Stainless steel failures raise voyager's concern
From Ocean Navigator #122 May/June 2002
Two of the failed stainless steel shroud turnbuckles. Analysis by a Lehigh University engineering professor found pits and checks in surface of the units, possibly leading to crevice corrosion.
My own experiences as a long-range sailor and commercial scuba diver reinforce this concern. Two different aspects of this experience are worth mentioning here.
In summer, 1986, I took delivery of a new 41-sloop in Houston that I named Laphroaig. During the second year of sailing this vessel, turnbuckles in the main rig broke under strain of normal sailing conditions. Enough of these "stainless steel" castings/forgings broke over a short period of time for me to complain to the local dealer, even though the initial one-year warrantee had expired. The company agreed to replace the original units and shipped me a full set of 10 turnbuckles directly from its factory.
I kept the old units, but replaced them with the new ones, which appeared to be identical. There were no further incidents, and I assumed that I had had a bad batch the first time.
About six years later, while single-handing on an overnight offshore trip along the New England coast, I heard a loud bang that seemed to come from somewhere forward. We were in moderate seas in good weather with winds from the southeast at about 13 knots. The boat was handling well under full sail, nearly 900 square feet, with the main and a 135 percent genoa pulling us along at about 7 knots. Locking the wheel down, (I did not have an autopilot), the boat held the close-hauled starboard tack; I moved forward and began to inspect the rigging.
After some time of checking with a flashlight, (and thus destroying my night vision), I found that one of the four starboard shroud turnbuckles had partially fractured. One side of the oval frame of the center threaded unit had broken about a third of the way up. The other side was still intact and thus, the turnbuckle had not totally separated.
Laphroaig is a masthead sloop with two sets of spreaders on a 51-foot aluminum mast. The broken shroud turnbuckle was one of the units I had replaced. Unlike most turnbuckles of its size, it did not have the center horizontal crossbar to strengthen the forging and set the space between the side bars. Nevertheless, only one side had fractured, leaving the stay attached to a broken oval of stainless steel. This was exactly the kind of break I had seen in the earlier units.
After tacking and shortening sail, we continued on until dawn, when smoother seas and lighter winds allowed me to swap the turnbuckle for one of the older ones that I'd kept as a spare. This served well enough for the rest of the voyage.
Following this incident, I had all of the broken turnbuckles inspected by a metallurgical engineering friend at Lehigh University, and his take was that there were several possible problems:
· The metal was crystallized at the point of the failures on each broken unit.
· The finish on the broken units was irregular and imperfect. Grinding and polishing of these units was irregular, and there were pits and checks in the external polished surface.
· The inside areas of each unit were extremely rough and unfinished.
· The broken units appeared to be stressed beyond their design loads.
· The quality of the metal was less than perfect.
· The lack of a crossbar in the center of the open section indicated that the unit probably had a design flaw that made breakage easier.
I did not have the material analyzed. All of the factory-made stainless steel parts onboard became suspect and were replaced over time. As we removed them, we continued to find that the parts and materials were of lower quality than those produced by other sources. For that reason, I replaced nearly all of the running- and standing-rigging parts that had the maker's imprint on them. I did this only after other running-rigging parts failed as well while under strain, including a snap shackle and blocks on the main sheet. All failed units exhibited the same characteristics of crystallized metal and imperfect finish.
My second case of suspect stainless steel is based on a series of inspections of several very new power vessels in the same marine environment. These were all 25- to 45-foot-LOA pleasure boats priced in the $100,000 to $500,000 range and made from what were purported to be top-quality materials. In each case, we found telltale brown stains and oxidation on the surrounding hull near key through-hull bolts. Usually these bolts secure outdrives, shaft struts, rudder fittings, swim platforms and other vital structures to the hulls.
Further inspection by dealers and maintenance crews found, upon removal of these bolts, they were rapidly breaking down despite stamped imprints on the parts that indicated the materials were of a high quality. The conclusions reached in each case were that the materials were sub-standard in terms of strength and corrosion resistance.
It is also appropriate to observe that suppliers for much of this stainless steel material are not based in the United States or Canada and not subject to, nor especially interested in, meeting industry specs as precisely as they should be. As more and more materials originate in the Far East and third-world nations, quality and reliability can be expected to decrease. Manufacturing and quality controls that we once took for granted no longer exist, and small boat builders do not, as a rule, have shipments of such materials analyzed. Price being the primary concern, this problem is not going to go away.
Because Laphroaig is a pleasure, non-racing vessel and has spent more than two thirds of her years in the tropical saltwater environment, about the only thing an owner of moderate means, such as myself, can do is constantly check fittings and rigging, watch for stains and small imperfections, carry spares and be prepared for failure when it comes. This may sound unduly cavalier, but I don't see much other choice, short of analyzing every critical metal part I buy and arguing with sellers about quality they don't control. I remain astonished, though, that given the price of a new boat today, manufacturers continue to use stainless materials of less than top quality and that no universal standard has been or can be applied to such critical hardware.
Jeff Stives is a sailor, freelance writer and scuba diver living in Vero Beach, Fla.