Mechanical Rigging Terminals: To Seal or Not

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photo by Ralph Naranjo

Technical Editor Ralph Naranjos 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 dont 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

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 dont 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 weve 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.

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