Here in
Maine, we have float flying opportunities for
three seasons, and snow flying in the
longest season - Winter. For several years have have
contemplated
getting a Seamaster but
installing electric power. Many models are hard to
covert to
electric, but it can be done.
Here, the big issue would be setting the center of gravity
without
major surgery.
Luckily,
Art's Hobby Supply of Skowhegan, Maine was able to obtain the Seamaster
in blue trim, rather than red. I think it looks much
better, and
besides at the other Seamasters in
the clubs I fly with were the red trim or modeler installed
variations. For the time being, I will
be a little unique. So, I threw away the fuel tank that
came with
the kit, and started working.
I also
decided to try a Turnigy motor. They are available from United
Hobbies in Hong Kong. My order
took a month to get here, but it was really
inexpensive. The
equivalent motor and ESC package from
Axi and Castle Creations would have been over three times as
much, at
least. And, it is performing
very well. I am pleased with the choice. Check
them out.
Final specifications are as follows:
Wing Area: 725 sq/in
All Up Weight: 7.5 lbs.
Motor: Turnigy C50-55A
400 kv Outrunner (equivalent of Axi 4120/18)
ESC: Turnigy 60 amp
BEC: Castle Creations 10 amp
Prop: 13x8.5 Master Airscrew E Prop
Battery: Thunderpower Extreme V2 5 cell 3850 mAh pack
Power: 83 watts per pound
Servos: Hitec HS-645MG
Receiver: Spektrum AR7000
Conversion to Electric Power and Assembly
The motor
pylon and firewall come assembled, and drilled for the
glow motor mounts in the kit. I measured the front cowl and
determined how far out I would have to mount the motor. It was 1
1/2". I bought four 1" and four 1/2" Nylon spacers at
Lowe's
together with some long machine screws and lock nuts to fit.
Total cost: $7.06. Hobby Lobby sells very nice mounting
sets that would go the job, but they are $25 or so.
Next, I
made a shelf of 1/8" liteply to mount the speed control
on. On the firewall, I also plugged the fuel line holes with
dowels. and made some hardwood tabs to mount the cowling on.
The speed control shelf was reinforced with a hard balsa triangle.
The rear
of the pylon was only made big enough for a servo wire to
pass down to connect to the receiver. I had to also send down two
heavy motor wires. The channel was widened with a Dremel tool and
router bit. Then, I covered the channel with balsa, painted the
top
of the motor mount with Polycrylic, and mounted it on the fuselage
securing it with a large screw through the bulkhead. By the way,
I forgot to add the screws supplied to screw the firewall/engine mount
plate to the pylon. A buddy caught the error when I sent some
in-progress photos around. I decided to skip the screws and
instead drill it out and used two hardwood dowel plugs, which I think
will be stronger.
From the
outset, I was concerned about balancing this model at the recommended
CG.
There is a plywood bulkhead at the front and rear of the pylon, so the
battery or batteries would have to go either in the nose or under the
wing. What to do? I marked the CG
under the wing with a small strip of tape on each side of the fuselage
(so I can reach under, feel the tape and balance the model on my finger
tips.)
In this photo, you can see two 4 cell
3850 mAh Thunder Power packs resting on the wing. I had taped the
tail pieces on temporarily, mounted the motor and ESC to the pylon,
rested the
battery packs there. I found I
needed 6 ounces of weight in the nose to achieve balance. That
was okay. Had I put the batteries in the nose, then a lot more
weight would have gone in the tail! And, I did not have to figure
out how to make a waterproof and removable front hatch.
(Ultimately, I determined that a single 5 cell 3850 mAh pack would be
better, but more on that below.) When I finished the model, I
balanced it again and added the needed weight to the front under the
nose cone with sticky backed lead weights from Great Planes.
Here is
were it all comes together. The guidance system is by
Spektrum, an AR7000. You can see the Castle Creations 10
amp BEC, and on the side an MPI arming switch. I can load the
battery, connect it, and bolt on the wing. The system is not
connected until I insert the plug. Of course, with Spektrum, you
don't have to worry about the plane suddenly leaping to life due to
someone getting on your frequency. But, it does allow me to wait
my turn to fly without running the battery down. You will notice
I make liberal use of wire ties. With all those wires, you have
to keep them out of the way. Also, all the electronic components
are off the fuselage floor. Sooner or later, water gets in all
seaplanes, so I mount everything off the floor.
I sealed the wing saddle by taping strips of Saran wrap to the wing in
the area were it mates with the fuselage. Next, I applied a
generous (meaning a lot) of clear silicone to the wing
saddle. The wing was bolted in place and left for a day.
The result is a perfectly fitted gasket. Some guys supplement
this with Vaseline applied before flying sessions. I found that
the mount is water tight, but I have not had a lengthy session of
touch-and-goes yet. That kind of flying gets the model really
wet, and some water is bound to leak in.
Speaking of water. The AR7000 has been treated with a coating of
Corrosion X. I took the case apart, soaked it and let it drain on
a paper towel before re-assembling it. It can safely be submerged
now, although I hope it never happens. Check Corrosion X
out if you float fly or use any equipment outdoors where it will get
wet. This stuff works.
I used
Hitec HS-645MG servos, which are high torque and equipped
with metal gears. Seaplane models take a beating, and I wanted
sturdy servos. It looks cluttered in there, but that cannot be
avoided. With spread spectrum technology, you do not have to
worry about electrical interference the same way you do with standard
FM R/C gear.
I have not
added any trim to speak of in these photos. I will
be adding some lettering. I did place day-glow orange Monocote
Trimfilm on the leading edge of the wing to help orientation. I
designed my own "windows" for the cockpit to give it a better
look. They are cut from Ultracote, as is the thin red stripe prop
warning line.
At the
trailing edge of the wing you can just see an address
label. It has my phone number and the promise of a reward if
found. AMA rules require that you have your name and address with
AMA number on your model, and it makes sense
anyway. You can lose one more easily than you think.
This chart
is produced by the software with the Eagle Tree
eLogger. If you fly electric, you have to get one of
these. The beauty of this is you can fly your model around with
this installed (it just plugs in between the battery and the ESC), and
it store all sorts of useful data. You can use it on the
workbench too. Then, you download the data to your computer and
study it to make
the best choices for equipment. You can see from the chart that
the setup I described at the beginning of this page is producing almost
650 watts of power. My original choice was going to be two 4 cell
Thunder Power packs of 3850 mAh capacity each. I figured on long
flying times and plenty of power. I found I would get a measly 48
watts per pound. Fifty watts per pound is good for a trainer, not
a seaplane. Thus, I went to the 5 cell pack, and the chart tells
the tale.
By the way, I now buy my battery packs from Light Flight R/C. I use
Thunder Power exclusively, and as of this writing, they have the best
prices, and they always give you super fast service.
Seven Seamasters belonging to members of Franklin County Aircraft Modelers
and Kennebec Valley
Model Aviators at
Lily Pond in Concord, Maine on June 14, 2008. Oh, yes,
there is one scratch-built Lakemaster there, which is
the creation of Art Aube.
Photos of the Seamaster E in flight by Joe Gilbert.
Video of the maiden flight (HD - 13.6 mb) is available here.
This is Joe Gilbert's website. He took the
video, and there are some
great photos and more video available there..
