Crack in aluminum mast : options?

[samgary]

Hello,

I have a 33' masthead sloop. As i was doing a routine inspection of the rig, i found two cracks just above the second spreaders. The cracks originate at the bottom screw holes for the spin topping lift sheave box and spread aft on either side for about 2 inches. The cause of the crack i assume is from possible corrosion coupled with the loss of structural integrity with the housing of the sheave, and the fact that the mast pumps when sailing to weather putting stress on this weak point. I have and use running backs.

The mast is a proctor 47' x 4"x6"

I have been advised to drill stopper holes at the ends of the cracks, then grind the cracks and have a pro TIG weld them. Next add a plate ( cut from the a forespar section of a broken mast) to be welded over the housing box to stiffen the mast. The plate is an elongated diamond with a rectangular midsection and rounded corners about 15 " top to bottom. The mid section spreads aft to cover the ends of the cracks. The plate is a 1/16" thicker than the mast walls.

Any feedback would be greatly appreciated!