Hi. I am a high school student participating in the Helicopter event in
Science Olympiad. I have several questions that I would like to pose to
the group. I would really appreciate if anyone could respond to some of
my questions or thoughts. Even though most of my questions are general
and apply to pretty much all free flight models here is some background
on the helicopter: I am using a standard design: top free rotor, bottom
fixed, 3.5 grams min weight without rubber. Rubber is around 1.5g and
1/8". The basic design can be seen on this page
(
http://freedomflightmodels.net/ <
http://freedomflightmodels.net/> ).
Both rotors are fixed pitch. Longest flight time wins.
Rubber Motors--
1. Consider the following statement: When you use a rubber motor for a
flight, you need to let the motor rest before you use it again. If you
don't, you need to put in more winds to get an equal flight time.
However, after a couple of hours of rest the "power" or "energy" of the
motor will be close to the origional. How true is this? If this is true
what is the best way to trim? A lot of trimming is trying to change only
one variable and see the effects, mainly on flight time. If I am trying
to see how the position of the rotor on the motor stick affects the
flight I would like any parameters related to the rubber motor to be
constant. If a motor gets "weaker" each time I perform a flight, how do
I know if a change in flight time depends on the motor or the different
rotor position. Perhaps the motor gets "weaker" only if it is wound
close to the breaking point? Then the solution would be to trim with
fewer winds than what you would use during a competition? (I remember
reading that FAI model supply suggests that you use a new rubber motor
each flight, but that this was only applicable if you were winding close
to the breaking point.)
2. What is the best way to prepare or break-in rubber motors? I lube
with armorall, but I have read advice on this group such as, "wrap the
rubber motor around the hotel door the day before the competition"
perhaps to prestretch the motor. Why is this done and what other
techniques in regards to rubber would be beneficial (and increase
times)?
3. For the first time in Science Olympiad, there is no restriction on
the rubber motor mass. However, in regular free flight, this seems
commonplace. Does anyone have any advice in regards to this new
"freedom"?
Rotors--My motors are fixed pitched so some of these questions are not
completely relevant but I am still interested.
4. How do you measure pitch? What is the pitch/diameter ratio? In one of
the previous posts regarding the helical prop blocks I saw one of them
28". How is pitch measured by a unit of length?
5. In my current design, the spars for the rotors are straight pieces of
balsa wood (see link). How great are the benefits of using a true
helical rotor design in which the spars are curved like most props in
advanced FF classes?
Thanks for reading,
Chris
Received on Fri Mar 23 2012 - 19:21:29 CET