Dave wrote:
On 18 Jan 2005 09:00:27 GMT, "Dag Stenberg"
said:

Another thing is, if you leave the mast up, you have to loosen the
stays and shrouds anyway to prevent the stress on the hull from the
shortening of wire in cold, so the additional nuisance of taking the
whole thing out is not so big.

How does the coefficient of expansion of aluminum compare to the coefficient
of expansion of stainless wire?

Good point! I found the following values (in m/m.K) from different sources:

Al 23.5 E-6
Al 23.7 E-6 Steel 12 E-6
Al 22.2 E-6 Steel 13.0 E-6
that last source Stainless steel (304) 17.3
Stainless steel (310) 14.4
Stainless steel (316) 16.0

"The thermal expansion coefficient of aluminum near room temperature is
about twice that of steel (the exact values depend on the type of
aluminum and the type of steel, but for most types it's around 24 ppm
per deg C for aluminum and 13 ppm per deg C for steel)"

OK, so we'll believe that pure aluminium has nearly double heat expansion
compared to stainless steel.

Aluminium alloy 6063 T6: 22 E-6, Stainless steel (306) 17 E-6

Aluminium alloys
(LM 25) 22 E-6
(6061) 24 E-6
(6082) 23 E-6

So we can still believe that aluminium alloys have much greater thermal
expansion than even stainless steel.

Where does that put us? I suppose one can then argue, that when it gets
colder, the aluminium mast shortens more than the stainless steel
shrouds, so those should actually loosen. Apparently I have been misled
earlier by incomplete information....

Dag Stenberg