[Brian Duff]

What do you mean 'bent' where it comes through the deck?
Are you going to have to discard a section of the spar, or are you buying a new section to splice on to the existing un-bent portion?


All I can tell you is what I normally do, which is based on my observations from assembling many spar builders two piece masts, and based on repairs we have seen hold up, or fail, and repairs we have done in the past.
It is not necessary to obtain a piece of mast section like yours and then cut it down to fit inside. This often results in a poor fitting mast splice piece anyway(the curves are all wrong). Our preferred method is to bend up some plates on the brake that can cover as much of the inside of the mast as possible. You will not be able to do anything about the area where the bolt rope track is. There may also be a conduit track in there that you will have to work around. That’s ok. Just get the plates to cover as much area as possible. The length of the mast plates should be twice the fore and aft section of the mast, so for you, 12" plates, plus whatever length you want for a taper. Very seldom are tapers seen on mast splices provided by the major builders. I can’t think of ever seeing a taper in those plates, actually. If you do chose to taper, and we do, then make the plates 18" long and taper the last 3" each side, removing the material from the sides of the splice plate and leaving the plates long on the front and back is my preference. The splice taper might best be described as a swallow tail taper.
On your mast, which is probably a bit over 5/32" wall thickness, I would use splice plates that are 5/32” or 3/16" thick. Use plates that are the wall thickness of the mast thick, or greater. We have even seen solid machined blocks of aluminum that seem to be working well, but this is not my preference.

I would fasten this mast splice with #10-24tpi Flat Head Machine Screws, 3/8" long. The fastener spacing you could use is 8x fastener diameter apart, as long as the fasteners are about as large in diameter as one of the mast walls is thick, this rule works well. The first row of fasteners from the joint should be placed 4x the fastener diameter from the edge of the joint. Stagger the fastener rows to create a more evenly spread joint.

It is not necessary to weld the joint. Many of the engineers I have consulted with concerning mast splicing argue it is harmful to weld the joint. We do not weld our mast splice joints.

Yes, it would help to use adhesive on the splice plates when making this joint. We use an epoxy from loctite, specifically designed for aluminum bonding, and recommend you do to.

This mast splice would be considered major overkill by many spar builders. We like overkill.

This is only my opinion on how to splice you mast, and you MUST consult the builder of your spar to discuss the technique they would like you to use. Spar builders are always happy to talk on the phone about their spars, so call them first !