Low Tide

Yacht Designer Tad Roberts' Web Log

The Real Weight of Powerboats

There is currently a moderate amount of interest by both designers and consumers in lighter weight (displacement) powerboats. The sketch above is a 11,000 pound displacement 35′ boat. At this weight she can just manage a top speed of 12 knots (in flat water) with a single 60HP outboard, burning 6usg per hour, roughly 2 miles per gallon. At 10 knots (requiring half the 60HP) she will burn roughly 3 usg per hour, or 3.3 mpg. This is an attractive concept.

Designer’s Michael Peters, Nigel Irens, Reuel Parker, and Paul Bieker have all created rather lightweight powerboat designs. I have only a rough idea of how well these experiments turned out.

Light boats can be built but most people have no idea of the rigorous attitude necessary…..For instance we just checked the real weight of a Phil Bolger designed Windermere (30′ by 8′ ply houseboat), design weight is just over 7000 pounds, the owner built her to the plans and afloat she’s just over 9000 pounds light ship, 10,600 pounds fully loaded with 3 crew aboard. The foam cored Yellow Cedar (38′ by 10′) and strongly built with lots of wood trim and generator etc was 13,000 light ship without ballast aboard. The first Hinckley Picnic Boat (foam cored glass, 36′ by 10′) was 10,400 pounds with strict weight control and no extras…….

Parker’s 43’9″ by 10’6″ power sharpie calls for a design weight of 10,000 pounds with 200 usg of fuel. I think it will be almost impossible to build a 44′ at 10,000……even more impossible to actually use her at that weight……

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