Frequently Asked Questions - 2012/10

Q557: I have trouble when it comes to tightening the propeller
nut on my electric motors. As I go to tighten the nut, the
motor shaft begins to rotate. When that happens I can’t get the
propeller tight up against the drive washer. I’d hate to damage
that washer if I used pliers to get a grip. Is there a better way?
A557: I received a good answer to this question from reader
and AMA member, Larry Bresson of Nampa, Idaho. Larry
made up his own spinner wrench that holds the motor shaft
in place while tightening the propeller nut. The wrench is
constructed from 1/16- or 1/8-inch thick aluminum obtained
from stores such as Lowe’s or Home Depot. Approximately $3
worth will make up to six wrenches. I suspect these wrenches
are made with the help of a hacksaw and a fi le.
Larry indicated that he has a CAD drawing of his wrench
that he would be happy to email to anyone. That’s a generous
offer and we thank you, Larry. I’ve listed his email address in
the “Sources” section.
Q558: I like using the Du-Bro EZ Connectors to attach
my throttle control rod to the throttle arm on my engine’s
carburetor. The problem is being able to easily access the screw
on that connector to make adjustments to the linkage. As it is,
you must come in from the side which often requires drilling a
hole in a cowl or fuselage side. Are there any alternate schemes
available that let you come in from the top?
A558: Reader Ron Ogren of Orchard Park, New York, sent in
a simple, interesting modifi cation to a Du-Bro EZ Connector
that will do exactly what you want. I hope the photos and
commentary will be clearly understood.
Ron basically drills and taps for a 4-40 screw that comes in
on the side of the connector as shown in the photograph. A
hex-head screw works the best. Ron cuts his 4-40 screws to a
length of between 3/16 and 1/4 inch. He suggests that you use a
3/32-inch, ball-end hex screwdriver.
As shown in the photo, it is then
possible to come down from the top
and access the hex screw directly to
make necessary adjustments. It is a
simple process, but it can save you time
when quick adjustments are required
at the fl ying fi eld. Thank you, Ron!
Q559: Several years ago, I read an
article about cleaning the exterior of
glow engines with a product made by Dawn detergent. I used
it and it did a great job. Unfortunately, I cannot fi nd it in my
shop anywhere so I must have thrown it out.
Would you happen to know the name of the product? I
think it was stronger than regular Dawn detergent that is made
for cleaning pots and pans.
A559: Reader Bob Lee helped with this answer. The name of
The Winged Shadow System’s new Sky Limit
device can limit your altitude or time. The
smaller component goes into the aircra and
the larger one is
used to program
the device. When
the pre-set limits
are reached, the
motor/engine
cuts o .
The Dawn Power
Dissolver is
e ective for
cleaning the
exterior surface
of your glow
engines. Don’t
leave it on the
engine for longer
than 20 minutes.
This illustration indicates
that the area of the wing
covered by the fuselage
is still considered part of
the total wing area.
the product is Dawn Power Dissolver.
This product was at fi rst thought to have
been discontinued, but that’s untrue.
I’ve listed the Dawn website in the
“Sources” section. It can be purchased at
Walmart or through Amazon. I found a
12.8-ounce spray bottle at Walmart for
$2.83.
Bob Lee noted that he fi rst plugs
the engine’s carburetor and exhaust
port with pieces of paper towel, then
sprays on the Dawn Power Dissolver.
He suggests not leaving the spray on
the engine for more than 20 minutes,
because it might discolor the aluminum.
This product does an excellent
exterior engine cleaning job.
Q560: This is something I have been
wondering about for a long time. On
kit boxes and in product reviews in
magazines, it often lists the wing area on
an airplane (which also lets you calculate
wing loading).
Is the wing area on a non-tapered
wing always wingspan multiplied by
chord, or do you subtract the part of the
wing that goes through the fuselage?
What if it is a parasol wing airplane
and the wing doesn’t go through the
fuselage, or a typical biplane, where the
bottom wing goes through the bottom
of the fuselage and the top wing is
essentially a parasol wing?
A560: Wow! This is a case where the
question is much longer than the
answer. I always considered the total
wing for the wing-area
calculation. But to
be absolutely sure, I
asked the true expert,
AMA Hall of Famer
Tom Hunt, who
replied, “Wing area as
a reference number is
always the entire wing,
including that blocked
by a fuselage or other
structure.”
Q561: What can you
tell me about that new
altitude-limiting device
for model aircraft?
A561: The device is
called the Sky Limit
and is manufactured
by Winged Shadow Systems. This
same company has a variety of related
onboard products, so be sure to visit its
website (see the “Sources” section).
The Sky Limit is actually two units.
A small 3.6-gram sensor rides inside the
aircraft. A separate plug-in programmer
lets you choose altitude and time. The
combination of the two items sells for
$54.90.
It will help limit your aircraft’s
altitude for Sailplane contests or it can
help you meet fi eld rules or regulations.
In regular operation, the Sky Limit
will cut your motor/engine throttle
at your chosen altitude or time limit.
It works with electric, gas, or glow
airplanes.
The altitude limit range is 50 to 9,999
feet and the time limit is 5 to 9,999
seconds. The company’s website explains
everything in detail.
Q-and-A Follow-up
At this point I have several follow-up
Q-and-As. I encourage all comments and
try to cover as many as possible for the
benefi t of our readers.
Follow-up to Q546 (Doculam or
Clearfi lm, April 2012 MA, page 82):
Reader Bob Whipple wrote,
“I have been using Doculam since
1979 with great success. It is light and
durable.
“There is one thing that was not
mentioned and that was using this
covering on fueled planes. I found that
the glue on the Doculam is loosened by
the engine exhaust and fuel. However, it
works great on electric-powered aircraft,
on Sailplanes, and rubber-powered
planes.”
I must apologize. Although I have
been totally into electric power for more
than 15 years, I used fuel for a much
longer period than that. I should have
been more sensitive to that point.
There are occasions where fuel-proof
paint can be applied over the Doculam,
but before painting an entire aircraft,
I would try applying the paint to a
Doculam-covered test structure, and
then spray some glow fuel on the test
strip to make sure you won’t have a
problem later.
Follow-up to Q554 (electric motors,
quick repairs, August 2012 MA, page
78): In this FAQ, I showed how easy
it is to remove the outer barrel of a
brushless outrunner motor. It is only the
magnetism that holds it in place.
A good fi rm pull, and off comes the
barrel (or stator), which also contains
the motor shaft. If you keep a spare
barrel in your fi eld kit you can instantly
repair a motor with a bent shaft at the
fi eld.
The way I wrote this answer, I made
it sound as though this technique
would work on any outrunner motor.
As Canadian modeler Chris Moes was
quick to tell me, that scheme works fi ne
on E-fl ite Park 180- and 250-size motors.
However, when you get to the Park 300
motor, there is a snap ring that must be
removed before you can remove the
barrel (stator).
The point here is that not every
motor can be fi xed the way I originally
described it. I hope the word will get
around about this technique. I also hope
that manufacturers will offer the barrel
and shaft as a replacement item.
Follow-up to Q550 (simulated windows
and windshields, June 2012 MA, page
72): In this Q-and-A, I mentioned that a
good source for black contact shelf paper
was Ace Hardware.
The material is fl at black and has
a peel-off adhesive on one side. This
shelf paper makes excellent simulated
windows and windshields for your model
aircraft. I use black on light-colored
surfaces and then white on dark surfaces
for the proper contrast.
Reader Brendan Schulman suggested
yet another source for the black material.
To my surprise, he suggested a fl at black
chalkboard contact paper that can be
obtained through Amazon. It comes in
18-inch by 6-foot rolls for $8.52.
This could be the same manufacturer
as the Ace Hardware material, but it at
least provides an alternate source.