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Old 03-04-2012, 07:24   #1
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What does this mean on a prop?

This is stamped on my props -RADICE ER20 X OR21 X 0S60C. I assume that means the brand is Radice, the diameter is 20" and the pitch is 21". I don't know what the 0S60C means. Are my assumptions correct? Also does any of that information indicate whether they are on a metric or SAE shaft?
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Old 03-04-2012, 07:37   #2
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Re: What does this mean on a prop?

Thats a course pitch if its 21.
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Old 03-04-2012, 07:55   #3
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Re: What does this mean on a prop?

Quote:
Originally Posted by clayzone View Post
This is stamped on my props -RADICE ER20 X OR21 X 0S60C. I assume that means the brand is Radice, the diameter is 20" and the pitch is 21". I don't know what the 0S60C means. Are my assumptions correct? Also does any of that information indicate whether they are on a metric or SAE shaft?
So the ER20 is the model type and diameter, the OR21 is the pitch and the OS60C is the material type which the italian manufacturers will refer to as "Bronze Aluminium" - it should be on a metric shaft.

However, you'll be best double-checking this with a technical sales representative at ElicheRadice:

serena@elicheradice.com

You'll find more information on their products here: Eliche Radice - www.elicheradice.com - Eliche

..and if your Italian is good then you can give them a call.

Good luck!

Phil
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Old 03-04-2012, 08:55   #4
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Re: What does this mean on a prop?

Phil, I had looked at the website but still find any info that would explain the code. Thanks for your help.
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Old 03-04-2012, 09:25   #5
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Re: What does this mean on a prop?

Boy, that is a course pitch.... planing powerboat?
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Old 03-04-2012, 11:04   #6
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Re: What does this mean on a prop?

I am not sure what "course pitch" refers to. These props are on a power cat, Maryland 37, with twin 160 hp Yanmar engines. At sea trial the cat exceeded its rated max RPM at WOT. Plus the speed was significantly less that what I have read it should be. So I want to change props. Based on what I have now I think the props should be 22x21. I have not seen the props yet but people that have (surveyor) said they have weird cupping, whatever that means.
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Old 03-04-2012, 11:12   #7
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Re: What does this mean on a prop?

wow, those are strange looking! If you go bigger diameter you may not have enough hull clearance which can cause "thrumming" noise as well as turbulance...etc. I think the rule is 15-20% of dia for clearance....? With that strange prop shape... maybe just a more conventional prop at same dia and pitch will make a differnce...? It would be nice to find some other owners and see what they are using... can you get the new prop supplier to guarantee to "get it right" or change them out?
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Old 03-04-2012, 13:06   #8
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Re: What does this mean on a prop?

Here’s their Displacement Catamaran Prop’ Spec Sheet:
http://www.elicheradice.com/linea58/...0%28ENG%29.pdf

Or, you might ask:
Eliche Radice S.p.A.
Via Valtellina, 45
20092 Cinisello Balsamo - Milano - Italia
Tel: +39 (02) 66.04.93.48 - Fax: +39 (02) 61.27.688
Eliche Radice - www.elicheradice.com - Contatti
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Old 05-04-2012, 22:43   #9
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Re: What does this mean on a prop?

If I'm not mistaken, most of those parameters are used to help develop a figure for slip. While a large container ship might only see 5% at the 113 rpm shaft speed, we in sailboats if spinning the screw in a direct configuration would expect to see 8%~18% slip, and all other calculations are straight forward if I remember my old classes. prop pitch X RPM = inches per minute of speed / 12 = feet per minute X 60 = feet per hour / 6082 feet = nm/hr. So assume you are direct drive spinning a 21" pitch prop at 2000 rpm. 21" X 2000 rpm = 42000" per minute / 12 = 3500' per minute X 60 = 210000' per hour / 6082 = 35.4 kt X .82 slip = 28.3 kt That seems fast for the rpm, maybe there is more slip than my range of 8%~18%.

Do you get 28 kt at 2000 rpm? Seems fast. Are you using a gear reduction? If so, what is the ratio?

I hope I still remembered how to do this, if not I know David M knows.

I think the last container ship I was on had a 21' pitch and at full ahead sea speed was turning at 113 rpm. 21' X 113 = 2373 X 60 = 142380 / 6082 = 23.4 kt X .96 = 22.4 kt, it was a fast ship.
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