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 past century has brought a quiet revolution in the field of naval architecture. Today, largely through the use of the towing tank, where models are tested under controlled circumstances, we have access to an extensive knowledge about the motion of ships and the factors affecting that motion. Military and large scale commercial interests prompted most of this research although, in recent years, the same methods have been used to design the expensive water toys for the obscenely rich. Eventually what is learned in less savory pursuits filters down for more prosaic use.

1.1 Background

Powerboats rely completely on their propellers in order to achieve their performance. The reasons 'why propellers' work and the factors influencing propeller design and performance become much more meaningful when we understand the engineering development of the propeller throughout its history. It is indeed interesting that, after the propeller was conceived from the original discovery of screw propulsion, it saw relatively modest further innovation. It may be that the first designs were remarkably good!

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.

This article documents a series of common points that are a useful pointers on yacht rigs today. It is by no means advice on how you should design your mast or how we would design your mast. But in any case there are a number of common traits shown on many masts today and it helps to recognise them and look at the 'big picture'.

There is nothing more flexible than a piece of paper, a pencil, and the human brain. Once you begin using a computer for hull shape design, you are forced into the limitations and idiosyncrasies of the program and its underlying hull geometry technique. In exchange, however, you get the following and more.

This article attempts to provide explanations for the basic sailboat design ratios used to compare boats with one another. Some of it is my interpretation of what I have read in the books, articles, and web pages I refer to below. I do not claim to know anything about these subjects so, as with anything you read on the internet, it's up to you to evaluate it's worth. I suggest you look at the sources I refer to, as well as additional sources, and draw your own conclusions. Email me at dan@pfeiffer.net