After derigging after another great sess at Inverloch noticed my Sailworks 100% carbon speed stick had a crack in it. - SDM
Crack is 2/3 way up on the bottom section(2 piece mast) and is about 1/3 around the diameter.

Can it be repaired/by whom?
Apart from dropping - what causes masts to crack?
Can you buy spare sections?
Who stocks Sailworks in Australia?( I brought it 2nd hand )
Can I still use it if I turn crack to inside of bend when rigging?
If it breaks, is it likely to damage sail?

Board Crazy at Belmont NSW are the importers of Sailworks product to Australia. They are a Seabreeze sponsor and have banner ads for Sailworks here. Not sure if there is a Victorian shop selling Sailworks gear.

Probably best to get it replaced. If its cracking the it will break and could rip the sail and leave you out in the water with a broken mast. Unfortunately the bottom section is normally the section that breaks so its unlikely you will be able to source a bottom section on its own.

Overtightening the boom could also be the culprit. Those 100% masts are expensive, so I feel your pain, but it's really stuffed.

IF you insist on repairing it, best not to use it way out in the ocean; just somewhere nice and safe where you can get back easy if (when) it breaks.

time to get a RDM
and some sails to fit

I wouldn't stick it up a good sail cause WHEN, not IF, it breaks you might bugger up a good sail as well. I use 100% SDM masts but don't leave them rigged on beach for long periods in hot sun. Also between the boom clamp and the mast I insert a piece of rubber cut from a hot water bottle. (it has a lot of serrations on surface)
It don't slip down the mast but also prevents crushing the mast with an over tightened boom clamp.

crack in mast - not good.

anyone out there with composite stress analysis experience that could go into the failure mode of a mast with a circumferential crack?

in general for beams (ie a mast) under load you will get maximum stress at the surfaces - hence any dings/gouges/defects at the surface will cause a stress concentration - exceed the maximum stress of the material and it's game over.

The resin properties used in mast manufacure can also be affected by excess temperature (dependant on the resin type), in general the strength is reduced as the temperature increases.

North puts a protective coating on the outside of their mast's to reduce surface damage and thermal effects (apparently).

You could attempt a repair by wrapping the affected area with unidirectional carbon tape - laminate with a good epoxy resin. I have repaired two masts that have had minor cracks - still going strong - touch carbon