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Sail & Rigging - Mast Through Bolts.. wear and replacement
14 April 2021 - 16:23
Join Date: 03 March 2007
Posts: 240

Mast Through Bolts.. wear and replacement

Dear all,

As I discussed in an earlier thread I am redoing the standing rigging on Stormsvale our Swan 40.  The stainless steel fittings on the mast to which the shrouds are attached have some hairline cracks.. so replacement is ongoing.. I am also replacing the bolts at the masthead and just below the spreaders. The bolt  at the mastheasd is Stainless steel circa 16.6 mm dia while the lower bolt is 25 mm dia  I believe it is titanium but not sure..  (Question for Lars)

I am replacing the  stainless steel tangs (where the pins go through)  both at the masthead and below the spreaders with Colligo cheeky blocks for Dyneema.  These use  titanium bolts, 16.6mm in diameter.. So at the mast head it is a direct issues. At the spreaders I will have to sleeve a 16.6 mm titanium bolt with a 316 Stainless steel spacer. Not a corrosion issue   but maybe a strength issue?? 

Question for the Professor, am I right that the original bolt at the spreaders is titanium? Any thoughts on this  and the process are appreciated!!

Of note, the bolt below the spreaders is much weakened due to wear  from the Halyards.. Yes Stormsvale has a lot of sea miles on her.  Anywa, just a heads up for your mast maintenence list... 

The dyneena shrouds are now spliced stretched and retretched and set for installatio.  While my wife was knitting I was splicing.. good relaxing winter activities...

Spring is here, and projects  are nearing completion... Quadrant and sheeves refurbished. New bushings in the binnacle, New Stainless Steel wire in the forestay with New bushings in the roller furler. Coppercoat to go on as soon as it heats up a bit more.  All chain plates removed checked and reinstalled.. Yes it has been a busy winter.. 

Fair Winds!!!!




15 April 2021 - 06:44
Join Date: 02 January 2008
Posts: 1547

Dear Mike

The bolt originally was stainless. It is suggested that you calculate the weight of the bolt in stainless and titanium, and determine which material it is by weighing.
It is likely that the halyard chafe on the bolt is on the forward side. Moving the halyards to the aft side of the bolt is likely to eliminate the chafe, as the mast usually has a small bend forward in the middle.
Kind regards

15 April 2021 - 18:35
Join Date: 03 March 2007
Posts: 240

Thanks Lars,


I  checked it with my machinist and I think it is some type of aluminum. 


As always your advice is much appreciated!!!


All the best







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