[Alberg30] Prop for GM25

[T. Kevin Blanc]

I still haven't installed the Indigo 10x 7.4 three
blade prop made specifically for the Atomic 4 that I
purchased last year. This prop hits the "optimums" a
lot better. You can visit www.atomic4.com to get
information on it. I'll let you know how it runs with
it when I finally get it installed in the Spring. 

Another good source for sailboat prop information: try
www.northbynortheast.com (did I get that right?) for
information about the Campbell Sailor prop.
Interestingly, they argue that sailboats should almost
never use a two-blade prop.

Then there's the Cruising Designs variable pitch
plastic prop that lots of folks with A4s love - but
they don't recommend it for boats with lots of
deadwood.
 
--- George Dinwiddie <gdinwiddie at min.net> wrote:
> The 7x13 is standard for both the Atomic 4 and
> Graymarine in the
> Alberg, but I'm not sure it's "optimum."  It
> violates a number of
> the normal rules of thumb.  For one thing, it has
> enough pitch that
> the rpms are kept well under the values normally
> recommended.  I
> think the Gray may have better low-end power, but
> the the Atomic
> 4 can't put out very much power at the 1500-1800 rpm
> that people
> normall use for cruising.  Also, the tip clearance
> in the aperture
> is much less than recommended.  I'm sure this must
> cause some 
> turbulence and noise.
> 
> In spite of all this, it seems to work just fine.  I
> think that
> choosing a prop is still an art form.  Even the
> experts often
> take several tries to get a good match.  My opinion
> is that it
> "ain't broke" and I'm sticking with the original
> 7x13.
> 
>  - George
> 
> > Robert Kirk said:
> > 
> > Surely someone must have figured the optimum prop
> for an A30 with Atomic 4; 
> > probasbly Mr. Whitby. Mine is a Michigan Sailer 2
> blade 7X13 which may be 
> > original.
> 
> -- 
> 
>
----------------------------------------------------------------------
>   George Dinwiddie                            
> gdinwiddie at alberg30.org
>   The gods do not deduct from man's allotted span
> those hours spent in
>   sailing.                                   
> http://www.Alberg30.org/
> 
>
----------------------------------------------------------------------
> 
> 
>
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