[Alberg30] Prop for GM25

[George Dinwiddie]

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/
 ----------------------------------------------------------------------

 +-----------------------------------------------------------------------------------------+
 |            The BT Global Challenge -- match racing in the Southern Ocean                |
 | http://service.bfast.com/bfast/click?bfmid=22673860&siteid=32743498&bfpage=bt_challenge |
 +-----------------------------------------------------------------------------------------+
_______________________________________________
 Public-list mailing list -- Public-list at alberg30.org
 http://www.alberg30.org/mailman/listinfo/public-list
 To unsubscribe: email to Public-list-request at alberg30.org
 Include command "unsubscribe <password>" in subject or body.
 Use command "help" for more options.

 981995854.0