Ballast Keel Cracking

[ducked]

A example from near you @ducked.

The Forth Rail Bridge has been coated with a glass flake epoxy formula paint which should suffice for about 25 years. It replaced an inferior paint system that had been in use since the bridge was built. These types of coatings are useful and many have used similar technologies on their keels to increase time between coatings, which is their main advantage. Of course there are lower cost options which will work but maybe requiring more frequent attention.

Wickipedia says they used boiled linseed when the bridge was built (I suppose with red lead). I was going to try that with aluminium but eventually decided not to, since the sunflower oil seemed to withstand the effects of rain exposure fairly well while still wet, and eventually sets, though slowly.

I have used it on the more exposed mast taburnacle, and will give it another going over when I take the mast down. Considering also using it on the boom but havn't decided yet.

If it was good enough for The Forth Bridge...

 

[AntarcticPilot]

Wickipedia says they used boiled linseed when the bridge was built (I suppose with red lead). I was going to try that with aluminium but eventually decided not to, since the sunflower oil seemed to withstand the effects of rain exposure fairly well while still wet, and eventually sets, though slowly.

I have used it on the more exposed mast taburnacle, and will give it another going over when I take the mast down. Considering also using it on the boom but havn't decided yet.

If it was good enough for The Forth Bridge...

The original paint job on the Forth Railway Bridge notoriously needed one end redoing immediately after they'd finished at the other end!

 

[ducked]

The original paint job on the Forth Railway Bridge notoriously needed one end redoing immediately after they'd finished at the other end!

Of course. But its quite a big bridge, so, without knowing the effort/unit time, that tells you almost nothing about the durability of the coating, though I would assume its quite a lot less than uber anally applied epoxy.

I would bet money that HnS considerations were a factor in the Nu Bru adoption, since the enclosure and scaffolding required will also protect the operatives working at heights which, nontheless, scared the **** out of me.

For my purposes if the underwater stuff lasts a season substantially intact I’ll be very pleased. Taburnacle and anchor doesnt even need to do that, since its trivial to touch up.

How about slurry blasting with a pressure washer, next time, if there is one?

 

[ontop]

How alarmed would you be about these, and what, if anything, might you do about them?

Local yardy opinion is its just surface filler. I dunno about that (the grey stuff is aluminium I ground on) but they have more experience than me…

I suppose a twin keel Trident might work?

If its an Iron keel, the rust is expanding & splitting the GRP

 

[oldharry]

If its an Iron keel, the rust is expanding & splitting the GRP

Only if the ballast was encapsulated, which it isn't on the Trident. It's never been reported through the Trident Owners Asscn, on even the most neglected hull.

 

[ducked]

Only if the ballast was encapsulated, which it isn't on the Trident. It's never been reported through the Trident Owners Asscn, on even the most neglected hull.

Well it wouldnt be, because it couldnt happen.

I suppose its theoretically possible that someone had attempted encapsultion post construction, but theres no sogn of that here.

I suppose its also theoretically possible that upward expansion of rust at the hull/keel interface could split the hull, but theres no sign of that either and I rather wish I hadnt thought of it

 

[neil_s]

The ballast keel on my 1977 boat was epoxy coated by a previous owner and this has now failed with many rust pimples forming. I have found that the mast effective treatment is to just go over it with a bit of sandpaper to smooth off the lumps and then slap a good coat of antifoul over it. My comment about the chipping hammer, in my case, is relevant to the cast iron drop keel that I have housed in the fixed ballast keel. To stop it jamming, it's necessary to chip off the build up of rust occasionally - that can be several millimetres thick. This exposes the real surface of the cast iron allowing you to assess it's real condition. Again, painting is problematic (I have tried Hammerite in the past), merely speeding the build-up. Cast iron is slightly porous and takes up salt when immersed and then has the seeds of it's own slow destruction built in. You could have an experimental tap over your crack and see if a big lump of rust falls off!

 

[ducked]

The ballast keel on my 1977 boat was epoxy coated by a previous owner and this has now failed with many rust pimples forming. I have found that the mast effective treatment is to just go over it with a bit of sandpaper to smooth off the lumps and then slap a good coat of antifoul over it. My comment about the chipping hammer, in my case, is relevant to the cast iron drop keel that I have housed in the fixed ballast keel. To stop it jamming, it's necessary to chip off the build up of rust occasionally - that can be several millimetres thick. This exposes the real surface of the cast iron allowing you to assess it's real condition. Again, painting is problematic (I have tried Hammerite in the past), merely speeding the build-up. Cast iron is slightly porous and takes up salt when immersed and then has the seeds of it's own slow destruction built in. You could have an experimental tap over your crack and see if a big lump of rust falls off!

I wouldnt, personally apply antifouling directly to exposed metal, since I think, depending on whats in it (copper, for example) it might encourage corrosion, and isn't likely to be a very good isolating barrier.

Re the drop keel, I think I've read of people, no doubt in the "bad old days", pouring some sump oil into centreboard cases to inhibit corrosion and fouling, and perhaps also to prevent rot in what would generally be a hard to access wooden structure. The oil would float on top of the seawater and the plate would be lowered through it, so some of it would be carried down with it and end up in your wake. Turbulence under sail would probably put more there, and maybe squirt some up through the case-top too.

Whether it'd be worthwhile to repeat this trick with a more environmentally benign oil like sunflower I'm not sure, but I'd guess not.

 

[ducked]

Of course. But its quite a big bridge, so, without knowing the effort/unit time, that tells you almost nothing about the durability of the coating, though I would assume its quite a lot less than uber anally applied epoxy.

I would bet money that HnS considerations were a factor in the Nu Bru adoption, since the enclosure and scaffolding required will also protect the operatives working at heights which, nontheless, scared the **** out of me.

Come to think ont, with a small dedicated in-house painting team, which is probably how it was done pre-epoxy/HnS, continuous painting is exactly and inevitably how you would optimally manage it, so the trope probably tells you nothing at all about the durability of the coating.

AI has "The myth that painting the 1.5-mile Forth Bridge is a never-ending, continuous task is no longer true..." suggesting its a bit confused about what "myth" means.