Mast pump

[Bob Pingel]

The classic answer to this question is, get the tuning video -- check in the catalog.

If you are seeing a tension difference from just wind loading on a spar, I would guess you are tuned far too loose.

There is a phenomenon called the Carman Effect, where even a properly tuned mast can oscillate due to the wind -- basically resonation is built up as the structure sheds wind vortices. The solution to this is to break up the wind flow to cause uneven turblent flow - a quick test is to hoist a fender aloft.

I would definitely start with a good tune, you can get there with a good rigger or Brion's video. If you still have problems, you can explore the Carman effect.

Bob