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Bryan Boatbuilding specializes in the custom
design and building of sailboats and low-powered engine driven craft.
We sometimes think this focus is forgotten because of the varied nature
of our activities. We are especially proud of the launches built
over the last few years where we have worked with an owner whose priority
is a fuel efficient boat. We become more and more committed to the displacement
hull and its quiet, comfortable, fuel-sipping nature.
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| Global Warming and the Planing Powerboat
The time has come to give up the planing powerboat. For the last several years awareness has been growing of an impending environmental crisis as well as threats to world security due to excessive burning of fossil fuels. We have known for sometime that transportation consumes a large part of this fuel. This awareness focuses on land transportation in which we have little choice whether or not to participate. While we can hope for a quick shift to mass transportation, today’s reality is that we need our vehicles for shopping, commuting to work, and most of the functions of life outside our homes. Powerboat use is discretionary. If we can easily achieve 30 mpg for automobiles, how can we accept that the vast majority of powerboats get only one to three miles per gallon. A current boat advertisement asks us to celebrate the fact that their boat gets 3 mpg. Recent issues of boating magazines feature; a 29’ boat with 575 hp, a 38 footer with twin 440 hp engines, and another which will consume over 50 gallons of fuel an hour at speed. The ubiquitous 75-100hp deep-V runabout will get 2 mpg at best. Our problem is making boats plane. It is actually quite efficient to move boats through the water as long as we don’t push the limits of displacement speed. Planing involves forcing a boat up and over its bow wave and lifting it onto the surface where it can skim. It is unfortunate that the designs that are most efficient at planing are usually the least efficient at displacement (non-planing) speeds Many years ago it was discovered that by keeping weight down and adding power we could make a boat plane. As power has continued to increase we have come to regard planing speeds as the norm. When we talk of modest speed, we think of 12-15 kts. But that is still planing. To achieve a meaningful increase of efficiency in recreational power boating (in the length of vessel most of us can afford) 6 kts. will be our top end. The only thing we give up is high speed. At displacement speeds, we can easily increase our miles per gallon by a factor of 4 or 5, and it is possible to achieve 10 times the present average. Our boat will be just as seaworthy, if not more so. It will be much more comfortable to use as well as considerably cheaper to buy and operate. The greatest incentive to switch to displacement powerboats is that we have no choice. Burning large amounts of fuel for pleasure, especially when we have the opportunity to do otherwise, is no longer an option. |