Myth, schmyth
Hello, If only it were so simple. Yes, aluminum shrinks more than identically-dimensioned steel, but there's more to the problem. For starters, each strand in a stay is quite a bit longer than the mast; they just wind around a bit on the way. Since contraction is partly a function of length, the extra length will at least partially offset the difference in coefficient. Next, aluminum doesn't necessarily change temperature at the same rate, or to the same degree, as it were, as steel. Paint, interior heat, wall thickness, and alloy type can push the differences even further. Next, an extruded mast section will absorb and radiate heat and cold in different amounts, with more action tending to come at the ends. Wire (or rod) is, as I understand it, more likely to be uniform in its behavior. Finally, the vessel itself can contribute to rig tension. Most are fairly unresponsive to cold, but it doesn't take much motion to make a lot of difference in tension. I'll see if I can come up with some specific numbers in a follow-up. Meanwhile, even without the above, I've simply had too much experience with moderately tuned rigs suddenly jamming head doors to dismiss this as a myth. Fair leads, Brion Toss
