Originally Posted by gramos
I used 5 x strips in total and by using Duralac ,which has little flexibility , I have monitored any movement , results ? = nil .the mast can be picked up by the extended section only and has enormous rigidity . It was impossible to fit one piece inside the mast as there are too many fittings /protrusions up there , it had to be done in sections . bear in mind though that I have actually carried this out , not theorised .
This is an old thread, but I came across it on the web when searching for info on repairing a bent/broken mast by sleeving.
I recently bent a Cal
20 mast (don't ask...)
A very knowledgeable rigger I spoke to walked me through the repair process and confirmed that a sleeve can be made with an identical diameter/profile piece of mast by first cutting off the section of internal track in the back (mine is a "teardrop" profile, not a round or oval mast) and then cutting the remaining tube into four strips. These can then be inserted (and later fastened) into a section of the existing mast --he said not to worry if they don't all touch each other inside the mast, if they're, say, 1/8" apart. Closer is better, but they provide great strength when fastened and attached to the added-on section of new mast.
He also said that the four sleeve strips should be "butterflied" --taper cut so that they're narrower on the ends and wider in the middle (where they meet the joint in the mast). He specifically said taper to about half their width until 8" from the ends. This allows the mast to flex a bit. And the ends of the sleeve pieces should be nice and rounded, to prevent hard spots on the mast.
I suppose the ideal, if it would fit in one's mast and such a piece was available, would be a one-piece internal sleeve that fits all the way around the inside of the mast to be repaired, but this isn't always available, and would be tricky to make (I guess).
NOTE: this is for a Cal
20, which isn't going offshore
(some do). If it were on a bigger boat for offshore
, I would probably hire a rigger experienced in mast repair, to be sure...or buy a new mast...