Tuning / Troubleshooting
Boat dives and will not plane
This is a pretty rare condition when built and
balanced as described in this manual. Diving is
often the result of the boat being balanced too far
forward. Additionally thrust line changes outside
of specification can cause the boat to dive.
Tuning Tip - Move the balance point of the boat
aft. In order for the boat to come up on plane it
needs to ride up and over the bow wake.
Sometimes shimming the motor so that the thrust
produced by the prop is angled down slightly will
lift the back of the boat and assist with riding up
on plane faster.
Boat skipping
Defined as the entire boat or bow bouncing up
and down out of the water especially in the
straights. This is typically the result of a severe
imperfection on bottom of the hull and to a lesser
extent the CG or balance of the boat.
Tuning Tip - Try installing a trim tab from thin
aluminum sheet at the transom to better control
the boats attitude as it comes up on plane. Bend
the tab down to force the bow into the water, up to
allow the bow to rise up. This tab will negate the
use of the optional water rudder.
Boat will not skid in turns
When at planing speeds (1/3-2/3 throttle) the boat
may stay “stuck” to the water on a chine or side
resisting turn input. Often it will appear as
thought the water flow will not release from the
sides of the boat or chines to produce the
characteristic airboat skidding turn. Occasionally
turn performance may be so bad that the boat will
actually roll out or against the turn even to the
point of flipping over.
Begin by verifying that the rudder is moving equal
amounts right and left and adjust if necessary.
Tuning should be performed on calm days so as
to minimize the influence of wind on the craft. If
the turning problem occurs only for right hand
turns this disparity is the result of motor torque
acting on the boat lifting the right chine of the boat
and driving the left deeper into the water.
Tuning Tip - Shim the motor so that more of the
prop blast is directed towards the opposite side of
the boat from the problem turn. That is to say, if
the boat is having difficulties turning right, direct
more thrust to the left side of the boat which has
the effect of countering the motor and prop torque
thus driving the right chine back into the water
and lifting the left producing a better right turn
performance.
Hopping in the turns
In a high speed sweeper the side of the hull on
the outside of the turn lifts then drops repeatedly.
Caused by having too much radius on the chines .
Unlike the square sided WaterBord
tm
we suggest
not applying a radius to the chines of the
WaterBoard Mini
tm
. Rather, leave the chines nice
and sharp.
Tuning Tip - Control hop by not
radiusing
the chine
Improving straight line performance
Airboats excel at drifting, sliding, and otherwise
gliding sideways across the glassy water surface.
But what about straight-line performance. You’ll
no doubt notice that this can be a challenge and it
will take practice to learn to stay slightly ahead of
the boat in the straights, anticipating corrective
inputs. Cross winds can present an especially
challenging situation where the boat will tend to
weathervane into the wind or list to a chine and
deviate from the straight and narrow.
Tuning Tip - Install the optional Water Rudder.
On the flat bottom airboat design of such light-
weight the only way to improve straight line track
and power-off turn performance is to install a
Water Rudder. The optional Water Rudder is a
carefully sized nylon part linked to the Air Rudder
and elastic loaded to allow the rudder to ride over
foreign objects in the water without damage.
While we have sized the Water Rudder to
minimize the impact on “drift” performance,
Build Instructions
© 2013 Stevens AeroModel all rights reserved.
Page 24 of 25
