ThiS column announces two meets,
has helpful hints for the FMA Direct Razor
and some related interference matters, and
shares new reader input on the Universal
Slow Charger.
The Fifth Old Time Eagles All Electric
Fly-In will be held Saturday May 12, 2001.
The meet is held near Hope NJ, and is
scheduled for 9 a.m.-4 p.m. It is hosted by
the Old Time Eagles model airplane club,
and Flying Models magazine is the Gold
Sponsor.
The fly-in is described as a fun-fly for
the promotion of all types of Electricpowered
models, including Radio Control
(RC), Free Flight, modern, vintage, etc.
One competitive event is planned:
Elexaco. For complete meet info and a
detailed description of the Elexaco event,
send a self-addressed stamped envelope
(SASE) to Contest Director Joe Beshar,
198 Merritt Dr., Oradell NJ 07649.
(Editor’s note: Model Aviation will
soon publish a complete description of the Elexaco event.)
An AMA license is required to participate at this fly-in! I
attended last year, and I am eagerly looking forward to doing
so again!
The second annual NEAT fair is scheduled for September 14-16,
2001 at the Peaceful Valley Campgrounds site in New York.
The Northeast Electric Aircraft Technology fair began in
September 2000, as a follow-on to the long-running but
discontinued KRC Electric Fly. You can read the coverage of the
inaugural affair in the February 2001 Model Aviation.
The NEAT fair will again be sponsored by SEFLI—the Silent
Electric Flyers of Long Island—and managed in part by Tom
Hunt of Modelair-Tech.
Tom tells me this meet will be much like last year’s, with
some modifications to the field setup to better accommodate
all attending—especially the expected growth. New this year
will be a Saturday-night barbecue social on-site and some
other goodies.
You can learn more at www.nyblimp.com/NEAT.htm. The
site offers lots of info, including photos and comments about last
year’s meet, maps, motel listings, etc.
I encourage you to attend; I had a great time last year, and am
looking forward to this year’s meet.
one of my new airplanes last summer was the FMA Direct Razor
flying wing. I chose the Speed 400 kit version from among those
offered.
This variation includes the motor-only part of the power
system, but the model has other features, including other motors,
Electronic Speed Controls (ESCs), receivers, etc.
The Razor is configured as a “pusher”—the motor/propeller
are at the trailing edge. The airplane is basically all-foam, but
it does have a few wood and formed-plastic parts: ailerons,
fins, cowling, etc. You can get more info from
www.fmadirect.com.
My model is equipped with an FMA Quantum receiver, two
Bob Kopski, 25 West End Dr., Lansdale PA 19446
RADIO CONTROL ELECTRICS
Author’s 21-ounce Speed 400 FMA Razor is mostly foam, with some wood parts he
MonoKote®d. Looks great in the air; recommended for those with flight experience.
“Nose holes” improve air flow over motor pack inside. Drill, then
sand and shape bores smooth with coarse paper glued on stick.
100 M ODEL AVIATION
102 M ODEL AVIATION
FMA S80 servos, seven 600AE cells, and a
Pixie 14 ESC. I’m flying it direct-drive to a
Gunter 51⁄4-inch propeller. All-up weight is
21.4 ounces. The Razor flies with a certain
“personality”!
In the process of building and flying
this airplane, I learned some things that
may be helpful to you. At least one point
has been expressed to me by readers
throughout the years, but prior to this I
could not relate to the information.
Regular readers probably know that I
favor good airflow over a battery pack.
Admittedly, airflow won’t make much
difference in some airplanes and some
kinds of flying. Such a case is when
flights are relatively short, as with
particularly high power-usage airplanes.
In these instances, airflow over highdissipation
packs for a short time will do
little to lessen pack heating.
On the other hand, cooling airflow
can be quite beneficial for models flown
more moderately with less average
power expenditure that also have
relatively long flights.
As designed and configured, the
Razor allows no cooling air to the pack.
Basically, the pack is nested in a nice,
hot foam box; as a result, it must be
removed between flights for cool-down
and recharge.
Since I prefer not to take packs out
unless absolutely necessary, I looked for a
compromise with my Razor.
It turns out that with the pack I have
Velcro™ed in its compartment, it was
possible to locate 1/2-inch-diameter “nose
holes” in the front of the pod, placing them
so incoming air would flow lengthwise
along the pack edges; i.e., along where all
cell ends are.
I also cut a rectangular opening above
and between these round holes, to permit
even more air intake to flow over the top
surface of the pack.
Bottom of Razor pod. Epoxied-on white plastic sheet material for
smoother landing. Dark-colored “grip strips” ease launch.
Razor’s seven-cell pack and aluminum foil-wrapped receiver.
Shielded receiver rests on balsa spacer on pack. Text has details.
There cannot be effective airflow
without an air exit, so I cut a fairly large
(1 x 2-inch) exit in the pod bottom,
located roughly between the end of the
pack and the beginning of the motor area.
I did all this “opening up” of the pod
after complete assembly and first flights
of the Razor.
These changes definitely provided
some pack-cooling—since I fly my
Razor fairly long and through the full
range of throttle. However, cooling was
still not adequate to permit charging
immediately upon landing on the
hottest days, so I use a blower into the
nose holes to expedite this.
As a result of the pack’s cooler inflight
behavior and the speedy
additional cooling after landing, now I
can enjoy the Razor more than when I
have to take the pack out.
What’s so pressing about removing a
pack?
This is a little harder to explain. But
in the case of my Razor, it involves
removing the Velcro™ed-on formed
plastic cowl, removing the receiver, then
getting the pack out. There’s more to it
than I deemed “nice” to do.
And this brings me to “part two” of
my Razor experience.
Through the years, I’ve experienced
and corrected “all kinds” of interference
problems in my Electrics and in other’s.
A tidy radio and power system
installation—where the components of
one system are separated from the
components of the other—and chokes in
the ESC/radio path are usually sufficient
to cure all interference problems. Not so
with my Razor.
As designed, the Razor installation
has the receiver located very close to the
motor pack. Basically, the receiver winds
up “on top of” the motor battery. I had
interference problems from the start.
After experimenting with chokes
(which usually work, but didn’t here),
changing receivers, then finally
realizing that the problem was not a
“range” issue (surfaces would jitter
104 M ODEL AVIATION
with the transmitter close), I knew this
was something special.
For the first time, I understood what
some readers have been telling me for years!
With the receiver “up against” the
motor pack, the receiver would pick up
noise from the motor pack itself
whenever the motor was running. If I
separated these even two inches,
operation was okay, but such a setup was
not flyable.
Then I tried to shield the receiver—
following a suggestion readers had
shared throughout the years, but for
which I had no prior need, hence no
experience to report!
Since the Quantum receiver is a
somewhat “open” physical structure, I
slipped an insulator of one inch of heatshrink
tubing over the entire length of
the receiver and connectors. I did not
shrink the tubing; it was just used to
protect the electronics when I then
wrapped the whole works in two layers
of ordinary kitchen aluminum foil.
It was not necessary to cover the very
ends of the receiver—only the long
dimension. (I don’t know if this is
different with other receivers.)
It’s important to close the foil wrap on
itself, which is ensured with the two
layers. Then I held the foil wrappings
together by slipping another length of heatshrink
over the whole thing. The resulting
package is shown in one of the photos.
In all this, it’s important that the foil
does not touch any of the receiver
electronics, and it’s not necessary (or
desirable) for the foil to be “grounded”
or otherwise connected to anything
electrical.
Technically, the foil is much like a
Faraday cage—a well-known classic
structure within electronics. It works so
well in this case, I can actually press the
pack and the receiver together with no
visible crosstalk.
In practice I have a small balsa
separator between the pack and the
receiver, but this is to allow space for
airflow, as discussed earlier.
Some Razor owners may wonder
why my receiver is down in the battery
compartment and not on top of the
“flap” that covers the battery
compartment, as intended.
The receiver would not fit on top; the
crystal supplied was too large, and the
interference problem was roughly the
same anyhow.
Two more items are visible in the
photos. I learned that covering the front
bottom of the pod area with smooth sheet
plastic aided in landing. Unless the
Razor is really “greased in” level, it
stumbles and tumbles all over the place;
the new slippery skid helps!
Also shown are “grip strips” on
either side of the pod. These are
roughly 1/2 x 41⁄2-inch strips cut from
self-stick 3M™ safety-tread material,
normally used to make stairs and
106 M ODEL AVIATION
walkways slip-proof. It’s available at
hardware stores.
This product makes a good skid
material for glider bottoms. It also makes
hand-launching a bit easier, since one
does not have to squeeze the foam pod as
hard to hold and launch the Razor.
My Razor is a bit “spirited” and does
display some in-air “personality,” so I feel
that it is most suited to fliers with some
experience. This was my first RC Electric
“wing” configuration, and it’s been a good
education.
Readers continue to send comments on
and queries about the Universal Slow
Charger (9/00 Model Aviation).
One reader reported building three of
the dual version, and another has two “in
the mill” as I write this. Anyway, several
questions have come up that I’d like to
share with everyone.
No, you do not have to use the
multiple output connector strips I used
on mine! Many readers have reported
substituting alternate connectors more
suited to their preference and need, such
as simple banana connectors.
Please feel free to substitute any
connector style that fits your particular
situation. But no matter what your
choice, make sure there is no metallic
connector contact with the metal case!
A few readers have reported missing
the jumper wires that are on top of the
holeboard, but underneath the integrated
circuit (IC) sockets. They discovered “the
error of their ways,” and fixed things by
installing these jumpers on the bottom
(conductor) side of the holeboard.
Just be sure these “repair” wires do not
come in contact with lands they are not
supposed to!
And contrary to one reported
experience, the specified wire and IC
socket pins do cofit in the holeboard
holes where shown—just use the
specified parts and material.
Some readers did not understand the
“#55” drill called out on the assembly
drawings.
I guess most modelers are more or
less familiar with the common
“fractional” drill sets. These drill bits
come in sizes (diameters) that are
fractions of an inch, such as 1⁄8, 13/64, and
so on. However, there is another fairly
common drill index: the “numbered” set.
I have two numbered sets of bits; set 1
is #1 through #60 and set 2 is #61 through
#80. A #1 bit is 0.228 inch in diameter, a
#80 bit is 0.0135 inch in diameter, and
there are many sizes in between.
A #55 bit as specified is 0.0520 inch
in diameter—just right for the
component leads that need to go in it.
This size is also small enough that the pc
land on the board is not broken by the
drilling; hence, my calling it out.
Most good hardware stores sell
numbered drill bits individually and in
sets—just like they sell “fractional” drills.
There are other drill sets besides these,
including “lettered” sets and metric sets.
It’s a “hole size for every need” situation!
Please enclose an SASE with any
correspondence for which you want a reply.
The formula is simple: I respond to every letter
I receive that is accompanied with an SASE.
If you sent such and have not
received a reply, I did not get what you
sent. (This happened to one reader.)
happy and numerous E-landings,
everyone! MA
