Dwight, I'm no expert on this, but a dedicated student. The owners manual states that max backstay tension should be kept below the tension that will stretch the Navtec Rod. Once metal stretches beyond a certain point, it remains that way. “As a rule of thumb, the maximum static backstay pressure should never exceed 25% to 33% of the backstay breaking strength.”
Check your backstay rod size and you should find it will be -10 or maybe -12 (12,000#) So much depends on rig tension prior to applying the backstay and sailshape. The backstay of the 34R is a Navtec Rod size –10 with a breaking strength of 10,300#, so tension should be maintained below 3399# or more realistically, 3000#. Typical tension varies between 600# at the dock, to a “hard on” setting of approx 2500#. Also, total bend in the mast should be maintained below 9” , according to Offshore Spars. The spar on a 35 MkII is probably less flexible than the 3 spreader Offshore section on our 34R? We need to adjust the length of the headstay and backstay, to provide less than 9” of mast bend when the backstay is pumped to 3000#. These adjustments can be checked and adjusted at the dock. The hydraulic system has a relief valve that should be checked that it relieves pressure when pumped above 3000#, in case an overzealous crew pumps the system too high. Last thought: I understand you typically sail in stronger winds; 15 to 25 knots, so I expect your boat will be setup rather tighter than mine because we race in 4 to 8 knots typically, with much headstay sag. Chuck Resolute 1990 C&C 34R Atlantic City, NJ ----- Original Message ----- From: "dwight veinot" <dwightvei...@hfx.eastlink.ca> To: cnc-list@cnc-list.com Sent: Saturday, November 24, 2012 11:55:02 AM Subject: Re: Stus-List Keel R&R 1500-2000 kpsi… whow !!! 1kpsi = 1000psi but I may be confused on units I think my Navtec adjuster reads in psi, not kpsi. I find 1500-2000 psi OK and sometimes up to and above 2500psi in real heavy air…your boat should take that without cracking IMHO. I have experimented with backstay tension a lot and on my 35 MKII performance does not seem to vary a great deal above 1200 psi...maybe just my design and the way I have my rig setup…I do release tension going downwind and that seems beneficial Dwight Veinot C&C 35 MKII, Alianna Head of St. Margaret's Bay, NS From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Tim Goodyear Sent: November 24, 2012 12:03 PM To: Dennis C.; cnc-list@cnc-list.com Subject: Re: Stus-List Keel R&R Good point. I do like a nice tight forestay... Upwind setting is between 1500 to max of 2000 kpsi, which I didn't think would be too much. Maybe a couple of longitudinal stringers in between the ribs in that area would help, or living with more sag / less pointing ability. Tim Mojito C&C 35-3 Branford , CT On Nov 24, 2012, at 10:43 AM, "Dennis C." < capt...@yahoo.com > wrote: Tim, Do you have a hydraulic backstay adjuster? Dennis C. Touche' 35-1 #83 Mandeville , LA <blockquote> From: Tim Goodyear < timg...@gmail.com > To: " cnc-list@cnc-list.com " < cnc-list@cnc-list.com > Sent: Saturday, November 24, 2012 8:55 AM Subject: Re: Stus-List Keel R&R Thanks, Jake. I'll take a look under the anti fouling around the top of the keel stub this year. I've had two yards try to solve the crack at the back of the keel (the C&C frown?), but it is back this year with a little water weeping out. It's (now) all solid fiberglass in that area, so I don't know where the movement is starting. Tim On Nov 24, 2012, at 7:54 AM, "Jake Brodersen" < captain_j...@cox.net > wrote: <blockquote> Tim, We found a number of hairline cracks in the keel stub. They were spread out and not really concentrated in one area. The boat was originally commissioned in Maine. I suspect that it had a hard grounding at some point. I didn’t notice any stress at the back of the keel, which is where you would expect to see major damage in a grounding. This past spring when I had the bottom paint soda blasted, we found some longitudinal cracks in the gelcoat and glass on the port and starboard side in the hull, less than a foot from the keel joint. One was over two feet long. They were grounded out and glassed in. It is all faired in nicely now. Jake From: CnC-List [ mailto:cnc-list-boun...@cnc-list.com ] On Behalf Of Tim Goodyear Sent: Friday, November 23, 2012 5:26 PM To: cnc-list@cnc-list.com Cc: < cnc-list@cnc-list.com > Subject: Re: Stus-List Cutting my keel Jake, I know you've documented your project, but what did the cracks look like before you started? Mojito has a couple of short hairline cracks at the hull / stub joint on the port side, and at the very rear of the keel. Thanks, Tim <blockquote> _______________________________________________ This List is provided by the C&C Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com </blockquote> _______________________________________________ This List is provided by the C&C Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com </blockquote> </blockquote> <blockquote> _______________________________________________ This List is provided by the C&C Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com </blockquote> No virus found in this message. Checked by AVG - www.avg.com Version: 2012.0.2221 / Virus Database: 2629/5416 - Release Date: 11/24/12 _______________________________________________ This List is provided by the C&C Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com
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