best design for mast sleeving

Greetings!

The mast of my Columbia '33 was dropped in the boatyard. The damage is about 2 and 1/2 feet from the base, below the winches and gooseneck. 38' is the total mast length.
Obviously, I want to cut out the dent. Then I will need to "sleeve" on the lower section, building up the tabernacle to compensate for the inches lost...right?

The extrusion is 7 1/2" by 4", the circumference 19 1/2". According to a mast sections chart in my book (From a Bare Hull), this appears to be:
S-203, 7.50 x 4.00, .140 thick, 3.214 lbs/ft, 16.672 IXX, 6.818 IYY, Alloys 6061-T6 or equivalent.


Intuitively, a close-fitting internal sleeve of identical alloy, and a 2 1/2'+ section of matching mast extrusion will allow me to maintain integrity with regard to both strength and dimension, while renewing the section below the dent.

SO, MY QUESTION:

1. Is there an extrusion out there that is intended for sleeving this size/shape of mast? I believe it is a 1960's Sparcraft product out of Costa Mesa and it seems that the manufacturer of this mast extrusion would sometimes sleeve mast sections, and therefore manufacture a sleeving stock of ideal dimensions. I would also like to renew the section below the dent if a short piece of S-203 is available.

2. As a matter of design, is any external sleeving or reinforcement necessary? and, also with regard to the sleeve/section assembly design: How much overlap is recommended, and is it better to weld or riviet or both? (I generally overbuild as a matter of personality and would never ridicule anyone for wearing suspenders and a belt, at the same time.)

Big Mahalos,
Patrick

 

Sleeves are usually internal. If you repair it, the tabernacle should stay the same. A dent may not be a major structural problem. Those boats have hefty masts. Also, it is possible to cut the dent and weld a new piece.

 

Generally masts are sleeved with the same extrusion they are made of. The back of the extrusuion (where the sailtrack is) is cut away and the sleeve is compressed and slipped into the mast extrusion. It is then fastened with adhesive, rivets, screws, or plug welds.

I doubt you will find any S-203 available. The best bets are to check with LeFeil or Dwyer to see if they have something similar.

Depending on how large and deep the dents are you might be able to cut the area out locally, sleeve internally, and then form/weld a section of plate into the cut out. That would be a bit of welding and annealing, so the area would not be T-6 anymore, but it still should be OK if the dented area that is removed is not too great.

One thing most people do not know is mast extrusions come from the mill in 40 foot lengths. Some specialty extrusions can be up to 44 feet, but 40 feet is generally the length (for shipping purposes).

So as you walk along the marina and look at all the masts, rest assured that almost every one you see on boats longer than about 30 feet have a splice in them. They are mostly welded and ground down, so after the mast is painted no one knows.

Therefore adding a splice to your mast is really no big thing.

If you are going to weld you have to cut oversized holes in the mast wall to plug weld the splice in place. You will have to use other fasteners, screws or rivets, to pull the splice tight to the inner mast wall before welding. Then you fill the cutout with weld and grind it down.

If you plan to rivet make sure you use monel structural rivets.

 

This is not a stand-alone unguyed mast so max stress is midway up not at the base. Unless the dent interferes with fit and function is there any need to do anything at all about it?

 

If it is a keel step you could convert to deck step using the bit you cut out to repair it.