BRe - Replacement of Stainless Steel Below the Waterline

[Stuart Roy]

Regular followers of the Technical Forum may recall various posts relating to corrosion of the underwater stainless steel components on BRe 035.

Corrosion of Stainless Steel Strip Bilge Keel Runners 13/5/2018
Lifespan of Self-bailers 28/10/2019
Centreboard Pivot Pin 31/7/2020

It is possible that the corrosion was the result of a nearby boat using "electric antifouling" but this has not been confirmed either way. 

The corrosion was monitored carefully for two seasons but continued to worsen.  Eventually the bilge strips started to break away, one of the bailers was pushed through the bottom of the boat without removing the bolts (in this event the boat doesn't sink - the sump just fills up) and the centreboard bolt was so wasted that it was impossible to measure its original diameter.  So the boat stayed ashore in 2020 to enable a solution to be implemented.

The work took five weekends of miserable work in the confined space under the boat.  Firstly the screws were all removed and the stainless strips were levered off.  The residue of the Sikaflex adhesive/sealer was scraped off and the screw holes filled.  Unfortunately the Sikaflex had adhered so well that it tore off patches of gel all along the keel area exposing dry glass.  This had to be repaired by laminating from underneath and then, after curing, cutting it all back with wet-or-dry to form a smooth flat surface ready for the new strips.  This preparation phase took more than 3 weekends to do and at times the job seemed insurmountable - though it would have helped if I was much younger with better mobility and quite a bit slimmer.

The new strips are 25mm x 4mm pultruded GRP bedded on Sikaflex with A4 stainless screws every 150mm.  Two bilge runners, two longer lengths alongside the centreboard and a central strip running forward to the waterline were all replaced.  The work was relatively straightforward although a bendy 3m strip, covered with Sikaflex on one side takes some handling when you are working under a trailer.  A palm-sized Ryobi electric screw driver was very useful. 

After fitting, the strips were painted with two coats of two-pack epoxy primer before being coated with Coppercoat to match the rest of the underwater areas.

I had wanted to avoid stainless steel for the centreboard bolt, but could not find any 14mm bronze rod which I thought would be preferable.  So I used A4 stainless steel and this was also painted with two coats of two-pack epoxy primer.  It should be relatively simple to change the pivot pin to bronze if it were to become available in the future.   

Finally the bailers were replaced.  A small gap was left around each bailer base in case the Coppercoat on the bottom had affected the stainless steel.       

So with luck this should be the end of the corrosion story.

Next year it will be time to get afloat and sailing again.  See you on the water!


     
       

[Graham W]

Stuart,

What a lot of difficult work - in the corrosive circumstances, worth the effort.  It certainly looks good and it’s now one less area of concern.

If anyone else is taking on difficult work underneath their boat, and the weather allows it and you have a garden with sufficient space, this post by Matthew shows what he did to make his task easier https://www.swallowyachtsassociation.org/smf/index.php/topic,1220.msg8676.html#msg8676.  As you’ll see, his reason for turning Gladys on her side was so that he could secretly fair in his boat’s centreboard slot and make her even faster than everyone else.

[Sea Simon]

What a lot of hard work, not to mention expense! I think you have been very unlucky; I'd be "jolly cross"!
Well done for all of your efforts. Really hope your problem is now solved.

Has the "potential offender" (pun intended) moored near you gone away, and stayed away?
If in doubt I think I would be moving mooring!

Mentioning moorings I assume that yours, and those nearby metals (chains, weights etc) have been checked?
Years ago, when I had access to a supply of part-used sacrificial anodes I attempted to preserve my own mooring system by attaching anodes. I don't believe that worked; no idea why not. Perhaps too much resistance between individual links and other components?

For the record, and further to our original posts on here, I can confirm that after another (almost) full season afloat on a tidal swing mooring, in a river, my BRe underwater metal fittings have not been corroded like yours.

[Graham W]

In the DCA Bulletin of 1992, one Olaf Swarbrick complained of erosion of the front of the stainless runners on his Devon Yawl.  He speculated as follows: "I suspect this localised corrosion, confined to where the boat lies on the bottom, is the result of the drying mooring on the deep salt mud at the top of Bosham Creek. I would expect that anaerobic conditions and sulphides are involved."  So it sounds like this has been going on for a while in parts of Chichester Harbour.

Like Matthew, he turned his boat on its side to do the repairs.

[Sea Simon]

I agree.....

anaerobic conditions and sulphides....

That could also cause these or similar symptoms, as could galvanic or electrolytically driven corrosion too.

OP should be careful to continue to keep those stainless fasteners, new self bailers etc under close watch!

Please keep us updated.

[Peter T]

I used to have a mooring at the top of Bosham creek and my recollection is that unless you were literally in a mud-berth in the reeds, the mooring areas weren't that muddy.  The bed of the harbour there is ancient compacted oyster shells.  Bosham Hoe, on the other hand, is muddy ( I had a mooring there too and proved it from time to time after making incorrect tidal calculations) but even so, can the conditions be described as anaerobic if the boat is afloat and not sitting in the mud 3 hours either side of every high water?

[Sea Simon]

Also agree with you PT, wrt anerobic muds.

We did discuss this briefly n original post, I think?
 If boat is floating/drying then my money is on the galvanic/electrolytic cause.

To me, the mystery remains;what is "driving" this?
Will be fascinated to hear more as time passes.