A group of pilots at the Heart of America Float
Fly show off their Model Aero Polaris aircraft.
Bob Mayhew scratch-built this beautiful de Havilland DHC- 2 Beaver. The 83-inch wingspan model
is powered by an O.S. . 91 four-stroke engine and weighs 14 pounds. Smith photo.
The front of the floats should now be
10-12% of the float length ahead of the
propeller disk. If the tips of the floats are not
far enough forward (and you bought the
correct length of float) you can modify the
step position by as much as 5% of the float
length by glassing in balsa blocks behind the
An incidence meter is required for
measurement. With the tops of the floats
level, the wing needs to be approximately
2° positive. This is a critical measurement.
If needed, you can use small blocks
of hardwood between the nose gear
blocks and the float top to achieve the
Unless you are flying in calm
conditions, you will need a water
rudder to have positive control of your
model while taxiing. Whether you need
one or two rudders is dependent upon
the design and size of your model.
Smaller models can typically get by
with one rudder, but larger models,
particularly high-wing airplanes, need
two for positive control.
The water rudder(s) must be
positioned so that they do not touch
the water when the model is on-step
(at speed). This means that the bottom
of the water rudder should only extend
roughly 1/2 inch below the bottom of
the rear of the float. At low taxi speeds,
the model rocks back toward the rear and this rudder location
gives good authority at taxi speeds.
The simplest water rudder is one that uses a wire attached
to the airplane’s rudder. I use a 1/16 wire with a loop at the top
for a 4-40 bolt. I use two rubber washers on each side of the
loop and a nylon insert nut so I can adjust the tension.
The rudder needs to be able to “kick up” in case you hit
something in the water or set it down against something on
shore. It only needs a small spade at the bottom.
When using rudder(s) mounted on the end of the float, you
can make your own, but it’s easier to use the ones available
from Ernst Manufacturing. You can be creative when attaching
pushrods or cables. I prefer to mount the servo in the top of
the float and run the servo lead up the rear strut to plug into
a Y-extension from the rudder channel. If you are mounting a
servo in the float, I recommend a waterproof servo.
I try to seal as many openings in the fuselage as I can,
including the wing saddle. Beyond that, I don’t do much
waterproofing. My logic is that if I tip one over, that model
can’t be flown for a few days until I can take it home and
thoroughly dry it.
An exception is the engine. I drain the fuel tank (if I think
there is any chance that water got in with the fuel), remove
the plug, and spin the engine with an electric starter to get all
of the water out. Then I refuel and start the engine. I want to
get it hot enough that any moisture in it evaporates.
Some modelers are using CorrosionX on their electric
components, which is available through the Internet. I
recommend it for your ESC if you are using an electric power
Scale Floats for Scale Models
There are two components to scale floats: detailing of the
floats and full struts, and bracing to attach the floats to the
model. Things to consider for scale detailing are nonskid
walkways, rails, float access ports, panel lines, and rivets. Scale
struts and bracing are also important for a scalelike appearance.
Scale ARF floats and float kits are available online.
41 Model Aviation APRIL 2014