Boat Design

A cruising yacht that won't break the bank

Let's face it: Boats are EXPENSIVE.

Assuming you want to own a yacht of an appropriate size for long-term cruising- say 12 metres (40 feet) LOA- you currently have four options:

  • Buy a new, ready-to-go cruising yacht, often with a price tag north of \$350,000.
  • Buy a new day-sailing boat and upgrade it to offshore cruising standards. The basic boat may be under \$200,000, but the design will often be inappropriate for offshore work and may require substantial hardware and systems upgrades.

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:

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?"

Length matters

Longer boats are faster. We tend to take that for granted, because it tends to be true. Put two boats of similar type in a race, and the longer one is almost certain to beat the shorter one to the finish line. The difference that length makes is quite remarkable, but we rarely get to look at it on its own- and that is the subject of today's post.

Starwind 860: Range and efficiency

Among the key questions that must be answered in any powerboat's design phase are: How much power does it need, and how far can it go between gas docks?

The Starwind 860 trimaran that I'm currently working on started life as a series of computer simulations to answer these two questions. In today's post, I'll take you through some of these calculations and the logic that led to the final choices.


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