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It is interesting to work out the required sizes and resultant weights for different materials. Often, because it can be tapered easily, a well designed hollow timber spar will be lighter than an equivalent strength aluminium alloy one (because although aluminium is about 3.7 times stronger than Douglas Fir, it is 5.6 times heavier, and can't easily be tapered much, or have a reduced wall thickness). The carbon fibre spar will be lighter, but at a substantial additional cost.

Now we will go on to working out a multiple spar rig – in this instance a yawl with mizzen and main. The principles will be the same for any multi-spar rig.

To follow soon – June 2014

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© George Whisstock. This article is for information only and may not be commercially reproduced in any form or used in any way without permission. Do not use this material as the basis for designing a mast without professional advice.