Research Ltd. The New U.L.D.B. Sailboats Ultra Light Displacement Boats - U.L.D.B.s typically weigh as little as one half as much as a conventional displacement hull sailboat. At the same time they usually exhibit twice the cruising speed of a moderate displacement design, along with being easier to handle and less expensive for their size. These long, sleek, feather weights tend to sail on their ears, making them less desirable as cruising vessels despite their other advantages.
Interiors also tend to be spartan with little load carrying ability for cruising stores.
The fact is that much experimentation is being done on the construction for boats of this type and there is still a lot to be learned. A boat that is capable of speeds in excess of 20 knots, which U.L.D.B.s are, require a hull structure considerably stronger than a boat that can not exceed 10 knots. At the same time I can not argue with the fact that high ballast ratios and slack bilges give these boats a tendency to lie down in moderate winds. My own research into U.L.D.B.s has lead to a somewhat different train of thought, which can generally be expressed as less ballast, more beam . Narrow waterline beam is as much a factor in the speed of an U.L.D.B. as is its light weight, but lack of flair in the topsides reduces interior space and lowers the angle of heel at which the boat will right itself.