two guys at my little sailing club here in Germany have recently acquired
Trifoiler hydrofoil sailboats. Well, these are boats, not windsurfers, but
they are so goddamn fast that I think a little note is appropriate in this
The trifoiler is a design by David Ketterman, known to the speed crowd for
his work with hydrofoil speedboats. His last all-out speedboat was the
`Longshot', which clocked a remarkable 43.x knots. It's a bit unclear
wether hydrofoils will go much faster, as the current technology has hit
a major wall in form of cavitation (which kills wing lift and increases
wear almost catastrophically).
Now, he's built a mere-mortal hydrofoil that's shaped like a `T', with the
top of the `T' forward. Two L-shaped foils are at the left and right corners
of the `T', and one T-shaped foil (which also is the rudder) is at the back.
The main hull is in the center, pencil-shaped shaped like a race car. Two
auxiliary mini-hulls are on the corners of the `T', to prevent capsizing of
the craft when the hydrofoils are not generating lift. Two windsurfer-like
sails of 10 sqare meters each are positioned on top of the auxiliary hulls.
The two sails are synchronously operated via a rod that connects both of the
`booms'. Extra stability for this two-sail rigg is provided by another,
static connection rod that connects the two mast about 1/3rd down from the
mast top. From the front, the assembly of beam, two masts and extra conrod
looks like a rectangle.
The pilot (yeah, pilot; and you should wear a helmet in this thing) is lying
feet-first in the center hull, with foot pedals for the rudder. Additional
controls are for sheeting in the sail and for lowering/raising the L-shaped
First, get the thing into the water. As it is very wide, wider than long,
you usually push it in sideways, with all foils hauled up. Then, one
manoevers into deeper water .. either by pulling it by hand, or by paddling.
You feel very silly, slow and crippled at this stage. Now you reach deeper
water and lower the rear T-foil by hand and lock it into position. This feels
like making a plane ready to start. You paddle a bit in between to prevent
the craft from drifting around in circles. Then you get into the seat
and adjust it's position so that you can reach the rudder pedals ... things
start to look better. No more paddling, and you can use the pedals to maintain
some kind of direction while you fiddle with the front foil controls to get
them down into the water. You make sure they are locked in position, else a
disaster would be round the corner. Now you sheet in and zoom off ... No,
you don't ! First you think `Am I going to survive this ?'
What happens next depends on the wind strength. If the wind is below 3 Bft,
you'll be mostly drifting and still be looking silly. Otherwise, or if you
catch a lucky lift-off puff (3-3.5 Bft), all hell breaks loose. The front
foils lift off first, your tail (with the pilots weight in it) drags a bit,
some spray may hit you during the transition. Then, the tail foil lifts off.
You realize (afterwards, at least), that your craft has just reduced it's
wetted surface area and drag by 90% ... don't strain your neck and hold on!
The apparent wind shifts quickly to very frontal, as your boatspeed component
is so big. Now you know why the sails have so little chord. Sheet in more.
At force 3-4 winds, the boatspeed indicator occasionally hits it's max at
35 mph. At force 6 winds, it will be stuck at the max all the time (we
measured speed against the local Search-And-Rescue boat and got roughly
70km/h, about 44 mph).
Let's assume that you haven't hit another sailboat yet. So, you regain
partial control of your senses and try to go in a straight line. Why the
hell is the craft still going level ? Because the Trifoiler has automatically
adjusting foil angles, with the leeward foil producing uplift, and the windward
foil downlift, locking the craft into the water. The mechanical system is so
good that it locks the wings into position with an accuracy of +- 2 inches.
You can hear the `feelers' that protrude forward from the auxiliary hulls
track the water surface many times per second, much faster than a human
Next step. The lake which used to be big is already at it's end. Your
approaching the shore. Time to jibe. How to do that ? Step on the rudder
pedal, mate. WHAM. Your head hits the outer side of the hull with full
centrifugal force. That's what the helmet's for ! You try to make the
turn tight (and it is very tight), so that you stay foilborne throughout
the whole manoever and don't need to lift-off again after completing the
turn. Again, the trifoiler stays level, even under the extra strain of
the centrifugal force in the turn. Time to accelerate ...
After an hour, you're worn out. You sail home. The people I've seen
step out of the Trifoiler look like they've just been pulled out of the
North Atlantic after their ship sunk: Quiet, small, literally mumbling.
But after you get used to it, it's part of the future of sailing: a
Winds permitting, we want to make a speed check. Me on my speed needle
against trifoiler, winds force 6. It seems that they will win, though.
Henrik `4.9' Klagges