| It was 1989 and shipbuilding students from Delft had been participating
in the International Waterbike regatta for 3 years and DWT had been
officially founded just one year before. It is a common phenomenon that
shortly after the start of participating in waterbiking events, new teams
attempt to build a complicated and/or spectacular boat (e.g. Af Chapman
II, Hydrodynamosaurus Austriacus…) and the Delft team formed no
exception.
The concept
After a long brainstorm session the hydrofoil concept was chosen over a
submarine and the concept was examined in greater depth. At the time only
two hydrofoils were active or under construction: Flying Magic (FH
Flensburg) and the legendary Af Chapman II (Göteborg), both using flaps
for controlling roll and pitch. Since history has taught that moving parts
tend to break down, the KISS principle (Keep It Simple, Stupid!) was
deemed of utmost importance and the hydrofoil was to be completely
flapless and self regulating. Additional advantages of a flapless boat
were (and still are) a less vulnerable foil and the option to reduce the
foil's thickness and reduce drag. Furthermore a correctly positioned self
adjusting foil will always be in an optimum position, thus having a very
favourable lift to drag ratio. All in all a rugged, simple and efficient
design was deemed ideal to lift the boat from the water with the limited
power available (about 800 W)
The project
So much for good ideas… Building a boat proved somewhat more
complicated than the abovementioned points may lead you to expect. The
main reason: Flapless hydrofoil theory was exactly that, a theory, yet
unproven in practice. Together with MARIN, the MATSO foundation and The
Royal Schelde a research project was initiated by Delft Waterbike
Technology with the goal to prove the flapless hydrofoil theory by
creating a working model (known as Flying Colours).
A V-shaped surface piercing foil
The solution to the problem was found in the characteristic V-shaped
surface piercing front foil, which controls the angle of attack on the
rear (main) foil, thus controlling total lift. The principle is in fact
very simple: the further the foil is submerged, the larger the
lift-providing surface. As the boat accelerates, lift on the front foil
will increase, thus lifting the bow of the boat from the water until a
balance is achieved between lift and weight on the foil. By trimming the
boat this way, the angle of attack on the main foil will increase, thus
making it produce more lift and allowing it to elevate the entire hull
above the water
Practice
Well… so much for theory…. Practice proved even more difficult.
Surface piercing foils have a bad habit of ventilating, sucking down air
from the surface to the foils, thus causing lift to collapse. This problem
first came to light in august 1990 during towing tank tests at MARIN and
before the problem could be solved, disaster struck: one of the guides on
the carriage failed and the boat was torn from under the moving carriage
and was severely damaged. Both repairs on the boat, solving the
ventilation problem and a full schedule at MARIN caused further tests to
be postponed until December of that year, when only the front foil was
tested. During these tests the ventilation problem was efficiently solved
by placing horizontal brackets on the foil. At the same time the drive
system was tested at the Delft towing tank. In march 1991,after all bugs
were solved, final tests of the entire boat were done at MARIN, to make
sure that the foils were tuned into each other perfectly. After this
Flying Colours was ready to participate in waterbiking events for several
years. Due to the extremely low weight of the boat (33 kg), some
concessions were made to stiffness, which made the boat too flexible to
keep flying after several years of operation. After extended service as
"Floating Colours" she was withdrawn from the races to make room
for other boats of the team from Delft.
At present Flying Colours is put on display at the department of marine
engineering at Delft University of Technology in the Netherlands.
Robert Hekkenberg, Delft Waterbike Technology
This introduction is mostly a short version of the article published in the
Delft University of Technology magazine "Delft Outlook", edition
4-1990. A Dutch translation of this article was published in "Delft
Integraal" 4-1990
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