Telltale Article - by George de Witte.
This short maintenance article was inspired while I was volunteering last year with the mast-stepping day on the Sunday following launch. It struck me that a lot of the boat owners are not aware of the process of cold welding and the destructive effect it can have on your expensive turn buckles and rigging screws.
So what is Cold Welding? Most of you may think that welding two pieces of metals together involves a high temperature acetylene/oxygen flame that sort of makes a molecular bond between the two parts. It makes intuitive sense: the two metals parts to be joined are heated until the metal flows and then fuse together when they cool off. However there is also a process called “Cold Welding”. It was first recognized in the 1940’s.and today is used extensively in the semi-conductor and aerospace industry. Cold welding happens when two materials are brought in contact under high pressure or vacuum without the application of heat. So two metals can make a molecular bond without heat if enough pressure is applied. This is really all you need to know from a boating perspective.
Most masts on a sailing boat are held up by a system of stainless steel wires called shrouds and stays. With the exception of serious racing machines, these wires are tensioned by turn buckles. These turn buckles have a right handed thread rigging screw at the top and a left handed one at the bottom and turning the buckle results in tensioning the wire. This is where the Cold Weld can happen. I have seen in many instances where if the turn buckle binds before the desired tension is achieved, the keen owner disappears down below to return with a bigger screw driver and wrench. DONT EVEN THINK OF IT. You are about to achieve a beautiful Cold Weld between the rigging screws and the turn buckle. If you do a good job, the thread on both rigging screws and the buckle first get welded together and if you keep going the thread on both parts of course gets stripped. By now the only proper recourse is to replace all parts. In other words a trip to the nearest rigging shop and a dent in your bar budget.
So in order to avoid all this potential damage to your turn buckles I recommend you take the following steps:
- Before stepping the mast remove the Turn Buckles completely
- Clean the rigging screws (both ends) with a regular solvent like paint thinner
- Step the mast
- Just before connecting the two rigging screw ends with the buckle apply a small amount of water proof grease to the screw ends and then start tensioning the rigging wire with the buckle
If all is done properly, the Turn Buckle will tension nice and smoothly and as an added bonus the two rigging ends will have a symmetric penetration in the buckle. For water proof grease I recommend Silicone or Lithium grease, both of which are easy to find in an automotive supply store.
It is most likely that you forget to follow my advice. However if on masting day you find yourself with a binding turn buckle, don’t over torque it. Remember the Cold Welding theory. If the screw penetrates 4 or 5 turns, it will hold the mast up for the time being and you can vacate the masting crane before your time limit expires. Afterwards you can deal with your negligence. You have to be careful what you do, but you can remove a turn buckle at the time using a halyard if necessary as temporary stay or shroud.