Flexofold has gotten better. When I replaced my prop a year ago, they wanted to know not only shaft size, but also information about my engine and transmission. This is how they responded:
Hello Matthew Thank you for the missing gear reduction. With a Westerbeke W40, max rated 37hp/3000rpm (V-drive) ( gear reduction ratio 1:2,00 ) we would recommend a 2-blade 17x12L or a 3-blade 16x12-3L propeller for your C&C 42. I ended up getting the two-blade and am happy with it. The best part is that it’s no big deal if I forget to send somebody down below to turn the shaft when we go racing. From: Dennis C. via CnC-List Sent: Monday, December 18, 2017 11:24 AM To: CnClist Cc: Dennis C. Subject: Re: Stus-List PROPELLER PITCH Take prop manufacturers recommendations with a grain of salt. Years ago I requested a recommendation from Flexofold. The rep at the time was Chuck Angle who was highly regarded. He said he didn't have a good prop recommendation for my 35-1. :) I went with Martec. In 2011, I repeated the request and got a recommendation for a 15 x 12. In 2016, I again asked and they said 16 x 12. Currently, Touche' is swinging a 14 x 14 Martec which seems a bit under pitched (or too small a diameter). I can run at 6.4-6.5 knots at cruise rpm (80% max, 2450 rpm) and flat water, no wind. On my list for next year's haul out is to measure and document (photograph) the prop tip clearance distance. I will also measure the hub and swing pin location. The swing plane for different props varies. I think prop selection is part science, part art and a bit of voodoo. Dennis C. Touche' 35-1 #83 Mandeville, LA On Mon, Dec 18, 2017 at 9:59 AM, Rick Brass via CnC-List <cnc-list@cnc-list.com> wrote: The problem that I see with this calculator is that there is no value for prop diameter (and slip is pretty intangible, though I suspect using .10 slip might be a good approximation for 90% efficiency). The rule of thumb that a local propshop told me is that changing prop diameter by 1” is approximately equivalent to changing the prop pitch by 2”. So diameter also enters into the calculation. I believe each prop maker has their own calculator for recommending initial diameter and pitch, based on boat weight, engine HP and targeted cruising RPM, transmission reduction ratio, and hull speed. Rick Brass Washington, NC From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of svpegasus38 via CnC-List Sent: Sunday, December 17, 2017 5:56 PM To: cnc-list@cnc-list.com Cc: svpegasus38 <svpegasu...@gmail.com> Subject: Re: Stus-List PROPELLER PITCH Try this propellor calculator. rbbi.com/folders/prop/propcalc.htm Sent from my T-Mobile 4G LTE Device Doug Mountjoy POYC Rebecca Leah Lf39 -------- Original message -------- From: Bunky via CnC-List <cnc-list@cnc-list.com> Date: 12/17/17 14:18 (GMT-08:00) To: cnc-list@cnc-list.com Cc: Bunky <richard.h.bernst...@uvm.edu> Subject: Stus-List PROPELLER PITCH Luna is a 1984 C&C 35 with a Yanmar 3gm30 engine. Does anyone know what the proper propeller pitch should be? She has an aftermarket Maxiprop, and based on engine performance, I believe the pitch may be set too high. Richard Luna, Lake Champlain, VT _______________________________________________ Thanks everyone for supporting this list with your contributions. Each and every one is greatly appreciated. If you want to support the list - use PayPal to send contribution -- https://www.paypal.me/stumurray _______________________________________________ Thanks everyone for supporting this list with your contributions. Each and every one is greatly appreciated. If you want to support the list - use PayPal to send contribution -- https://www.paypal.me/stumurray -------------------------------------------------------------------------------- _______________________________________________ Thanks everyone for supporting this list with your contributions. Each and every one is greatly appreciated. If you want to support the list - use PayPal to send contribution -- https://www.paypal.me/stumurray
_______________________________________________ Thanks everyone for supporting this list with your contributions. Each and every one is greatly appreciated. If you want to support the list - use PayPal to send contribution -- https://www.paypal.me/stumurray
