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Daily Archives: April 12, 2015

Okay, I’ll admit that I don’t know exactly what to call this thing, but I know what I want it to do – what I hope it will do, if it is robust enough to do so. First, some background:

Two years ago my deck lamp was knocked out of the fixture, including the lens (I think), by an errant halyard slap in high winds. Well, that wouldn’t be too bad, except that I had just replaced it. It’s one of those two-pronged halogen 20 watt lamps, and they are sort of pricey. Not only that, but I hate going up the mast. Now I’d have to do it again! There has to be a better system. I imagined then, that some sort of cage of rods would be an adequate protection against another halyard slap. I’ve seen them on other boats, but I’ve never seen one advertised for sale, so I have no idea of availability or price. But how hard can it be to make something like that? While the mast is still horizontal and I have time before launch, I thought I would give it a try. I should be able to come up with something.

I went to the hardware store today to look for materials, and came home with 36″ of 1/8″ aluminum rod, eight stainless #6 screws, and a drill bit and tap for #6 screws.

Back in the shop I cut the rod in half and flattened the ends of the two pieces with a 3-pound maul against my closed vice, then drilled holes in the ends for the screws. I used a mill file to clean up the sharp edges.

Back at the boat, I estimated the lengths, attachments points, and the approximate locations of the bends. Without a vice on site, I found convenient places to capture one end of the rod while bending the appropriate place against a leverage point. This is what I came up with:

I managed to get one leg of the smaller piece longer than the other.  Doesn't really make a difference.  It attached to the mast without complication.

I managed to get one leg of the smaller piece longer than the other. Doesn’t really make a difference. It attached to the mast without complication, but it does bother me that the legs are not exactly the same length. . .

I located the larger piece on the mast first and marked the attachment points. Using a steel punch, I made a small divot point in the mast at each screw hole location to get a clean start with the drill bit. Carefully locating the drill bit, I used significant pressure and slow speed to start the hole (the mast is a curved section, remember? Hard to drill a hole in something like that without having the bit walk all over the place). Each hole started and finished cleanly. I cut threads into each hole with the tap, then ran a screw into it to ensure clean threads. If you never tapped a hole, it’s an interesting process. Everything is extremely low tech, except for the tap itself – which is hardened steel, tapered at the point, with the cutting threads beginning immediately. I use a small adjustable wrench to turn the tap a quarter turn at a time as I guide it into the hole as perfectly perpendicular as possible. It’s helpful to back the tap out a quarter turn after every complete turn or so, to clean the metal debris from the cutting threads.

I marked, drilled, and tapped for the second (port-starboard) piece next, then mounted both pieces with screws well bedded in TefGel. TefGel is a non-conductive corrosion inhibitor, and it allows me to use stainless fasteners into an aluminum mast without threat of galvanic corrosion. Every place I’ve used it on the mast has been completely corrosion-free since I refit the mast eight years ago.

In case you’re wondering, sheet metal screws, or self-tapping screws are an inappropriate fastener for this application. In fact, anything screwed into the mast should be done with machine screws. They have much finer thread than self-tapping screws, and hold much more securely. I like what Don Casey says about sheet metal screws in a mast: “I’ve never seen a sheet metal mast . . . ”  Point taken.

After fitting both pieces, I linked them with a zip tie, reasoning that having them linked together would give them a bit more rigidity (4 attachment points, vs 2).  Here’s the finished product:

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Nice rounded features should allow halyards to slide right off and past the light. Cost? About $10, including the drill bit/tap set. We’ll see if it does what I hope it will. Although the rod is quite bend-resistant, the fasteners could be the weak point. As long as they don’t get wobbly, I think it will be fine. They are torqued as tight a I dare and seem quite sturdy, although it may be smart to install lock washers under the fastener heads. Any opinions out there about this?

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