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kcdonohue
03-30-2013, 01:05 PM
I am building Grey Seal and have come to the interesting part of pouring the 1150 lb keel. Has anyone else done this? WB89 was useful along with the cautionary tale in the build series. But I would like to hear from anyone who has done this or something similar. Lead shrinkage on cooling is my current obsession. If the bolts are embedded in the pour in order to get the 10 holes right then if they move on cooling this causes no end of trouble. A couple of forum threads here were interesting and bathtubs are now out with the stock of kitchen sinks as melting vessel rising. Any thoughts or experience?

Bob Cleek
03-30-2013, 02:25 PM
I'm sure you'll get lots of advice, but I'll just throw this bit out to you. I would not cast keel bolts in place. I've cut up several keels, notably some commercially cast by production boat companies, and I have found in a few instances that as the casting cooled and shrank, it did so around the bolts INSIDE the casting. In other words, you couldn't tell by looking at the finished casting. This may have been due to dissimilar metals (these were all stainless/monel bolts) or due to the shape of the casting (all were modern fin keels), I don't know. Perhaps the metalurgists in here can explain the science of it. What you end up with when the keel is cut up is something like a geode... it looks fine on the outside, but there's this crystaline, pulled apart void around the bolt inside the cast lead. In a couple of instances, the bolts had actually pulled loose. These had L shaped ends, apparently intended to hold fast, but there was nothing around the L at the end and only a couple of inches of lead around the bolt on the outside of the casting. For this reason, I would through-bolt or tap and thread the bolts into the casting (the L.F.Herreshoff method.) That approach also solves your problem with the bolts moving if cast in place. (More likely, it is the shrinkage of the casting that causes them to appear to have moved.)

Another reason not to cast keel bolts in place is that you cannot easily fair the top of the casting went the bolts are in place. Without the bolts, it only takes setting up a jig (or the edge of the form, if it's level to begin with) and run a router mounted on a sled to true up the top of the casting. (You'll need to pour the casting a bit deeper than your finished dimension in order to have material to mill off. The top of the casting will not be flat when it cools. There will likely be dross on top you'l want to clean up and a hollow in the center from shrinkage upon cooling that will have to be faired out.)

skaraborgcraft
03-30-2013, 03:57 PM
I need to do a slightly lighter ballast casting than you, and i will definately pour it as a whole and drill the holes after.

donald branscom
03-30-2013, 06:46 PM
I am building Grey Seal and have come to the interesting part of pouring the 1150 lb keel. Has anyone else done this? WB89 was useful along with the cautionary tale in the build series. But I would like to hear from anyone who has done this or something similar. Lead shrinkage on cooling is my current obsession. If the bolts are embedded in the pour in order to get the 10 holes right then if they move on cooling this causes no end of trouble. A couple of forum threads here were interesting and bathtubs are now out with the stock of kitchen sinks as melting vessel rising. Any thoughts or experience?

Think about thhis:
1 cubic foot of lead weighs 760 lbs.

You DO NOT have to pour all the lead at once.

You can make a pour and it will still be hot for hours.
Then make another pour and that will melt into the first pour and so on.
Filling a bath tub with lead is risky as far as safety is concerned.

Just a drop of sweat can make it explode.
The smaller the melting pot the safer you are.

Keep the pipe the lead is coming out of short and keep a hand
held propane torch nearby to heat that exit pipe
in case it cools down and the lead gets clogged.


Wear good protective clothing. NO Chinos or sandals !!!

MN Dave
03-30-2013, 06:58 PM
Bob is right about the bolts not moving and causing shrinkage cavities when he said "it is the shrinkage of the casting that causes them to appear to have moved." Whatever holds the bolts when the lead is poured has to let the bolt move with the lead as it shrinks. There are ways to hold inserts in a casting that would allow them to move with the shrinking and cooling metal, but none that work as well or are as easy as drilling and tapping lead.

It will be difficult to line up the mounting holes in the keel with the bolts if they are cast into the ballast. They have to be parallel and precisely located. You are much better off drilling the holes through the keel into the ballast.

andrewpatrol
03-30-2013, 07:14 PM
Hi KC, welcome. I am also building a GS. Where are you and which version are you building? I am in Melbourne Australia, doing the centreboard with gaff sloop rig that Iain drew up. Currently at the 3rd plank stage and I have a stash of lead waiting for me to get my finger out and mould the ballast, so I am very interested in the outcome of this post. I know of another GS in build at mo and he is up to doing the cabin top but he's getting his ballast cast by a foundry. Do you have any photos?
Andrew

Bob Cleek
03-31-2013, 05:20 PM
Just a drop of sweat can make it explode.
The smaller the melting pot the safer you are.

Let's not scare the kids too much, Don. :D :D :D

What causes the aforesaid "explosion" is simply steam expanding quickly and bubbling out of the lead. So, in order to get this effect, the molten lead has to run over the water in such a way that the steam has nowhere to go but through the lead when the water boils. A "drop of sweat" landing on the top of a pot of molten lead would behave the same as a drop of sweat hitting a hot skillet. It would just sizzle away instantly. Now, on the other hand, let's say you've welded that hunk of pipe to the bottom of your bathtub, or whatever, for a spigot and there was a bit of moisture that ran down into the pipe and you poured a bunch of molten lead down the pipe... BIG problem! The steam has nowhere to go and you've created a "lead bomb." But, if you loaded the lead into your container and built a fire under it, the water would boil off at 212 degrees F., long before the lead melted at somewhere in the 700's F.

Nor is moisture the only problem. The only time I ever saw a molten lead "explosion" was due to air, not water. A friend had a pot of molten lead working and he was melting down a bunch of old lead pipe he'd gotten from who knows where. The lead pipe had been bent up double here and there, such that the end of a piece of pipe was crimped. He shoved the OPEN end of the pipe down into the molten pot, with the crimped end up. The air in the unmelted pipe expanded quickly and had no place to go but out the end of the pipe that was submerged in the pot. The result was a "bubble" of lead that blasted out all over the place. Ironically, he'd been extremely careful to make sure all the pipe he was melting no longer contained any fluid!

Prudence and common sense are a must, but fear not a drop of honest sweat!

kcdonohue
04-04-2013, 03:51 PM
Thanks Bob. That makes total sense to not cast the bolts into the pour. I appreciate the thoughts.

kcdonohue
04-04-2013, 04:04 PM
good thoughts. I will be very careful about moisture and not have bent metal. But my takehome message and the thing that is most valuable is that I'm figuring out that this pour can be done a little at a time. It will be 12 gallons of lead which I would really like to not have to deal with all at once. It is too heavy and dangerous. But 3 gallons is a kitchen sink worth of it and that can be handled with a reasonably small rig and propane burner. This is sounding a bit more doable.

Canoeyawl
04-04-2013, 04:27 PM
I'm figuring out that this pour can be done a little at a time.
In my experience this will not work unless you don't mind discrete layers of lead. Lead oxidizes quickly and achieving a bond between layers seems unlikely to me.

3 gallons of lead is 300 lbs at 700, you are not going to carry that to the mold.
If you are going to the trouble to make a set-up to pour 300 lbs you should go ahead and make it the full amount.

There have been many thread on this topic; here is one for a grey seal http://forum.woodenboat.com/showthread.php?2842-Ballast-keel-mold&highlight=lead

Bob Cleek
04-04-2013, 08:25 PM
In my experience this will not work unless you don't mind discrete layers of lead. Lead oxidizes quickly and achieving a bond between layers seems unlikely to me.

3 gallons of lead is 300 lbs at 700, you are not going to carry that to the mold.
If you are going to the trouble to make a set-up to pour 300 lbs you should go ahead and make it the full amount.

There have been many thread on this topic; here is one for a grey seal http://forum.woodenboat.com/showthread.php?2842-Ballast-keel-mold&highlight=lead

The trick is that once you have a sufficient mass of molten lead, when you add more solid lead to the pot, it melts very quickly. Getting a mass of solid lead hot enough to flow from a "dead stop" takes much more time than melting a similar amount of lead by adding it to a quantity of molten lead. In such fashion, then, it is pretty easy to pour (or in this case, ladle) and add solid lead to the pot as you go.

Three gallons isn't a serious amount, really. That can be done in a cast iron Dutch oven on a turkey fryer burner stand. (But make sure the burner can hold the weight of the lead and pot, or build some sort of brick or whatever stand that will hold it... some of those turkey fryer burner stands are pretty flimsey to my eye.) Get a gallon or a gallon and a half melted and you can then ladle molten lead and add solid lead and you'll be ladling molten lead non-stop no problem.

J.Madison
04-07-2013, 12:33 AM
Standing there ladling the molten lead for an hour or more in the name of safety seems like it may have missed the point of safety. When I made a similarly sized ballast pour I used this setup:
http://i1123.photobucket.com/albums/l545/JMadison1/Backbone/leadpour018.jpg

All the lead was in there at once. Once it was molten (which didn't take very long over a hot fire) the pipe was rotated down into the mold, the slug of solid lead in the pipe was melted with a torch, and it all came rushing out into the mold. The whole pour took about three seconds. Wooden cores made drilling the bolt holes easy.

Do make the sides of the mold much higher than the final casting, or the bubbling that occurs when the wood off-gasses will splash out some of the metal before things calm down.

WX
04-07-2013, 01:24 AM
Post 1101 shows a photo of my timber mold with 3/4" wooden dowels fixed in place for the keelbolts. These turned to pure charcoal and made it easy to drill the holes later.
http://forum.woodenboat.com/showthread.php?88318-Redwing-update/page23

Post 1133 shows some photos of the actual pour. The mold was cemented in the ground with 10 sand 1 cement mix.

PeterSibley
04-07-2013, 03:35 AM
Seconded on WX's pour, it worked very well.

the_gr8t_waldo
04-07-2013, 11:57 AM
i've seen quite a few castings in iron, and have come to enbrace making the plug out of this type of foam http://building.dow.com/na/en/products/insulation/rigidfoam.htm (the pink type is the same stuff, just different manufacture.) straight cuts are made with a "hot wire".curves by hot wire and sanding to final shape. this foam takes wooden dowels rather well( allow the ends of the dowels to extend an inch or so that if coated with cement , the cement will lock in the position of the dowels- or longer for casting sand). make sure it is made to accomdate for shrinkage and a little for, planing to fit. once made you can easly hand it off to a foundry, or coat it with cement and diy. btw hot wire instructions here- http://www.instructables.com/id/Hot-wire-foam-cutter/ by all means pour all at one time!

WX
04-07-2013, 03:25 PM
i've seen quite a few castings in iron, and have come to enbrace making the plug out of this type of foam http://building.dow.com/na/en/products/insulation/rigidfoam.htm (the pink type is the same stuff, just different manufacture.) straight cuts are made with a "hot wire".curves by hot wire and sanding to final shape. this foam takes wooden dowels rather well( allow the ends of the dowels to extend an inch or so that if coated with cement , the cement will lock in the position of the dowels- or longer for casting sand). make sure it is made to accomdate for shrinkage and a little for, planing to fit. once made you can easly hand it off to a foundry, or coat it with cement and diy. btw hot wire instructions here- http://www.instructables.com/id/Hot-wire-foam-cutter/ by all means pour all at one time!
Just wondering how toxic the foam is as it burns away? Given the fact that you're already dealing with lead than can be quite toxic.