MODEL HYDROPLANE Skims
Pusher prop spun by model-plane
engine gives high performance.
Construction is easy and fast
By ROY L. CLOUGH JR.
ydrofoils have been around for some
time, but even so, nothing on the boating
scene draws every eye like a hydroplane
lifting out of the water as it gains speed.
Even the U.S. Navy has been attracted
to foils, and has tested them on its fast
The PS model shown here can be completed in a couple of work sessions. Surface-piercing foils and air-prop drive give
it speed and stability with minimum complexity. Construction is far simpler than
you’d guess from the performance.
Basically, these craft deliver greater
speed because resistance against several
small areas (foils) is considerably lower
than against a complete, submerged hull.
Resistance declines as the craft rises.
Completely submerged foils are the
most efficient, but they require sensing
140 POPULAR SCIENCE
and control systems to keep them at
proper depth. Surface-piercing foils automatically adjust for depth—but they
also have a tendency to create air bubbles that reduce lift. The PS model uses
a foil design that minimizes this undesirable side effect.
Instabilities can develop in either type
of foil. This is particularly true of models. Simply put, the angle necessary to
make the foils “fly” at low speed can also
make them hop out of the water at high
speed and spill the boat. The model has
a designed-in, relatively steep foil incidence and a high thrust line to minimize
the possibility of this happening.
Building the model. Typical modelplane construction techniques are used.
But keep in mind two important construction hints: Cut all parts very accurately. Use ordinary pins to hold the
components while the glue dries.
Build the cabin first, complete with
tail boom and rear foils. Cover the lower
half of the cabin with lightweight model
tissue before doping, for a smooth and
watertight finish. The windows are simply clear plastic (I cut mine from bubbletype packaging).
Next, make up the front foils, floats,