casting a lead keel

[PeterSibley]

Now I know there have been numerous threads on this and I have reread them however I have a couple of other queries.

I have to pour a 5600 lb keel,its a simple shape,roughly 9" wide ,12" deep x 12 ft long with some taper.The top is flat. I intend to make the mould from 2 layers of 3/4" ply heavily braced and buried in the ground however I realise the ply will scorch badly and cause gas bubbles etc.So I need to line it with something refractory.....any suggestions? I had thought of sheetrock screwed to the inside of the mould ? Does anyone know a better product?

Second query.Does anyone know the shrinkage allowance for lead ?

and a very healthy and prosperous 2005 to all
smile.gif

[kc8pql]

I've read of plaster of paris being used for this. The caution is that it must be completely dry before pouring the lead to avoid a steam explosion.

[bromleigh]

You need do nothing more than ensure that the ply is dry. It will release quite nicely on its' own!!!!

[bromleigh]

A further ex. The cool of the substrate will prevent the ply from scorching, and, I assume you will be allowiny .25 inch all round for
shrinkage, so not to worry you should be power-planing smooth anyway. Regars, and a very Happy New Year to you and yours.

[mmd]

Hi, Peter. Happy New Year to you, too.

I wouldn't recommend using anything that can absorb and hold moisture as a liner for your mould. Sheetrock does this in spades, and messing about with nearly three tons of liquid lead is nothing to take lightly. The last keel casting I was involved in (31,600 lbs), we built the mould out of scrap steel plate, and then sold the scrap plate back to the scrapyard. I suppose you could line your plywood mould with light (14 guage?) sheet steel - the cost would be miniscule compared to the mould and lead. Plain steel would be best, but galvanized would do as long as you pour outdoors and have a breeze (natural or artificial) to waft away the noxious fumes that molten galvanizing gives off.

Shrinkage will be around 3/16" per foot, or about 1-1/2%, but this is dictated by the shape & size of the casting. Breadth and depth will be in this range, but length not so much. The top of the casting will sink inwards to compensate for contraction. If your top-of-keel flatness is critical, you may want to consider casting it upside-down. This will ensure that the faying surfaces are really flat, and your shaping/filling will be on the exterior surface of the casting.

Are you casting-in the keelbolt holes or will you drill them after the fact?

[Jay Greer]

I've cast a few keels in my time. If you choose to use ply wood as a mold, it is a good idea to coat the inside with several coats of sodium silicate, known as "Water Glass". Be sure to allow plenty of drying time before using the mold. The mold should be well banked with soil or sand and shored up as well; even safer if it is poured below ground level. A small amount of Antimony added to the molten lead will make it easier to drill file and plane later. If using metal cores for bolts, they should be coated with graphite powder to allow withdrawl.
A note on pouring below grade is to look out for gophers. I had a friend who poured ten thousend pounds of lead down a maze of gopher burrows that connected to the mold he dug.
It took him weeks to reclaim the lead!

[NormMessinger]

I would like to have seen the look on that gopher face when he saw that wall of molten lead coming at him.

[PeterSibley]

mmd ....that is a good suggestion re the sheet metal.I hadn't thought of it ! How did you do the round overs on the mould ? Regarding the sinking on the top ,I had imagined setting aside a couple of hundred pounds and feeding it in as the rest hardened,maintaining a pool with a weed burner.I'll give the upside down pour some thought.

For the keel bolts I plan to core openings in the sides of the keel ,about 6" down from the top and bore down through the top of the timber keel .It is a method Larry Pardey used and will save a lot of boring and bolt material.

Jay,I have 5 gallons of sodium silicate here,I'll try an experiment on the ply.Perhaps make up a small, say 20lb ,mould and see how the molten lead affects it.No gophers here in Austtralia :D We've got everything else !

[Frank Wentzel]

Do not use either drywall or plaster of paris. Both are composed of gypsum (calcium sulfate) that sets by combining with two molecules of water for each molecule of calcium sulfate. The casting temperature of lead is high enough to cause the release of this water. On very small casting jobs this may not be too much of a problem. That is the heat capacity of the small volume of lead may not be enough to cause a serious eruption. With the lead in the multiple ton range you will have all the caloric input you need to cause a spectacular steam explosion.

/// Frank ///

[PeterSibley]

OK Frank, bearing your advice in mind I have found an old copy of Classic Boat ,January 1997,with a very useful article on casting a lead keel.

The author used a 50/50 mix of kaolin and aluminium oxide plus a bit of PVA as a refractory wash over chipboard for a 3 ton casting and reported success.How would you feel about that ? (Properly dried of course).

[mmd]

Hi, Peter.

The casting was done with sharp corners and power-planed to shape to fair in to the hull form after installation on the keel. Another complication on that ballast keel was that the keelbolts were cast in place to line up with the structural floors, requiring pretty high precision in assembling the mould.

Keeping a molten puddle on top while the casting cools and contracts will work. There will need to be a bit of shaping of the faying surface to serve it up tight to the keel, but not much.

Pocketting the keelbolts in the ballast keel is a good way to go. Just be selective of what you use to fill the pockets when finished - someday somebody will have to dig it out to do an inspection or replacement, and you wouldn't want to make their life too difficult.

[PeterSibley]

Hmmmmmmm
Pocketting the keelbolts in the ballast keel is a good way to go. Just be selective of what you use to fill the pockets when finished - someday somebody will have to dig it out to do an inspection or replacement, and you wouldn't want to make their life too difficult.
Bondo or concrete after covering the threads in a plastic bag ?

[Dave Fleming]

Pine Tar the threads and the interior threads on the nut,assemble, tightening well, fill pockets with a pack of stiff concrete mixed with red lead, smooth off and let dry.

NOTE: this should be done after all fairing of the lead is completed. Grit from the concrete will play havoc with tool edges, don'cha know.

[mic]

Hang on guys! tell me more about this system of pocketing the keel bolts, i always thought keelbolts were cast into the mould. What's the advantage of coring into the side of the keel cause i dont understand the exact fixing detail.

[John Meachen]

As I understand things, by pocketing the keel for the lower end of the bolts,the bolts do not have to extend to the bottom of the keel.You create a horizontal rectangular recess into which the lower ends of the bolts are inserted and a nut is fitted.After the keel is tightened,the cavity is filled.As you may have seen from the thread,using too tenacious a filler will not earn any praise from the man that has to dig it out.

[Paul Scheuer]

The Kings Cruiser had pockets in the cast iron ballast, about halfway down. They were soft wood blocks driven in and faired. They weren't cosmetically perfect but they don't have to be. One advantage is shorter (cheaper) bolts, and that can be inspected or worked on without a high lift, while the boat is in the cradle.

[Syd MacDonald]

Smear a layer of grease on the inside of your wood mold. I did it and it works. Make sure you get grease on any part that the lead will contact, including any cros braces at the top of the mold.
The grease will smoke a bit snd may even catch fire, a minor detail. But it will prevent any moisture from boiling out of the the mold wood and giving you a rough finish on the lead.

[PeterSibley]

Wooden filler blocks sound even easier ! It will give the worms something to eat that I don't need to care about!

Thanks for all the advice,
Wishing Everyone a Happy and Healthy 2005 smile.gif

[cbob]

Peter, My keel is about 2' high, 6' long, and 1' wide, shaped, 2.25 tons. It hangs on ten 5/8" sil bronze bolts, nuts, washers and wicking at each end. bored down through the deadwood. The aftermost eight have their lower ends in about 2/1/2" dia. counterbores, filled with cement, no sand just pure cement, smoothed after some what set, this is up so it needs to a fairly stiff mix with the water. The forward two are in pockets, which are basically about a 3" or 4" horizontal hole, bored 2/3 of the thickmess deep with the upper 1/4 arc (I assume) chiseled flat to seat the washer, with wicking beneath. When these were removed, the eight in counterbores, were easily removed, with the keel underside with about 12" clearance. The bolts were driven downwards, breaking out the cement and then after removal of the nuts and washers, easily forced upwards with an automotive screw jack, inserting 1/2 inch roundstock stubs, to fill the space between the bolt lower ends and the jack. The two forward most, in pockets, at opposite sides and different depths, for an unknown reason??? were removed, after a treasure hunt to find the pockets, by chipping out the cement, and then driving the bolts downwards several inches at a time, and sawzalling out, a series of stubs, a hard job for the sawyer, read heavy in a tough position, up top inside a 30# button set, read heavy too. Why I'm going through this, with your 12" deep keel casting, it would seem easier to me to counter bore for through bolts, rather than the pocket method, very little, if any keelbolt stock saved, easier to counterbore, than bore and cut pockets, and much easier removal for examination or replacement. My the two pocketed bolts may have been removed upwards, but most likely been destroyed at the lower nut end, and unsuitable for reuse, and if not already broken mid-lengeth. Sorry, no casting advice, except for the cautions about explosions and lead vapor poisening, already well covered. Hope this helps. cbob

[PeterSibley]

Thank you ...read and will be considered !