Shortening the Mast

[tacooooo]

Hello Cruisers Forum!

So we just purchased a 1975 Contest 36 Ketch, and we love her. Our rigging was just inspected and all is well, EXCEPT for some corrosion forming at the base of the mast, where the aluminum mast is in contact with the stainless steel mast heel.

Our surveyor suggests cutting off the mast corrosion, then raising the mast step up to keep the masthead height the same. That makes sense to us, but we're not sure how to re-incorporate the mast heal into the equation without having the same corrosion issues resurface down the line.

Since the mast heel inside diameter is roughly the outside diameter of the mast, we don't see how we could re-use the heel and not have the same problem come up down the road.

We've considered losing the mast heel altogether, engineering a new mast heel with room for some sort of galvanic isolator (hdpe plastic maybe?), or re-installing the heel with some sort of anti corrosive paste between the metals.

We're not sure what the best option is but would love to hear any input from the crowd especially those who may have encountered this issue. Any insight is very much appreciated!

[Jim Cate]

That corrosion, as seen in the photos, isn't all that bad looking in terms of structural strength. It has taken nearly 50 years to reach that state. In your place I would look for a second opinion, 'cause it is quite possible that simply cleaning it up and reinstalling it would suffice for a good many years to come.

Jim

[Benz]

The best paste to isolate two metals is Tef-Gel. Use that when you reassemble and the mast step will outlast all of us.

[mike d.]

As Jim said ! Or you could have it cut off, then have an aluminum sleeve welded inside to make up the difference in height, then, then just have an outer layer put on that to make up the outer diameter difference ! Our mast had that done by the prior owner ! ours is stepped in the bilge, so not quite the same, but !

[RaymondR]

Originally Posted by Jim Cate

That corrosion, as seen in the photos, isn't all that bad looking in terms of structural strength. It has taken nearly 50 years to reach that state. In your place I would look for a second opinion, 'cause it is quite possible that simply cleaning it up and reinstalling it would suffice for a good many years to come.

Jim

Way to go, there's not enough corrosion there to cause any significant reduction in the strength of the mast at that point.

I would consider liberally smearing both the mast foots OD and the inner surface of the base with a marine sealant when replacing the mast then making sure the drainage holes are clear. Keeping water out of the crack between the SS base and aluminium mast will stop the aluminium acting as an anode for the SS base.

[neilpride]

Originally Posted by Jim Cate

That corrosion, as seen in the photos, isn't all that bad looking in terms of structural strength. It has taken nearly 50 years to reach that state. In your place I would look for a second opinion, 'cause it is quite possible that simply cleaning it up and reinstalling it would suffice for a good many years to come.

Jim

+1 .

[neilpride]

Duralac and keep going..

[mike d.]

That looks like a boot or shoe if you will, over the mast it self, which sits in the mast base on deck ! It also looks like there is corrosion between the the external part and the mast ! I would be wondering what the actual mast base looks like inside that part, if you can get it off ! But as I posted previously if it is really bad it would just be a matter of cutting off the bad section and welding a sleeve, and new piece the same diameter as the original !

[wyb2]

Yeah, unless I’m misunderstanding the configuration, I don’t see how we could make any judgment about mast corrosion. You need to take that SS heel off and see/show what the aluminum that sits inside it looks like.

If your new heel is aluminum, you don’t need to isolate it from the mast, you want to isolate it from the SS step. HDPE is pretty soft, and can creep under constant load. Something reinforced, like G10, might be a better choice.

[mike d.]

Also I am not seeing any drainage holes in the shoe/heel ! So if you have internal halyards the water will collect in the shoe/heel until it flows over, but always leaving a pool of polluted water from ie salt air etc, and if the heel/shoe whatever you want to call it !

[tacooooo]

Wow guys, thanks so much for all the input. You've definitely given me a lot to work with going forward.

I think since we have the mast removed already, we may as well try and knock that heel/foot/whatever it is off and do a bit of looking around. I love the idea of just replacing the foot with a larger aluminum foot if the mast requires some trimming.

Whatever happens i'll be sure to post our progress! Thanks again ya'll!

Rob

[Cheechako]

Originally Posted by wyb2

Yeah, unless I’m misunderstanding the configuration, I don’t see how we could make any judgment about mast corrosion. You need to take that SS heel off and see/show what the aluminum that sits inside it looks like.

If your new heel is aluminum, you don’t need to isolate it from the mast, you want to isolate it from the SS step. HDPE is pretty soft, and can creep under constant load. Something reinforced, like G10, might be a better choice.

Yeah, This^^
If you eliminate the SS sleeve, You may be able to put some thin isolating plate in the bottom of the SS deck fitting... maybe 1/4" thick, material that's good in compression (although I doubt it's too high for most anything) . Then wrap the mast perimeter in thinner material to fill the gap after removing that sleeve that is on the mast.

However, if the aluminum inside that sleeve is still fairly good, whatever was done held up very well. Adding Tef Gel or any of those isolating materials will only make it even better.