replacing tabernacle pin

[RyanN]

Any materials engineers out there?

I'm considering replacing my tabernacle pin. The old pin was 3/4" stainless rod sleeved to 1.3" with aluminum inside the mast and with a 1.25" bushing at the tabernacle.
Unfortunately, the pin froze inside the sleeve and since a 1.3" sleeve won't fit through a 1.25" hole, removal was a nightmare.

For a new pin I'd like to use a piece of 6061 extruded rod machined to 1.3". The tabernacle hole would be enlarged from 1.25 to 1.3"
There are higher strength alloys, but I'm not sure they will be suitable in a marine environment.

Some specs:
The mast is about 50' high
The vertical loads on the mast should be transfered to a wedge block under the mast and not to the pin.
The mast wall thickness is 1/2" and the holes is 1.3"
the tabernacle is made of 3/16 stainless and the hole is 1.25"
The gap between the tabernacle and mast is minimal.

Another possibility is a piece of 1.25" titanium rod (about $100) in an aluminum sleeve. The titanium shouldn't react with the aluminum.

[Brion Toss]

Hello,
Oh, how I hate those frozen sleeves. I am sure that dealing with that thing was a nightmare; what form of explosive device did you use to remove it?
As for the new pin I would recommend... a sleeve. You could build a 1.3" rod, and it would likely have a strength of well over 100,000lbs, but what's the point? The idea is that any shear loads on the mast wall should be transferred to a maximum number of aluminum molecules, to prevent deformation; hence the oversize pin. It has nothing to do with required bolt strength. So sleeving a smaller pin is actually a fine option, if you isolate the metals with Tef-Gel. Better yet, consider shouldered bushings and a lathe-cut nut thread, so no one can overcompress the bolt and thus the mast.
Glad to hear that you are working to get the load to the deck via that wedge, though of course much of it will be borne by the bolt.
Fair leads,
Brion Toss

[RyanN]

Thanks for the advice. Once the mast (with tabernacle) was off the boat, I pried the two apart just enough to get a hacksaw blade in there. I had to do this on both sides. The paint on the mast was already well bubbled so there was no permanent damage to the mast.
The current plan is to use drill out the hole in the tabernacle from 1.25" to 1.3" then use a 1.3" aluminum rod. The rod will be drilled and tapped on both ends to a depth of 1" and a 5/16 stainless bolt and fender washer on either end will secure the rod laterally.

I think that this would be the cheapest solution, and the shear load should be well within the strength of a 1.3" piece of aluminum rod.

The previous wedge was two pieces of mahogany and a 1/8" piece of high density plastic totaling about 1.75" total. I don't think there was any "wedge" to the block, all angles were 90 and the block was just knocked in while the shrouds were loose. My thought for the new wedge (or block) was to use aluminum rather than wood with some 1/8" UHMW between the wedge and the tabernacle and between the wedge and the mast base.

To isolate the sides of the mast from where they touch the tabernacle I was thinking of using UHMW tape. Does this hold up to UV long term?