Mechanical Rigging Terminals: To Seal or Not

Posted by Darrell Nicholson at 01:35PM - Comments: (4)


photo by Ralph Naranjo
photo by Ralph Naranjo

A polyurethane sealant is applied to the wires and internal components of a Norseman fitting prior to assembly.

Technical Editor Ralph Naranjo’s recent market survey of mechanical rigging terminals in the June 2015 issue of Practical Sailor demonstrated just how long these terminals can last if they are installed correctly. That report came close on the heels of rigger Brion Toss's photo essay on what can go wrong if they are not assembled correctly, or assembled without any sealant.

What is interesting is that some of the makers of mechanical terminals do not make it entirely clear on where they stand with regards to sealants. Some recommend using a caulk or sealant, but don’t specify the type—and as we know from our previous sealant tests, there are many.

One company, Hi-Mod, advises that installers use Loctite 262 or a similar thread-locking compound to prevent galling. Hi-Mod makes no mention of using a sealant in the installation guide. StaLok, on the other hand, advises that the terminals be sealed, and Sailing Services, a Miami Rigging company who has consulted PS in the past, suggests Life Calk. The Sailing Services website offers a detailed description of the StaLok installation procedure.

Naranjo, who used both a polyurethane sealant and Loctite on his sloop Wind Shadow, recently had an opportunity to examine the results after years of marine exposure. The photo below shows a Norseman fittings that Naranjo installed nearly a decade ago. Although there is some rust staining at the wire ends, it is minimal. Now compare that photo to the one of corroded fittings that Toss photographed for his report.

photo by Ralph Naranjo
photo by Ralph Naranjo

Upon disassembly, mechanical fittings installed nearly ten years ago on Technical Editor Ralph Naranjo's Ericson sloop showed very little corrosion.

If you need more details on how and where you apply the sealant and the thread-lock during installation, Naranjo describes the process in a step-by-step description of installing a mechanical terminal for wire rope accompanying his market survey in the May issue.

Currently, we don’t have much data on how well a “sealant-free” Hi-Mod installation will hold up in the marine environment (some riggers add sealant anyway). Why advise against a sealant? One concern we’ve heard is that a strong adhesive sealant will make it hard to disassemble for inspection. We have not found that to be case—except with 3M 5200 (which interestingly does not adhere well to stainless steel).

There is no question that a thread-treatment such as Loctite 262, Loctite 242 is necessary. This is good protection against galling, a common affliction for any stainless fitting that is under load. As far as the use of a sealant goes: in our view, a sealant (used correctly) offers good insurance against water intrusion in a saltwater environment. We would recommend it regardless of brand of terminal you use. 

Many riggers prefer silicone sealant, but aboard Wind Shadow, polyurethane sealant worked well. Sailing Services recommends Life Calk; the polyurethane sealant 3M 4000 UV is also excellent, as it adheres better to metal than other sealants. We do not recommend 3M 5200.

Comments (4)

In 1994, I rerigged my Gulfstar ketch using 316ss, one 32nd larger than the original 304 wire, and used Stalock fittings with Lifecaulk sealant. Over the years of cruising, I have had occasion to open fittings for one reason or another, and once an overall look at all of them. So far, no rust problems in any fitting, or at wire ends. I changed the cups each opening, and a former or two, otherwise its all the stuff I installed in 1994; One exception, the forestay was replaced in 2013, from wear damage where the roller furling abraided it at the top.

I carry extra toggles in the event I need to shorten an end. So far not. I do shoot WD-40 into the top of the lowers on a regular basis. It may impair the caulk, but seems to drive any non-oxidized water from the inside of the fitting. I think it is probably impossible to completely seal the wire ends with caulk, since it will not readily flow into the spaces between the individual wires, and yet the WD-40 flows in more easily than water.

Posted by: William N | May 26, 2015 9:48 AM    Report this comment

Any concerns about rust staining re unwarranted. Such staining is probably due to transferred iron from the tools used to cut the wire and/or assemble the fitting. Most commercial 304 stainless parts go through a iron removal (electro-polish or passivation) to remove transferred iron from the manufacturing process. That can't be done at the assembly step in the boat yard.

Posted by: Ed C | May 23, 2015 7:14 PM    Report this comment

I only sealed the very end of cone before tightening .

Posted by: john r | May 22, 2015 3:19 PM    Report this comment

This right after I installed a Hi-Mod terminal on my fresh water boat. Seeing as I'm in fresh water and I used Loc-tite to lock the threads, I think I'll be ok. I'd probably take it apart and seal it if I were in salt water.

Posted by: james s | May 20, 2015 1:50 PM    Report this comment

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