What's the best way to straighten a bowed aluminum mast?
Tom Wood responds:
It depends on where it is bent and how badly. Let’s start with the best-case scenario and work from there.
Many aluminum spars have a slight, even, gentle bow when at rest. This can be removed by normal rig-tuning procedures. When the boat is being sailed hard, you may end up with more tension on some shrouds than on others, but this isn’t a major problem on most cruising boats.
If the bend cannot be removed by rigging tension alone, you have a problem that should probably be attended by a qualified sparbuilder. Sometimes it is possible to strip the spar, lay it across sawhorses and induce a bend in the other direction. There is also a method of heating the spar on one side with a blowtorch and then suddenly quenching it with cold water. This makes the aluminum on that side shrink, removing a bend. But the heat also takes the temper out of an aluminum mast, causing it to have less strength in that area permanently.
If the bend is really more of a kink—especially if it is near the deck on a through-stepped mast, anywhere around the gooseneck, or near the spreader roots—the preferred method of removing the damage is to cut the spar in two at that point, splicing it back together with a sleeve inside. The spar might end up an inch or so shorter but this can be corrected with a plate under the mast step.
At this point, you might as well consider a new mast. A well-built new aluminum spar with all the modern bells and whistles is usually a good deal cheaper than most people imagine. In some cases if the spar was bolted together of cast parts (masthead, winch pads, spreader bases, etc.) and you can duplicate the section, you can even do the work yourself if you’re handy with a drill and tap. If it is a welded and painted piece, then a spar shop will need to do at least the basic work. But I would call the SailNet Spar Shop for a quote before I assumed that a new spar was totally out of the financial picture.
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