Dennis Vogel wrote:

Thanks Jeff, but the mast gets too hot to touch hanging horizontal waiting
to be painted. So it's a lot more than a few degrees.

If your mast is currently setting on sawhorses, you can test how much it expands
very very easily. Fix one end, and pad the supports, and tape a ruler to another
sawhorse at the free end so you can measure the expansion.

You can look up the coefficients yourself and figure it out, I calculated that a
50' mast undergoing a 50 degree F change in temp will lengthen by .411" if it
made of the alloy with the highest possible expansion rate. More likely it'll be
between half and a quarter of that, say between 3/32" and a 1/4". Is that enough
to affect tuning, when the shrouds & stays are also undergoing thermal
expansion?

I'd suggest not.

If thermal expansion were a problem, then it wouldn't be likely that so many
racing boats have black painted spars (OUCH! especially in the South), or
perhaps that sailmakers would have a temperature incorporated into their tuning
guides.

Next question.

Fresh Breezes- Doug King