[alberg30] Propeller Specifications

[Rick Leach]

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More Prop-talk!

Obviously there is as much art as there is science to this field, even
"experts" will give widely varying answers to seemingly simple questions.
Ultimately, it a guessing game backed up by trial & error.  
In response to George's recommendation of a 13x7...on Sugar Magnolia my old
13" wheel leaves very little in the way of tip clearance.  This results in
some significant noise and vibration, especially at higher revs.  Also, with
the prop spinning so close behind the deadwood, a two-bladed wheel
effectively "unloads" twice per revolution, creating another type of
vibration.  My best guess for anyone except the serious racer would be a 12"
three-bladed prop, the pitch would be the last variable to match to your
powerplant characteristics.  
With an Atomic 4, I was convinced that I wanted a bronze 12x6 three-bladed
sailer prop until I heard about the Indigo prop specifically designed for
the A-4 power curve.  But it's made of 316 stainless, and I'm concerned
about crevice corrosion...so the waffling continues.  

Rick Leach
Sugar Magnolia, #121

> -----Original Message-----
> From:	John G. Morrison [SMTP:goalnet at direct.ca]
> Sent:	Thursday, August 31, 2000 10:51 PM
> To:	alberg30 at egroups.com
> Subject:	Re: [alberg30] Propeller Specifications
> 
> John: Campbell recommended 12x10 for my Yanmar 2gm.Can see no evidence of
> reduced speed under sail with this prop.I sail in the Vancouver area where
> Campbellis from and they are highly regarded here. Certainly I am happy
> with
> it.Must  admit I have not mastered going astern under control at slow
> speed.
> Fair winds to you  John  ,Antares
> 
> ----- Original Message -----
> From: John Birch <sunstone at idirect.com>
> To: <alberg30 at egroups.com>
> Sent: Wednesday, August 30, 2000 9:28 PM
> Subject: Re: [alberg30] Propeller Specifications
> 
> 
> >
> > Actually, I think you are supposed to go down 1" in Dia for a 3 blade -
> I'm
> > not sure though as I would never put one on my boat - cuts the sailing
> speed
> > too much.
> >
> > John
> >
> > George Dinwiddie wrote:
> >
> > >
> > > I think a 13x7 is probably appropriate, whether 2 or 3 blades.
> > >
> > > Jim Rogers wrote:
> > >
> > > > Can someone tell me what the specifications should be for a
> three-bladed
> > > > propeller are for use on our A30s?
> > > >
> > > > My engine is the GM25
> > > >
> > > > Thanks,
> > > >
> > > > Jim Rogers
> > > > XANADU II, #90
> >
> >
> >
> >
> >
> 
> 
>