[C38] New Owner w/Roller and prop question

[Les]

Oversized props have lots of issues, from adding propwalk, to under
reving the engine (which damages diesels and decreases fuel economy).
Almost every engine expert will tell you that the engine/prop/boat
design combination should let the engine just about reach maximum RPM at
the boats best speed.  If this is not true, or if you have more RPM with
no increase in boat speed, the prop is beginning to cavitate, causing
prop erosion and other issues.  If the prop gets too close to the hull,
it has insufficient "feed", and will not produce effective thrust, and
actually slow the boat down.  There are other issues as well, entire
books have been written on prop selection and on engine/boat/prop
design.  This is a good reading subject, and you will learn a lot about
hydrodynamics, power, thrust, and other issues vital to good boat
design.

	And remember that our boats are displacement boats, so planing is not
part of the design and probably not possible with any reasonable (and
probably not even with unreasonable) amount of horse power.

Regards,
Les H
On Tue, 2010-01-12 at 14:44 -0600, millsdan at verizon.net wrote:
> Thanks Steve, I'll look through some of the previous listserve
> questions.
> Dan
> 
> 
> Jan 12, 2010 02:32:59 PM, listserve at catalina38.org wrote:
> 
>          
>         Dan,  I'm not sure a 18" diameter prop will clear your hull,
>         as I've not heard of anybody using that large a diameter.  I
>         would call Marten (562-435-4494) and get their advice.
>         We had a 16 x 14 Marten and went to a Slipstream geared prop
>         of 16 x 11 prop- also sold by Marten and cruise at 2200-2400
>         with your same engine.
>         Cheers, Steve Orton
>                 -----Original Message-----
>                 From: listserve-bounces at catalina38.org
>                 [mailto:listserve-bounces at catalina38.org]On Behalf Of
>                 millsdan at verizon.net
>                 Sent: Sunday, January 03, 2010 6:48 PM
>                 To: listserve at Catalina38.org
>                 Subject: [C38] New Owner w/Roller and prop question
>                 
>                 
>                 We (Dan & Marcy Miller) recently purchased C-38 Hull
>                 #108 "Blonde Stranger". I'm sure it has the original
>                 Hood Roller Furling.
>                 Was it a #6 or #7 luff tape system? If it was a #6,
>                 could a #7 fit or would it be too tight? I've read in
>                 other listserve questions here
>                 that a Martec 16x12 is overpropped for the boat. We
>                 will be bringing the boat to the Chesapeake Bay where
>                 it is rare to have
>                 5 and 6 foot seas. I have the oportunity to get an
>                 18x12 Martec III. If I would normally run the 2454
>                 engine between 1800 and
>                 2200 rpms, do you think I would be okay? In my
>                 experience on the bay, most storms only have the
>                 oportunity to generate
>                 3 and 4 foot seas. My direct email is
>                 millsdan at verizon.net . Any and all replies would be
>                 appreciated. I'm also sure I will be asking more
>                 questions in the future. Thanks, Dan
>                 
>         
>         
>         ______________________________________________________________
>         
>         _______________________________________________
>         Listserve mailing list
>         Listserve at catalina38.org
>         http://catalina38.org/mailman/listinfo/listserve_catalina38.org
> _______________________________________________
> Listserve mailing list
> Listserve at catalina38.org
> http://catalina38.org/mailman/listinfo/listserve_catalina38.org