On Pegasus I replaced my 18x12 2 blade, with a 18x11 3 blade. The 3 blade
has much less prop walk and I can stop. Both props are fixed pitch as my old
transmission doesn't care if the shaft turns.
Doug MountjoysvPegasusLF38 just west of Ballard, WA.
------ Original message------From: Gary Russell via CnC-ListDate: Fri, May 15,
2015 10:08To: C&C List;Cc: Gary Russell;Subject:Re: Stus-List Prop Walk C&C
29-2I could be wrong, but my understanding is the prop walk is caused by the
fact that the prop shaft on a sailboat is almost never horizontal (except for a
Sail Drive). This has the effect of increasing the pitch on one side of the
prop while reducing it on the other. It's possible (I think) the effect is
exacerbated for props with increased pitch (smaller diameter). Comments?
GaryS/V Expresso'75 C&C 35 Mk IIEast Greenwich, RI, USA
~~~~~~~_/)~~~~~~
On Fri, May 15, 2015 at 12:54 PM, Martin Kane via CnC-List
<cnc-list@cnc-list.com> wrote:
MichaelI expect you are right about the impeller vs screw analogy, because
while the 12x6 is correctly sized going forward given the 2.21:1 gear box, vs
the 2:62:1 that is most common in 2GMs, it needs to spin faster in reverse than
a prop that was properly sized for a 2.62:1 gearbox. So its seems that I’ve
solved the inability to hit max rpms and cruise at ~80% cont max, but created a
different problem. Financial practicality aside, I’m wondering if a feathering
prop where the forward and reverse pitch can be set independently might work.
Any listers have experience with this style of prop and are they 2 or 3 blade?
Martin martink...@sympatico.ca 905 848 0925 From: Michael Brown
[mailto:m...@tkg.ca]
Sent: Thursday, May 14, 2015 5:21 PM
To: cnc-list@cnc-list.com
Subject: Re: Stus-List Prop Walk C&C 29-2 You could plug your specs in here and
see what the recommendation is:
http://www.vicprop.com/displacement_size.php
I would have guessed a Gori 15X10 to be a little big, maybe the 14X9.5 is OK.
The 12X6 seems too small. If it cannot "bite" the water and stay connected
it will churn - cavitation - and the effect may be prop walk. Acting more like
a centrifugal impeller than a screw.
Michael Brown
Windburn
C&C 30-1
Date: Thu, 14 May 2015 16:10:22 -0400
From: Martin Kane <martink...@sympatico.ca>
To: <cnc-list@cnc-list.com>
Subject: Stus-List Prop Walk C&C 29-2
Message-ID: <blu437-smtp450fc0619106756cf69f2abd...@phx.gbl>
Content-Type: text/plain; charset="us-ascii"
Boat was significantly over-propped when I acquired her. Largely because
transmission ratio is 2.2:1 not 2.62:1 as stamped on the casing. While the
props that came with the boat (a Gori 15X10 and a 3 blade fixed 14X9) were
too big, prop walk was not an issue.
Just installed a Campbell Sailor 12x6 and the prop walk is severe (in spite
of the additional tip to hull clearance). It is basically impossible to turn
the bow to port in reverse . The bow swings to starboard and then once there
is some movement through the water will crab sideways, but the bow will not
swing around to port. I have not found any combination of throttle and
rudder position that makes the situation any better.
I need to replace the prop to avoid getting into trouble in close quarters
at some point. Question to C&C 29-2 owners: Has anyone found a prop that
works well going forward and in reverse.
Thanks in advance.
Martin
Recalculating C&C 29-2
Mimico Cruising Club
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