When performing a rig inspection, one of the most often overlooked areas are the clevis pins and cotter pins. While some people may think of these as regular metal connectors, they are actually much more than that!
Clevis pins are metal cylinders that are made of stainless steel and fit into a hole that is a specific diameter in relation to the pin. The pin and hole are such a close fit that the sheer forces on the pin are evenly distributed and the whole assembly is incredibly strong. If you placed a smaller clevis pin in the hole, the pin would deform and break at a relatively low load, simply because the pin was being point loaded by the sides of the over sized hole.
Clevis pins have a head on one end and a hole on the other end for the cotter pin to retain the whole assembly in place. When a clevis pin is installed, it should always be installed so that the head of the pin is higher than the retaining side.
Secondly, the cotter pin should always be oriented so that the head faces up and the legs face down. The legs should be splayed around 10 to 15 degrees to ensure the pin will not fall out while trying to avoid stressing the metal legs. When the legs are over-bent, they can snap off, making it easier for the pin to fall out.
The reasons for the clevis and cotter pin orientation may seem nit-picky, but they make perfect sense when you factor gravity into the situation. Orienting the clevis pin head up, and the cotter pin head up provides many levels of safety to prevent the stay from coming disconnected.
- If the leg on the cotter pin breaks, it will be held in place due to gravity until it is found during an inspection and replaced.
- If the clevis pin rotates and the cotter pin is now upside-down; and a cotter pin leg breaks off and the cotter pin falls out or the cotter pin legs are not open enough and the cotter pin slips out: the clevis pin will still be held in place by gravity.
If the clevis pin were placed with the head down, it could easily fall out if the cotter pin were to fail. Orienting the pins with their heads up simply adds more levels of safety to the system, making the connections more forgiving in the event of a failure.
In lieu of cotter pins, ring pins can be placed to secure a clevis pin in areas where there is enough space or where the risk of fouling the cotter pin legs is high. Check stays and running back stays. are typically connected with a ring pin to avoid snagging the headsail if it rubs over the side of the mast. Lowers typically use cotter pins because it is nearly impossible to fit a ring pin between the two stays. Orienting the clevis pins so the cotter pins face each other protects the legs from snagging and fouling any lines or sails. This keeps them safely tucked out of the way, yet easy to service and inspect.
Next time you look over your rigging, be sure to take a close look at the clevis and cotter pins!