What sort of bolts should I use.

[jacksevens]

I would like to bolt some casted lead on to the outside of the bottom of my keel to add more balast. I was wondering what sort of bolts would be the best to use with lead as I do not want to have any electrolic action between the bolts and the lead. I was thinking of stainless steel bolts would they be best ?

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[Avocet]

What is your keel made of, cast iron?

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[jacksevens]

concrete in a glass fiber hull

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[paulrossall]

Surely it must have lead balast in the keel allready, or is it iron, certainly must be something heavey built in.

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[oldsaltoz]

G'day Jack,

When you drill the holes thru' the keel, they will need internal sealing to prevent water getting into whatever the keel has been filled with.

To do this, drill the holes 12 mm oversize, apply a couple of coats of resin and fill the holes with closed cell filler or fibres, when cured, redrill to suit the bolts you plan to use.

I hope this helps. . . . . . .



<hr width=100% size=1> Old Salt Oz /forums/images/icons/cool.gif Growing old is unavoidable. However, growing up is still optional.

 

[Gordonmc]

Stainless steel should really not be used below the waterline as it relies on the presence of oxygen to form its protective layer. Crevice corrosion is the result and its probably more vigorous than galvanitic reaction.
Go for galvanised or, best of all, bronze.
I tend to agree with the other replies, that you would be better increasing the density of the existing ballast in the void designed for the job. Hanging new bits on the side/bottom of the keel introduces new complications.

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[richardandtracy]

I second the 'No SS' motion. Crevice corrosion can be a real problem for SS, and once it starts, it severely accelerates fatigue effects.

The trouble with bronze bolts is that you'll need more (they have a lower yield point than steel bolts).

Personally I'd advocate heavily galvanised steel, grade 8.8, but no stonger as they tend to get a bit brittle at higher strengths than that.

Is the structure of the boat OK to take extra leverage of more weight at a the end of the keel? Do be careful with this, and possibly ask the designer.

Regards

Richard


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[jacksevens]

You would have thought so - but so far in my exploratory sweating and puffing and chipping into a very hard concrete (made of flint stone presumery becauise of its' density) I have not found any signs of any metal balast in there yet. The reson why I am thinking of adding the lead to the outside is because I ca'nt bear the thought of months and months of hacking out the old concrete! The boat is deafenately under balasted and far too tender for the type of boat that she is - 26 ft Folksong.

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[Oldhand]

I would only recommend Monel Alloy for your intended fasteners. As Monel bolts may not be readily available you would proabaly have to use studding and A4 stainless nuts.

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[jacksevens]

Thanks for your suggestions folks - now I am not sure if I should just put up with the hacking at the old concrete and add the balast that way by making acouple of insertions into the concrete say 18 inches wide through to the bottom and filling those with lead and sealing them with resin; or go for the lead on the outside idea -any thoughts?

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[BarryH]

What about casting the lead in two teardrop shapes. Afix these either side of the keel with something like a polyeurethane adhesive then encapsulate the lot in grp. Fair the thing in to give a nice smooth finish and then antifoul.

Looks more like it should be there, better water flow and not a bolt on carbuncle. Fit and forget. You'll need to do a bit of maths though to find out what sort of weight you have to add.

Well, thats a stinkies view on it anyway.

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[Avocet]

If it was me, I'd get the biggest hammer drill I could lay hands on and find the biggest masonry bit it wouldturn then drill as many holes as deep as possible into the concrete and fill each one with lead. Drip the molten lead in reasonably slowly to avoid the heat building up and cracking something.

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