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OS AX .46 11x6 Shootout

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Old 11-29-2008, 01:45 PM
  #1
rainedave
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Default OS AX .46 11x6 Shootout

I tested my AX .46 on five different 11x6 props. This was done to establish a comparison with my Super Tigre S.45.

The numbers in parentheses are for the Super Tigre.

Temperature: 46°, cloudy and windy
Fuel: Powermaster GMA 5% Nitro, 22% castor/synth blend
Glow Plug: OS #8

MA 3 Series:
13,274 (13,477)
6.55 lbs. static thrust
1.19hp
65.5mph

MA Black:
13,134 (13,550)
6.01 lbs. static thrust
1.04hp
64.8mph

Evolution:
12,864 (13,146)
6.35 lbs. static thrust
1.13hp
63.5mph

APC:
12,541 (12,853)
6.21 lbs. ststic thrust
1.10hp
61.9mph

Graupner:
12,224 (12,406)
6.71 lbs. ststic thrust
1.23hp
60.4mph

I think the colder weather had an effect on performance. I expected the MA Black to turn higher than it did. This engine is relatively new with only about 1/2 gallon run through it.

David
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Old 11-30-2008, 12:58 AM
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Default RE: OS AX .46 11x6 Shootout

Hi Dave
I think you meant the S-2 series?
I’m' not entirely convinced of the accuracy of The "Thrusthp" or the "prop-power-calculator" in regards to horse power and thrust.
Also you would be surprised by the actual pitch of some props are when measured on a pitch gage so figure pitch speed only as a ball park but it's nice data to have.
Air testing is the truth teller with on-board air speed or gps data. APC makes fantastic props but sometimes the MA S-2 series is faster with a higher rate of climb with sport engines/planes, you have to try both brands to find the best for your set up. When the tip speed is realy wound up and you can hear the prop, than I switch to the APC.

One out of every three of my planes had the best performance by a visible margin with the MA S-2 the rest are running APC.
Good info Dave! It may suprise a few guys.

Karl
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Old 11-30-2008, 07:23 AM
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Default RE: OS AX .46 11x6 Shootout

Is that calculated thrust?

So the older super tiger beats the os on all props....
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Old 11-30-2008, 09:03 AM
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Default RE: OS AX .46 11x6 Shootout

Quote:
ORIGINAL: Mr Cox

Is that calculated thrust?

So the older super tiger beats the os on all props....
It sure looks like it. He lists data only for the OS.

There may be an error with his S-3 data, He may have meant to use factors for S-2 (formaly known as scimitar).
The thrust shown is corrected for the drag of a high wing trainer, not just a bare prop. The mph shown are nautical not statute so use the formula if you want to convert:

nautical miles x 1.15 = statute miles

"prop-power-calculator" program www.mvvs.nl/prop-power-calculator.xls Try it your self, its kinda cool.
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Old 11-30-2008, 09:20 AM
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Default RE: OS AX .46 11x6 Shootout

Hi Karl. All data was calculated using Pe Reivers' spreadsheet. This is far superior to ThrustHP or prop-power-calculator because it takes into account prop brand, pitch and other factors. The impetus behind the testing was a discussion (debate) about the loads that different brands of props put on a given engine. The data is only intended to provide a comparison between the various brands of props that are marked and sold as 11x6's. In fact, a wide spread in performance was exactly what was expected, since most people agree that all 11x6's are not created equal. And, yes, it is a Master Airscrew G/F 3 Series prop.

Mr Cox, see the attached screenshot. Pe's spreadsheet calculates static thrust and prop thrust, along with a lot of other useful data.

I plan to run the AX .46 test again on a warmer day closer to 60° using the same Fox Long plug I used in the [link=http://www.rcuniverse.com/forum/fb.asp?m=8189268]ST .45[/link] tests (all of the ST data are in that post). That will eliminate two more variables.

One subjective observation (it's all subjective, to be honest) is that the ST is a lot easier on the ears. The OS Powerbox muffler has a very harsh, grating/raspy effect on my ears above around 12.000rpm, and this engine has brand new aftermarket stainless steel bearings.

David
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Old 11-30-2008, 09:31 AM
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Default RE: OS AX .46 11x6 Shootout

Ahhhhh!
I see it now, those turkeys only put the "G-3" on the prop, not the parts listing. I've never tried those, always the S-2, good to know.

It looks like the Pe Riever's is the same as prop-power-calculator, I confirm all your numbers exactly.
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Old 11-30-2008, 09:55 AM
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Default RE: OS AX .46 11x6 Shootout

They are the same! MVVS NL and Pe Reivers are one and the same.

David
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Old 11-30-2008, 11:43 AM
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Default RE: OS AX .46 11x6 Shootout

Thanks, I do know of the prop calculator. I was just hoping that maybe someone had done an actual measurement of the thrust, in order to see if the correction factors are useful/valid.
(I think CP did made a "thrustometer" a while ago, should have a look for that again)

I'm mainly into 1/2a stuff and there, to me, it can not simply be a single factor for the type of brand. Instead it seams like every size would need its own correction factor, correcting for mislabeled pitch and changes to the blade area etc.
From my own, very limited, practical testing, the APC seems to give high revs (sounds great on the ground) and little thrust (compared to e.g. wide bladed cox), so using the calculator and measuring revs on the ground is not very meaningful...
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Old 11-30-2008, 12:07 PM
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Default RE: OS AX .46 11x6 Shootout

Mr Cox, I agree 100% with what you're saying. The main point of this exercise was to show just how much variation in load the various 11x6's put on an engine. All that my tests really prove is that designating a prop as an 11x6 doesn't necessarily mean a whole lot. Spreads of 1,071 and 1,050 rpm's are pretty substantial for props that are supposedly manufactured to the same pitch. This only reinforces the need to do actual flight testing in order to select an "ideal" prop for a particular model and flying style.

A while back I also rigged up a thrust measuring device using a digital fish scale. It was crude, but it did give a better idea of how much thrust various props produced.

David
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Old 11-30-2008, 12:26 PM
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Default RE: OS AX .46 11x6 Shootout

For reference the numbers below are for 10 x 7 props on an older ST .45. Thrust was measured but varied several ounces.

ST .45 Italian with A-3 plug, 15% fuel

10 x 7 APC
12,600 rpm
4# 10 oz to 4# 14 oz thrust

A later measurement to recheck
10 x 7 APC
12,800 rpm
4# 15 oz to 5# 2 oz thrust

10 x 7 MA Simitar
13,600 rpm – surprised me
5# 6 oz to 5 9 oz thrust

10 x 7 MA black old style
12,300 rpm – 12.200/12,300 rpm was also verified at a later date
5# 7 oz to 5 8 oz thrust

Bill
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Old 11-30-2008, 12:32 PM
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Default RE: OS AX .46 11x6 Shootout

Thanks Bill. Sorry if I've already asked you this, but what club do you fly with?

David in G'boro
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Old 11-30-2008, 01:31 PM
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Default RE: OS AX .46 11x6 Shootout


Quote:
ORIGINAL: freakingfast

There may be an error with his S-3 data, He may have meant to use factors for S-2 (formally known as scimitar).
FF,


I was a bit surprised, when I got on the [link=http://masterairscrew.com/propellers.aspx]Windsor Propeller[/link] web site and did not immediately see the Scimitar Series props, except in wood... But from the image and the description, I could easily identify the new S-2 as what was formerly known as the Scimitar Series.

I used them in the past and they were significantly better than the original MA black props and somewhat better than the Series 2...

I have not flown anything with a Series 3 prop.
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Old 11-30-2008, 01:42 PM
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Default RE: OS AX .46 11x6 Shootout

Kinda funny, Windsor is 5 minutes from me, Macs is 15 and APC is 40 minutes.
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Old 11-30-2008, 04:06 PM
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Default RE: OS AX .46 11x6 Shootout


Quote:
ORIGINAL: rainedave

Thanks Bill. Sorry if I've already asked you this, but what club do you fly with?

David in G'boro
I am a member of GRAMS in Brown Summit and occasionally fly in High Point and occasionally in King.

Bill
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