Lead Meltdown For BB14 - shrinkage ?

[DanO]

After lots of thought,preparation, inspiration and perspiration, I'm ready to start pouring the 900 pounds for my lead keel. I took these photos today and hope to pour tomorrow. Weather's been unusually mild for the last few days, and I've got all things ready to go (I think!).

http://www.imagestation.com/picture/sraid194/p2b5119e3ac145341e337d8e637acebc0/f17c2c03.jpg

http://www.imagestation.com/picture/sraid194/p2368bb529cef70a24679ab09459f068a/f17c2c05.jpg

http://www.imagestation.com/picture/sraid194/p1fdfa77cf828af54127c33636e52a456/f17c2c04.jpg

In my last minute anxieties, I'm wondering once again about how much the lead can be expected to shrink. The inside of the mold is a few inches over 6' and the deepest part is just shy of 10". The width at max is just over 7". In anticipation of shrinkage, I've allowed almost 2" for the length, about 1/2" for depth and about 3/8" for width. Am I close here? I guess I'm just looking for some last minute reassurance to make sure my "guesstimates" aren't way off base. By the way, the lead is comprised of wheel weights. This is my stack, ready to go:

http://www.imagestation.com/picture/sraid193/p40fadeddf690dbe9f9d29fc6987a72c9/f1963e3f.jpg

Thoughts on the shrinkage factor?

Dan

[ 11-12-2005, 08:51 PM: Message edited by: DanO ]

[Canoeyawl]

My old Machinery’s handbook says 5/16 inch per foot. I have found this to be very close…

[DanO]

Canoeyawl, thanks for the quick reply. Based on those numbers, my guesstimates might be ok after all. This lead casting project is a bit nerve wracking for lots of obvious reasons!

Dan

[StevenBauer]

Maybe you should have a dedicated phographer as you will likely be too busy. :D

Steven

[DanO]

I'm not sure I'll want this firedrill recorded, but yes, I've got a few people who are interested enough to stand upwind and a safe distance away to tell me all the things I probably don't need to hear. I'll let them take photos, since no one will be able to recognize me anyway in my full face shield respirator!

Wish me luck!

Dan

[Bob Cleek]

I expect you will find that most of the shrinkage will be on the top of the keel. Have some hot lead ready after the pour because it will "deflate" on top and you want to fill that. The standard percentage shrinkage figures are as good as it gets. You may wish to leave yourself a little extra width at the top faying surfaces so you can plane it fair to the keel after she's hung. Another trick is to mold the keel in a box with top edges perfectly parallel to the lofted top of the keel. Then pour a bit extra. When it all cools, you can take a router on a sled and run it along the edges of the mold at the right depth and get a perfectly flat faying surface at the right line.

[ 11-12-2005, 10:48 PM: Message edited by: Bob Cleek ]

[Ken Hutchins]

If you pour the lead quickly, say from a big pot all melted open a valve and let it pour the shrinkage will be in ALL directions. A quick pour will also leave a hole in the middle unless you gradually fill the hole as it cools. If you pour gradually a bit at a time the shrinkage will be less, but still in all directions. Pouring gradually could result in seams between layers.

[N. Scheuer]

The "hole in the middle", or shrinkage, can have serious consequences, if there is any way water can get into such a cavity.

A friend once had an O'Day ballasted by solid lead bedded inside the fiberglass keel/hull molding. The unreinforced polyester used to "Puddle over" the top apparently cracked with age, and rainwater or spray that came into the boat, and drained down under the sole to the top iof the keel, found it's eway through the cracked "puddle" iand further down into the shrink cavity.

When the entrained water froze in winter storage on the hard, the ice pushed out laterally, right through the keel molding.

Being underneath in the trailer cradle area, the rupture escaped notice when launched the following summer and the boat almost sank while underway with the owner and his mate aboard.

Your's being exterior ballast, you won't have the danger of sinking, but you wouldn't want an ugly rupture on the side of your keel either.

Keep feeding the casting from the ladle as the lead shrinks in the center.

Moby Nick

[TimothyB]

By the way Dan, she looks lovely! I wish you luck in your pour, but given your careful, methodical nature I'm sure it will come out fine.

[Canoeyawl]

The depression that occurs on the top from shrinkage can be repaired after the pour with an oxy-acetylene rosebud and a bit more lead. You can melt the lead locally at the spot in question and add more, just keep it level, no problem.
I have finished off some pretty ugly lead castings with a cheap power plane; In fact I planed off more than two hundred pounds from one – just a few hours… LOL. Wear a mask.

[michigangeorge]

Looking forward to lots of photos of the pour- I,ve allways been afraid of attempting this process without some hands-on experience; but then THEY say experience starts when you begin! Best of luck---------

[DanO]

I'm back from the pour, with all fingers, toes and face unscorched! While everything went generally ok, I was shocked to see that I was running out of lead towards the end of the pour. I looked inside the cooking drum (an old welded seam water tank from our cottage) and saw that cakes had formed at either end from cooling. I suspect that as the liquid drained down, the ends (which were over the cinder blocks and probably not as hot) started to cool.

Now another problem! my pour looks like it's about 1 1/2" shy of where it's supposed to be. I can't believe that I ran short, since I melted 1,035 pounds and this is a 900 pound keel. Yeesh!

Anyway, all I can do now is to wait to see what the final block looks like. I wonder if I can heat up the cast and ladle on the extra 1-2"? If not, I'll probably have to cut it up, add some extra and remelt the whole thing. At least I learned how this process works, and on balance it's not that difficult, although I was a bit nervous. Take all safety precautions if you're ever going to try this!

http://www.imagestation.com/picture/sraid194/pf848689087c2d5fa8ad4d3c3e0536250/f1790981.jpg

This is the lead ready to go.

http://www.imagestation.com/picture/sraid194/pd5d8bc10990efb57c0a3b5303d2a9b2d/f1790980.jpg

Getting everything hot!

http://www.imagestation.com/picture/sraid194/p6ac8fb87d6756a965cb99279847aaf75/f1790864.jpg

If you look closely, you can see the lead partly melted.

http://www.imagestation.com/picture/sraid194/p77eef335bdd6cca1a3346bd774c6b196/f1790843.jpg

This is the whole pour cooling off. The casting should be much closer to the top of the wood mold. Like I said, it's probably 1 1/2" below where it should be. Anyway, we'll see what happens!


Dan

[ 11-13-2005, 05:14 PM: Message edited by: DanO ]

[sdowney717]

How interesting to see this done. I take it you are concerned the lead layers would be a problem?
How is this lead keel attached to the boat?
I would think if the bolts are in the center and run deep into the keel adding more on top would not be a problem.
Any chance of taking an oxy torch, sticks of lead and melting the remaining lead into the keel top welding the lead together?

[michigangeorge]

thanks for the pics. did you start with all the lead in the boiler or add a bit at a time? If you had held a torch at the end of the boiler would the rest of the lead have melted and run to the tap?

[Canoeyawl]

Congratulations - Nice job… Thanks for the informative post.
I always had a good bit of smoke from the wooden mold when I did this; your pour must have been cooler than mine ever were! This is safer for your health of course.
I would be tempted to just leave it right there and pour more lead right on top of that if you have 1-1/2” to go. Drill some 1-inch holes at odd angles to act as lead drifts to keep it located. I don’t think a lead laminate will be a problem - bolts will be through all. You can join any rough edges later with a rose bud and/or use fairing compound.
If you want to start over, it’s easy to cut up with a skill saw…LOL

[N. Scheuer]

My GAAWWD, DanO how your photos remind me of my lead-pouring experiences!

My objectiove was to pour a pair of 200-lb square blocks od solid lead ballast for installation under the saloon seats in my Shearwater Yawl.

The first pour was accomplished with salvaged 1/8" lead sheet cut up small enough to fit inside a galvanized bucket (fitted with a pair of pipe handles for pouring), heated over a charcoal and wood fire, shielded from the wind with scrap plywood (which ultimately burned) and poured into a mold of appropriate dimensions.

Elapsed time; 4 hours; which incluides a shopping errand to get more charcoal.

The salvaged lead had come from a plating tank and the surfaces were covered with a thick layer of lead oxide, which yielded an awfull quantity of dross when melted, whereupon a couple of quarts of flux powder (I had a Chemicl Engineer friend who was a coworker for an employer which operated a large Zinc die-casting operation) was added.

The second pour had to be terminated when the seam rumnning up the side of the buchet opened, dumping 200-lbs of lead into the charcoal fire!

Time lost; 4 hours.

The third pour, this time using a stainless steel kitchen sink, purchased for a song because it was dented, with the drainb hole covered by a welded-on stainless disc, and a rented propane-fired "corn boiler" burner was much more successful. The sink was fitted with the same pair of pipe handles used on the bucket. The fuel was our current tank "borrowed" from our charcoal grill. It was so eay I kicked myself for not thinking of kall this earlier.

Time required; two hours.

TRUE NORTH now has her added 400-lbs of ballast.

Moby Nick

[DanO]

Just to add a couple of responses:

This tank was seated on angle iron bracket that I bolted together so the tank wouldn't roll. The whole unit sits on a 3-legged base which came from an old wood stove that I scrapped a few years ago. The cinder blocks are there for added support.

The whole idea was to melt this all at once, so I did not add lead as I went. As I think back on this, I should've stirred the inside of the tank with a shovel while the lead was draining, and I think things would have been fine.

I'm very interested in the idea of sort of "welding on" another layer of lead with the casting in place. That would be the easiest way to handle things. Otherwise, it's heavy lifting time again, this time with a chainsaw!

Timothy B, thanks for the comments. Have you settled on a new (or old) project?

Dan

[ssor]

When we used to pour lead it had to be hot enough to char a maple stick. A large propane burner such as is used by the roofers to seal rubber sheet roofing will be the best source of heat for the large volume and surface area that you have. The boat and the pour look good , you may have lost some height if the sides bulged a little.

[Bob Cleek]

If you weighed the lead and know for sure how much you have, and you are down an inch and a half, either the calculations for the shape and weight of the keel were wrong, or your mold was not properly reinforced and she bulged out on you. The stuff doesn't evaporate.

I think you may find it difficult to "weld" lead. I've never found much luck trying. The mass of the cold lead is so great that it operates as a huge heat sink and just soaks up the heat, but doesn't get hot enough to melt partially. I suppose an oxy/acetilene torch might melt a little divot, but not much more than that.

[DanO]

Though it doesn't look like the sides bulged out on me, it may be that I overcompensated for the shrink factor (which was the point of this whole thread) and ended up with an overall shape that had more volume than I thought. I doubt LF Herreshoff was that far off on his calculations, although he did have multiple misspellings on the plans he drew for this in 1945.

I guess I could also have a leak, but I doubt that as well. It was also interesting to note the little stalagmites (or stalagtites, I can never rememeber which is which) that grew under the threaded pipe by the gate valve. It didn't amount to much, but it's fascinating in a way, because I used a heat resistent gasket cement and really torqued that pipe on. Goes to show you that molten lead will leak through the tiniest of cracks.

Dan

[DanO]

Just thought I'd report progress on this lead recasting part of my Buzzards Bay 14 project. Like most other parts of this construction, I've got myself into a bit more work than anticipated.

Last weekend, I cut up this lead casting, hoisted all 1,035 pounds back into the tank and tried repouring. This time, I really reinforced the mold so that the sides wouldn't bulge out on me (like they did last fall). Everything worked great...until the mold sprung a leak! About 200 pounds (I'm guessing) leaked and made a couple of soccer ball-sized lumps under the mold. Since I casted the mold upside down (so that the faying surface would come out as true as possible) the casting is once again not deep enough. I'm now planning to lay on a 3" or so layer of lead to finish the lead ballast to its desgined draft. I don't have any current photos (camera also died!), but the photo below taken last fall shows my first "right-side-up" pour. I've also shown Chip Flanagan's BB14 drawing as an illustration of what this keel should look like.


http://www.imagestation.com/picture/sraid194/p77eef335bdd6cca1a3346bd774c6b196/f1790843.jpg


http://www.chipboat.com/buzbay.gif
Here's my question... Should I drill some holes in the existing lead, so that the new pour will be "drifted" into it? These 2 layers will be through-bolted in several areas when finished, so I don't think structural integrity should be a problem. However, this 900 pound keel is heavy to manhandle and I'd like the 2 pieces to hold together as much as possible. I've read the other recent post on lead "welding" and I guess my thoughts about pouring one layer on top of another isn't too far fetched. Thoughts?


Dan