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Offline Motorman

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« on: April 26, 2018, 05:35:47 PM »
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« Last Edit: December 04, 2021, 09:17:24 AM by Motorman »
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Offline TDM

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Re: Going too slow
« Reply #1 on: April 26, 2018, 05:46:31 PM »
Speed it up.   :)
Seriously how do you expect to get any practical feedback with the information you provided.
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Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Online John Rist

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Re: Going too slow
« Reply #2 on: April 26, 2018, 06:32:16 PM »
How are you doing on battery usage?  Do you have room to push harder?  Higher pitch prop more RPMs etc.  Also 69 ft lines could be a bit long.  Also what motor, speed controller, cell count, timer etc?
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Offline Mike Haverly

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Re: Going too slow
« Reply #3 on: April 26, 2018, 08:29:48 PM »
Better check the date on Paul's set up.  It might be a little different now.

Edit:  FYI, I fly my 72 ounce airplane with an 11 X 5.5 prop at 5.4 secs. on 69.5' .018 lines.  I usually have 27% battery left on my 6S TP batteries.  You have other problems.
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Mike

Offline Jason Greer

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Re: Going too slow
« Reply #4 on: April 27, 2018, 06:47:20 AM »
Have you checked the RPM with a tach to make sure it really is turning 9500 or is that the RPM you've set in the software?

Jason
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Offline Dennis Toth

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Re: Going too slow
« Reply #5 on: April 27, 2018, 08:24:23 AM »
MM,
I agree with Jason, check the rpm with a tach. I have had ESP's and timers fight each other and not get to the set rpm. Also based on the information you gave the rough lap time on 69.5' lines with the 5.5 pitch @ 9500 should be around a 5.4 ish lap. For the numbers you posted you are around 8000 ish rpm. Some'm aint right in the setup.

Best,   DennisT
 
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Offline Tim Wescott

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Re: Going too slow
« Reply #6 on: April 27, 2018, 11:19:03 AM »
Quote from: Motorman on April 26, 2018, 05:35:47 PM
Flew my 69oz ARF SV11 maiden flight today on .018" x 69' and couldn't get the speed up. prop was 3 blade 12-5.5 @ 9500 rpm and lap time was 6.5 sec per lap.

Not use to big plane and big lines so, looking for advise on my next move.

Thanks,
Motorman 8)

If you were flying at exactly your pitch speed (72.6ft/s) with the handle kept at the center of the circle then you'd be doing 6.0 second laps (with rounding).  So 6.5 second laps isn't astounding.  More pitch.  More RPM.  More something.

You are measuring your lines from handle to canopy, yes?
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Offline Tim Wescott

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Re: Going too slow
« Reply #7 on: April 27, 2018, 11:39:27 AM »
Quote from: Motorman on April 27, 2018, 11:34:43 AM
You know I just got these lines and i didn't measure them. I spec 66' eyelet to eyelet and figured 3 more for the plane and handle but maybe they were made too long.

The plane is surprisingly quiet in flight so maybe the rpm is not where I set it. What would cause this? It's a Hubin timer with a CC ice lite 50 and a 6s batt motor is Cobra 35/20-14.

Your assumptions for line length sound about right.  I'd jump up and down about always doing a final measurement -- but I did mine the way you did.

You haven't said how you're setting RPM.  If you're setting numbers into the timer & ESC, then the RPM could be off if the pole count of the motor is off.  (Short version: motor pole count is, roughly, the number electrical cycles of current to the motor per revolution.  Different motor models have different pole counts, and the ESC has to know it to get the RPM right).
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The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Mike Haverly

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Re: Going too slow
« Reply #8 on: April 27, 2018, 03:34:42 PM »
The kV on that motor is 850.  It will not work on a five cell and the big club of a prop.  What Paul was using 9 years ago isn't even close to what he is using now, and what you are using is even farther off.  Do the math and you'll find that the motor you are using needs way more rpm to be happy.  It will overheat on five cells, especially with that prop.  The motor Paul was using in that set up had a much lower kV requiring a larger prop.  This is an apples and alligator comparison, both words start with "a" and that's about it.
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Offline Mike Haverly

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Re: Going too slow
« Reply #9 on: April 27, 2018, 05:06:44 PM »
With eggs square on my face I see I was looking at specs on the Cobra 28-14.  OOPS!  I would still go to a smaller prop, even drop back to an APC 13 x 4.5 and see what you get.  On that same 72 ounce pig of mine, I was happy with that one or APC 13 x 5.5, ESC at the time was CC Ice Lite 75.  I know you have your own home built props but it might be wise to go back to some stuff we know works and go from there.  With the 4.5 pitch prop you will need to be somewhere around 10,200 RPM.
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Mike

Offline Mike Haverly

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Re: Going too slow
« Reply #10 on: April 28, 2018, 01:05:39 AM »
"I think to get what I want I'll have to go up over 10K is that normal?"

Yes
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Mike

Offline James Mills

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Re: Going too slow
« Reply #11 on: April 28, 2018, 08:39:14 AM »
I didn't see this mentioned (I might have missed it) but have you checked prop on a pitch gauge to make sure it's what you think it is?

James
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