Boats

Outboard motorboat power calculations

Every year, mixed in with the usual chatter around the boatyards, I hear at least a few comments along the lines of "I beefed up the transom of my 14-footer so it can take 60 horsepower!"

Er, no. That's not how it works.

Maximum power ratings for small outboard vessels are calculated according to the size and design of the boat, taking into account the following factors:

  • Length of hull (longer = higher power rating)
  • Beam at transom (wider = higher rating)

Understanding monohull sailboat stability curves

One of the first questions people ask when they discover I mess around with boat designs is: "How do you know it will float?"

Well, making it float is just Archimedes' principle of buoyancy, which we all know about from elementary school: A floating boat displaces water equal to its own weight, and the water pushes upward on the boat with a force equal to its weight. What people usually mean when they ask "How do you know it will float" is really "How do you know it will float upright?"

The twenty-year refit

I've been browsing the brokerage ads again. (A dangerous habit, I know.) There's a trend in some of the listings that has me a bit worried: boats that are less than a decade old, but are advertised with "Just finished a major refit!!!".

A major refit after less than ten years is a sign that the boat was poorly specified and poorly set up to start with. Builders should be embarrassed and humbled if their boats need a major refit so soon after launch.

A reasonable ten-year refit might include, as major items:

Outrigger struts for the Starwind 860

It's time for another boat parts update! The only way this project is going to make it to completion is if a little bit of work gets done at every possible opportunity. So, slipping in a task or two a day, we are making slow but steady progress on the Starwind 860 trimaran.

The struts that link the 860's crossbeams to her main hull have aluminum end sleeves and a red oak core.

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