The term "shop brass" usually refers to a low-quality, copper-based alloy that can be made on-site in many production facilities. After doing some research on various copper alloys referred to as "bronze," I was disturbed to discover that few of the industry-standard alloys are marine-grade bronze. Marine-grade is made up of the classic alloy of copper and tin, which should be used in a marine environment.
The marine-grade bronze is intentionally devoid of zinc, since copper and zinc immersed in salt water makes a fairly good battery. The zinc can decompose in the marine environment, weakening the bronze bolt, screw, or plug. The bronze can also decompose, which is a sinking hazard. Since many yacht yards cast fittings that are particular to their specific boat models, the customer may be at the whim of the yacht yard as to what the bronze contains.
My Uncle Charlie purchased a brand-new Cheoy Lee, Luders-designed Clipper 36. This Ketch-rigged sailboat was a beauty: teak decks, black fiberglass hull, teak taffrail around the cockpit, wooden masts, a wooden bowsprit (complete with "Dolphin-striker"), and lots of chrome-plated bronze fittings that were made right at the yacht yard in Hong Kong. As you may guess from the description, these bronze fittings might be more properly described as "shop brass," since no one independently tested the alloy to ensure it was really fit for marine use.
After a day of sailing in late September, my uncle anchored and tucked in for the night. About 2:00 a.m., he awoke to a rather odd series of noises. First, there was a series of creaks, then a scream of tearing metal, followed by another loud noise. The rigging of the sailboat started reverberating after receiving a huge jolt.
My uncle turned on the spreader lights and went up on deck. He found that the bobstay that fastens the bottom of the bowsprit to the hull had detached from the hull. The entire 800 pounds of rigging was hanging from the eight-foot-long bowsprit, which was arched up about 12 inches at the end. Luckily, it was laminated into the decks and hull, or else the mast would have come crashing down, with potentially deadly consequences.
After motoring rather gingerly the next day, my uncle was able to get some assistance with repairs. Further analysis determined that the failed fitting was made of a bronze that was not sufficiently strong to hold the huge amount of stress that the wind on the sails would cause. It was not assayed to determine the exact alloy, but it was likely shop brass. Today, it is likely that this fitting would be made of stainless steel. Any experienced yachtsman knows that there are issues with stainless as well, but that is another story.
This entry was submitted by Dwight Bues and edited by Rob Spiegel.
Tell us your experiences with Monkey-designed products. Send stories to Rob Spiegel for Made by Monkeys.