Lead Ballast in steel

[steelfloats]

I am about to add lead trim ballast to the hollow steel keel of my yacht. I intend to melt and pour in, I am aware of safety procedure, moisture (not) splashing etc. Can anyone advise me if there would be electrolysis once the lead is in place, and would it be wise to cap of the lead surface with 1) cement or 2) a steel plate seal welded? Many thanks in advance

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[MainlySteam]

It should not be a problem as far as I am aware as long as no water can get in there as any coating system will have been burnt off during the pouring of the lead. However, if the cavity is open to bilge water then I would steel cap over the top of the lead and fill the voids between the lead and the steel plating of the boat with diesel to prevent any corrosion.

We have a fin keel and the whole of the void from the top of the lead up to the bottom plating of the boat is the fuel tank. Perhaps you could use the space in some similar way.

John

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[richardandtracy]

Shouldn't you keep some trim ballast 'mobile' - or do you have enough booze you can move?

Anyway, back to the main point..
Could I advise against pouring a lot of lead into the keel in one go.
If more than a couple of pounds of molten lead goes in you'll be supplying enough heat to distort the keel, and it won't be able to go back when the lead solidifies. You could end up degrading the boat's performance and maybe locking in rather high stresses. Another, less obvious, problem can occur with large pours of lead. It stays hot for a long time, and this can allow grain growth in the steel. It would have the effect of reducing the locked in stresses (beneficial), but at the price of a general reduction in the steel strength properties, increase in ductility and increase in fatigue sensitivity. Some steels (eg grade 43 or S275 [depending on how modern the boat is]) are to all intents & purposes immune to the grain growth problem though.

As an alternative - cast some near to final shape lead blocks using a green sand cast or something similar and then position the blocks in the keel once cool. The last job would be to pour a small amount of lead over the block as glue.

If you prevent moisture getting to the lead, there will be no corrosion, so you could use paint, steel, concrete or epoxy. Personally I'd go for steel capping, but wear a fume mask when you attach it just in case you manage to boil off any lead when welding.

Regards

Richard.


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[MainlySteam]

I agree with your warning about the effects of heat. I was not present when our keel was poured (it is a fin so the short bottom piece filled is not at much risk of distortion) but I believe from memory that the yard packed the ballasted part of the keel with lead ingots/bits and then poured lead about them.

John

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[Talulah]

This is what we did when pouring our keel many years ago. Made ingots by melting lead in a saucepan. Led cools, turn saucepan over, ingot drops out. The sides of the keel were then lined with lead sheet, the ingots put in situ and the gaps filled with molten lead. Finally the lead was sealed in with fibreglass. The sides of the keel became very hot. The boat is still sailing today 20 years later with no adverse effects from molten lead. Note. We did not do the whole keel in one go. Maybe 4 inches at a time.

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[steelfloats]

Thats good positive feedback, I think that lining with sheet, big ingots and then fill the spaces with molten lead, finally cap with steel. The steel is all 43A, then to use the rest of the volume as fuel tanks I guess a good power wire brush and some fancy paint??? Thats the next question! Seriously, I will be completing the ballst this weekend, would it be possible to use the remaining void for water (water being more dense than Diesel) and any ideas of paint or lining systems. I was put onto a rig coating of Aquaeous Bitumastic but have failed to come up with a supplier. Many thanks for all the help

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[MainlySteam]

A point to remember in case not thought of is that the lead should be restrained from moving if the boat is ever inverted. In our keel (a fin) there are a number of vertical steel floors that run from top to bottom. A semicircle was cut out of the bottom of each floor so that molten lead would flow through, locking the whole of the ballast in place once it had set.

Our water tanks are integral to the hull (in the bilges) and are coated with a two pot epoxy system (no topcoat needed) - many of the primer/undercoats commonly used for coating boats are food grade approved and are used in the food industry. We had a problem with the paint we used as for several weeks the water had a very strong chemical taste, much to the surprise of the paint manufacturer, but went entirely away in a short while - mention it in case you experience the same. Was a nuisance as we were living aboard at the time.

I would be wary of storing water in a keel if that is where your ballast is unless it is entirely separated from the lead (both for health and structural reasons) and the tank so formed is easily accessible for inspection and repainting in the future. If a fin keel you may wish to consider any possible effects on the integrity of its structure should the water storage at some stage cause corrosion in it.

If the keel is a fin and you use it for fuel storage then if not already thought of, it may pay to check that your engines fuel pump can cope with the lift. Ours can as best as I know - we have never had the tank less than 1/4 full however.

John

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[AndrewB]

My yacht uses a varient, where the lead ingots (or more accurately, fragments) are encased in concrete rather than molten lead. This avoids the heat problem, but obviously the resultant mix isn't quite as dense. The only problem has been that in time (10 years) the surface of the concrete has tended to degrade under bilge water, until the water starts to penetrate. After several failed solutions such as painting with conventional bilge paint and capping with GRP, I think I've now solved this by drying out, chipping back the affected concrete a couple of inches and replacing with a fresh concrete cap, then painting with bituminous epoxy. There is no sign of corrosion or electrolysis.

 

[boatmike]

As lead is inert there is no problem with electrolysis to concern you. Pouring lead into a steel keel should be done in stages though as others have rightly suggested. A good plan I have followed in the past is to weld cross ties (say 1/2 bar) across the keel plating inside at approx 1ft vertical intervals before pouring. this minimises any plating heat distortion when pouring lead and serves as an anchor for the ballast when set. If in doubt start with small quantities. If you raise the temperature of the hull plating enough to discolour it on the outside slow down!
Oh and one silly point. I did see a pratt (professional in this case) in San Remo once who set light to a boat and burned the shed down by trying to fill an antifouled keel..... If you do have the keel shotblasted first it enables you to immediately identify if you are heating the plating when pouring the lead but it's obviously not necessary..... Capping it in by the way is just creating a cavity which can promote cavity corrosion from within. Personally I wouldn't. Most surveyors would prefer to inspect the ballast at intervals. Lloyds and DNV class hulls subject to periodic survey are usually never fully encapsulated. Often however there are "floors" created just to tie the top of the keel above the ballast. these are usually flat plate with a full pen weld from the top say 1 ft long with a 2 ft gap in between. Thick application of weld through primer on the bottom face before welding in and a bucket of nice hot tar on top to finish off and it should last for longer than the rest of the boat! Good luck!

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[boatmike]

Just read this again. Forget the hot tar! coat top with an epoxy based undercoat to ecapsulate lead, and paint out with tank liner. Contact any marine paint company for advice on food quality liner paint for water or diesel resistant paint for fuel. Hempels, International or Blakes will all offer products and have technical depts that are helpful.

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[Birdseye]

Cant comment about the lead, but when I last checked epoxy coats none of them were food grade approved. mostly this seemed to be because of the cost, but several were nasty and toxic. naturally, no one would commit themselves to their coating being suitable for water tanks when they had not gone through the approval procedure.

remembering that diesel is often cintaminbated with water, I would be inclined to make a simple grp tank for diesel or water to sit on top of whatever is holding the lead in situ. you know what will happen if you use a design that will not allow removal of the tank / inspection of the ballast. you will hit something, penetrate the keel and the surveyor will want access. sods law.

<hr width=100% size=1>this post is a personal opinion, and you should not base your actions on it.

 

[boatmike]

Do you want to read my post again? I said (if I was not clear first time) seal the lead with epoxy and THEN paint out with either food grade resin or diesel resistant resin. As I am by discipline a boatbuilder I suggested contacting professional paint companies for suggestions on a final tank lining. They generally know what their products are for and are very helpful.

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[MainlySteam]

Seems I am making a habit of being with Mike for a change, twice in one day /forums/images/icons/frown.gif, but have to say that there are plenty of epoxy paints (including those used in the marine industry), which are food grade. They are widely used here in food processing plants.

Regards

John

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[boatmike]

My turn to agree with "Steam" in public this time (mustn't make a habit of this!) Much better to use the void as a diesel tank than a water tank. No corrosion problems with diesel! I would still seal the top of the lead with a hydrocarbon resistant epoxy though as I think (not sure) that the diesel might pick up lead traces and contaminate the fuel. Probably good for anti-knock though.. Leaded diesel fuel.... Hmmm......

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