Have you ever heard the old axiom “Righty-Tighty, Lefty-Loosey”? You probably have. Anyone who knows which end of a hammer to use has probably used this little ditty to help them remember which way to turn a wrench or screwdriver. It applies in almost all situations where a threaded fastener is being used. That is until you board a sailboat.
Left-hand threads are very common on sailboats, which can be confusing to the uninitiated. Follows is a short primer on the left-hand threads on your boat.
A critical part of a sailboat’s rigging is the turnbuckle, used for adjustment and the maintenance of tension of shrouds and stays. Almost all the sailboats built in the U.S. use a turnbuckle with a right-hand threaded stud at the top and a left-handed threaded toggle at the bottom.
Many older boats built in Europe have just the opposite using a metric, left-hand coarse thread at the top and a metric, right hand coarse thread a the bottom. More recently European builders have jettisoned the metric coarse threads and now use the same turnbuckles as U.S. builders do. This can also be confusing as they are still using metric sized wire with imperial sized turnbuckles.
In the good old days lifeline studs on a boat would all be left-hand. Today there is a movement towards right-hand studs but the manufacturers are still producing plenty of both right and left-hand fittings.
Fun Facts about Left-Hand Threads
Decades ago many cars had left-handed lug nuts on the left hand side of the vehicle
Some people credit the Wright Brothers with inventing the left-hand thread as a way to keep the left side pedal of their bicycles from coming unscrewed while pedaling.
Snails, including sea snails and freshwater snails have sprially coiled shells that are mostly right-hand. Some snails have left hand shells but only a very few species have examples of both.
How to tell the difference
Hold the stud straight up and look for the direction of the thread’s slope. The left-hand thread will slope up to the left and a right-hand thread will slope up to the right. A right-hand threaded stud will tighten as you turn it clockwise into a turnbuckle (Righty-Tighty!), just like a light bulb. Unless the light bulb in question came from the London Library where, for a time, they used left-handed light bulbs to discourage pilfering. One wonders how many thieving bibliophiles made home only to be disappointed that their ill-gotten bulbs wouldn’t screw in.
What does it all mean?
It means that when replacing sailboat rigging or lifelines the direction of the thread is very important. Be sure to identify the direction of the threads when ordering new rigging or lifelines. If you have questions or need help identifying some threads please let us know!