lead in aluminium

[ted655]

If you put lead ballast in an aluminium keel, aren't you well on the way to making a battery? Add saltwater and something is going to errode. No?

[Cian Groves]

Make your keel into part of your fuel tank and run fuel around it.

Cheers,
Cian

[Raggi_Thor]

People do that, and it seems to work OK, maybe because the top of the lead is covered with epoxy?
When we attach a lead bulb to an aluminium keel, we make sure there is a layer of epoxy between the two metal parts.

[ted655]

Finally... back online. (hurricanes are a mighty force)
Actually, I want to "fill" a hollow keel space. Pouring in hot lead prevents any coatings between the 2 metals. After pouring, the top could be coated to stop contact with bilgewater.

[Tim B]

should be ok as long as it's kept dry everywhere (and that includes water seeming in from the outside of the keel.

Or you could turn it into a ballast-water tank... as long as you coat the inside with epoxy first.

Tim B.

[ted655]

Thanks. This is a Sharpie flat btm. A cubic foot of water weighs around 9lbs, a cu.ft. of lead is 700lbs., I need the space so I can't afford the tank size.
I should be able to keep it dry if I epoxy the top.

[PAR]

A cubic foot of water weighs a lot more then 9 pounds (you're thinking about a gallon). Try over 62+ for fresh and over 63+ for salt.

There are several methods for isolating dissimilar materials. It shouldn't be a big concern.

I wouldn't pour your lead in, but cast ballasting pigs of stackable and carryable sizes, that could nest in the keel. The lead will shrink when it cools and will likely cause wholesale plate distortion to boot. The pigs can be adjusted to trim out the boat during launch or if major changes take place (engine upgrade, etc.) These same liftable pigs can also lighten the boat by a substantial amount if stuck on the hard someplace far from a tow. Toss them over the side with a line and float. wiggle the lighter boat off and pick up your ballast again (it's cheaper then SeaTow) They can be fixed in place in a number of clever ways.

[ted655]

Good advice all around! Thanks, I will do as you suggest. Duh! I was thinking gallons, and... I should have caught it. The displacement formula was my clue.
A fellow can't be handsom AND smart I guess. :D

[PAR]

I manage to struggle through some how. It's difficult being this handsome and smart too, but a burden I wear . . .

[JimCooper]

Ted

If you want the metal experts to give you advice you should probably post in the metal boats area. I found that the experts tend to inhabit only certain areas of this forum.

Your question was argued already by the knowledgeable laddies

see the box:

http://boatdesign.net/forums/showthread.php?t=5963&highlight=Aluminium&

I have been aboard an alloy trawler that a roll of copper pipe ate several holes in her hull. I think lead would do the same if it was in contact.

Cheers
Jim

[JimCooper]

Ted
I should hae said

That area to post is

Boat Design Forums > Construction > Boatbuilding > Metal Boat Building

cheers
Jim

[ted655]

Does'nt sound like a method was settled on. I'm thinking lead shot, poured into suitable lengths of PVC pipe, then fit into place is the answer. these little 6"dia "logs" would fit nicely into the space and there would be no contact between metals.

[MikeJohns]

I just added an interesting observation to the thread/posts Jim refers to above.