I'd like to run internal halyards this spring before the mast goes up. I was wondering if there is a rule of thumb as to where you should have lines coming in and out of the mast without compromising its structure?
Dan Dickison responds:
You should know first of all that drilling any holes in your mast will leave it with less structural integrity than before. But don't worry, it can be done without severly weaking the spar.
The thing to avoid is concentrating the holes in any one area because this really weakens the mast. And make sure that you don't add holes that are opposite one another in a horizontal plane because that too can create problems. Instead, stagger the heights of the holes that you cut. For example, if your main halyard is going into the mast on the port side just above the gooseneck, and the genoa halyard goes into the mast on the starboard side, make sure that the genoa halyard enters the mast somewhere higher or lower than the main halyard's entry point. Also, remember that the cutouts you make in your mast should have rounded corners to reduce the stress concentration there and lessen the chance that a crack will start.
If you have to add sheaves at the masthead or elsewhere for the halyards, the same principle of staggering the holes applies up there too. And while you're engaged in this project, try to make sure that any fasteners you use don't protrude too far into the mast so that they cause chafe on the haylyards or the electrical wiring that's run inside the mast. Here's hoping you finish with your project soon so that you can get back out sailing with minimal delay.