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Old May 01, 2012, 07:33 AM
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Quote:
Originally Posted by khoysagk View Post
And supposedly running 2 stock blades is faster than 4.
K....The V6 has a 500kv motor that turns the stock 4 blade prop about 5800 rpms....Nitroplanes advertised prop dimensions of 14X8 turning 5800rpms gives us a whopping pitch speed of 43 mph.

To remove 2 blades or run a 2 blade prop of the same 14X8 dimensions will create less drag of the prop and increase the rpms a bit.....effectively giving you more speed and less amp draw. The speed difference will not be tremendous, but if you increase the pitch to 12 you'll be pulling similar amps and rpms as the 4 blade prop but with much more speed...if thats what your looking for.
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Old May 01, 2012, 08:17 AM
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United States, OH, Cleveland
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Are most people running the 14x12 or 14x10?

I think Im going to make the jump to a 2blade apc.
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Old May 01, 2012, 09:28 AM
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United States, OR, Astoria
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Quote:
Originally Posted by LICobra View Post
K....The V6 has a 500kv motor that turns the stock 4 blade prop about 5800 rpms....Nitroplanes advertised prop dimensions of 14X8 turning 5800rpms gives us a whopping pitch speed of 43 mph.

To remove 2 blades or run a 2 blade prop of the same 14X8 dimensions will create less drag of the prop and increase the rpms a bit.....effectively giving you more speed and less amp draw. The speed difference will not be tremendous, but if you increase the pitch to 12 you'll be pulling similar amps and rpms as the 4 blade prop but with much more speed...if thats what your looking for.
If you look at a few posts back this thing started with me just wanting a prop that doesn't break as easy as the stock blades. I'm not really looking for more speed, but am not against it.
Thanks for the explanation though, I was wondering why 2 blades would be faster than 4.
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Old May 01, 2012, 11:10 AM
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United States, CA, San Diego
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Quote:
Originally Posted by khoysagk View Post
If you look at a few posts back this thing started with me just wanting a prop that doesn't break as easy as the stock blades. I'm not really looking for more speed, but am not against it.
Thanks for the explanation though, I was wondering why 2 blades would be faster than 4.
I work with a guy who used to compete in u-control racing, and he told me the most efficient prop is a 1 bladed one. I think more blades = more mass and drag then what you get out of them? I don't know why it would be different for full scale planes, unless your blades would get so long that your landing gear would get really tall! Maybe it's one of those reynolds number things. Maybe full scale planes get around it by having variable pitch. Something I'd like to learn more about, too.

It just occurred to me that perhaps more blades are better for lower speeds since you can have more prop out there at the cost of less pitch, but those one blade props can have a lot more pitch since your pushing less blade with the motor? And since our models are flying at incredible scale speeds for their size, it's much more effective for them. Just thinking out loud...
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Old May 01, 2012, 02:02 PM
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Originally Posted by xmech2k View Post
I work with a guy who used to compete in u-control racing, and he told me the most efficient prop is a 1 bladed one.
I've never seen a 1 bladed prop....how does it balance...
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Old May 01, 2012, 02:22 PM
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USA, NY, Amsterdam
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More blades are only better on variable pitch props, which real warbirds have.

I've seen 1 bladed props and rotors on Nightflyyer's youtube page. You just need to add a counter-balance to them.

Todd
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Old May 01, 2012, 07:39 PM
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As Prowler 901 said, they just have a counterweight, which I guess fit under the spinner.
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Old May 01, 2012, 08:42 PM
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Originally Posted by xmech2k View Post
I work with a guy who used to compete in u-control racing, and he told me the most efficient prop is a 1 bladed one.
Im sure that guy thought what he said was true....just like Obama said he would create jobs 3 years ago and straighten out the economy.

I don't see anyone flying a 1 bladed prop, and the economy is still in the toilet...
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Old May 01, 2012, 09:15 PM
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Wellington, NZ
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Quote:
Originally Posted by khoysagk View Post
If you look at a few posts back this thing started with me just wanting a prop that doesn't break as easy as the stock blades. I'm not really looking for more speed, but am not against it.
Thanks for the explanation though, I was wondering why 2 blades would be faster than 4.
Glad I am not the only one with this problem!! I, too, keep breaking those darn props. It is expensive trying to get the landing just right on a grass strip. I think I have been erring on the too slow side.

But I mothball my P-51 in winter as the grass is wet and there are sandy worm casts which don't go well with the retracts, especially the rear one.

Finding it hard to pinpoint a suitable 2 blader on HobbyKing.
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Old May 01, 2012, 09:57 PM
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http://www.clspeed.com/node/7
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Old May 02, 2012, 06:23 AM
cmd
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Niceville, FL
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One blade is more efficient because it isn't in the prop wash (turbulence) of the preceding blade. The single blade prop gets "clean air" as the NASCAR folks would say. Single blades are balanced with a mass on a short stub opposite the single blade prop.

We go with two blade props because they are easier to balance and one doesn't need to worry about the mass balance attachment or the mass falling off.

War birds in WWII went from two blades just before the war to three blades to four or more as the engine horsepower increased. (Look at the evolution of props on the Spitfire). The extra blades were added to couple all that horsepower to the air and generate lift (thrust). It would have been more efficient to lengthen the blades rather than adding more, but the designers were constrained by the length of the landing gear and the need for prop clearance on the ground. You will also note that the blades got considerably wider as the war went on. Again, this was trying to gain the most lift (thrust) using the available horsepower.

Quote:
Originally Posted by xmech2k View Post
I work with a guy who used to compete in u-control racing, and he told me the most efficient prop is a 1 bladed one. I think more blades = more mass and drag then what you get out of them? I don't know why it would be different for full scale planes, unless your blades would get so long that your landing gear would get really tall! Maybe it's one of those reynolds number things. Maybe full scale planes get around it by having variable pitch. Something I'd like to learn more about, too.

It just occurred to me that perhaps more blades are better for lower speeds since you can have more prop out there at the cost of less pitch, but those one blade props can have a lot more pitch since your pushing less blade with the motor? And since our models are flying at incredible scale speeds for their size, it's much more effective for them. Just thinking out loud...
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Old May 02, 2012, 09:40 AM
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Originally Posted by cmd View Post
We go with two blade props because they are easier to balance and one doesn't need to worry about the mass balance attachment or the mass falling off.
Never mind that one blade just looks stupid.
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Old May 02, 2012, 01:19 PM
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USA, Texas Hill Country
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Quote:
Originally Posted by cmd View Post
One blade is more efficient because it isn't in the prop wash (turbulence) of the preceding blade. The single blade prop gets "clean air" as the NASCAR folks would say. Single blades are balanced with a mass on a short stub opposite the single blade prop.

We go with two blade props because they are easier to balance and one doesn't need to worry about the mass balance attachment or the mass falling off.

War birds in WWII went from two blades just before the war to three blades to four or more as the engine horsepower increased. (Look at the evolution of props on the Spitfire). The extra blades were added to couple all that horsepower to the air and generate lift (thrust). It would have been more efficient to lengthen the blades rather than adding more, but the designers were constrained by the length of the landing gear and the need for prop clearance on the ground. You will also note that the blades got considerably wider as the war went on. Again, this was trying to gain the most lift (thrust) using the available horsepower.
Well done, and nicely explained......and yeah, one blade props are not stylish at all.

Dick
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Old May 02, 2012, 04:13 PM
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I'll take dirty air over dirty looks!!
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Old May 02, 2012, 05:11 PM
yea, that was a loop
United States, TX, Little Elm
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Anybody know a good source in the US for a V6 w/o electronics? Every time I locate one, they are sold out.
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