| The building of the X-3 went together without a lot of
hiccups.
I used 1/8 balsa for the sides and the bottom. The transom was 3/32 bass
wood. The bulk heads where made with 1/4 balsa and the front nose area
had 1/4 hard balsa stringers to reinforce the booms. I used an arrow shaft
for boom material and some aluminum tubes in the sponsons. The sponsons
where made with 1/8 hard and soft balsa with a 1/4 reinforcements for the
boom tubes. The sponsons where hollow so I designed a false tip from soft
balsa to act as a bumper and prevent the main structure from cracking open
in the event I hit something. The boom tubes where placed low on purpose
so that a stick 6-cell pack could slide and fit over them into the nose
area. By moving the bulk of the weight forward it would make it easier
for the boat to plane out. Hardware was made out of bent 1/16 aluminum sheet
and the strut was made with sheet/tube brass and a soldering gun. Not very
pretty -but it works. The motor mount and coupler where purchased from
Wharehouse Hobbies(The Enforcer People). The the boat was further reinforced
on the inside with 3/16X3/4 hard balsa sticks that where Superglued from
one end of the boat to another, even without the epoxy coat the hull was
stiff. I didn't thin down the epoxy to seal the hull. If I new then what
I know now... If I would have thinned down the epoxy top coat the boat would
have been stiffer and lighter. Thick epoxy isn't to good for sharp water
slicing edges either. At first I was using a 540 sealed can motor I got
at a discount electronic store, not bad for $2.50 . So I set to conquer
the local pond with my homemade rigger... |
| So the time came to launch this bad boy. I had no turn fin, running
a cheap 540 stock motor and sport 1500 cells. The boat weighs a few ounces
over 2 lb. ready to run. I launched the boat by hand it picked up some
speed and then the rear end just would go deep into the water and the prop
would cavitate like crazy. I had made provisoins for adjusting the strut,
so I ran it as deep as I could and pointed the prop down, hoping it would
give me the lift Ineeded at the back end. The X431 prop for Octura isn't
known for it's high lift characteristics and it showed me just that. After
the boat was launched it would start out great and then the rear end would
drop and the prop just blew bubbles at me. This process took about two
afternoons after which my speed control a formula 10 from tekin got wet
from my crapy wood hatch and cut the experimentation short. A few days
after that I visited team Reesor Boat Works . They also had scratch built
a 6 cell rigger but they had some small sponson in the back... It took
me a day to build my own spoonsons I sealed them attached them with hot
glue and off I was to testing. The boat seemed to like the sponsons but
I could not make the things brake free from the water . It seemed that
as the boat went faster water would pass over the sponson preventing the
boat from getting up on plane. I increased the angle of attack and tried
it again. When the batteries where all peaked out the boat for a small
instant of time broke free from the drag of the water over the sponsond
and -The lake sduddenly seemed so much smaller. Unfortunetly It only planned
out a few times in those 4 minutes. I knew I needed more power... |
 |
 |
| I had this crazy idea, I put my paradox stock motor from my racing
touring car into the boat. If the pond seemed small before it was getting
crowded now. The X-3 was handling great the turning radius was large but
this was because the boat was sliding through the corners. A turn fin quickly
fixed the problem. You know this whole fast electric boating is nice.
Then my speed control got wet agian and the boat almost plowed through
the concreate barriers. I knew I had to get more reliabilty aout of the
boat waiting till the wind brought back the boat was getting really boring.
If epoxy can seal the wood it can seal my electronics too. I opened the
case of the speed control and brushed two coats of epoxy and made sure
it got into every knook and crany. To test my idea I dipped the control
into a glass of water as it was turing a motor and it seemed to work good.
Next I took the balsa hatch off and installed some lexan sheets secured
with some extra cross linked rubber bands. The boat was quite reliable
know. I got tired of waiting for the motor to cool down so I installed
a cooling coil and some brass tube brush hood heatsinks. Now when I finish
running the boat the motor doesn't smell like it's baking. Actually I could
install a larger prop but I prefer to maximize handling and runtime. Other
modifications to the design include newly designed rear sponsons with a
reduced contact area and a sloping side to let the rear slide in the corners.
It's not as precise as the flat ones but it helps keep the speed through
the corners. At this point I think I might experiment with a good 4 cell
pack and a 10 turn modified motor. According to R/C Boat Modeler the power
out put should be higher and the weight lower. That sounds like a faster
boat to me!!! |
|
