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Sail & Rigging - Crack in mast, repair suggestions?
08 February 2022 - 12:29
#1
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cosmolittle
Join Date: 02 March 2007
Posts: 83

Crack in mast, repair suggestions?

After a presale rig survey, a slot was discovered in the front face of the mast, about 30cm from the deck. This had been covered with a small plate with two pop rivets. The surveyer noticed stress cracks from the ends of the slot ( which I had never noticed in 15 years)

The surveyer said that the mast was past repair. I am not yet convinced of this.

The riggers have suggested sleeving the mast with a long internal sleeve up to gooseneck level.

perhaps an alternative would be to drill the cracks to stop them speading, and then weld (using tig welding) a plate over the whole area.

 

slot position

detail

detail
08 February 2022 - 14:04
#2
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matteosalamon
Join Date: 29 January 2007
Posts: 1019

Dear Cosmo,

your pictures demonstrate these masts are incredibly strong and really built to last forever.

I agree with the suggestion to insert a sleeve from inside, a repair already done on more than one S&S Swan over the years, and which proved itself to be perfect (I had the corrosion problem underneath the stainless steel boom plate, so it was quite serious too, and I welded a patch too. Mast was then painted white). 

The crack looks as it wants to go further, and by the way welding is not good for anodization.

Lars will be more specific, of course.

I had a similar problem on Vanessa mast, in 2015, and a (half) sleeve was inserted and screwed from outside, I am checking it regularly and after 7 years I am noticing zero problems.

Fair winds!

matteo (47/069 Vanessa)

half sleeve going in

Half sleeve screwed from outside
09 February 2022 - 16:42
#3
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the professor
Join Date: 02 January 2008
Posts: 1547

Dear Cosmo and Matteo
The mast lower part mainly sees compression loads, but if the mast has been bent or pumping, this caused tension in the forward part, as shown by the cracks continuing outwards from the hole.
The recommendation is to sleeve the mast on the out- or inside to the width of the total length of hole and cracks. The sleeve length and screw spacing can be taken from the mast half height joint. 
Drilling holes at the end of the cracks should stop them from growing any longer, but an eye to be kept on them 
Kind regards
Lars
10 February 2022 - 09:14
#4
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cosmolittle
Join Date: 02 March 2007
Posts: 83

Dear Lars,

Thank you for the reply. Allspars have agreed that a sleeve is the best solution, however we are undecided as to whether any welding should be attempted after the sleeve is fitted. Possibilities are to weld up the slot with tig welding, and/or weld an aluminium cover plate over the slot, or just to cover it up with a stainless plate pop riveted to the mast.

  Regarding the sleeve, this could be 5mm or 6mm aluminium. Is there any problem with making the mast too stiff in the lower section?

What size of drilled holes do you recommend to stop the cracks progressing?

regards

 

Cosmo Little

 

 

 
10 February 2022 - 16:55
#5
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the professor
Join Date: 02 January 2008
Posts: 1547

Dear Cosmo
Thank you for the information.
The hole and cracks can be welded in addition to the sleeve reinforcement, but take care to remove the anodization in the welding area, and open the cracks to V-shape for proper penetration. 5 mm holes suggested. 
The screws at the top and bottom of the sleeve to be staggered for making the stiffness transition more gradual.
I would not weld a cover plate over the repair, instead attach a very thin anodized aluminium sheet by gluing - same colour as mast.
Kind regards
Lars
03 November 2022 - 15:04
#6
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snowwolf
Join Date: 11 November 2010
Posts: 18

Got a very similar slot cut into base of Snow Wolf's mast (Swan48) so must have been something Nautor's did but I don't know what it was for.
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