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Props-More Myths Busted - 12/17/2006 2:41:10 AM   
speedster 1919



Posts: 1463
Joined: 12/17/2004
From: Martinsville, IN, USA
Status: offline 		OK boys I've been wanting to do this for a while and today I tested 10" props. In the spring I'll go for 12" props, All I hear is APC's the best and 3 blades are inefficent pieces of crap.
Mule engine is a Italian Super Tigre S-45 ringed with lots of time and down on compression a little. So breakin is a non issue . Fox RC long idle bar plug (new) Mac's one piece light muffler and home brew fuel is 5% nitro ,syn and castor blend with castor 10% ,syn oil 90% of a 19% total oil fuel. RPM is with Glowbee and Thrust is digital Berkley. This is my trainer races plane with wing attached for full plane thrust resistance and tied to stand allowed to roll on wheels. The HS needle was set on the Zinger 3 blade extra rich because it won't be touched again and the 10x8 props might load a little more. Fuel was topped off 3 times. This was all done to test the merits of each prop and not a tuning or fuel switching issue. Today was a windy one with gusts and bouced plane around a little but we tried to keep readings as even and fair as possible. Oh yes those stupid APC props you can't see running nicked my tach.

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< Message edited by speedster 1919 -- 12/17/2006 12:35:37 PM >

_____________________________

Hey Buddy -That was the most spectacular crash I've ever seen , That rolling cart wheel with parts slinging out was cool...
       Post #: 1

RE: Props-More Myths Busted - 12/17/2006 5:04:17 AM   
Flyboy Dave



Posts: 13286
Joined: 3/20/2002
From: San Bernardino County, CA, USA
Status: offline 		PROP------------------------------idle RPM------8,500 RPM----thrust--------WOT RPM----thrust

9x6 three blade plastic ZINGER -----3,300--------8,480--------1 lb 3oz .........13,800------4 lb 4oz
9x7 three blade plastic MAS--------3,120--------8,480--------1 lb 11oz ------12,300------3 lb 12oz

10x4 MAS /G ----------------------3,660 -------8,460--------1 lb 2oz -------14,970 ------3 lb 14oz
10x4 APC -------------------------3,200--------8,550--------1 lb 3oz -------12,500-------3 lb 11oz
10x4 wood TOP FLITE...................3,460--------8,550 -------1 lb 11oz ------12,010-------3 lb 1oz

10x6 MAS scrimtar profile ----------3,600--------8,480--------1 lb 14oz -----14,160 -----4 lb 14oz
10x6 MAS /GF/3 wide-------------- 2,970------- 8,580 --------2 lb 2oz ------11,970------4 lb 2oz
10x6 APC--------------------------3,270--------8,490---------2 lb 2oz ------11,940------4 lb 2oz
10x6 ZINGER wood ----------------3,120-------- 8,520---------2 lb 3oz ------11,280------3 lb 15oz

10x8 MAS /GF/3 wide --------------3,270-------8,490---------2 lb 10oz--------10,950------4 lb 2oz
10x8 ZINGER wood ----------------3,330------- 8,550----------2 lb 9oz -------10,980------3 lb 15oz
10x8 APC--------------------------3,000 -------8,580----------2 lb 5oz-------11,050------3 lb 7oz
10x8 MAS /G ----------------------3,240--------8,490----------2 lb 10oz------11,400------3 lb 4oz

Things I learned about my tests
#1 MAS scrimtar had the most thrust at WOT by far ( because of higher rpm ) notice the high
idle ( less resistance) This would be the high speed winner
#2 ZINGER 3 blade ,yes I said 3 blade got second place (all I ever hear is 3 blades inefficient –
BULL$&*T )
#3 You can't take the size stamped on prop for granted –sometimes a big difference
#4 The 10x6 MAS GF/3 has the lowest idle and the new GF/3 is better than the older G props
#5 The 10x8 MAS GF/3 had the best mid range thrust and would probably make the best
sport flying prop.
#6 I thought the 4 pitch would be the stump pullers in thrust but it looks like the 11" diameter
might be a better choice.
#7 I arranged the props in each size range according to me with top being best and bottom the
worst.
#8 My best guess in the whole world the 10x6 would be the most popular size and I rate the
MAS and APC dead even except the MAS is far tuffer if it hits the ground.



< Message edited by Flyboy Dave -- 12/17/2006 5:27:18 AM >

_____________________________

An engineer says.... "That won''t work".
A mechanic says..."Oh yeah, watch this".
"Old Age, and Treachery will overcome youth and skill".
Revver Bro #4.

(in reply to speedster 1919)
       Post #: 2

RE: Props-More Myths Busted - 12/17/2006 5:17:09 AM   
Sport_Pilot



Posts: 7405
Joined: 1/21/2002
From: Acworth, GA, USA
Status: offline 		Very good info here. Just want to point out that the only way to really be sure of what is going on is to test the props at the same revs and measure the airspeed of the prop blast. The latter would take some additional instrumentation, but for our purpose your 8,500 RPM test was and eyeopener. I have had good luck with the Top Flight props in the few sizes available, and your test bears that out, at least for the 10-4. Still I don't use them much because they are so easy to break.

(in reply to Flyboy Dave)
       Post #: 3

RE: Props-More Myths Busted - 12/17/2006 8:14:26 AM   
DarZeelon



Posts: 6911
Joined: 4/9/2003
From: Rosh-Ha'Ayin, ISRAEL
Status: offline 		Randy,


The mid-RPM thrust tells us much more then you think...

At this RPM, the aerodynamic and centrifugal forces that are applied to the prop's blades, have not yet reached a level that is sufficient to flatten their pitch.

So the visually attractive appearance (they do look efficient) of these props translates into effective pulling power.


Are you sure the RPM for the 10x6 MA Scimitar is not a misprint?
It's ~2,200 RPM faster than the GF/3 and the APC...

Also, these numbers tell us very little about the power level in flight.
My own experience tells me the MA black GF/2,3 props become significantly less effective at speed.

Do you want a few Bolly props to try out?

< Message edited by DarZeelon -- 12/17/2006 8:19:57 AM >

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Dar Zeelon - ISRAEL - ddzeelon@gmail.com
MVVS - Jett - Nelson - Bolly - Mejzlik

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       Post #: 4

RE: Props-More Myths Busted - 12/17/2006 12:20:45 PM   
speedster 1919



Posts: 1463
Joined: 12/17/2004
From: Martinsville, IN, USA
Status: offline 		Thanks Dave for correcting file but I went back and redid with just one offset problem. Yes DAR I would test bolley props but I don't have a source. I checked the MAS scimitar twice and it is thin to begin with and is a different plastic than a GF/3. The 8,500 was a little hard to achieve because my beater VG 400 throttle has click positions . One click down too slow and one up too fast. I will order a 10x8 MAS scimitar prop , 10x6 TOP FLITE and some 11x4 3D props to test again. The engine was set just right to work with all the props I used. I do have a radar gun but it scary because I have to stand in field and be a target (flown at) so much for reading a tennis ball at 90 feet HAH Hey Dar I should have used my temp gauge on a 10x4 compared to a 10x8 HAH

< Message edited by speedster 1919 -- 12/17/2006 12:37:38 PM >

_____________________________

Hey Buddy -That was the most spectacular crash I've ever seen , That rolling cart wheel with parts slinging out was cool...

(in reply to DarZeelon)
       Post #: 5

RE: Props-More Myths Busted - 12/17/2006 1:38:57 PM   
pe reivers



Posts: 2454
Joined: 1/23/2002
From: Arcen, , NETHERLANDS
Status: offline 		I re-hashed the numbers to grams and comma separated values, so they can be imported in spreedsheets.
The first row is titles
PROP ,idle RPM ,about 8500 RPM, thrust gr,WOT RPM, thrust-gr
9x6 three blade plastic ZINGER ,3300,8480,539,13800,1931
9x7 three blade plastic MAS ,3120,8480,767,12300,1704
10x4 MAS /G ,3660,8460,511,14970,1761
10x4 APC ,3200,8550,539,12500,1676
10x4 wood TOP FLITE ,3460,8550,767,12010,1392
10x6 MAS scimitar profile ,3600,8480,852,14160,2215
10x6 MAS /GF/3 wide ,2970,8580,965,11970,1875
10x6 APC ,3270,8490,965,11940,1875
10x6 ZINGER wood ,3120,8520,994,11280,1789
10x8 MAS /GF/3 wide ,3270,8490,1193,10950,1875
10x8 ZINGER wood ,3330,8550,1164,10980,1789
10x8 APC ,3000,8580,1051,11050,1562
10x8 MAS /G ,3240,8490,937,11400,1477

It is interesting to see how there are differences in thrust with different pitch (Thrust-HP says no!)
It also is interesting to note that so-called stalled props still achieve higher thrust with rpm increase. Something to ponder what stalled means when talking props. In my opinion, props dont realy stall like a wing when more pitch is applied, unless the pitch becomes excessive (like more than 1D as in a 10x10 prop)
From the data it becomes clear why MA props are popular with the RCcombat crowd. They provide excellent thrust, at reduced engine loads.

< Message edited by pe reivers -- 12/17/2006 7:32:52 PM >

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Pe, MVVS, MTW, Mejzlik. www.mvvs.nl
There is sanctuary in analisys.

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RE: Props-More Myths Busted - 12/17/2006 2:47:12 PM   
buzzingb


 

Posts: 1506
Joined: 9/4/2002
From: Bruce, MS, USA
Status: offline 		It looks to me like there isn't enough difference to worry over, just go to the prop bag and pick one, screw it on and it will be fine. Nice testing just to let us all know we are worried over nothing.

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Buzz

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RE: Props-More Myths Busted - 12/17/2006 5:59:15 PM   
speedster 1919



Posts: 1463
Joined: 12/17/2004
From: Martinsville, IN, USA
Status: offline 		Well Buzz I don't think it was that simple and even. Just think your plane weighs in at 4 lb 8oz and you do a nice large loop and you picked out a max thrust 3 lb 11oz prop. you'll be slooooowwwwwiiiiinnnnngg down at the top. Now say you picked a prop that produced 4 lb 14oz max thrust. This is more than the plane weighs so going over the top is a non issue.

_____________________________

Hey Buddy -That was the most spectacular crash I've ever seen , That rolling cart wheel with parts slinging out was cool...

(in reply to buzzingb)
       Post #: 8

RE: Props-More Myths Busted - 12/17/2006 6:18:47 PM   
MyWay


 

Posts: 451
Joined: 2/21/2004
From: Benicia, CA, USA
Status: offline 		The best thrust can be achieved by picking a prop with a tip speed of about 600 mph. The larger the dia. the better.

(in reply to speedster 1919)
       Post #: 9

RE: Props-More Myths Busted - 12/17/2006 7:15:59 PM   
DarZeelon



Posts: 6911
Joined: 4/9/2003
From: Rosh-Ha'Ayin, ISRAEL
Status: offline
quote:

ORIGINAL: MyWay

The best thrust can be achieved by picking a prop with a tip speed of about 600 mph.



Wrong!


That would give you the worst noise, as air-flow around the blades becomes trans-sonic and even supersonic at some points, over the blade-tips.

Prop manufacturers limit their permitted RPM, so the limit of Mach 0.7, or 475 mph is never exceeded.

'Sawmill' like prop sounds will get us all chased away from flying fields.




_____________________________

Dar Zeelon - ISRAEL - ddzeelon@gmail.com
MVVS - Jett - Nelson - Bolly - Mejzlik

(in reply to MyWay)
       Post #: 10

RE: Props-More Myths Busted - 12/17/2006 7:31:34 PM   
pe reivers



Posts: 2454
Joined: 1/23/2002
From: Arcen, , NETHERLANDS
Status: offline 		Ditto that,
Better still, keep tip speed at mach 0.6 or lower, and prop thrust will be at it's best whilst reducing noise. That noise is energy that eats thrust and damages your ears.

_____________________________

Pe, MVVS, MTW, Mejzlik. www.mvvs.nl
There is sanctuary in analisys.

(in reply to DarZeelon)
       Post #: 11

RE: Props-More Myths Busted - 12/17/2006 7:36:17 PM   
pe reivers



Posts: 2454
Joined: 1/23/2002
From: Arcen, , NETHERLANDS
Status: offline 		The prop issue is such, that you take some close ones, and try them on your plane. You will settle for one, because there is a very noticeable performance difference between them in flight. The best one static, may not suit your needs best, but at low speeds, you will not be sorry you picked it.

_____________________________

Pe, MVVS, MTW, Mejzlik. www.mvvs.nl
There is sanctuary in analisys.

(in reply to buzzingb)
       Post #: 12

RE: Props-More Myths Busted - 12/17/2006 7:55:58 PM   
RVM


 

Posts: 1975
Joined: 3/12/2006
From: Sacramento, CA, USA
Status: offline 		Great info there. I'm gonna have to try some wood MA Scimitars I have laying around and see how they perform. I knew I ordered a bunch of different props for a reason... now where is that time I needed?

Do you think you could move past 12" and go into 14"-18"? Supposedly the differences between the prop manufacturers are much more noticeable and significant as the size goes up.

Thanks for the results! Very useful!

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There is no substitution for human competition.

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RE: Props-More Myths Busted - 12/17/2006 7:58:10 PM