Eliminating Cable Slap in Your MastRecently we installed a new radar on the mast of our Bristol 38.8 sailboat Star. The first part of the installation was easy. We mounted the radar and used a weighted string as a sentinel to pull the cables through a small hole near the radar all the way to the bottom of our keel stepped mast. The difficult part was how to prevent the cables from slapping against the inside of the mast which my wife told me could end our cruising life. Our initial approach was to install a bristle of wire ties every foot or so along the cable but this did not work and the noise persisted. Traditionally people take the mast down in an installation like this and run the cables through PVC pipe which is then attached to the mast using rivets. This is an expensive proposition which can easily exceed the cost of the radar. Estimates ranged from $1500 to $2000 whereas our radar only cost $1000. Furthermore the plastic PVC tube/rivet can come loose and cause a worse problem as happened on two boats that we know of. Another problem with PVC pipe is that it is a one shot fix and you cannot install additional cables – you have to run more pipe.
We talked to a lot of cruising friends we know and no good ideas emerged. Lots of folks simply live with the noise. Finally after much thought, we came to a good solution which cost $10, was installed in ½ hour, is robust, can grow easily and looks quite professional.
The parts consist of a #8 threaded stainless rod about 20 inches long, A small stainless steel eye strap about 2in wide (or any finished metal backing plate), some washers, nuts and two nyloc finish nuts. We bent one end of the stainless rod into a rounded u-bolt with a diameter of about 2 inches. The ends of the u-bolt were made parallel to each other and spaced the same distance as the holes in the eye strap. Note that working a stainless rod is straightforward if you get it red hot with a small torch before you try to bend it otherwise it just breaks. We then drilled two small holes in the mast about 2 inches apart using the eye strap as the template, and fished the u-bolt into one of the holes. It was then easy to hook the problem cable and pass the other end of the u-bolt through the second hole in the mast from the inside side out. We attached the eye strap to both protruding ends of the u-bolt with washers and nuts and drew it up nice and tight. We then cut off the excess rod leaving about ¼ inch on each end to attach the nyloc finishing nuts and we were done.
While the eye strap is not functional the results look pleasing and the cable inside of the mast is snug and will never rattle again. We only needed one strap and u-bolt on our installation, placed about half way up the mast to solve the problem. Immediately after we installed our fix, another cruiser rowed over to look at the installation. He just had PVC pipe installed and it had come loose on his first day out in rough weather. We gave him a spare rod and he was a happy camper.
Our web site at http://YachtSoftware.org describes this solution along with other fixes and software that we have developed while out cruising on Star.