Aero Mail

Aero Mail
Decvember 2009 7
Antitorque Update
I read with amusement, and a bit of shock, the article
featured in Model Aviation, about adding “weight” to the right
wing of a model aircraft, to counteract torque and prevent
swinging to the left on takeoff.
I am amazed that a magazine that caters to “modelers”
would print something so erroneous! So with an extra pound
in the right wingtip, how safe, and how stable is that model at
slow speeds, like say, when it’s time to land?
Quite a strange antidote for Yaw.
Frank Tiano
via e-mail
Your reaction isn’t surprising; it was mine as well, until I talked about the idea at
length with the author. However, we’re pleased at this point to see how many readers with
the same problems cited in the article are expressing the success they are now having,
thanks to Mr. Hunton’s idea.
The method is probably best considered a fix best suited for RC pilots with less
experience, but it can help ensure that new models get into the air more safely. When
those pilots gain more experience, they can explore other trimming methods. But in the
meantime, they don’t hate aeromodeling because they can’t get their models off the
ground.
The antitorque device can help some RC pilots, which makes the article worthwhile,
don’t you think?
Michael Ramsey
MA Editor
I am deeply honored that you would take time to comment on the anti-torque article. I am
also pleased to read Michael Ramsey’s reply with which I agree fully. I have received a few
other comments from highly experienced pilots like yourself that are in favor of people
learning to correct for torque, P-factor, etc. at takeoff by proper utilization of the controls.
For the RC pilot that intends to excel at flying the tip weight system is not for them. But for
the average Sunday flyer who just wants to see their creation in the air the tip weight system
will work well and, as Michael Ramsey suggests, they can learn the proper controlling
methods after being able to take off and fly successfully. Thanks for your comments.
John Hunton
[email protected]
I read John Hunton’s story “The Antitorque Device” and said to myself, “That’s
crazy!” You build a plane to balance nose to tail and tip to tip. Then you say I have to add
weight to the right wing? Madness. That will add drag on takeoff to the right … hey …
wait a minute … hmmmm.
All joking aside, that’s an interesting challenge to the lateral balance paradigm. And of
course as the article states, this is just if you need it. But if you knew that an aircraft (like
my Yellow Aircraft P-40) pulled to the left and needed right rudder on takeoff every time,
a person might build a spot into the wing during construction that could hold the needed
Anti-torque Device. And still allow for changes as needed. Thanks John!
Jeff Edstrom
via e-mail
I read your article in Model Aviation and I will try your weight idea. I am new to RC
and having problems with left torque.
When taking off I have crashed the plane twice on takeoff and repaired it. The plane is
Great Planes Extra 300, with a 62-inch wingspan and Magnum .65 engine. It looks like
1.25-1.30 oz on the right wing would help.
I also have a 54-inch Ultimate biplane with 1.20 two-stroke. What would be the correct
weight and which wing, upper or lower, to install the weight on?
Marcus Vann
via e-mail
Your experience is exactly the situation that this antitorque device is designed to cure.
Please try it with the weights that you suggest and let me know how it goes. Be advised,
however, that for any model that flies inverted, the weight, while helping on takeoff, will
have an opposite effect during inverted flight.
On the biplane, I suggest that you place the weight on the lower wing, because it will
have a very small tendency to help keep the nose down on takeoff. As to the amount of
weight, just try something small, say an ounce, and add or subtract until your takeoffs are
completely torque free.
John Hunton
®
October 2009 $4.95
SINCE 1936
Official Publication of the Academy of Model Aeronautics
AMA thrills
at the XFC!
Don’t be a
victim of torque
Quarter-scale
electric Bebe
Continued on page 142
I read your interesting article in the
October issue of Model Aviation. Good info.
However I have one question. The weight on
the right wing: How will that affect the plane
if you are landing with reduced power and or
dead stick? It appears that the plane would be
rolling right because of being out of balance.
I’m flying a scratch built Starduster Too;
82 inch wingspan biplane, G-62 for power
swinging a 22-10 propeller and weighing 32
pounds.
I just finished a scratch built P-51, 102-
inch wingspan, 3W 75i for power swinging a
26-10 propeller and weighing 31 pounds. I
would appreciate any input you can provide.
Chet Ferrel
via e-mail
There are three aspects to the landing
scenario and perhaps the overriding one is
(1) if the landing approach goes awry and
you have to suddenly apply power to go
around, then this system works just like
takeoff and prevents the adverse effects of
torque. Many models without the weight are
lost in this scenario.
If we look at normal trimmed cruise flight
without the weight, the controls are set to
counteract the torque produced at cruise. If
power is increased the model will turn left
and climb; if the power is reduced the model
will lose altitude and turn right.
With the weight (2) when power is
increased the model is less apt to turn left and
the opposite for a decrease in power. So the
weight helps in accelerating flight and in
decelerating flight such as when approaching
for landing.
So the area of stall (3) is of question. If the
model stalls, of course the weight (although
small because of the long moment arm of the
wing) would tend to make the right wing drop
first. But if you look at the dynamics of a stall,
the model must decelerate to get to the point
of stall and the weight will help counteract
the trim that was put in it at cruise.
For your particular model I would
certainly add the tip weight conservatively
and examine the reactions of the model in all
phases of flight.
John Hunton
I came to the same conclusion many years
ago when taking my early flight instruction.
The given information (still today) for PFactor
is of course, right rudder as power is
applied. This is said to counter a spiraling
prop wash hitting the left side of the vertical
fin. The reason is: the most powerful control
at zero airspeed is, of course, rudder.
Your theory is correct, and I hold the
reason the plane will swing left is simple
torque—putting more mass or pressure on
the left wheel. I have tested this with
ribbons held in the prop wash—full scale
and models and saw no spiral. To the new
aviator though, rudder is what you have to
work with! I enjoyed your words.
Lee Gann
via e-mail
Your article described to a tee what
happened last week when I was flying my Eflite
Texan. On takeoff it began to roll left and
although I applied right aileron it continued to
turn left. I’m not sure how but I managed to
save the plane.
The Texan has a 54-inch wingspan and
uses a Power 25 motor. I’m thinking using
your formula—0.5 ounces of weight would be
about right. Also the plane has right thrust
built into the motor mount. Would this
possibly have an adverse effect using your
device?
Thanks for the great article and any advice
you can give me about my plane. Another
takeoff like the first one may result in a heart
attack.
Glenn LeCartz
via e-mail
I am very glad that you were able to save
your Texan. This design is noted in model and
in full-scale sizes for having bad tip-stall
characteristics.
The built-in right thrust should not have
much effect on the theory, although you may
not need quite as much weight, but for the
Texan I would start with it all, possibly with
stick-ons, and reduce it if necessary. Good
luck!
John Hunton
Thanks for getting back to me so promptly.
I tried a half ounce on Sunday with
noticeable, positive results. Now all I have to
deal with is the rest of the quirks of flying a
Texan. Thanks again! MA
Glenn LeCartz