Hi Josh,
Were you able to get the hydraulic ram displacement vs. back stay
load? That would help those of us who don't have a working pressure gauge.
Gary
S/V Kaylarah
~~~~~~~_/)~~~~~~
On Fri, Aug 3, 2018 at 5:28 PM, Josh Muckley via CnC-List <
cnc-list@cnc-list.com> wrote:
> 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/1B6F6OQU8b7L5tVgvvWKViQHS5UVL1
> Srx6HV7xPKRC40/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/0B8pEh5lnvP1ySXFBdDhrX0ZaMz
>> NnazViYkZzRVRoODlSSUd3/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
>> ~~~~~~~_/)~~~~~~
>>
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