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" longThe 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?)
GaryS/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/0B8pEh5lnvP1ySXFBdDhrX0ZaMzNnazViYkZzRVRoODlSSUd3/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 MuckleyS/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,GaryS/V Kaylarah'90 C&C 37+East Greenwich, RI, USA
~~~~~~~_/)~~~~~~
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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
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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
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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
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_______________________________________________
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
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