Here's the data guys. It looks like there is a loose corollary (in my case) between hydraulic psi and backstay lbs load. My hydraulic pump relief valve is seized and appently set at ~2600 psi. So I'm safe in that no matter how much I pump it will never exceed even 25% of the backstay load limit. As for the transom load limit...who knows.
https://docs.google.com/spreadsheets/d/1B6F6OQU8b7L5tVgvvWKViQHS5UVL1Srx6HV7xPKRC40/edit?usp=sharing Josh Muckley S/V Sea Hawk 1989 C&C 37+ Solomons, MD On Fri, Aug 3, 2018 at 1:48 PM, Bruce Whitmore via CnC-List < cnc-list@cnc-list.com> wrote: > I'd love to see that as well Josh. > > Thanks! > > Bruce Whitmore > > (847) 404-5092 (mobile) > bwhitm...@sbcglobal.net > > > ------------------------------ > *From:* Josh Muckley via CnC-List <cnc-list@cnc-list.com> > *To:* C&C List <cnc-list@cnc-list.com> > *Cc:* Josh Muckley <muckl...@gmail.com> > *Sent:* Friday, August 3, 2018 10:22 AM > *Subject:* Re: Stus-List 37+ Backstay tension > > With that info I'll head down to my boat and apply various psi to the > hydraulics and then measure the tension with my loos gauge. > > Josh > > On Fri, Aug 3, 2018, 10:17 AM Gary Russell via CnC-List < > cnc-list@cnc-list.com> wrote: > > So... I went over to Kaylarah this morning and found the following: > > The back stay diagonals are 235" long > The spread between the attachments is 80" > Doing the math, that means if the maximum tension on the vertical rod is > 5000 lbs., then the tension on the diagonals is 2537 lbs. > From here you can apply any safety factor you like, just maintain the > ration of 2537 : 5000. > Because the angle between the diagonals is so small (smaller than I > thought), it is pretty close to 2:1. > > Personally, I'm going to try and keep the tension on the diagonals less > than 2000 lbs. which keeps the upper rod below 3942 lbs. (Now where did I > put that Loos gauge?) > > Gary > S/V Kaylarah > '90 C&C 37+ > East Greenwich, RI, USA > > > ~~~~~~~_/)~~~~~~ > > > On Thu, Aug 2, 2018 at 9:00 PM, Gary Russell <captnga...@gmail.com> wrote: > > Actually, if you look closely at the manual, you will notice that the > 4125 lbs. refers to "wire limit", and 5000 lbs. refers to "rod limit". > Since the vertical part of the back stay assembly is rod, I will assume > that the 5000 lbs. refers to the vertical. I will go over to the boat > tomorrow and try to measure the back stay angle, to see which limit gets > exceeded first, the rod or the wire. C&C could have made this a lot > easier. I've got to believe the transom will fail before the wire, yet the > wire is all that is specified. > > Gary > > ~~~~~~~_/)~~~~~~ > > > On Thu, Aug 2, 2018 at 8:52 PM, Josh Muckley via CnC-List < > cnc-list@cnc-list.com> wrote: > > Absolutely without any doubt in my mind the backstay tension of 4125 is to > be measured on the mainline. This works in opposition to the head stay > which is equally sized #12 rod. > > Josh > > On Thu, Aug 2, 2018, 8:41 PM Gary Russell via CnC-List < > cnc-list@cnc-list.com> wrote: > > Hi Josh, > Oops! I missed that. I looked in the chapter about rigging and > didn't find it there. Silly me! I even searched for the number 4125 and > found nothing. I guess the document is an image rather than text. Now the > question, is that the tension in the vertical part of the back stay? I > guess, the safest assumption is that it is. > > Gary > > > ~~~~~~~_/)~~~~~~ > > > On Thu, Aug 2, 2018 at 8:33 PM, Josh Muckley via CnC-List < > cnc-list@cnc-list.com> wrote: > > Page 68 of the manual pdf file which I linked before has the pre-load and > max load limits. > > Again I am corrected in my preconceived notions regarding the correlation > between a hydraulic gauge and the tensile load on the back stay. > > Josh > > On Thu, Aug 2, 2018, 8:13 PM Gary Russell via CnC-List < > cnc-list@cnc-list.com> wrote: > > Hi Josh, > Where did you find the 4125 or 5000 lb. limit? I don't see that in > the Owners Manual? Is the 4125 lb. limit for the lower angled segments of > the the back stay or the upper vertical part. You can't simply measure the > port back stay tension and multiply by two, because of the angle between > the two. You would have to measure the angle and apply some trig to get > the right value. Mike Cotton's boat was the one I was referring to in my > email above. > > Gary > > ~~~~~~~_/)~~~~~~ > > > On Thu, Aug 2, 2018 at 6:31 PM, Josh Muckley via CnC-List < > cnc-list@cnc-list.com> wrote: > > The manual says limit to 4125lbs and then says absolute max of 5000lbs. > https://drive.google.com/file/d/0B8pEh5lnvP1ySXFBdDhrX0ZaMzNna > zViYkZzRVRoODlSSUd3/view?usp=drivesdk > > I never considered that the hydraulic pressure psi could/would be > independent of tensile load. When I had my hydraulic pump rebuilt by Lew > Townsend he tried to adjust the relief valve but mine adjustment knob was > seized. He gave up and just hydro-tested it anyway. He found that the > relief was roughly 3500. I rarely go over 2500. Now that I have to > consider the corollary between psi and lbs I'll be pulling out my Loose > tension gauge and get back to you. Since it is split I'll remember to add > together or double a single. > > As for the attachment to the transom, I agree it does seem slightly poor > engineering. In fact when we were shopping around the first boat looked at > wad named Blue Pearl and had been owned by Mike Cotton who was and may > still be on this list. It was evident that some past event had caused the > port aft attachment to separate the flat horizontal (cap) part of the > fiberglass casting from the curved (body) potion. The hydraulic pump was a > single piston and pump combo that attached between the port anchor amd the > port side of the back stay. Evidently a sheave communicated the tension to > the stbd size at the point where the single rod attached from the mast > head. It seemed as though maybe the sheave didn't roll smoothly and failed > to split the tension evenly between the port and stbd anchor on the > transom. That of the fiberglass layup was uneven and the port side was > just coincidentally weaker. > > I was attentive to this weakness when I continued shopping and found Sea > Hawk. I discussed the issue with the PO and he showed his engineering > answer. > > https://drive.google.com/folderview?id=0B8pEh5lnvP1ybDFIZ0ZZTU1XdHM > > I'm not convinced that it is "correct" but it is certainly better than > nothing. I had decided years ago that I was going to engineer a > reinforcement of my own with some G10 FPR. I still have the G10 but have > never acted on the project. My idea was to back the entire corner of the > transom with 1/2" G10 FRP by epoxying it in place and then fill the > attachment cavity (the bump out) with epoxy. Longer u-bolts and a spade or > mortise bit to countersink a flat load bearing "pad" for the washers and > nuts to drive against and I would be done. > > Josh Muckley > S/V Sea Hawk > 1989 C&C 37+ > Solomons, MD > > > > > On Thu, Aug 2, 2018, 5:53 PM Gary Russell via CnC-List < > cnc-list@cnc-list.com> wrote: > > Does anyone know the maximum back stay tension allowed on the C&C > 37+. My problem is the hydraulic back stay adjuster pressure gauge has > failed and I don't even know what the maximum pressure spec allowed is, > anyway. I'm concerned that at least one owner has had the attachment > points on the transom fail presumably due to excessive tension/pressure. > Frankly, the attachment points don't instill a lot of confidence as there > aren't any backing plate; just a couple of holes drilled in the hull. I'd > feel more comfortable putting a Loos gauge on the wire and calibrate the > extension of the back stay adjuster to it. Any thoughts / ideas out there? > > Live Slow / Sail Fast, > Gary > S/V Kaylarah > '90 C&C 37+ > East Greenwich, RI, USA > ~~~~~~~_/)~~~~~~ > > _______________________________________________ > > 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 > > > > _______________________________________________ > > 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. 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