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Sail & Rigging - Mast corrosion on Swan 38
15 December 2018 - 11:46
#1
Join Date: 01 April 2007
Posts: 83

Mast corrosion on Swan 38

Dear all,

(I decided to start a new thread, because the other thread was under Matteo's swan 47 title)

after several posts on the forum about galvanic corossion, I removed my boom fitting on the mast, see picture: rather big hole.......

 

next thing is to remove the spreader fitting.

 

will keep you informed......

 

 

 

jan

 

yulunga 38/110 

 

19 December 2018 - 16:39
#2
Join Date: 01 April 2007
Posts: 83

19 December 2018 - 16:50
#3
Join Date: 01 April 2007
Posts: 83

Dear All,

See above picture of a gooseneck repair on Daniele Fua's swan 41. I wonder if a repair like this is strong enough for my situation (see first post).

Matteo's repair (sleeve inside) on Vanessa is probably stronger but also much more complex. Or is it (only ?) a cosmetic difference ?

Any thoughts or advice on this matter ? 

Kind regards,

jan, yulunga38/110

 

19 December 2018 - 17:49
#4
Join Date: 01 April 2007
Posts: 83

Sorry, photo of Daniele Fua's swan 41 now below (above didn't work).

jan

22 December 2018 - 08:26
#5
Join Date: 02 January 2008
Posts: 1312

It would be of interest if Daniele could disclose if there are two welded patches - one flush with the mast wall, about the size of the stainless fitting, and another, slightly bigger over it on the outside?

Anyway, the stainless fitting probably needed modification in order to fit onto the outside patch.
Merry Christmas to all!
Lars

23 December 2018 - 14:58
#6
Join Date: 30 January 2007
Posts: 428

Dear friends,

I do not know exactly how the problem was fixed and if there is something hidden under the large visible patch.  My guess is no because the only pictures I received from the man who fixed it are the ones shown: "before the cure" and "after the cure".  Apparently a wide margin of healthy aluminum was used and this reassures me; the attached picture shows the pencil marks which define the boundaries of the new patch. Unfortunatele the man who did the job, passed away few years ago so presently I have no way to know more than this.

At that time I was much more trustful in people, I knew less and tended to accept what yard workers would suggest without asking very much. Not any more...

Daniel, 411/004 Luna Menguante.

23 December 2018 - 17:39
#7
Join Date: 01 April 2007
Posts: 83

Dear Daniele,

Thank you very much for your reply.

If the corroded part is not removed and no patch is inserted, then the visible patch is "it". The question remains the same: is it as strong as the original mast and will it be sufficient ?

I noticed also that the welding seam is not continuous ? Why is that and is it possible for salt water to enter between the patch and the mast ? Why not make a continuous welding seam ? 

Kind regards,

jan 

yulunga 38/110

09 January 2019 - 09:52
#8
Join Date: 30 January 2007
Posts: 428

Dear Jan,

I enclose more pictures made few days ago which display the patches installed in March 2005 on my mast.

As you can see, the patches are rather thick: 10mm at the gooseneck and the lower end of the vang, and 8mm elsewhere.

I still do not know what is under the patches but my guess is that there is still the old "rotten" aluminum. Following Lars advice I will try to check it with an endoscopic camera sending the fiber through the halyard openings.

Indeed the weld is discontinuous and, yes, in principle some water could seep between the mast and the patches but the metals are the same and no galvanic corrosion is expected.

As Lars suggested, the inner curvature of the stainless steel plates was changed in order to match the new curvature of the surface.  Plastic sheets keep the different metals galvanically insulated.

There is no anomalous sign of bending of the mast where the weld was made.

I am sorry I have no answer on why the work was performed like this but, overall, everything appears to be quite strong and after 14 years nothing seems to have changed.

Daniel, 411/004 Luna Menguante

Patch at the gooseneck

Patch at the lower end of the vang

Patch at an eye on the mast

20 January 2019 - 15:08
#9
Join Date: 01 April 2007
Posts: 83

Dear Daniel,

Thank you very much for your answer and pictures.

Yes, you are right that water ingress is no real problem because the patches are of the same material ! And it is reassuring to hear that it strong enough (14 years !). Still I can't think of a reason for the weld to be discontinous.

 

My “mast-man” suggests to cut out the corroded part and then to insert strips in the mast of about 80 cm length. The strips will be welded by means of holes in the mast to the strips.

 

Because the weldings and the strips are of aluminium there will be no galvanic corrosion.

 

Then the cut-away part will be padded with a new piece of aluminium and also welded to the mast.

 

In his opinion  this solution is quite easy and very strong.

On the other hand he cannot explain why it is better than your solution, but it eliminates the need for changing te gooseneck.

 

I am considering however to make a similar patch as yours in addition to the welded strips and to have a aluminium gooseneck made. Then I will have a solution that will not corrode.

 

Kind regards,

Jan, 38/110 YULUNGA

 

 

 

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