mast splicing

[mikestevens]

I have been doing my research and I think I have found a source for the extrusion that matches my offshore spar, which is bent where it comes through the deck of my S2 9.1.
I think I know how we might make a sleeve to insert into the mast by quartering a piece of extrusion and re welding it back togeter.
Questions:
1. What about the part inside the mast extrusion on the back side of the channel for the boltrope of the main? Would I just leave a gap there when making the internal sleeve, or would I fashion a concave section that would span the gap?
2. What is the rule of thumb for sleeve length? the spar is 6 x 4"
3. What do you mean by taper the ends of the sleeve (from previous post)? By how much?
4. What type of fasteners would one use to connect the sleeve to the mast extrusion and what pattern/spacing might one employ? Tapped bolts or rivets?
5. Is it necessary to weld the joint?
6. Would it help to add adhesive when assembling?