Mast corrosion

Swan 47/59

Hello,

We are replacing our rigging and have taken the mast of.  The yard has warned us that there is little corrosion at the bottom of the mast.  He is proposing three solutions to be discussed: do notthing, cut 2cm of the mast and option1: put a plate 2cm thick below the mast, option 2 introduce in the mast an aluminium protection with rivets.

Anybody with experience in this matter?

Ludovic

I had a similar issue about 15 years ago with the mast on my Swan 41. I think I went for your 3rd option which was to slieve the bottom of the mast which seemed to work very well. It was done for me by Proctor masts (now defunct) who had a mobile service unit who did a couple of other jobs on the mast and boom at the same time in the Hamble boatyard.

After having it done I made very sure that I kept the drains from the adjustable mast step clear so that this area stayed as dry as possible.

Gavin

This is the way the mast of my 411 was fixed 7 years ago: your 3rd solution.
I reckon it was not a perfect job as I would have preferred a better fit of the insert and more rivets but good enough.

Regards
Daniel, 411-004

Thank you to both of you, I think indeed that fitting a piece inside seems the best solution.  In this case I beleive the best is not to cut the mast but probably just clean it very well and ad the piece inside. 

Ludovic 

Dear Christophe,

After some work this is how the bottom of the mast looks like.  

I would not fit a staineless steel piece in the mast as you will have even faster corrosion but an aluminium piece.

I cleaned my shoe mast and did two holes in the middle so that the water trapped inside the mast can leave.  I even plan to rince with fresh water inside the mast at the end of holiday season.

Did you check the keel bolts below the shoe mast? (see the post on this issue)

Ludovic

Ludovic,

Many thanks for your input which is a valuable feedback to me.

I also like the answer from Federico who believes a good cleaning and repainting may be enough for this specific mast. Indeed it has already been reinforced at the bottom.

Kervilor Vanek who are working on the boat are recommending that the mast be cut and a specific piece of stainless steel be inserted inside the mast. They have mentionned the holes to prevent water from staying inside the mast. I have attached the drawings that were sent to me. Has any one any piece of advice?

As far as the keel bolts are concerned, I don't think I can check in which state they are without taking off the piece on which the shoe mast lies which is rusted as well as you can see from my pictures. However, Kervilor Vanek seems of the opinion that they should be OK. What I have asked them to do is to wait until we have a feedback from Nautor Swan spare parts to find out if we can still find a replacement for the piece on which the shoe mast lies as it seems rusted. I am waiting for a response from Nautor Swan.

Best regards.

Christophe

Christophe, as already mentioned, I would strongly discourage adding stainless steel parts in contact with aluminum. Indeed it looks that your mast was already fixed and presently it does not need much intervention.
Ludovic, the work done on your mast looks extremely well done and I have only a question about the bolts: if they are of stainless steel be sure to use a lot of duralac/tef-gel. I would suggest using titanium bolts if you can find them.

Daniel, 411-004

Thanks Daniel.

I will liaise with Kervilor again to relay the message.

One of the question I still have is that apparently the shoe mast is stainless steel. It is by definition in contact with the mast, in aluminium. Is there any trick that I have missed?

Best regards.

Christophe

Christophe,
yes, you are right: the shoe (the mast step) is made of stainless steel and, in fact, it is the main reason for mast lower end (heel) corrosion in the presence of water. I do not have a reply for your question but I remember a previous discussion. I think that the best solution would be insulating the two metals but there are at least two problems: 1) lightning grounding and 2) extremely high pressures. While the first can be solved with a well studied additional electrical link, I do not see an easy and durable way to solve the second issue.
The best palliative is keeping the parts as dry as possible but it is a condition hard to maintain in the long run.

Daniel, 411-004

Many thanks to Daniel and all for your valuable comment.

As far as the bottom of the mast is concerned, we will take the existing paint and rust away, see how the aluminium is, once cleaned, and hopefully repaint it without more to be done.

I still have a question on the piece of metal which lays underneath the shoe mast. I have attached some pictures which show rust. We will sand it and clean it but I am not sure this will be enough to do the trick. It seems that removing this piece of metal is quite a job. I was wondering if any one of you has had similar experience or has any good piece of advice for me.

I have liaised with Nautor Spare parts to find out if they can still provide a replacement of this piece and am still awaiting their response.

Best regards.

Christophe

Further pictures

Dear Christophe,

I had the same problem onboard Only You, and this winter I had the mast step cleaned, got rid of the rust, and as the "fresh" steel appeared I had it coated with a special paint.

Below some pics of the condition before and after.

Fair Winds

Matteo (38/067 Only You)

Dear Swan lovers,

As I started this post in 2012 I thought it would be nice to keep you updated of my observations.  

In 2012 we sanded our original mast and discovered the mast corrosion at the gooseneck and kicker stainless junctions plates.  We cleaned, filled with specific material and painted the mast.  The situation is showed on the two pictures. 

The idea was that if we could avoid contact between aluminium (the mast) and staineless steel we would be safe.

Very quickly (one two years) we could see some corrosion bubles below the staineless steel plates and therefore we decided to have a new check of the rigging during the winter 2018.  We were very suprised to see that corrosion had continued with a worsening of the situation. 

Ounce again we were advised to strongly isolate the two material and had a new painting of the mast.

See next post for the following observations

Ludovic from Rumtrader (swan 47)

situation winter 2011-2012 after sanding the mast

Situation winter 2011-2012 after isolation and painting

Situation winter 2018

Cher Ludovic,

which material did you get to separate aluminum and stainles steel plates?

matteo (47/069 Vanessa)

PS as you know I had the very same issue and in 2015, and I separated the plates and alu mast with TefGel, which I am told is better than the more traditional Duralac. So far it worked (checked last year)

The work done in 2018 did not prevent corrosion to continue its destructive work.  In winter 2023-24 we had a new look (see picture) and it becam clear that if I wanted to keep the mast a new strategy was needed.

After discussing at the Swan boot at Dusseldorf and with some rigger I reached the conclusion that nothing can stop the corrosion between aluminium and staneless steel.  It is even worse when there is an isolant between the two materials as electron exchange will even be more important.

The best is to never paint the mast.  I have indeed seen some original mast never painted that seems to have less problems. 

Unfortunatelly our mast was painted probably long before we bought her.

With the boat yard we decided to replace the staineless steel by aluminium (see pictures).   The thickness and the contact area were increased and special wearing rings were produced so that the staineless steel axis would not be in contact with aluminium.

The plates were fixed by aluminium rivets.  

After one year I can only be positive on the solution, we will modify to Monel rivets this year.  I feel more secure and when I walk to the mast it is a great satisfaction to see these two new items.  Off course the original plates are here at home and will join the box of all original sparepart of our Swan.

Fair wind to all of you.

Ludovic form Rumtrader

gooseneck plate

gooseneck plate finished