| Hull
Design |
This hull design is 'shallow Vee' with spay rails
that run the length of the hull which provide lift,
thus raising the hull up out of the water to reduce
drag. The spray rails stop water riding up the sides
of the hull by deflecting the water downward. As shown.
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| Surface
Drive Propellor |
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Leading
power boat designs now almost always incorporate what
are termed semi-submerged, super cavitating, surface piercing,
or surface drive propellers. As the name suggest, the
propeller isn't completely under the water all the time
but runs very near to the surface and actually only partly
in the water.
"But doesn’t that mean that you only get
half the thrust?" |
Higher
propeller speeds are obtainable because less of the
propeller is in the water. If only one blade is in
the water, it doesn't pass through the wake made by
the other blade or blades and so can take a clean
bite at undisturbed water. For more information on
surface drives, have a look at; www.simplicity-marine.com
Surface drive propellers boats can go faster than
a boat with a submerged drive for the same amount
of engine power. There is virtually no limit to the
size of propeller that will work. The designer is
able to use a much deeper reduction ratio, and a larger,
lightly-loaded, and more efficient propeller. Surface
drive propellers are used on outboard engines, stern-drives
and outdrives. As the propeller is surface drive,
normal propellers don't work very well at all. Adjusting
the amount of the prop that is above the water line
might well damage the blades so make sure you have
enough props until you get it right.
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| Glues |
Three adhesives have been recommended to us by model
makers but you can try others.
1) Stabalit Express
2) Superglue
3) HART
'Hart'
glue does hold ABS but easily melts and distort ABS.
Superglue is good but you have to get the parts in
the right place first time unless you use thick or
slow-set super-glue. Stabalit is best as it comes
in the form of an epoxy and gives you about 20 minutes
working time before it sets. If you want to increase
the setting time use less powder but don't use too
little as it won't have its full strength when set.
Just before Stabalit sets, excess glue can be cleaned
off with methylated spirits. Rough the surfaces to
be glued with sandpaper first to provide a key and
thus ensuring a good bond.
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| Running
Gear and Electrics |
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The greater angle the universal joint has to work
with, the more power it will drain from the motor.
"What about when you turn the boat using
the rudder, don’t you lose power?"
Correct, limit the turning angle of the rudder to
about 10 degrees each side of neutral. The less
change in direction that the drive line has to deal
with, the less power will be lost and thus more
power delivered to the propeller. The boat won't
turn tight circles like his. When fitting the shaft,
ensure that there is lots of Stabalit around and
under the shaft at the transom because it will soon
be covered by the radio box floor. Be careful when
fitting the rudder unit to get the clearance around
the prop. The control rods from the servo to the
rudder took some real bending to get right. Use
of nail polish to lock in the grub screws can be
substituted by super glue on metal components as
it doesn't hold permanently.
A bulkhead of 3mm ply was fitted behind the motor
to prevent water splashing all around the boat.
Leave room in front of the gearbox to allow the
cover to be removed for servicing but trying to
get it back on again in situ is next to impossible.
A piece of foam holds the two battery packs in place
or use Velcro.
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| On
the Lake! |
Centralise
the rudder and steering servos to the
transmitter and check range. Oil and bed
in the running gear and you are ready
for the lake! Down at the lake on one
third power our engine whirred like a
food mixer and gurgled and burped until
the propeller got to grips with the water.
At full speed the whirring increased relative
to the speed. It takes a few seconds for
the propeller to grip the water from a
standstill, so a steady acceleration is
needed from the throttle for a quick takeoff.
The roster tail of spray from the propeller
does look really good!
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| Aiming
to Win? Possible Modifications for your IC
Craft |
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high
performance motor
high power batteries
water cooling
high performance running gear
direct drive running gear
metal props
electronic speed controller.
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