power system and two cell 7.4V battery your
WaterBoard Mini™ will be on the ragged edge of
flight through high speed turns and may flip if a
gust of wind catches it. Be prepared (you did
bring recovery items to the pond today right?) and
build speed only as you become comfortable with
the boats operation.
In the event of a capsize. IMMEDIATELY cut
throttle to the electric motor. Running the motor,
even only briefly, while submerged may over-
current the electronics and cause a failure (i.e.
letting out the “magic smoke”).
Retrieve boat. As water has filled the motor
mount hold boat inverted to allow water to drain
from motor mount then right boat, clear prop, and
run fan to clear out water and check function of
electronics. You may, at this time, wish to remove
the electronics hatch lid to inspect his area for
moisture.
Fresh water will have no effect on the motor and
the recommended servos have proven to be
remarkably water resistant. Thus a capsize event
that’s quickly resolved will not typically result in
loss or damage to electrical equipment. Also note
that salt water is highly corrosive to the fittings
and electronics in this boat.
This boat has not
been designed to run in salt or brackish
waters.
Battery tips and estimating run times. LiPo
batteries are easily damaged if over-discharged
and, unlike the familiar NiCd and NiMH cells,
require specialized care when charging and
discharging. If unfamiliar with the use of LiPo
b a t t e r i e s p l e a s e c o n t a c t y o u r b a t t e r y
manufacturer for instructions regarding proper
care.
A unique feature of LiPo chemistry is the small
voltage drop between the charged and
discharged state. A 7.4 volt LiPo battery is
considered 100% discharged when the battery
reads 6.0V and 100% charged when the battery
reads 8.4V. Compare this to the typical 6 or 7 cell
NiCd or NiMH pack of equivalent pack voltage
which can typically be run to an almost zero
voltage condition and it becomes clear that LiPo
powered electronics are not going to go behave
as though the batteries are running dead. Thus it
becomes tough to discern when/if it’s time to
return to shore and “refuel”. Add to this the fact
that your electronic speed control (ESC) has been
designed to protect your pack from over
discharge by turning off the fan motor when the
battery pack voltage reaches ~6.2V and it
becomes clear that you may find yourself
stranded with a dead pack while in the water.
The way to prevent being stranded is to strive to
use only 3/4 of the rated pack capacity during a
normal session leaving you with ample reserves
to get back to shore. Without a watt meter or
some other onboard monitoring device this can
prove tricky. However, I’ve found the following
method to work quite well: Start with 5-8 min
sessions, return to shore and check your battery
voltage, if you find the battery voltage to be at or
slightly over the packs nominal voltage (7.4V for a
two cell pack) then it’s a good bet that you’ve only
consumed 1/2 of your available power and can
most likely extend your session by 1/2 of the time
spent on the water during your initial session. If
you find the pack voltage to be well under nominal
you should consider not extending your session
times between charge cycles.
Run times will be influenced by how heavy
handed you are with throttle, the prop pitch and
diameter run, wind conditions, battery capacity,
battery “C” discharge rates, and ambient
temperature. In general we’ve found the
suggested power-system with 550mah 7.4V
battery and 5x3x3 blade propeller to provide a
comfortable 10 min of leisurely run time or 6
minutes of “racing”.
Note: Longer run times and
more suitable entry level performance may be
achieved by using a two bladed 4.5x3 propeller
instead of the performance three blade prop as
listed above.
End of session procedures. Upon returning to
shore remember to
keep clear of the prop!
remove the electronics access hatch lid.
Disconnect your battery. Turn off your radio.
Wipe dry the outside of the boat and remove any
water that may have found it’s way inside the
hatch. Leave the hatch cover off of boat when in
storage so that gasket will remain spongy. Store
boat in a cool dry environment.
Build Instructions
© 2013 Stevens AeroModel all rights reserved.
Page 23 of 25
