 Dick
Perry discovered the Great Planes Combat Corsair ARF and concluded
it's scale fidelity was excellent for our purposes, within the
required ±5%. With a wingspan of 43¼", it sounded like it would be
good for Class 2. Available through standard hobby channels for about
$110.
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXGJY8&P=ML
I got one and
went to work. It is designed for .15-.25 glow engine, so we will be
overloading it with electric hardware for Class 2.
The model is pretty straightforward to build for R/C, but several
modifications for control line add to the required effort. The main
modifications required are beefing up the fuse structure for the
bellcrank and battery support platforms, adding landing gear (the
model was intended for belly landings so no landing gear was
included,) adding the tailskid and hook, and adding the line slider. |
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I chose the Kontronik
Tango 45-06 motor,
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXHEW1&P=ML
and it is really a nice inrunner motor. Unfortunately, the price was
high when I bought it and has gone up since then. There is a
substitute to consider for the future, the Scorpion HK-4025-630
http://www.innov8tivedesigns.com/product_info.php?cPath=21_25_68&products_id=369
which, at $115, is a bout one third the present price of the Kontronik.
The power specs are similar, and the Scorpion weighs an ounce more at
11.5 ounces. I also bought the Kontronik Jazz 55-10-32 speed
controller
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXHYK6&P=ML
and that, too, has gone up in price. I have been using Castle Phoenix
controllers in my electric Skyrays and have been very happy with them.
http://www.castlecreations.com/
They will release in about four weeks their new series of ICE
controllers with lots of new features, including an on-board data
logger, on-board switching BEC (battery eliminator circuit,) and
voltage capability for 8 LiPo batteries in series (referred to as 8s).
I'm looking forward to this release and think this will be worth
buying. There are lots of companies making motors, controllers, and
batteries, and I am only listing what I think might be cost effective.
I just can't list all the good companies and good products here, but
would be happy to pass on whatever I know. I had planned on using 10s
batteries, but had the 8s setup so I'll try using it. I think it will
work fine. I paid $200-$250 for the batteries. They should be good for
50-100 flights. In Class 2, 50 flights cost me $200-$250 for 65% nitro
fuel, so the batteries don't sound so bad. And the good news is that,
at Toledo this year, the cost of batteries continues to drop, and some
brands sell similar battery setups for half what I paid only a year or
so ago. So while Class 2 carrier is not a cheap event, the cost for
the components for electric class 2 now are on a par or less than with
the gas components, and the operating costs seem to be less for fuel
and, of course, glow plugs. (Class 1, Skyray and Profile events are
cheaper, of course. I'll get to that.) It's just the startup costs
that look scary.
Anyway, let's look at more technical details of the Corsair and
applications for other classes. Most electric carrier models use the
same three-line bellcrank system as the glow models. Instead of
operating a carburettor arm, the throttle control is through a 50kohm
potentiometer.
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=309NPC503-ND
works for me.
They have a similar model, 308NPC503-ND, which costs less and should
have a longer lifetime, but I haven't tested it. These pots are
connected to a Utronics control unit, made by Clancy Arnold
clancyarnold@juno.com and
available for $15 each plus $3 shipping. It's really simple and works
very well.
The Corsair goes together according to the instructions with a few
other things. The bellcrank has to be anchored solidly in the
fuselage. |
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 Fuselage
with bellcrank platform installed.
I added two 1/8 ply bulkheads to help tie the 1/8 ply bellcrank
platform to the fuselage sides and distribute loads. You can also see
the simple linkage to the control pot. |
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 Fuselage
with battery platform installed over bellcrank platform.
I added a
1/16 ply battery platform over the bellcrank platform, and strap the
batteries to the bellcrank platform with hook-and-loop straps from
Eflite. It's important to anchor the batteries well so they don't come
loose in a hard landing and smash into something fragile. |
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 Tailhook
and tailskid assembly.
The tailskid/tailhook assembly is based on a plywood strip inserted
into the fuse bottom and tied into three ply bulkhead that come in the
model. |
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 Fuselage
with batteries installed.
The motor is mounted with an aluminium commercial motor mount
assembly. Hobby dealers and web stores should find a mount system for
your chosen motor. I reinforced the firewall with a few pieces of
plywood filler in the lightening holes that came on the back side of
the laminated firewall so that blind nuts for holding the motor mounts
would mount easily. |
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 Motor
mount with speed controller Velcro-ed to the motor mount.
It's important to make the motor mount as rigid as possible. Sometimes
I have encountered severe vibration, even with a balanced prop. The
solution has been either to make the motor mount more rigid or to
reduce the moment of inertia of the rotating parts by, for example,
replacing a heavy plastic prop with a lighter wood one or a
lightweight plastic electric prop. |
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 Bottom
showing landing gear installation.
Add the landing gear before joining the two wing halves together.
I used Sig landing gear blocks for 1/8" wire. The bottom skin of the
wing has to be cut open where the landing gear blocks will go, the
ribs reinforced with 1/16 ply doublers around the block location, the
blocks epoxied in place, and the wire bent to fit. I was able to do
all the internal surgery and gluing through the openings for the
blocks and the opening at the wing center. |
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You can add your own
line slider arrangement as you see fit.
I used plywood "hinges" on the ailerons to lock them in place. I'll
cover the gaps with Monokote
later.
The Corsair balance point for R/C is given in the instructions, but we
may need something different. When the weather warms up a bit, I can
get in some test flights and let you know what I learn. There's always
a lot to learn, and I hope to have it sorted out for the busy contest
season ahead. |
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