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Old Jan 27, 2012, 10:45 AM
Ascended Master
Sparky Paul's Avatar
Palmdale, CA
Joined Oct 2000
13,223 Posts
I've had a Hershey bar plank that would pulse in flight, but it was deliberate, I could do it on command. No motor at all.
Slowed it up, and it would "pulse" in a semi-stall.
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Old Jan 27, 2012, 12:26 PM
I DS slower than I build!
Cory's Avatar
Idaho Falls
Joined Jul 2006
2,336 Posts
Quote:
Originally Posted by Sparky Paul View Post
I've had a Hershey bar plank that would pulse in flight, but it was deliberate, I could do it on command. No motor at all.
Slowed it up, and it would "pulse" in a semi-stall.
That's called a hyperstall. It's usually caused by the CG being too far forward but can also be caused by excessive control throw. Plank wings are particularly susceptible. They are sensitive to extremely small CG changes. Just a couple of millimeters change in CG could cause it. What happens is that the elevon stalls repeatedly while trying to pull the heavy nose up. It should happen more easily at slower speeds or during positive G commands, however the slow speed hyperstall will happen at higher speeds the further forward the CG is and thus can happen at fairly high speeds. I could see the prop noise on a hyperstalling wing make a pulsing sound as the airflow through the prop rapidly changes angle.
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Old Jan 27, 2012, 01:14 PM
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lectroglide's Avatar
United States, WA, Puyallup
Joined Aug 2006
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Originally Posted by Gary Warner View Post
Can you determine if it's an RPM change, or is it change in the sound (without RPM change)?
definitly an RPM sound..just changed motor and ESC so will see what happens today,stay tuned
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Old Jan 27, 2012, 01:32 PM
York Electronics
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Dallas Tx USA
Joined Apr 1999
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Cavitation?
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Old Jan 27, 2012, 02:38 PM
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Joined Oct 2004
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Have you tried actually changing the prop? A small crack in a blade might not be visible, but will affect the rpm as the motor spins up and the blade deforms.
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Old Jan 27, 2012, 03:26 PM
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United States, WA, Puyallup
Joined Aug 2006
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I think we gotta C rating problem, dont know what it is cuzz the labels worn off but Im sure it isnt anything under 25 ......flew fine for about 2 min into the flight but started acting up shortly after , its also after I changed motor/ESC, so the other gear wasnt the problem........next step try a higher C rating
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Last edited by lectroglide; Jan 27, 2012 at 07:48 PM.
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Old Jan 27, 2012, 03:33 PM
Herk
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Virginia USA
Joined Jun 2007
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Originally Posted by lectroglide View Post
I think we gotta battery C rating problem, dont know what it is cuzz the labels worn off, but it didnt do it about 2 min into the flight but started shortly after , its also after I changed motor/ESC, so the other gear wasnt the problem........next step try a higher C rating
That will definitely do it. I had a helo with an inadequate battery C rating. When the battery heated up it lost voltage and the ESC dropped out. Bad mojo - fortunately I was only about six inches off the ground. This battery had no C rating marked on it. I had to go online to the supplier to find out it was only 6C.
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