Okay guys - here's the fly in the ointment. When you are doing your testing/adjusting/optimizing you are setting up the model for the conditions that are in effect on THAT DAY and THAT TIME. When you fly in slightly different conditions your trim settings and power requirements might need to be slightly different. If you're flying in Johnson City conditions with a storm front moving through and lots of humidity your model may barely fly with your optimized settings.
I'm not saying that there's anything wrong with the approach. It's just that you have to be prepared to make changes as conditions require. Sometimes events are won or lost depending on flyer's ability to adjust to prevailing conditions. You probably don't even need to ask me how I know this!
----- Original Message -----
From: torqueburner
To: Indoor_Construction_at_yahoogroups.com
Sent: Thursday, November 30, 2006 9:24 AM
Subject: [Indoor_Construction] Re:prop pitch
--- In Indoor_Construction_at_yahoogroups.com, "Bill Gowen" <b.gowen@...> wrote:
>
. . .Optimal pitch is the one that gives you the highest flight time. . .
>
. . .Adjust the cruise first. Get the best combination of prop pitch and model trim for the
cruise. Then go for the ceiling height with launch torque adjustments. . .
Brant, our experience with SO planes agrees with what Bill has suggested. Last year my
students modified an Ikara prop so that had an adjstable hub that allowed for changes in
pitch. They set the pitch, then made several flights each with a variety of rubber sizes that
differed by 0.005". They found that there was a range of pitches that seemed to give them
pretty comparable times if matched up with the appropriate rubber size.
If the pitch was higher than this range, flight times dropped - it was tough to get it all the
way up to the top. If the pitch was too low, the plane climbed so well that they had to back
way off on the turns, and the times were lower as well.
One interesting thing we discovered at last year's state competition: the students had
found what they considered an optimal combination of pitch and rubber by flying half
motors in our gym. But at the competition, the plane just wouldn't climb out, even when
launched at a much higher torque than they had used in practice. When we got home, we
measured the pitch of the prop they had been using - it had changed to a higher pitch! So
I guess when they heated/twisted it to repitch it, it relaxed over time back toward the
original pitch.
Has anyone else seen this problem with repitched plastic props? If so, any suggestions as
how to prevent it?
Dave Drummer
Kutztown Sr. High School
[Non-text portions of this message have been removed]
Received on Thu Nov 30 2006 - 08:32:30 CET
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