Features December 2002 Issue

Shackles

Considering some of the loads involved, it's no wonder that shackles are made to be reliable. Wichard's 'D' shackles are excellent. Tylaska makes a top-quality snap shackle, but you won't go wrong with Schaefer or Wichard.

In Nelson's time, to make a shackle, riggers first cut off a length of fat iron rod and handed it to a blacksmith, who heated it, pounded flats on the ends, and quenched it cool. 

Here's a pair of large-size Nab Shackles af-
fixed to a 5/16" Dacron line with a soft-spun
finish.

The smith may not have been aware of all the thermal work he was doing, but he was heat-treating the iron. Neither did he know that by all the hammering he was strengthening the iron... by the simple process that became known as forging.

Holes were drilled in the flats and the piece was heated again and beaten into a "U" shape against the horn end of the anvil. The smith aligned the holes so the rigger could get a good fit for a throat bolt. A quarter pirouette  changed the "U" to a wide "D", and there was another "D" shackle. They elected to call it a "D" shackle to avoid confusion with a "U" bolt.

The bolt the rigger used to close the shackle was a short piece of iron rod peened on one end to form a head, The other end was drilled to accept a wire or a tapered hardwood peg that could be pounded home. The bolt came to be called a clevis, which is believed to be of Viking origin—from an earlier word: clevi, dating from about 1600, or possibly named for an early girlfriend of Kirk Douglas. The wire that secured the bolt became a half-round, bent like a hairpin whose legs could be flared; they called it a cotter pin.

The word shackle has another altogether different meaning. One definition, of course, comes from the Middle English shakel, meaning to fetter or hamper. The word shackle is also used (or used to be used) synonymously with "shot," as in a shot of chain. This is a standard length of chain as it comes from the maker. In the British Navy it's 12-1/2 fathoms, but in the US Navy and merchant services it's 15 fathoms. Each length of chain is joined to the next by a shackle; thus a length is shackle's worth. (And surely you know how deep the water was when the kid yelled, "Mark, Twain.")

The basic "D" shackle hasn't changed much since then, except that it now comes in dozens of varieties, including the bow shackle, which is just a "D" with a bloated head radius to accept anchoring gear.

It was, strangely, a long time before the tinkerers with devilish minds made threads on the clevis pin (as the "bolt" came to be known). Then, somebody figured out that it wasn't too hard to fix the clevis pin  so it couldn't unthread itself. In fact, once the naysayers were thrown into a deep pit where they continued to chant, "That isn't right," the tinkerers discovered several ways to do it... with little dogs, tabs, double threads, O-rings, ears, and springs.

Perhaps the most noteworthy innovation has been the snap shackle, which may have been invented because skippers grew weary of watching shackles (or their pins) bounce off the deck and over the side. And now, there are a half dozen varieties of snap shackles.

Generally speaking, "D" shackles with captive pins are used by almost all sailors for main halyards, while snap shackles are used by all racing sailors and most cruising sailors for headsail halyards, because of the more frequent sail changes.

However, there are remarkable changes coming over the horizon. One of these is the "soft shackle," made mostly out of high-modulus rope. Practical Sailor is has a bunch of these in hand, and will be reporting on them in the next issue or two. In this report, though, we'll be talking about recent developments in the hard-body shackles more familiar to us. While nothing terribly radical has occurred, the fundamental need to eliminate excess weight aloft has finally taken hold at the grass-roots level, and the urge to purge even an ounce or two has brought some startling changes in the plain old verbindungsschakel, as German sailors say. Between the reductions in weight and a few new moves in materials, design, and engineering, there's plenty to mention.

For this report, Practical Sailor gathered up a lot of shackles (in various sizes). All are metal, except for the British-made, molded Delrin "Nab Shackles." These are made in two sizes, for 3/16" or 5/16" line. They're for low-load applications like light-air spinnaker sheets.

For the metal shackles, PS did no testing to verify the manufacturers' claims about strength. Even though modern line often is far more powerful than the hardware to which it is conjoined, shackles don't often break, even the extremely light stamped shackles used on small, one-design racing boats. They'll usually bend and distort first.

All were closely examined for fit and finish; ease of use; susceptibility to accidental opening; price, and weight.

"D" Shackles
In the United States, the big money players in regular shackles are Schaefer (the Massachusetts employee-owned hardware maker); Wichard (the famed French forging company); Ronstan (the predominant Australian hardware manufacturer), and Suncor (also in Massachusetts), which is gaining on the big boys.

Seen less often are shackles offered by, among others, RWO, Lewmar, and Barton (all English companies), Plastimo, (a French manufacturer with global reach) and Harken (the widely known and respected American company), as well as the "Anja" shackles (imported to the U.S. by Euro Marine Trading) and others imported from the Far East (like the Sea-Dog Line). Very light duty shackles (for one-design sailors) are a specialty of another U.S. company called Race-Lite.

The old reliable Massachusetts company, Schaefer Marine, makes both forged and stamped shackles in a good range of sizes, from a 3/16" stamped "D" with a safe working load of 1,000 pounds up to a 5/8" "D" that can stand up to 8,275 lbs.

Because the people at Schaefer believe that "breaking strength" can be a misleading term, they supply only safe working loads (SWLs), beyond which they say one should not go.

Outstanding are Schaefer's heavy-duty stamped halyard shackles. They are lightweight and have spring-loaded captive pins in the 1/4" size (SWL: 1,550 lbs.) and twist pins in the 5/16" (SWL: 2,500 lbs.). The latter weighs but one ounce.

Ronstan has an even larger line of forged and stamped shackles—from a tiny 3/16" stamped "D" with a slot-head pin (it weighs only two-tenths of an ounce) to a 5/8" standard "D" that, if the load is evenly distributed on the pin has a breaking strength of 30,800 lbs. (Any shackle suffers greatly when unevenly loaded; and they usually are.)

Although perfectly servicable, the Australian manufacturer's shackles seem, by comparison, to be less finely finished. That may account for their price, which is about half that of the most expensive shackles. Ronstan takes pride in saying, "Strong, reliable and economical."

Since Wichard entered the marine field about 20 years ago, the French company has become a major force in the shackle market. Wichard has 165 employees busily thumping away in a town called Thiers, producing extraordinary stainless steel forgings for use in medical, automotive, aeronautical, and marine applications. Wichard stainless is admired for its high polish, and it's not just for looks; the polish deters crevice corrosion. They're more expensive, of course.

Wichard has a very full line of forged shackles. It makes no light-weight stamped shackles. The forged versions include those with key pins, very snag-proof Allen-head pins, threaded captive pins, thimble ends, and Wichard's patented standard threaded "Ds." These last have two indentations at the end of the threaded portion of the clevis pin that lock the pins in place.

Wichard also offers "HR" (for "high resistance") shackles, made of 17.4 PH stainless steel or a TA6V titanium alloy (which gives racers a 40% weight saving).

Suncor is a relative late-comer (established in 1985) but now claims to have (besides a fine selection of stainless steel chain and chain connectors) the "world's largest collection of stainless and titanium shackles."

Suncor handles a dozen kinds of "D" shackles alone, including several in forged titanium alloys, plus almost as many snap shackles, with about half of them available in titanium.

Also the maker of three kinds of stainless steel anchors, Suncor is rapidly expanding its line of deck hardware, some of it patented designs and all of it reasonably priced.

Ordinary shackles are not expensive, and comparing prices by characteristics is a bit difficult. Consider, for instance, the matter of strength, which is the most important selection factor. Schaefer uses "safe working load." Suncor uses "working load limit," and Wichard and Ronstan use "breaking strength." We prefer the way Schaefer and Suncor set their limits, but in any case we have no reason to doubt the engineering statements of any of these manufacturers. No sailor would want to press the limits of a shackle, and no manufacturer wants to face the loss of reputation and, quite possibly, litigation that might follow a failure or two below the stated safe limits. Thus, shackles tend to be over-engineered across the board.

An actual price comparison would run like this: From the "Pacific Rim" (as offered in the Defender catalog), a plain loose-pin "D" shackle with a 1/4" threaded pin (shackles are sized by pin diameter) and a breaking strength of 760 lbs., costs but $3.29. The same size from Ronstan, with a breaking strength of 3,080 lbs., costs $4. Suncor sells a similar 1/4" shackle with a working load limit of 750 pounds for $5.99. Schaefer's 1/4" loose pin forged model is about $7. It has a stated safe working load of 1,000 lbs. The equivalent Wichard costs $7.50, and has a breaking strength of 3,525 lbs.

Snap Shackles
For snap shackles, Gibb (British); Ronstan (Australia); Sparcraft and Wichard (both French), and Schaefer and Tylaska (representing the United States) are the heavies in the game.

In the smaller sizes, Ronstan has a good and very reasonably priced line of standard snap shackles, plus its uniquely articulated trunnion shackles, which tend necessarily to be on the heavy side.

However, the very strong Wichard shackles and the very soundly made Schaefers seem to be dominate.

For big boats, the snap shackle roost was ruled for years by Sparcraft and Gibb, both in the medium-sized pin-lock versions (Sparcraft's Presslock was "it") and in the big trigger release models. Sparcraft and Gibb were the best on the market... and they're still very servicable. However, both makes tend to appear indifferently made, especially when compared with the well-engineered shackles being produced by Wichard and Tylaska.

Introduced several years ago, Wichard's "Quick Release," which opens with a tug on a lanyard, is outstanding. Wichard also offers the only forged trigger-operated shackle. Made in three sizes, it appears to be—size for size—the strongest trigger-release snap shackle made.

For big boats (and big bucks) Tylaska shackles are the ultimate. Tim Tylaska, an engineer who has a PhD in theoretical kinematics, has made an art, science, and career out of snap shackles. Looking for the geometry that cancels out tremendous loads when released, it was, for him, a matter of inclined planes, friction angles, surface characteristics, etc., all combined using vector calculus. He patented his work, made scores of prototypes, and became a student of machined, forged, and cast materials (settling finally on 15-5PH investment castings). He tested them almost endlessly, and emerged with what he calls J-Locks and the T-series snap shackles. Tylaska J-Locks are sleek, beautifully made, easy to use, and expensive. They have keyway-fitted double-locking pins (another patent) that are guaranteed not to flog open. The three sizes go at discount for $70, $75, and $92.

The snap shackles, all trigger-operated, come in five sizes, with standard or large bails. To get the precise shape needed, Tylaska uses castings, which generally are inferior in either strength or precision to forgings or machined parts. So, because it's always possible to get a flaw in a casting, every piece is proof-tested to half of its rated breaking strength before going out the door.

How about snap shackle prices? Looking at standard bail, swiveling snap shackles, a Nicro/Ronstan with a safe working load of 1,250 pounds is $26. A small-sized Schaefer with a SWL of 2,250 is $43. A comparable Wichard is a bit more, but has a safe working load of 2,645 pounds. A Wichard Quick Release goes for $60. A Tylaska discounts for $81, but has that one-hand trigger release.

The Bottom Line
Selecting "D" shackles is like voting in Florida—confusing enough to dimple your chad. There's a clear choice between manufacturers like Schaefer, Wichard, Ronstan and Suncor, but it's often a strength/price decision. Suncor is making some fine hardware at prices that come close to matching those of Ronstan. And Schaefer  shackles are good examples of this old company's very reliable products. However, in the final run-through, the strength and fine corrosion-fighting finish on Wichard's forged shackles, plus their smooth, snag-free captive pins make them worth the higher cost. Ronstan and Schaefer are the Best Buys.

For snap shackles, there's no question. For their excellent strength/weight ratio, Wichard and Schaefer are the Best Buys, while Tylaska's J-Locks and trigger snap shackles are the downright ultimate.

 

Also With This Article
Click here to view shackle photos.

 

Contact - Barton (IMTRA), 508/995-7000, www.imtra.com. Euro Marine, 800/222-7712, www.euromarinetrading.com. Gibb (Navtec), 203/458-3163, www.navtec.net. Harken, 262/691-3320, www.harken.com. Lewmar, 203/458-6200, www.lewmar.com. Plastimo, 866/383-1888, www.plastimousa.com. Ronstan, 727/545-1911, www.ronstan.com. RWO, 770/945-0564, www.rwo-usa.com. Schaefer, 508/995-4882, www.schaefermarine.com. Sea-Dog, 425/259-0194. Sparcraft, 401/683-0164, www.sparcraft-hardware.com. Suncor, 781/829-8899, www.suncorstainless.com. Tylaska, 860/572-8440, www.tylaska.com. Wichard, 800/852-7084, www.wichard-usa.com.

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