Part I: Why Birdsmouth Spars?

By Shane Hall

Students from South Portland High School have been building a hollow mast for their sailing dory currently under construction in the shop. Working with young people means that most of the time we aim to simplify things as much as possible. Building a hollow mast is essentially the opposite. We are adding many steps and complicating things by creating a series of eight tapered interlocking staves engineered to minimize weight without compromising strength. Why do we bother with this?

A hollow mast is considerably lighter than its solid counterpart and can be built out of more readily available and economical 1x lumber; we use clear Eastern White Spruce. The math involved can be very complicated but it can also be broken down into a couple of basic equations. The main reason that we opted to make a hollow mast is that the planning and building processes involve many opportunities to introduce and practice a variety of boatbuilding and math techniques. Also we’ll end up with a finished product that is really cool. Stay tuned for more about this process from paper plans to finished mast.

Here you see two of the spar builders posing next to the dry fit mast prior to glue-up.

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For a great introduction to Birdsmouth Spars see: Clint Chase Birdsmouth Spar Power Point Demonstration