Glow Engines Discuss RC glow engines

difference in prop types

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Old 01-19-2013, 06:47 PM
  #1
jjoos99
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Default difference in prop types

not sure if this is the right forum to put this in but what is the difference between all the different types of wooden props. I have seen type a, c, d, and e. I was wanting to order a new prop for my os 70 4 stroke and wasnt sure the difference between all the props.
thanks
Jeff
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Old 01-19-2013, 07:12 PM
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Default RE: difference in prop types

Not all props are created equal to put it simply. In general wide bladed props work best with 4 stroke engines while narrow blades work well with screaming 2 strokes. However it seems there are no hard rules, I prefer to grab a handful of props in the general size range and fly each one then decide.
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Old 01-19-2013, 09:05 PM
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Default RE: difference in prop types

Try a 12x7 and 12x8 on the engine
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Old 01-19-2013, 10:58 PM
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Default RE: difference in prop types

Have you looked up the manufacturers specifications to see what is a good starting point???
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Old 01-20-2013, 07:43 AM
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Default RE: difference in prop types

Depending on the drag factor of the airframe the engine is to be used in, I prop about 700-1500 RPM less (static) than the maximum RPM of the engine.

If the engine is to be installed in a WW-I biplane start W/the smaller spec'ed props. If it's going into a P-51 Mustang, go W/the larger spec'ed props.
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Old 01-20-2013, 09:05 AM
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Default RE: difference in prop types

I like a 13x6 Master Airscrew K Series on my 70 four stroke. As already stated, try a few to see what you like.

edit
the K series is plastic, didn't read the original post very well
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Old 01-22-2013, 08:42 AM
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Default RE: difference in prop types

Iuse 10,000 rpm as a limit for static rpms on any prop for mid sized 4S engines.
In other words I ground test any prop I am interested in trying and if it turns over 10,000 static it might over rev the engine and cause wear, stress on the engine.
I allow slightly higher rpm limits on smaller 4S engines.
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Old 01-22-2013, 11:11 AM
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Default RE: difference in prop types


Quote:
ORIGINAL: jeffie8696

I use 10,000 rpm as a limit for static rpms on any prop for mid sized 4S engines.
In other words I ground test any prop I am interested in trying and if it turns over 10,000 static it might over rev the engine and cause wear, stress on the engine.
I allow slightly higher rpm limits on smaller 4S engines.
That's a good bench mark for medium sized 4-strokes.

My CDI fired Saito FA91S was spinning a 15 x 4 @ 10,300, a bit more than I liked.

I went to a 15 x 5 & the revs dropped to 9,700, a bit more cushion against overreving in the air.
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Old 01-22-2013, 04:11 PM
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Default RE: difference in prop types


Quote:
ORIGINAL: SrTelemaster150


Quote:
ORIGINAL: jeffie8696

I use 10,000 rpm as a limit for static rpms on any prop for mid sized 4S engines.
In other words I ground test any prop I am interested in trying and if it turns over 10,000 static it might over rev the engine and cause wear, stress on the engine.
I allow slightly higher rpm limits on smaller 4S engines.
That's a good bench mark for medium sized 4-strokes.

My CDI fired Saito FA91S was spinning a 15 x 4 @ 10,300, a bit more than I liked.

I went to a 15 x 5 & the revs dropped to 9,700, a bit more cushion against overreving in the air.
Whats the typical rev range for the average OS or Saito 4-stroke?
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Old 01-22-2013, 04:36 PM
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Default RE: difference in prop types

Quote:
ORIGINAL: 1QwkSport2.5r


Quote:
ORIGINAL: SrTelemaster150


Quote:
ORIGINAL: jeffie8696

I use 10,000 rpm as a limit for static rpms on any prop for mid sized 4S engines.
In other words I ground test any prop I am interested in trying and if it turns over 10,000 static it might over rev the engine and cause wear, stress on the engine.
I allow slightly higher rpm limits on smaller 4S engines.
That's a good bench mark for medium sized 4-strokes.

My CDI fired Saito FA91S was spinning a 15 x 4 @ 10,300, a bit more than I liked.

I went to a 15 x 5 & the revs dropped to 9,700, a bit more cushion against overreving in the air.
Whats the typical rev range for the average OS or Saito 4-stroke?
Saito FA91S specified max is 11,000 RPM.

Mine idles @ 1700 RPM W/CDI firing things off 11* BTDC @ idle.

Initial full advance timing setting is 35* BTDC.
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