the boatbuilding.community

Electric powered boats have definite advantages. They are environmentally friendly, and very quiet; they run with only a whisper of sound. They are reef friendly, quiet in harbours, are cheaper to run and emit no pollutants. So why are we still using fossil fuels and Marine diesel engines to provide propulsion for ocean going vessels? Consider the typical internal-combustion engine. From the time a charge of fuel ignites in a cylinder, it has to push pistons, turn a crankshaft, turn a camshaft, open valves, pump water, pump oil, turn an alternator, and submit to reduction from a transmission to step the engine's thousands of revolutions down to something a propeller can use. By the time that's done, the engine's efficiency is somewhere below 25 percent. Also, diesel engines are rated at their maximum rpm--and on sailboats are rarely operated at that speed.

What makes the propeller work? How do we choose the best propeller? And just how can we get the most performance from our propeller design? This is a multi-part article on the engineering basics of what makes the propeller work. In “History & Design of Propellers, Part 2”, we'll look at the parts of a propeller and. advanced propeller design and propping techniques.

Let’s first understand the different parts of a propeller, so that our terminology is consistent.

"The only noble thing a man can do with money is to build a schooner."
- Robert Louis Stevenson

Reuel Parker's Terrapin 42 is an exceptional design for any boatbuilder. I had dreamt of building my own wooden boat, and many are the plans that I had studied with care. I wanted a cruising boat for the Gulf Coast, Bahamas, and something capable of extended trips throughout the Caribbean. It had to be large enough for four adults, but manageable by two when one does not plan to sail round-the-clock. Moreover, since the intended cruising grounds showed that there are many appealing anchorages that can accommodate a draft of 32 in., but not 5 feet, a centerboard seemed appropriate.

There has been a growing interest in twin keel boats in North America. Although some design work has been done here on sail craft of this type, there are more numerous examples in Europe, particularly in Britain.