Requesting Advice: Corrosion on Lower Mast & Mast Step

[Ken Fry]

Originally Posted by Breaking Waves

I guess the mast step will need to be replaced in any case.

I think that the step might be ok once it is removed and sandblasted... although there is no way to know from a video. The step is cast and under compression... the sort of load it can easily handle. A skilled welder could fix pits and a crack or two. But if a new part can be found for less than $200, then replacement would be a good bet.

The mast butt is thin and could soon buckle... but again impossible to tell from a video. The mast should be pulled and evaluated

Once the mast is out and thoroughly inspected, the bottom foot could be cut away and a new section welded in, possible with a sleeve at the joint.

The OP should be aware that shortening the mast can devalue the boat, and will likely require new shrouds, etc. Raising the step requires some engineering, because doing so creates a moment load that the original step almost entirely avoids.

If a new step is required but not available, a new part could be created from aluminum plate milled to the correct dimensions. A manual milling machine and a good operator could do this faster and cheaper than a most CNC machines (with the required programming.)

In NYC or close there will be several foundries that could cast a new step, given a pattern that the boat owner could create out of wood.

[jt11791]

Meh, doesn't look so bad to me. Clean it up with a wire wheel and repaint the next time you pull the stick.

[Breaking Waves]

BTW - OP - Nordic 40 - really nice boat, great choice. Good luck with the mast.

[toms-gonesailin]

Awesome! Thanks for the going through all my questions and all the great suggestions.

I think I have better idea of what needs doing now. Going to start with pulling the mast to get a better look. Will post an update once I get the mast off and have had a chance to get a closer look at the inside of the mast and at the mast step.

More to come!

[kish]

Originally Posted by toms-gonesailin

Hi guys!

Just discovered a bit of corrosion on my lower mast and mast step and would love feedback from you kind folks on the best approach here. My questions are:

1. What's the best solution/treatment now so it doesn't get worse?
2. How bad is it On a scale of 1 - 10? ("10" being OMG go deal with that right now before your mast falls off and "1" being meh it's fine.
3. What's the recommended approach for the most comprehensive fix?
4. Does anyone have riggers in the New York state area that they trust and recommend?

I've included a link to a video that should give you a better sense of extent of the corrosion. Feel free to mute the sound if your not into the music...

Thanks for your time and help. Much appreciated.

That is extreme corrosion


You must investigate the source of corrosion.

It is most likely electrolytic corrosion caused by dissimilar metals,

The cables at mast base appear to be unsupported and probably chafing the remainder of the original cable exit point They are unsupported and have probably partially chafed to allow copper to contact the aluminium mast.
In summary copper and aluminum in a salt water environment have wreaked havoc.
Check all cables and equipment on on mast at spreaders and masthead for signs of corrosion and chafe.

Remove all cables and masthead fittings and inspect and replace any damaged cables.
Protect all cables from chafe.


It would seem prudent to shorten the corroded base, but first seek separate advice from a reliable rigger or two about a sleeve for the mast base as an alternative to cutting.


Good Luck!

[Patrigo]

About 27 years ago I replaced my Adams 28's deck stepped mast with a keel stepped mast. I used a 20th century idea, developed in Fremantle, which has given me a keel stepped mast which does not leak. It does not leak because it cannot leak. If you use a method of mast stepping (most of the world does) which was around long before the Spanish Armada, it will leak. Get with it, although I do admit to 2 or 3 cobwebs over nearly 30 years.
I have posted on this subject quite a few times, but few have shown any interest. Sailors are VERY conservative. So don't question me, get on to someone in Fremantle. I am over it. My mast fitment is faultless and cannot leak. I don't care about others wet bilge problems.
Get with it, or live with it. Quit whingeing.

[toms-gonesailin]

Hey guys,

Just a quick (not very exciting) update here. Looks like I'm not going to be able to pull the mast until early March so in the short term on recommendation of a trusted friend I've hit it with a wire brush, some zinc chromate lower unit primer and enamel spray paint. Hopefully this helps keep it from getting worse over the winter. Hoping

Also I've added another video on YouTube. Hoping to document this process on YouTube as well as link back to this thread from Youtube so that other people can use as a reference. Welcome feedback on the approach and idea as well.

https://www.youtube.com/watch?v=TRB3cy6A_GM&t=2s

[thinwater]

Originally Posted by tkeithlu

Even with the video, I can't really come to a conclusion about structural integrity, although it looks scary. You may be in the market for a good surveyor....

What he said.

How old? If that were a 10-year old boat I would ask more questions. If it is a 40-year old boat the progression is obviously slower. This is also the lowest stress portion of the mast (no buckling potential, only compression).

The required inspection can be done with the mast in-place, using ultrasound. This is done in industry all the time. I do this as part of my day job.

[toms-gonesailin]

Originally Posted by thinwater

What he said.

How old? If that were a 10-year old boat I would ask more questions. If it is a 40-year old boat the progression is obviously slower. This is also the lowest stress portion of the mast (no buckling potential, only compression).

The required inspection can be done with the mast in-place, using ultrasound. This is done in industry all the time. I do this as part of my day job.

Sorry just saw the other part of your message that for some reason it didn't appear when I first read your response.

Would love to hear more about how you would go about this with ultra sound. Sound like you might need some fancy equipment.

Also the boats from 1987 so no spring chicken.

[thinwater]

A good a-scan unit is $3-5K, but there are serviceable thickness-only gauges for ~ $200.


Learning to use one effectively is another thing. You can learn a lot through Google.

• Read a known good spot to get nominal thickness.
• Measure pits with a pipe pit gauge (~ $15 on Amazon).
• Read thickness near pits to determine general metal loss. An a-scan unit gives information about backside roughness; with thickness only more guesswork is involved.

Finally, is the matter of judgment, relating to how much metal remains. UT techs and inspectors are certified for hulls and tanks.


A good surveyor should be able to examine the mast step in-place. We sure don't pull refinery tanks out to inspect them!

[jt11791]

Originally Posted by toms-gonesailin

Hey guys,

Just a quick (not very exciting) update here. Looks like I'm not going to be able to pull the mast until early March so in the short term on recommendation of a trusted friend I've hit it with a wire brush, some zinc chromate lower unit primer and enamel spray paint. Hopefully this helps keep it from getting worse over the winter. Hoping

Also I've added another video on YouTube. Hoping to document this process on YouTube as well as link back to this thread from Youtube so that other people can use as a reference. Welcome feedback on the approach and idea as well.

Yes! Looks good. Go sailing and enjoy.