Mark,
Since your theory is all about efficiency and assumes that maintaining
highest efficiency also delivers the highest TIME, I think you should have to
stick to a non flaring prop for this experiment. Is not a high flaring prop,
which presumably flares away from the pitch it was formed to, generally accepted
as somewhat less efficient than a (reasonably pitched) non flaring prop, all
other things equal?
You will have seen my request to the CD for rule clarification on this
point. That clarification may make this discussion moot. I don't know enough
about props yet to give an opinion. I won't have time preparing for this
contest to undertake extensive prop development. But if I find any indication that
changing the pitch, up or down, by flare, will improve the efficiency, I
will give it a try. I expect that, except for unintended flaring at launch, my
prop blades will be rigid by intent. Without time to test prop theories, I
will be proceeding on certain simple assumptions, including initially a rigid
blade. Right now I don't even know what the prop will look like, whether it
would be capable of flaring. I do know that I will not be using positive
flaring with the intention of controlling RPM.
All other things are never equal. ;-) Changing one thing usually affects
many other things.
"So how will you KNOW what is more "efficient?" "
Since we are involved in a contest, rather than a lab experiment, that has
to remain my secret, at least until the contest is over. ;-) I will give you
a hint. The published method does not work. I tried it.
And after that, you may discover that a less efficient, heavier motor
swinging a bigger hammer less efficiently, can lead to more TIME.
If I discover that, I will let you know right away. That is the whole point
of the experiment.
Oh, please, please innovate a better prop, at least if measured by time. I
will gladly copy it, fly with it, and give you the credit.
Some of my ideas have to do with constructing the prop, attaching it to the
plane and testing it. Some of that may result in a more efficient prop, the
indirect effect of which will be a longer time.
Agreed. So get your model trimmed with your rubber, and I will then mail
you a few grams of the rubber I intend to use, 7/97 Tan II. It should only
give you more cruise, and not wreck all your equations.
Thank you for the generous offer. I warn you that I burn rubber as fuel.
;-) To optimize the motor I need a torque curve derived under conditions that
match flight use, requiring at least two test specimens, and flight test
data from at least two flights in one of which the motor will be essentially
destroyed. I may be able to use flight test data from my 2/99 Tan II in
combination with a torque curve from your 7/97 Tan II to size the motor. It would
make better sense to test both methods using the same rubber on the same plane
under the same ceiling.
I generally like to have two or three motors, because many flights are not
completed successfully. I did a flight last week that looked like it might
break my previous best and the plane landed in a basketball hoop. Two points!
On another possible record breaker, four boys ran under the plane and their
wake upset the wing, producing a sideslip into the ground. One of my best
early flights was made after the motor hook pulled out and disappeared,
catapulted by the fully wound motor. I stuck a straight pin in the stick, wound the
motor back up and flew. The process of gathering data can be very messy.
Your footstooge that holds a prop by its hub, stretched against the rubber
for winding will not work with LPP, of course.
Actually, I have used the footstooge to wind the EZ Penny. Worked fine.
May not work for this one, though. We'll see.
I spent a pleasant hour going through my boxes of kits collected during
those decades when I was too busy and became a kit collector rather than a
builder and flyer. I found four Penny Plane kits that may be built to LPP
specification. I will need to build a more sensitive balance than the decigram
balance I now use and torque curve for my rubber.
Welcome to Indoor as we know it.
Thank you. I've been here for a while. Now that I am retired, I hope to
spend a lot more time in the Gym. There is so much to learn.
Gary Hinze
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Received on Sat Mar 24 2007 - 00:58:12 CET