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Old Sep 16, 2007, 06:07 PM
White Mountains in NH
dlabrie's Avatar
In the White Mountains of NH
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Question
Letters on prop sizes: RD, DD, HD, EP, Etc.

Can anyone tell me what the various letters on the prop sizes mean?
Thanks,
David
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Old Sep 16, 2007, 06:27 PM
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United States, AZ, Mesa
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Quote:
Originally Posted by dlabrie
Can anyone tell me what the various letters on the prop sizes mean?
Thanks,
David
In what context? Props are measure by their diameter and pitch, with diameter listed first. There are various kinds as well, like Slow Fly, Thin Electric, Wood, etc... the letters you listed are probably manufacturers codes... like GWS uses "EP" on some of theirs... like the EP1060 that comes with a Slow Stick... it's a 10x6.0 Electric Prop as far as I know. Other manufacturers use different letters. APC uses E on some and no letters on others, like the "Slo Flyer" props have no letters, only a measurement like 9x4.7, which means 9inch diameter and 4.7 inch pitch.

4.7 inch pitch means the prop would pull forward 4.7 inches with each rotation if there was no resistance.
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Old Sep 16, 2007, 06:50 PM
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Just a guess:

HD = Hyper Drive
DD = Direct Drive
EP = Electric Prop
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Old Sep 16, 2007, 10:31 PM
Gilbert, AZ
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I never understood the difference between the DD & HD GWS props. They both look the same to me .
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Old Sep 16, 2007, 10:49 PM
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Well, I found out (the hard way) that APC 8x6P means Pusher.
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Old Sep 16, 2007, 11:16 PM
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The letters on a GWS prop mean absolutely nothing. Here are two GWS props.

Upper prop is a GWS EP-1060

Lower prop is a GWS EP-1080

This is why GWS props are used to stir epoxy at my house...

Chuck
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Old Sep 16, 2007, 11:40 PM
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Quote:
Originally Posted by NoFlyZone
The letters on a GWS prop mean absolutely nothing. Here are two GWS props.

Upper prop is a GWS EP-1060

Lower prop is a GWS EP-1080

This is why GWS props are used to stir epoxy at my house...

Chuck
They sure do look different... same diameter, but the top one has a pitch of 6 and the bottom one has a pitch of 8... it might need that weird shape to get the higher pitch correct but I'm not sure. Those letters are just part of the stock code.
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Old Sep 16, 2007, 11:44 PM
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Well.... like I said... the letters tell nothing about the prop... EP just means "Electric Prop".

Chuck
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Old Sep 17, 2007, 05:34 AM
White Mountains in NH
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In the White Mountains of NH
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Thanks for the responses.
I understand the length and pitch numbers, but had no idea about the Letters. I guess I won't worry about them when I order props; other thean the P for pusher
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Old Sep 17, 2007, 05:47 AM
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Maybe you shouldn't worry about them, but you should be aware.

Two letters which I'm aware of are EP (or just E) and SF, which stand for Electric Power and Slow Fly: They mean that the props are designed lighter -- for use in electric models, where there isn't motor vibration -- and shouldn't be used on glow models because they risk breaking up. I believe they're also shaped differently from "normal" props so that they will work more efficiently at the relatively low rpm most electric motors work at compared with glow.
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Old Sep 17, 2007, 07:49 AM
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Quote:
Originally Posted by NoFlyZone
The letters on a GWS prop mean absolutely nothing. Here are two GWS props.

Upper prop is a GWS EP-1060

Lower prop is a GWS EP-1080

This is why GWS props are used to stir epoxy at my house...

Chuck

The upper one is what I would call a 10x6 GWS HD (hyperdrive - though somehow even some of these larger diameter props in this series are listed as DD - direct drive). I use my own terminology and call only the 4" or smaller props with square blades DD (e.g. the 3x2, 4x2.5 and 4x4) - all the rest with the same blade shape as this 10x6 (even as small as 3x3, 4.5x3) I call HD. The larger props in the HD series are safe to about 80,000rpm/diameter (maybe more - I had an 8x4 at 13800rpm (110,400rpm/diam!) the other day - that was close to its limit!).

The lower prop is a 10x8 GWS RS (reduction series) - often incorrectly called a slowflyer (which has long been the Landing Products designation for their APC SF series). These RS series props - especially the larger higher pitched varieties are not very safe above ~40-50,000rpm/diam.
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Old Sep 17, 2007, 11:18 AM
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Quote:
Originally Posted by Dr Kiwi
The upper one is what I would call a 10x6 GWS HD (hyperdrive - though somehow even some of these larger diameter props in this series are listed as DD - direct drive). I use my own terminology and call only the 4" or smaller props with square blades DD (e.g. the 3x2, 4x2.5 and 4x4) - all the rest with the same blade shape as this 10x6 (even as small as 3x3, 4.5x3) I call HD. The larger props in the HD series are safe to about 80,000rpm/diameter (maybe more - I had an 8x4 at 13800rpm (110,400rpm/diam!) the other day - that was close to its limit!).

The lower prop is a 10x8 GWS RS (reduction series) - often incorrectly called a slowflyer (which has long been the Landing Products designation for their APC SF series). These RS series props - especially the larger higher pitched varieties are not very safe above ~40-50,000rpm/diam.
Hi Dr. Kiwi,

I'm printing out your response and tacking it to my workshop wall. Thank you very much for an excellent breakdown!

Chuck
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