116 MODEL AVIATION
A special gift from Iraq
Electrics Greg Gimlick | [email protected]
Also included in this column:
• An in-depth look at Bob
Violett’s Electra Jet
• The “Animal” and the Hacker
• FMA Direct Cellpro 4S
Sean Hayes flies his T-Rex extremely well and knows how to pick a location. Welcome
to the main parade field in Baghdad, Iraq. Larry Mulholland photo.
Bob Fiorenze (L) and Bob Violett prepare new BVM Electra Jets for demo flights at
Joe Nall. This model leads the way in electric ducted-fan technology.
I’M GOING TO stray off topic a bit to
cover some things from a recent trip to the
Joe Nall Giant Scale Fly-In and touch on a
few interesting items: jets, big models, and
cool chargers. I can already tell there’s not
enough space!
A Gift to Me From Iraq: Soldiers Sean
Hayes and Larry Mulholland must have
known my birthday was near because they
sent me—an old, retired Army helicopter
pilot—the coolest pictures I’ve seen in a
long time. Larry shot the photos while
Sean flew his T-Rex under the crossed
sabers marking the entrance to the main
parade field in Baghdad.
Sean saw the photo of Hayes Hobbies
in the June issue and knew the shop well. I
look forward to meeting him there upon
his return. I doubt that the former “leader
of Iraq” would have approved of this great
usage. Thanks a million, guys.
Electric Jets Top Joe Nall: I love this flyin
and make no bones about it. It’s big
airplanes, and more electrics are showing
up and doing more than holding their own.
I’ll feature others in the next few months,
but I could spend a whole column
covering just the new Electra Jet from Bob
Violett (www.bvmjets.com).
If you have followed model aviation
for any time at all, you probably know the
name Bob Violett as one of the great jet
innovators. With the introduction of his
new electric line, I have jet fever for the
first time in my life. These are the finest
jets I’ve seen since the electric-powered
versions started showing up at fly-ins.
I thank Bob Fiorenze (www.rcavia
tion.com/fiorenze/) for taking the time to
disassemble his jet so I could get shots of
the inside and all the components. His is a
real work of art and a lesson in perfect
finishing techniques. I’ll have more about
that later.
The Electra Jet spans 60 inches, has an
area of 710 square inches, and is 67 inches
long. It weighs 13-15 pounds when
complete. Everything is made in the US at
the Bob Violett Models (BVM) plant in
Florida, and the fuselage, vertical fin, and
cockpit components are beautifully molded
fiberglass with carbon fiber and Kevlar
reinforcements.
The wing and stabilizer are built from
laser-cut balsa and plywood with one-piece
wing skins. To help absorb landing and
flight loads, the wing spars are extruded
carbon fiber, and all braces, landing-gear
plates, and special parts are injectionmolded
carbon fiber.
Jet designers are the kings of access
panels, and BVM is no different.
Everywhere you need to access something,
or think you might need to in the future,
there is a hatch that molds perfectly into
the body.
The specially designed Electric VioFan
(EVF) power units are BVM fans matched
to specifically designed Neu motors, and
they come in 10S and 12S versions. Both
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October 2007 117
Greg’s newest charger is the Cellpro 4S
that will do Li-Polys and A123 cells. It’s
easy to program and full featured.
Be careful when you ask Andy Jesky to “bring it in a little closer” because you will get
what you asked for. This is his incredible Radiowave Extra 300.
Check out this model’s finish down to going inside the inlet. Its
design and care in finishing this area can improve performance
when coupled with the proper tailpipe.
Bob Fiorenze shows his two 5S Flight Power 5000 mAh saddle
packs right after landing. They were warm, but not hot.
are listed as 4,000-watt systems, and with
37 and 44 volts under load respectively,
you can do the math and see that they are
sucking some current.
Bob was using a Castle HV-110
controller in his system to do the work.
Check out the BVM Web site for more
information about the EVF.
An interesting component of the BVM
system is the saddle cells used to slide in
the sides of the jet along the fan unit. They
are nicely made and make the most out of
the fuselage’s design to get cooling air.
The prices for the model, power
system, and retracts aren’t for the faint of
heart, but neither is flying a 160 mph jet!
The performance is on par with the small
turbines and is actually less expensive. For
the first time since getting into electrics I
can see myself wanting a jet.
My hat is off to Bob Fiorenze: one of
the masters of finishing. I overheard
arguments among spectators at the Joe Nall
event about how his Electra Jet was done
and how many coats of clear coat were on
it. Guess what? No clear coat was applied.
Bob used 3/4-ounce fiberglass cloth and
Z-Poxy to cover the jet and then two coats
of primer wet-sanded each time. Once that
was complete he used PPG Single Stage
Automotive paint, sanding each coat. For
the final finish he sanded in stages all the
way down to a 4,500-grit paper and
finished with compound.
I would have bet the model had several
layers of clear over the paint if Bob hadn’t
told me the process. By doing it his way
the jet gained only 7 ounces and you could
see your reflection in the finish. His Navy
jet weighed 11 pounds without batteries.
The “Animal” and Hacker: Andrew
“Animal” Jesky was at the Joe Nall event
with his 35%-scale, Hacker-powered
Radiowave Extra 300. Hacker’s new A150
outrunner motor on Thunder Power 14S2P
9600 mAh Li-Polys powered the 104-inch
monster.
Spinning a Mejzlik 27 x 12 propeller
producing 7,400 watts, the Extra pulled a
whopping 180 amps static at full throttle.
Andy didn’t spend much time at full
10sig4.QXD 8/22/07 1:25 PM Page 117
600 square inches, and the
airplane is projected to weigh 6 pounds.
With Li-Polys and our new equipment
we’ll use that as a target for the final
electric weight too.
We want the aircraft to be aerobatic, so
we want at least 80 watts per pound. Six
pounds at 80 watts per pound equals 480
watts.
Let’s also say we don’t want to be in
the super-high-current crowd, so our goal
is to stay near 30 amps to keep our Li-
Polys happy. So 480 watts divided by 30
amps equals 16 volts.
With our Li-Polys delivering roughly
3.7 volts under load, we can divide that 16
volts by 3.7 and see that we’ll need 4.32
cells. Since they really don’t come in
fractions, we’ll decide between a 4S (14.8
volts) and a 5S (18.5 volts) pack.
480 watts/14.8 volts = 32.4 amps
480 watts/18.5 volts = 25.9 amps
Which is the right choice? Either one,
if you ask me. It may come down to
deciding whether or not your equipment
can support the 5S pack. If your charger
only accommodates four-cell packs, you
want to go with that option unless you’re
willing to buy the new charger.
Since I have chargers that will go well
beyond either pack, my choice is the 5S
because I like the higher voltage and lower
current. Either setup is going to fly your
model nicely and result in similar
performance, depending on your propeller
choice.
Final Approach: Next time we’ll look at
using the simulation programs to check
our plan and see how we can determine the
missing motor constants when we get only
the Kv from the manufacturer. MA
Sources:
Castle Creations
402 E. Pendleton Ave.
Wellsville KS 66092
(785) 883-4519
[email protected]
www.castlecreations.com
FMA Direct
5716A Industry Ln.
Frederick MD 21704
(800) 343-2934
www.fmadirect.com
Hacker Brushless USA
2122 W. 5th Pl.
Tempe AZ 85281
(480) 726-7519
[email protected]
www.hackerbrushless.com
Bob Violett Models Inc.
3481 State Rd. 419
Winter Springs FL 32708
(407) 327-6333
www.bvmjets.com
JTEC Radiowave
Box 1847
Mooresville NC 28115
(704) 799-1658
[email protected], jtec@