Visit our Popular Forums

Whimsy · 09-07-2011, 21:12

Met some Sea Scout folks this afternoon (seems to be 3 adults and one teen) prepping a newly acquired 1969 36' Columbia sailboat for delivery back to their home port. The boat is on stands in the marina yard. They are apparently volunteers, are several hours drive from their homes, and have been working long hours out in the heat for many days to get the project done, sleeping on the boat or wherever.

The stick was down and all but a couple of the OEM Merriman bronze 1/2" turnbuckles/rigging screws were missing on the project as they received it, possibly stolen.

They had some new 1/2" SS turnbuckles on hand to use but were concerned if they would be adequate. I offered to seek the advice of this most excellent forum regarding the matter as they have limited web access and time.

The units they have are marked QHM and I have found this picture and spec sheet:
http://www.qmh-inc.com/products/0803.asp
This shows a SWL of 1800#. What is "SWL" (standard working load?)?

A spec sheet for another "Economy" SS turnbuckle that appears of somewhat similar construction: http://www.bosunsupplies.com/products2.cfm?product=s0105
Shows a WLL of 2200# for 1/2" unit. What is "WLL" in this context?

So far I have no luck finding specs to compare on the Merriman bronze 1/2" turnbuckles (Merriman is out of business), or any other 1/2" bronze turnbuckles. Hayn makes some but they don’t seem to publish specs.

Whether these QHM SS units would be unsuitable in any case, would suffice for awhile but should be replaced soon, or if they are fine for the long run are concerns they may be interested in having addressed.

I'm sure any comments or advice would be appreciated and I'll pass it on to them ASAP.

Unicorn Dreams · 09-07-2011, 21:27

Go to Discount Marine and Boat Supplies - Inflatable Sales - Defender , they always give specs on their rigging components..

Amgine · 09-07-2011, 21:54

SWL = Safe Working Load
WLL I'm not sure about, but may be Working Load Limit?

ShaunJ · 09-07-2011, 22:14

Its a great thing you are doing, Helping the Sea Scouts.... that's how I started sailing mini fish's.... I hope all goes well

**Adelie** · 09-07-2011, 22:29

I looked at the strengths of bronze and stainless and didn't come to much of a conclusion. There are 2 pretty common grades of stainless, 304 & 316, used in marine applications. There are a plethora of bronzes, and I don't know which are used in marine applications.

The better way to go, analytically is to check the wire size for the shrouds, or better yet the forestay which should be the largest wire on the boat. Using that size and assuming, 304 stainless, you can look up the SWL (Safe Working Load) of the wire and buy turnbuckles to match. If you don't have a micrometer this would be hard to get right.

The empiracle method is to go around to all the chainplates and the swaged eyes on the wire ends and find the largest clevis pin that will fit in each. You may have several sizes so you need to keep track of how many of each size there are. Be careful, some of the holes may be elongated or slightly oversized. The best thing to do would be to match each wire end with each chainplate and whichever has the smaller pin will be the size you want for the connecting turnbuckle. It would probably be worthwhile to color or scratch numbers in the different sized pins you use to test to help keep track of them.

Take the pins you have used to size the eyes and chainplates and use them at the Chandlery to figure out what turnbuckle size goes with each size pin. Use the highest strength turnbuckle that just barely fits each pin.

daddle · 09-07-2011, 22:45

Generally bronze turnbuckles are the GOOD ones. SS being the cheap ones that gall and jamb.

If you stick with turnbuckles from a marine catalog and don't screw around with non-standard pin and wire sizes you can assume it's already been worked out. That is, if you have 1/2" screws on the wire a like sized turnbuckle body in a rigging catalog will be fine.

Whimsy · 10-07-2011, 05:56

Quote:

Originally Posted by Adelie

...check the wire size for the shrouds, or better yet the forestay which should be the largest wire on the boat. Using that size and assuming, 304 stainless, you can look up the SWL (Safe Working Load) of the wire and buy turnbuckles to match. If you don't have a micrometer this would be hard to get right.

Thanks for the replies thus far.

I had considered cross-checking against the working load of the wire, and will go to the marina later this morning, when I can, with a digital caliper, a decimal-to-common fractional size conversion chart I already have, and a working load spec sheet for rigging wire I will try to dig up on the web.

Your reminder that the forestay is likely of a larger size (Thanks much!) brings to mind this idea:

They might use the two remaining bronze OEM turnbuckles for the more concentrated loads - forestay and backstay, then using the new SS units for the shrouds, which it seems tend to divide the loads among more wires, and where where the failure of any one unit may possibly be less catastrophic.

Any advice or comments on this idea would be appreciated, as would be a link to a wire strength chart.

Whimsy · 10-07-2011, 06:12

Quote:

Originally Posted by daddle

Generally bronze turnbuckles are the GOOD ones. SS being the cheap ones that gall and jamb.

Yes, although many builders have gone to SS turnbuckles and it now seems to be somewhat of an industry standard, especially in the smaller sizes. This note I saw on a mfg spec page for SS turnbuckles acknowledges and addresses your point:

"Please Note: It is suggested that you use an ANTI-SEIZE LUBRICANT
on all stainless steel threaded fittings to prevent galling/seizing."

My next concern/topic of research in this direction would be the possible galvanic effects of copper-bearing or other metallic-based anti-seize lube used with various marine alloys. I've heard it called 'ever-seize' in some applications...

Any advice on the correct anti-seize lube would be appreciated.

PS: Does anyone still call these 'rigging screws', or was that ever correct terminology?

Unicorn Dreams · 10-07-2011, 06:30

Turnbuckles-American
Rigging Screws-British

psneeld · 10-07-2011, 06:55

WLL - working load limit maybe?

Can the turnbuckle idea altogether and use lashed eyes like in the old days. Sea Scouts should go back to basics and be taught to think outside the box. I was in scouting for many years as a leader and it seemed like very little effort was being made to make scouts "think" which included doing their own research in prep for trips or projects.

An outside the box suggestion I would make is have a scout or two contact a local (or distant by email) engineering /naval architecture firm and have them present their problem. Most professionals I have worked with will volunteer a SMALL bit of time to help in cases like this. Suggesting the right thread size based on material should be a "small" amount of help they may be glad to assist with.

I believe there is a Never Seize that is specifically used for marine applications. We use OMC gasket liquid. Comes in a bottle with a brush. We screw/bolt a lot of SS hardware to/through aluminum on our workboats and without this or some antisieze...the stuff welds itself together. The OMC goo works well because it never hardens and keeps moisture out like the antisieze and it's redily available around our area.

Whimsy · 10-07-2011, 08:12

Quote:

Originally Posted by psneeld

...there is a Never Seize that is specifically used for marine applications. We use OMC gasket liquid.

Yeah, very good stuff, and many thanks for the reminder. After a marine mechanic recommended it to me years ago I use it on all marine nuts and bolts and have never had a seized bolt where it has been used, even SS into aluminum on outboards, which seem like they can seize in a year if uncoated.

Am wondering if it provides enough high-property lubricity to prevent galling in the SS-on-SS application of coarse-threaded turnbuckles where fine thread was the standard. A heavy, water-resistant marine bearing grease is may be as good as any for this app.

Whimsy · 10-07-2011, 08:35

Quote:

Originally Posted by psneeld

Can the turnbuckle idea altogether and use lashed eyes like in the old days. Sea Scouts should go back to basics and be taught to think outside the box... have a scout or two contact a ...engineering /naval architecture firm

Your 'lashed eyes' suggestion has sparked an idea that maybe eye-to-eye lashings can be made after the turnbuckles are installed - a sort of belt AND suspenders approach giving an added measure of backup safety against metal failure. I have used lashed eyes to good advantage back in the days when I could little afford 'fancy' hardware. Thanks for your input!

Yes, I agree ideally the Scouts would be tasked with the research here. I'm a volunteer tutor and mentor and place as much emphasis as possible on this 'learning to think' and 'learning to research' approach in my efforts there. But this is less about those ideals and more about adult volunteers, working long, hot hours many miles from their home port, to get this (donated?) boat home ASAP. I'm sure there will be one or two projects for the Scouts after the delivery is complete...

**GordMay** · 10-07-2011, 09:06

WIRE SPECIFICATIONS for 1 x 19 Stainless Steel Rigging Wire:

Diameter - Approximate Breaking Strength

1/8" - 2,100#
3/16" - 4,700#
1/4" - 8,200#
5/16" - 12,500#
3/8" - 17,500#
7/16" - 23,400#
½" - 29,700#

**Adelie** · 10-07-2011, 09:23

Quote:

Originally Posted by GordMay

WIRE SPECIFICATIONS for 1 x 19 Stainless Steel Rigging Wire:

Diameter - Approximate Breaking Strength

1/8" - 2,100#
3/16" - 4,700#
1/4" - 8,200#
5/16" - 12,500#
3/8" - 17,500#
7/16" - 23,400#
½" - 29,700#

I am assuming that is for 304 stainless which is the most common sold in the US.