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Mar 22, 2004, 11:35 AM

SF, E, HD props differences

OK, so I've seen these propellers around my LHS. There are 2 sorts of GWS propellers, one which is the SF style which is like the ones made by APC, and the other ones HD & E propeller are the ones that look like they are used in gassers.

But what is the difference between these an SF, E, and HD propeller? And what does HD stand for?
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Mar 22, 2004, 11:46 AM
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Heavy Duty?
Mar 22, 2004, 12:26 PM
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SF = APC SlowFlyer (geared electric)
E = APC Electric (direct drive glow/electric)
RS = GWS Reduction Series (geared electric)
HD = GWS Hyper Drive (direct drive electric)

In general the SF and RS props are intended for geared applications. They are optimized for the highest thrust at slow RPMs APC lists the SF props as being useful for 65000/diameter. So a 9 inch SF prop has a practical upper RPM limit of 7222RPM. The GWS RS props seem to have a lower upper RPM limit because they vibrate loudly when spinning fast.

The HD and E props are designed for direct drive so they have lower thrust than the SF or RS props for a given diameter at a given RPM. But they also seem to be slightly more efficient at any given RPM.

I've found that when you want to substitute an E or HD prop for an RS or SF prop you need to got up in diameter to have the same thrust.
Last edited by thunder1; Mar 22, 2004 at 02:41 PM.
Mar 22, 2004, 12:47 PM
Perfect. Just what I needed to know. And:

Just what does more efficient mean? The GWS props are total crap and I'm not going to get another one. APCs are hard and they dont break easily. Unfortunately, the APC doesn't stock a 12x6 SF prop. Does it?

The closest I can find is a 11x4.7 SF prop. Nothing larger. I'm putting a 12x6E prop on the Slooooow Stick and I'm using an EPS350C (D gearing).

What do I gain from using an E prop instead of an SF?
Last edited by csisfun; Mar 22, 2004 at 12:57 PM.
Mar 22, 2004, 01:28 PM
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Hyper Drive! Very nice.

Mar 22, 2004, 01:53 PM
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Originally posted by csisfun

The closest I can find is a 11x4.7 SF prop. Nothing larger. I'm putting a 12x6E prop on the Slooooow Stick and I'm using an EPS350C (D gearing).
I own an 11x7 SF prop and has a 12x6 SF prop for sale. Take a look:

Mar 22, 2004, 02:06 PM
Can't buy something off the net.
Mar 22, 2004, 02:40 PM
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Efficiency for props is the amount of thrust per energy input i.e. amps go down.

So the SF and RS props "waste" slightly more energy to give the same amount of thrust. The tradeoff is usually the ability to produce thrust in the lower end of the RPM range. Which is why I mentioned the HD and E props need to go up a diameter to produce the same amount of thrust at slower RPMs.

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