Re: Hints for Cat IV LPP flying

From: ykleetx <ykleetx_at_gmail.com>
Date: Wed, 24 Mar 2010 23:48:00 -0000

I welcome all of your comments.
I was probably unclear in my previous postings. I didn't mean to say
that the partial motor method is flawed. Rather, that I implemented it
incorrectly.
In the 1/6 partial motor experiment where I used a 0.5g motor and a
dummy motor that weighed 2.5g, I was able to consistently achieve 25' of
climb and a duration of 2:50, with a max of 3:02. But I implemented
this method incorrectly because my dummy motor was too short. With a
full hook to hook distance of about 9", a 1/6 motor correctly applied
should be used with a dummy motor of 7.5". The 1/6 motor, about 4" long
when unwound, should be attached with a hook to hook distance of 1.5".
In my first experiments, I used a dummy motor of 6" long, so that the
1/6 motor was attached with a hook to hook distance of 3.0". In these
first experiments, the results were good.
In the second experiments, I used the correct dummy motor length of
7.5". The wound motor when attached was only 1.5" long. But in this new
experiment, the plane climbed less than 20' with a duration of about
2:30. The initial unwind seemed weak, the climb was weaker than
before, and the flights ended with lots of turns left.
(I also tried the full 3.0g motor to observe the full winding and
unwinding. I noticed the lack of tail hook clearance, which I changed.
I noticed that the initial unwind seemed weak as well. The behavior
seemed consistent with my second experiments where I applied the partial
motor method correctly. I did not fly with the full 3.0g motor to avoid
damage in the ceiling.)
I did not use a sleeve. I know that it's possible for the rubber to get
caught between the prop hook and the MS, but I did not see it in the 4
or 5 times that I unwound the motor.
--- In Indoor_Construction_at_yahoogroups.com, "Bill Gowen" <wdgowen_at_...>
wrote:
>
> Sorry if this has already been discussed but are you using sleeves?
>
> As far as a full motor having less power - how did you determine that?
Are you taking torque readings while unwinding the motor? It doesn't
make sense that a full motor would have less initial power than a
partial motor unless knots are dragging somewhere. A full motor wound to
the same maximum torque and backed off to the same launch torque should
deliver the same launch torque (power in your terms) as the partial
motor but more importantly it should do it for much longer. For example
the number of unwinding turns from .7 in-oz to .5 in-oz in the full
motor should be six times as many as in the 1/6 motor. This is why the
whole partial motor concept works.
>
> Another potential problem is if the motor is new and the rubber is
still stretching your .7 in-oz of launch torque may really be a lot less
by the time you get the motor on the model.
>
> None of this is intended to sound preachy. I'm just trying to figure
out where you are in the learning curve.
Received on Wed Mar 24 2010 - 16:49:02 CET