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-   -   Newport 41 Prop Shaft Diameter (http://www.sailnet.com/forums/gear-maintenance/29962-newport-41-prop-shaft-diameter.html)

Fstbttms 03-05-2007 05:31 PM

Newport 41 Prop Shaft Diameter
 
Anybody happen to know what it is? Thanks.

sailingdog 03-05-2007 06:02 PM

I think this would depend on what the prop shaft was made of—stainless steel or bronze, as well as the size of the engine used in the boat. If the boat has been repowered, it may be a different size than the original.

Tartan34C 03-05-2007 06:10 PM

Standard shaft in a Newport 41 Mark II with a 4108 is 1 1/8”
All the best,
Robert Gainer

Fstbttms 03-05-2007 06:22 PM

Quote:

Originally Posted by Tartan34C
Standard shaft in a Newport 41 Mark II with a 4108 is 1 1/8”
All the best,
Robert Gainer

Thanks a lot.

Fstbttms 03-05-2007 06:24 PM

Quote:

Originally Posted by sailingdog
I think this would depend on what the prop shaft was made of—stainless steel or bronze...

Why would the diameter be dependant on the material it was made from?

sailingdog 03-05-2007 06:52 PM

Different materials have different tensile strengths, and as such, may need to be made in different diameters, based on the strength of the material and the strength required for the given purpose.

For instance, rigging made from 304L stainless is often slightly smaller a diameter than that made from 316L stainless, because 304L stainless has a higher tensile strength.

Fstbttms 03-05-2007 07:02 PM

Quote:

Originally Posted by sailingdog
Different materials have different tensile strengths, and as such, may need to be made in different diameters, based on the strength of the material and the strength required for the given purpose.

I'm sure this is true in regards to standing rigging, but prop shaft sizes tend to be based on engine and transmission size and are quite standard, regardless of material used. My experience is that, for instance, a Catalina 27 is always going to have a 1" shaft. It is a rare production boat where shaft sizes vary from one vessel to another. I have it from two separate sources now that the Newport 41 uses a 1 1/8" shaft and I would be very surprised if the Newport 41 I'm going to put a zinc on later this week were different.

sailingdog 03-05-2007 07:13 PM

I wasn't saying that they would vary within a standard production line... but if the boat, like my friend's Alberg 30, has been re-powered, the shaft and such may not be the same diameter as the original.

Many sailboats are old enough that they may be on a second or third engine... and in the case of my friend's A30...the rudder and prop aperture had to be re-built after an accident while on the hard. Even Robert said "standard shaft size", which makes an allowance for a non-standard shaft being a possibility.

Fstbttms 03-05-2007 07:52 PM

Quote:

Originally Posted by sailingdog
I wasn't saying that they would vary within a standard production line... but if the boat, like my friend's Alberg 30, has been re-powered, the shaft and such may not be the same diameter as the original.

I'm not disputing that there are cases where reshafting to a different size has occurred, but these cases are definitely the exception, rather than the rule. I've replaced enough zincs to know what most common production boats are going to need without looking and I can't think of very many instances where I came upon one that had a shaft size that was not standard for that particular model.

BTW, I've had a third confirmation on the 1 1/8" diameter (I went to the Newport owners web site and e-mailed every listed owner of a Newport 41. :D )

Tartan34C 03-05-2007 08:34 PM

Fstbttms,
Shaft material does make a difference. But in the real world most boats of similar size have similar engines and with a limited number of available sizes it doesn’t vary much. But it will matter in some cases. By the way its stiffness not strength that makes the difference.

Sailingdog,
The rigging size is also tied to clevis pin diameter so if you change to a stronger stainless you will probably stay with the same diameter anyway because changing diameter forces you to change tangs and chainplates. Changing stainless really just adds to the safety factor and nothing else.
All the best,
Robert Gainer


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