Keel Bolts/Nuts/Backing Plates Issue (see pic)

[iangrant]

DO NOT use stainless - they will rot away faster then any mild steel bolts/studs.

Some keels have a thread tapped into them, some have a lock nut in a cavity in the keel (nut either end)

New studs whatever the fixing and new bolts and plates or you'll never trust the integrity of the keel. It needs to come off for a new hull keel seal in any event.

Ian

 

[rhumlady]

Ian,
can you clarify why you wouldn't use stainless in this situation please. I have a 1980 Westerly Konsort which has 8 keel studs into the cast iron keel. All have been removed and show no sign of any corrosion in fact they look as good as new. I am not getting at you by the way. I would like to know why you say this.

 

[srp]

Ian is probably talking about crevice corrosion, which stainless steels are prone to in some situations - usually involving little or no access to oxygen, possibly with scratches or microscopic pits already present. The resultant corrosion, if it occurs, progresses fairly rapidly and looks as though the metal has been attacked by a worm. Not long ago I saw a 1 year old prop shaft which had corroded exactly where the prop fitted, on the taper, to about half its' original section. The rest of the shaft was perfect. The metal doesn't have to be under water to be affected. If it is a critical component that can't be easily inspected then even 316 stainless is not very satisfactory.
Mild steel, while not ideal, is easy to monitor and will corrode more on the visible parts - just like the photo in the first post. I would bet that the threaded stud under those nuts is in pretty good condition compared the nuts themselves.

 

[Dipper]

My studs and nuts were high tensile steel.

I agree with your earlier post about glassing them in. My original nuts were glassed in and minor cracks in the fibreglass allowed water ingress which led to rust which expanded and enlarged the cracks etc etc. A few good coats of primer/bilge paint as per manufacturer's instructions would be better. I painted mine with several coats of the old fashioned rubberised car body underseal and 8 years later they are still rust free.

 

[iangrant]

Got here too late it's been answered.

When I replaced the keel bolts on an old Jeanneau I imediatly though they should be stainless, then the engineering company making them showed me what happens to stainless when you starve it of oxygen.
Can be seen on stainless deck fittings, rust streaks will appear pretty quickly on bits bolted together.

Ian

 

[rhumlady]

I must try a magnet on the keel studs then. Thanks for the info.

 

[Slowtack]

Why then are so many boats built with S/S keel bolts? Over the past few years I have seen keel bolts removed for inspection from UK and Scandinavian built boats dating from late 70s, to late 80s. All were stainless and showed no deterioration.