My wife, Gail, and I recently installed a new radar antenna on the keel-stepped mast of our Bristol 38.8. The first part of the installation was easy. We mounted the receiver and then, using a weighted string as a messenger, pulled the cables through a small hole in the mast near the unit all the way down to the bottom, The difficult partfiguring out a way to keep the cables from slapping against the inside of the mast when the boat rockedcame next. It was also an essential part; mast slap could, Gail intimated, very well end our cruising life together.
My first idea was to install a cluster of wire ties every foot or so along the cable, but it didnt work. I should mention that the traditional solution is to take the mast out of the boat, then run the cables through PVC pipe and attach the PVC to the mast with rivets. This can be an expensive undertaking; the cost can easily exceed that of the new radar set. In fact, the estimates we received ran several thousand dollars.
I was aware of problems with this arrangement. One is that the tubes can come loose, making the problem much worse; it happened to at least two boats weve met in our travels. A second problem is that its a one-shot fix; in most cases you cant install any additional cables without running more pipes. Many of our cruising friends had decided they would live with the noise, but that wouldnt work for us. Finally I came up with a solution I think is robust, can accommodate additional cables, and, best of all, took me only half an hour to install. I might add that it looks pretty professional.
The parts I used were a #8 threaded stainless-steel rod about 20 inches long, a small stainless eye strapany finished metal backing plate would workabout 2 inches in length, some washers and nuts, and two Nyloc cap nuts. I bent one end of the rod into the shape of a rounded U-bolt and made sure the final shape would fit in the holes in the eye strap. I then wrapped the threads of the bolt with electrical tape to prevent chafe.
I experimented with various U shapes until I got one that would hold the cables snugly against the inside of the mast. Its important that the rod not grab the cables too tightly because they could be damaged when the locking nuts on the outside of the mast that secure the rod are tightened. As with a PVC installation, the cables can move a little without making noise. Depending on the mast section, it may be helpful to make a template of the mast section and use it to create a shape that will provide the proper clearance for the cables after the locking nuts have been tightened.
Shaping the stainless rod is pretty straightforward; I heated it to red hot with a small butane torch before I bent it. If you dont, it will break. Next, using the external eye strap as the template, I drilled two small holes in the mast and then fished the U-bolt section of the rod into one of the holes. Heeling the boat slightly made it easier to hook the problem cable; I held onto the long end of the U-bolt while I maneuvered the short end of the U-bolt back out through the second hole in the mast.