As previously posted heat cycling can help get it tight and right. When
cycling the clamp (cold-hot, cold-hot, etc) you should tighten at the
end of the hot cycle before cooling the clamp to take advantage of the
expansion and contraction which is the reason for temp cycling.
I also found in assembling 3x TH7's and other antennas with hose clamped
slitted tube sections that 2 or 3 tightening cycles are needed. After
some thermal cycles and a few days the stresses redistribute in the
connection. If you can create larger thermal cycles on purpose, it
helps - e.g. leave the antenna in the sun and then sprinkle with cold
water. Then retighten each clamp. So far, this has worked with no
loose elements after years of service. The boom clamps can also benefit
from this approach. Retightening bolts after a few thermal cycles is a
standard manufacturing process when fastening systems are near their
stress limits.
CTE of Aluminum is about 13, CTE of stainless is about 6 (ppm/deg C)..
This would imply that you should tighten the clamps at the *coldest*
temperature, not hottest. As it warms up the aluminum expands more than
the SS, so it will get tighter.
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