Perry Design Review: DynaFlyer 40

DynaYacht and designers Matt Brown and Bill Burns brought us the prototype of this 40-footer last year in a modified Hobie 33 configuration. Apparently they have been successful with that model because here is a new 40-footer using the same design concepts. This is an unusual boat and of course the bottom line has to be: "Is it fast?"

Race results from this year's Chicago-Mackinac race, in which the DynaFlyer 40 Red Hornet sailed with both Peter and JJ Isler aboard, indicate that the boat is about as fast as most 50-footers. Sailing in a class of "experimental" boats, it's hard to correlate the results exactly, but you can figure that this 40-footer will sail boat-for-boat with the Reichel/Pugh-designed One Design 48s. That seems to be quite a feat, but remember that Red Hornet has the accommodations of a trailerable 26-footer. This boat is built purely for speed.

Above the water, the DynaFlyer 40 looks like any other sport boat. The ends are short, and beam is modest. Styling is frugal at best. Below the water the differences show.

The heart of this design is the canting fin-and-bulb keel. This keel can be canted 55 degrees to weather to dramatically improve the righting moment of the boat. Consider this: At zero degrees of heel, with your center of gravity and center of buoyancy lined up vertically, you have zero righting moment. The normal boat develops righting moment only as it heels. This design with its keel canted starts off at zero degrees of heel with a 9,000-foot-pound righting moment. At 20 degrees of heel, canting the keel increases the righting moment from 8,700 foot-pounds to 15,500 foot-pounds. In short, it almost doubles the stiffness and sail-carrying power of the boat. The canting operation is by battery-powered hydraulics activated by a push button, which means that this boat will have to race with special rule dispensations.

So, with your keel canted you are gaining righting moment but losing the lifting effect of the keel. This is compensated for by using twin fore and aft rudders. These are the lifting surfaces that will pull the boat to weather. Note the extreme aspect ratio of these two fins. They are very efficient fins. They are also coupled together in the same way that the old Blackaller-driven 12-meter was back in 1987. The 12-meter was never perfected, but the twin-rudder concept was proven. I might have some concern sailing a boat like this in our log-infested waters of the Northwest. Things that go bump in the night are better bumping against the leading edge of a lead keel.

The hull shape is ultraclean. Beam is minimal for a 40-footer at just 10 feet. The BWL is only 7 feet. The brochure lists two displacements: 6,000 pounds and 7,000 pounds. Designers are usually overly optimistic about the weights of their boats so I'll use the 7,000 pounds for a D/L of 72.88. Wetted surface is absolutely minimal, and the boat shape shows no effort at all to gain what is called "form stability" or stability gained through hull shape.

The SA/D of this design is 29.2, and that's a lot of horsepower per pound in anyone's book. There is a retractable bowsprit for carrying asymmetrical chutes. The jib is nonoverlapping. Spreaders are swept to 25 degrees. Despite its aggressive appearance, by all accounts this is a very easy boat to sail.

Construction of the new 40 will be by the capable Westerly Marine Company of Costa Mesa, California, using all composite materials and vinylester resin. If boat speed is your thing, then you should be looking at a boat like the Red Hornet.

Boat Specifications

This story originally appeared in Sailing Magazine, and is republished here by permission. Subscribe to Sailing.