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PROPELLER DEPTH
The depth of the propeller has an influence on both engine
performance and boat handling characteristics. Running the
engine with the center line of the prop shaft above the bottom
running surface of the sponsons produces less "load" on the
engine and allows the engine to reach peak performance.
Running with the propeller too high will result in diminishing
returns. Too high a propeller depth will noticeably affect
handling. Running in a straight line, the boat will be
unmanageable. A "bucking" or "hopping" ride will occur. Or,
the boat may suddenly fall off its supporting cushion of air
and hook.
In a turn, it might hook violently and dive under the water.
Turning ability will be decreased.
The propeller depth needs to be lowered to correct these
handling issues. Determining the correct propeller depth or
"Sweet Spot" requires test running the boat. Different
propellers work best at different propeller depths. The set-up
board side of the Starting Stand/Set-up Board will provide
an accurate method of determining propeller depth.
The term "flying the hull" is used when evaluating how the boat
is running. When running in a straight line, a tunnel hull should
appear to "ride free" which means that it should ride "lightly" on
the back 1/3 of the sponsons, as if riding on a cushion of air.
The hull should exhibit a smooth ride attitude without
excessive "porpoising" (bouncing). Adjustments to the balance
(adding or subtracting weight), propeller depth, thrust angles,
and type of propeller will all affect the ride attitude.
Propeller thrust angle and propeller depth are key factors in
a tunnel boat's cornering characteristics. While cornering,
the hull should carve a smooth, consistent arc without
"hooking" (spinning inwards) or sliding out of the turn. If the
boat is submerging and/or hooking in a turn, adjust the
propeller thrust angle to a slightly more positive angle.
Lowering the propeller will assist in correcting a sliding
condition while cornering. When properly trimmed and
balanced, a tunnel boat should be able to "cut" a tight corner
at full throttle.
Like any high performance car, airplane, or boat, optimal
outcomes in cornering and speed require "fine tuning" the
variables listed above.
Model tunnel boats are best suited for operation on calm
water locations. Wind and waves present challenges to
running a tunnel design. An increase in wind will create
choppy water conditions, allowing the possibility of "blowing"
the boat off when running into the wind.
RUNNING THE TOP SPEED 2
LAUNCH PROCEDURE
❏
1. Turn the power "ON" to the transmitter and receiver (in
that order).
❏
2. Start the engine. (Before running the engine, read the
instruction manual that came with your engine.) The
propeller will begin spinning as soon as the engine is
started. Be sure to stay clear of the propeller.
❏
3. Gently place the boat in water that is at least 8" deep and
free of obstacles (weeds, rocks, sticks, ducks, muskrats, etc.).
Be sure to stay clear of the spinning prop during the launch.
❏
4. Slowly advance the throttle to full speed and note if the
boat has a tendency to turn right or left. Adjust the steering
trim knob on your transmitter until the boat runs in a straight
line when the steering wheel is at neutral.
❏
5. When finished running, stop the engine and turn the
power "OFF" to your boat and transmitter (in that order).
MAINTENANCE
RADIO BOX MAINTENANCE
Lining the forward interior of the radio box with paper towel
prior to running will provide cushioning for the radio
components and absorb moisture.
Placing the receiver in a rubber balloon will provide added
protection from moisture.
Use a water resistant tape when sealing the radio box lid to
the radio box.
When finished running, remove the radio box from the hull
and wipe away water on the radio box and in the radio box
compartment. Remove the tape from the radio box lid and
check for moisture.
Should moisture gain access to the radio box, all
connections should be dried thoroughly. Hobbico
"Duster
™
" Compressed Air (HCAR5500) will provide a blast
of air capable of blowing moisture out of connectors.
Remove any sticky tape residue from the radio box top and lid.
Goof-Off
®
is a product that works well for removing tape residue.
HULL MAINTENANCE
After running, the exterior of the hull should be cleaned.
Common household cleaners can be utilized for cleaning.
Areas exposed to fuel/engine exhaust residue should be
thoroughly cleaned. Agents in the fuel/exhaust residue can
attack the finish if allowed to remain on the surface over time.
15
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