MBounds - you mentioned a reinforcing kit to strengthen the mast under the mast rator arm.
"The one-piece mast rotator arm (it's the same on all the boats) works well on the 14. You need to install the reinforcing kit (look closely - diamond shaped plates on the mast) so you don't collapse the mast section."
Do you suppose that a similar support, larger and riveted on, would help support a longitudinal split in a mast, to keep it from collapsing due to compressional force? viewtopic.php?f=20&t=22613
Thanks for your thoughts.
"Compression" in the context above is the transverse compression of the rotator arm. The reinforcing kit would not do anything in your situation - if anything, it would make the mast weaker.
My suggestion in your case is to take the mast to a professional aluminum welder and have him run a bead along the crack. It shouldn't affect the strength too badly as long as he keeps the bead small.