing it was done right. I don’t know thing one about welding, but I know a thing or two about wood and epoxy.
Plus making a hollow wooden tube 33′ long is cool.
And making two of them is super cool!