PS Advisor December 1, 1999 Issue

PS Advisor

That Slippery Shock Cord
Can you recommend a knot to be used successfully with shock cord?

Marv Sannes
Salem, Oregon

Shock cord is tough to tie. It has a tendency to slip out of its skin like a snake. That’s especially true of the new varieties that have a braided synthetic cover. Shock cord (a.k.a. bungee cord) used to have cotton covers, which were much less slippery.

Whatever the cover, the rubber strands under the cover tend, when stretched, to crawl free of any knot.

You can eliminate or minimize that crawling by starting with a simple overhand knot in the end. A Granny Knot is another name. Pull it tight.

Then, if attaching to a padeye or ring, use a bowline. If using an eye strap, just use the Granny. If the Granny isn’t big enough, use a Figure 8 knot, as on the ends of your sheets.

If a loop or bight is needed—meaning that the shock cord is doubled back on itself—a bowline will do. If you want the loop to draw down tight, use a common slip knot and pull it hard. If a thimble is used, use a really tough sewed whip made of waxed line or cotton line (which you can shrink on with hot water).

In most cases, the Granny knot in the end keeps the shock cord from working free of the various bights. Any doubt about it, apply a piece of tape near the end and tie the Granny right on the taped portion.

There are various shock cord end fittings—from the one-piece nylon moldings with a hole for the shock cord (which must then be knotted) to the two-piece cylindrical types that often have “teeth” or a slip ring gripping feature. There also are stainless steel hooks with decreasing diameter coils for holding and what are called hog rings (the crimp-on hogrings are cheap but the pliers needed to apply them cost more than $20). The metal fittings, whether ss or the abominable plastic coated versions, never have seemed very desirable.

For peanuts, you can make a shockcord loop (for keeping idle halyards off the mast) with a piece of dowel with a hole drilled for one end of the shock cord and a simple bowline loop in the other. Ronstan makes a plastic molding that makes up to a handy adjustable loop; it’s in the West Marine catalog. The BOAT/U.S. catalog has a new line of Starbrite cord and end fittings.

Gelcoat Stink
In 1996 I reinsulated the icebox on my 1977 Northern 29, installing refrigerator-type foam panels and covering them with a skin of fibreglass mat and two layers of gelcoat. The new materials had to be added to the inside of the unit. With a new 12VDC E-Z Kold holding-plate fridge, the new insulation and a somewhat reduced size, the improved icebox works very well. Except for one problem. Even after three years, the gelcoat continues to off-gas. The fumes permeate food unless it is stored in Tupperware-type containers. Any solutions to turning off the gas? The factory icebox liner was also fiberglass but fumes were never a problem. The new gelcoat appears to be fully cured (no tacky spots) and I have cleaned it many times with soaps, vinegar, etc.

At this point, I am considering relining the icebox with ss sheets. But would the fumes sneak by this tactic?

Mike Patton
Toronto, Ontario

One solution is to post cure the gelcoat by applying heat to it. You might be able to elevate the temp inside the box with a heat lamp. Most resins do not fully cure at room temperature, at least quickly, though we would have thought that after three years all of the molecule chains would have cross-linked. Maybe not in your case.

We doubt that a stainless liner will be odor-proof, so you might have to consider some sort of paint or film, but their effectiveness in masking odors is also problematic.

In addition to fiberglass and gelcoat, paints and adhesives can also be causing odors…check around.

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