Spectator — October 2001
By Tom Fexas
See How They Run, Part I
elusive “nice-running boat.”
I am in a boatyard surrounded by many vessels on the hard. Strangely, the bottoms of all the boats look exactly like mattresses complete with the swirled stitching and faded pastel flower patterns. The bottoms are soft to the touch. Then I awake.
While I am sure shrinks out there will have their own twisted analysis of this dream, I tend to be a practical sort, and to me the meaning is simple. I have always been obsessed by the way boats go through the water–especially through rough water–and these mattress-bottom boats were simply a manifestation of my desire to produce smooth-running hulls. Take that, Sigmund!
GREYHOUNDS AND DACHSHUNDS
The greyhound is one of the most graceful animals at speed, and the dachshund is one of the clumsiest. The greyhound makes long, fluid strides as it effortlessly moves forward. The dachshund takes many choppy steps and struggles for headway. The greyhound/dachshund analogy applies to boats of all sizes at all speeds. Offshore speedboats, trawlers, and everything in between can be greyhounds or dachshunds.
You can determine how
a boat runs by simply analyzing a picture of her underway. The picture
on this page is of one of our 43-foot Mikelsons running at about 20 knots.
I have superimposed numbers on the photo to illustrate the two critical
aspects of a boat’s performance. This information applies to monohulls
at speeds up to about 40 knots.
Entry angle (a measure
of forebody sharpness) is key here. The finer the entry of the vessel,
the cleaner she will cleave through the water and the smoother she will
ride. This applies to both slow and fast boats. Entry angles are best
made as sharp as possible while still allowing reasonable accommodations
forward. Long, skinny hulls can have entry angles of only 8 or 9 degrees,
while wider boats might have angles of 15 to 25 degrees.
This article originally appeared in the June 2003 issue of Power & Motoryacht magazine.