I've broken a few booms over the years but not here on the tail piece like this. Only a couple of seasons old and no major impacts I can remember. Just metal fatigue? But is that section under much load?
I've never seen that before, but just thinking about it, that crack will close as you close the arms and open up as you open them. So the arms are forced more open as the boom flex's with riders weight and when it's at minimum extension. So just a guess here, but looks like you've put load on it at close to minimum extension.
Does that make sense?
I'm calling maybe metal fault from the start - mandrel bending stretches the tube a helluva lot so any fault in metal would be a weakness, later tempering could have been a bit off, who knows.
A clever metallurgist type would pick that easy from the grain structure
Id say its where the tube is seam welded. Probably the worst place to be on a mandrel bent curve. It would try to sheer between the stretched outside and compressed inside curve. Possibly already unseen cracked before use. Culprit ,cheap tube.
i think its a good time to get a carbon boom .
done a few alloys ,it usually breaks at the adjuster ?? weird one ...had a carbon boom for 9 years now .great investment .
Select to expand quoteImax1 said..
Id say its where the tube is seam welded. Probably the worst place to be on a mandrel bent curve. It would try to sheer between the stretched outside and compressed inside curve. Possibly already unseen cracked before use. Culprit ,cheap tube.
Good point, they don't use SHT for booms huh
It's green. That's what happens when you make your booms out of garden cuttings. You need proper teak.
So maybe a fault, or s***y tube. Thanks for the thoughts. Like to go carbon but...$$$ ... maybe tho
At least I found a decent tail piece in my boom graveyard to replace it. I'm also wondering how long I've been chugging around with that crack, or how much longer it would have held on...
Select to expand quoteMax Phunn said..
Any chance water was left in there and it froze at some time?
Not so much in Queensland 
www.seabreeze.com.au/Classifieds/Windsurfing-Accessories/~-4j0a/Aeron-Carbon-Booms.aspx?_page=1&search=kUAz4ywlWw9x4uvKNrfOmw%3D%3D
there are some for $500.not a bad price .
Select to expand quoteMark _australia said..Max Phunn said..
Any chance water was left in there and it froze at some time?
Not so much in Queensland
Sorry, I am from Canada eh. 
