Mast Step Replacement

[nolandinsight]

It's time to replace the mast step on our 1972 Morgan 35. What am I getting into? Anyone here done this before? I don't know how the step is secured to the keel, and access to the step is limited, except for a10 inch inspection hole on the starboard side of the mast.

[Hudson Force]

Whew! Likely past time, but good of you to catch this before a catastrophe. Morgan had a practice of setting the aluminum mast on a steel step plate. It appears that the mast is not too damaged from corosion. I've heard of others that were wondering why their shrouds kept going slack; only to find that their coroding mast was growing shorter from the bottom! I don't think there's an alternate solution other than to remove the mast; gain access; cut out the remnants of the old step; and build a new step without contact between different metals. I would also recommend opening a larger space near the new step to allow more ventilation.

[Cheechako]

Just got to get all the rusty crud out of there, clean it up and buiild a new support. By the time you get it cleaned up I suppose you will come up with the best scheme. What you do may have a lot to do with how good the access is. You could use treated wood, a welded support, or even cast in a cement support. I imagine you will have to have the mast removed while you do this (?) Be sure to take measurements before removing the mast to determine where you want the top of the new support to be, both vertically and fore aft position...

[nolandinsight]

Past time yes, I completely agree! To your knowledge in these keel stepped masts, is the mast actually fastened to the step, or does it simply rest on top of the step or partners? Also, is the step generally bolted somehow to the hull or keel, or placed in position and then glassed in?

[nolandinsight]

Ah, that makes a lot of sense. And yes, I'll have to take the boat to the yard and have the mast unstepped, and I assume trim a little of the damaged bottom.

[Lojanica]

I am finishing a mast step replacement now. Same issues.

I used a 304 Stainless steel beam to wood bulkheads tabbed in with glass and of coarse sealed with epoxy. Then I made a 1" shim between the beam and aluminum mast out of dense rot proof wood again sealed with epoxy.

In that way corrosion will be kept at bay and I overbuilt the whole deal. Oh yeah and airflow is good as mentioned

You good also put the formaldehyde pouches in your deep dark bilges as the gas only goes down due to density and it will keep rot at bay. Just remember to seal it up tight and then always air out the boat while on the vessel. If extended cruising take them out and seal up in an airtight container.

[nolandinsight]

Lojanica,

Did you secure the mast to the step at the shim/step, or is it held on place by the standing rigging?

[Cheechako]

It should be secured, sometimes a casting that slips in the mast is used. I dont see one on yours. May just have tabs welded to the support that interface on the sides and ends of the mast inside.

[Lojanica]

Originally Posted by nolandinsight

Lojanica,

Did you secure the mast to the step at the shim/step, or is it held on place by the standing rigging?

Custom mast plate out of aluminum. I shortened the mast 1" due to base corrosion. Used the 1" cut-off piece as a mold for the new plate. Just buy plate and the weld verticals to hold the mast in place. Or you can template some hard wood and saw out a plug and glue and screw to another piece of wood. The aluminum is better though. As far as shims are concerned if you are worried about rot or have no access and want to set it and forget it just get a piece of 1/4" thick G10 to separate the aluminum from the steel and use tefgel on the bolts securing the aluminum step to the steel.

There are 10 ways to do this and all are OK. The principles are apllicable.

Reduce point loading and spread the load on the hull
Reduce corrosion
Secure the base
Allow drainage and air circulation

[nolandinsight]

Thanks a bunch, that definitely cleared some things up for me.

[skipmac]

Had the same problem on my Pearson, steel step in the bilge with aluminum mast sitting directly on the steel. I had to cut 3" off the end of my mast where the Al corroded away.

I started with a 3" slab of UHMWPE to get back the 3" I lost on the mast. The old steel step was attached to the keel with 4 lag bolts. I bought 4 bronze lag bolts 3" longer to attach the UHMWPE to the same spot. Took another 2" slab of PE and cut a hole in it to match the mast shape and attached that one to the base with 16 bronze screws to make a socket to hold the mast.

I was be concerned that the movement of the mast would gradually wear through the UHMWPE so sandwiched a sheet of 6061 Al between them for the mast to sit on. Be sure to isolate the Al from all of the bronze fasteners or you will have an electrolysis problem.

Also make sure you cut drain channels in the mast base and in the step so the water that will get in there can drain.