Shrinkage of Lead

[Sam III]

I'm tooling up for a lead bulb for the keel on our production boat.

Does anyone know the 'shrinkage' per Inch for lead? I need to oversize the mold to allow for shrinkage when the lead cools.

Any input for a souce of lead for keel bulb casting?

Thanks in advance.

Sam

[whoosh]

from my exp it does not shrink, for instance when poured into a mold, if it shrank it would pull away from the mold, or shell keel, and it does not, it stays clued to the box, or shell , steel or alloy

[waikikin]

http://www.hrtrains.com/classnotes9.html

See how that looks http://www.mechanicalbanks.org/foundry/Downloads/Excerpts-Patternmaking.pdf

[PAR]

Actually lead shrinks quite a bit. Most molds for ballast castings take this into account and are made slightly over size. This procedure has a second benefit, which permits some trimming up to fair things out.

The size of the pour and the general dimensions of the casting also can have a substantial effect on the amount of shrinkage. If you post the general dimensions of your appendage, I can tell you how much shrinkage to expect.

The avarage rule for lead casting is about 1/64th in length, which is about an inch across 10'.

[Sam III]

The bulb is 1350 mm long and 212 mm at it's widest.

That would make for 2.6 % (5/16/12) or 1.5 % (3/16/12) or .1 % (1/64/12) depending on which chart you use.

I can do that automatically with the software I use just a lot of discrepency between 1/64th and 5/16th's.

The number I got for the keel fin (cast iron) was .8 %.

Hmmmm.

Sam

[PAR]

~21 mm shrinkage along it's length, 3 mm (or less) across it's width.

[Jimbo1490]

If you use lead recycled from lead/acid batteries you get basically zero shrinkage. That lead is alloyed with antimony, which is one of only two metals that expands when it cools. When carefully alloyed with lead (to which it is similar in physical characteristics), the shrinkage and expansion are in perfect balance. I don't know if it's going to be practical or even of value to do this, just a thought. :)

Jimbo

[Stumble]

Sam,

unless you have a lot of experience working in lead I would recomend you outsource the keel fabrication to a specialty shop for two reasons.

The first is that since you are in the US you will have to deal with all of the OSHA requirements for working with a toxic substance. I don't know what they are for lead off hand, but the cost just for the equipment could be pretty expensive. Certainly in the range of the extra cost of haveing a reputable company that specializes in keels make them.

Secondly there are a number of liability issues that could arrise from doing the work yourself. First of course is the long term health effects from workers being exposed to toxic substances. In the event someone does have long term health effects from working for you, the potential exposure could be huge, and while workers comp would likely cover it, you may also be caught under the Jones act or Longshoreman's Act either of which could drastically increase the liability of this type of problem

The second legal issue is that the most common major problem for new boats is keels falling off due to faulty construction or poor enginearing. By outsourcing the manufacturing you have a chance that should something go wrong you can make a claim against them for any incurred damage. Particularly if there is a chance they screwed up the keel in the manufacturing process.


Of course if you are really ready to pour your own keels, good luck. But as an attorney these are a few of the things that would concern me.

[PAR]

I've poured lead several times and didn't have OSHA show up once. Stand up wind and work with care. Insure the mold is dry (really dry) as any moisture will produce an explosion of molten lead, which you honestly don't want raining down on you. My last few pours were done in a cast iron bath tub.

In a production environment, you will have liability issues and OSHA will have to be consulted/conformed to.

Many production facilities do job out their keels for this reason. If you want to control production quality, then an in-house pour, will offer the best oversight.

The keels that are falling off boats are typically racers, where the engineering margin of safety is fairly low, in an effort to increase ballast/displacement ratio, which makes them go faster. On most production boats, this isn't a big issue, with literal hundreds of thousands of keels still hanging onto the bottoms of their mother craft, decades after construction.

[Stumble]

Par,

I only mentioned OSCA since he said this was for a boat about to go into production. Which I assumed meant he was the builder of (indicating a commercial operation).

And true keels don't exacally have a habit of falling off. But from a liability standpoint the potential cost of even one doing so is huge. One case I know quite well, the asked for damages were in the tens of millions since one of the crew was lost as sea. And happen to be makeing $500,000+ as a doctor.

[Sam III]

I have a very small shop and will not expect employee's / contractor's to do the casting. I actually enjoy it.

I have a 'boutique' shop and expect to only build 10 or so boats a year.

As for liability, I agree, that there are all kinds of exposures in the boat building business that's why I have liability insurance.

I am having the keel fin cast by a foundry, much higher tempuratures and health risks. Not ready to invest in a full blown foundry....

But based upon the quotes for the bulb which is realitively low temperature casting, only 700 degrees F, seems to be pretty high. This premium is more than I think it's worth for the job and I can take the savings and spend 1/2 of them for more liability insurance if I want.... Though I am a bit insurance poor at the moment. ;-)

As for the safety issure, work in an open area, wear protective clothing (cotton fibers, they burn through, but don't ignite and melt on you), organic resperator, face shield, welders gloves and welders apron. Don't let anyone stand around to observe unless they are dressed up to work as well.

I've done this before but didn't need to maintain the accuracy needed for a production boat.

Thanks for the input all.

Sam

[whoosh]

yes well since your post Par, I found a 12 foot length does shrink 8 mm, or 5 sixteenth inch
so seeing as my pours were 14 inch, wide in compartments I noticed bugger all shrinkage
strange really ,exp rates, lead melts at lo temps, you would think exp would be low, but its actually higher than most

[TeddyDiver]

http://www.rutuonline.com/html/the_keel.html DIY lead keel...

[mozart]

I have planned to fill a fabricated stainless steel ballast keel consruction with lead.
Size of keel construction is 3 feet long, 2 inches wide, 6 inches high.
The stainless steel material is approx 1/8 " think. What will haoppen when filled with lead? Will it shrink so that there is a risk of having air insted of lead in both ends of the completed casted ballast keel?
What can be done to aviod it?

Thanks in advance.
Mozart

[alan white]

It ought to be possible to remove the lead once cast and bed it in thickened epoxy.
If you coat the removed lead with several coats of epoxy and then also bed the lead into the cavity with thickened epoxy you will both eliminate any gaps and seperate the lead electrically from the stainless steel. The pre-coat will ensure the electrical barrier is thick enough where it might otherwise create a contact point between the metals when reassembled.

[Submarine Tom]

Sam,

Tell me, what does it matter if it shrinks a bit?

Tom

[Fanie]

I have a couple of questions regarding this -

If you have a metal rod structure inside the keel, why can you not pour the lead directly into the keel, but not everything at once, pour layers instead ?

From experience I know lead stalls on the outside first where it cools of the quickest. the scrinkage is in the center. If the 'layer' you poured dies have some cavities from scrinkage it will be filled when the next layer gets poured.

This way it is much easier to handle the lead, you have iron inside for aditional strength, and you are sure that there are no air pockets or hollows in the lead, and scrinkage should play no role.

I can also imaging if you provide structure as part of the keel protruding to the inside it should make a proper bond for the lead to hold on.

As for keels falling off, I can imagine a bit of an overdesign on surface and structure where it adhere to the hull should resolve this.

[Sam III]

Sam,

Tell me, what does it matter if it shrinks a bit?

Tom

I was concerned with how much larger to make the pattern for the bulb to plan for the shrinkage. My designer offered finished dimensions and I needed to hit the size, form and weight targets as the bulb was for a performance sailboat.

Sam

[TeddyDiver]

Lead tends to stick fast on a steel mould unless the mould is water cooled..
Anyway what I've found out with "tiny" 1 to 4kg pours..

[apex1]

I was concerned with how much larger to make the pattern for the bulb to plan for the shrinkage. My designer offered finished dimensions and I needed to hit the size, form and weight targets as the bulb was for a performance sailboat.

Sam

Sam
it was mentioned here long time ago, add antimony to the lead. That makes it harder and the shrinkage is almost gone. Common practice in the industry.

Regards
Richard

[mozart]

It ought to be possible to remove the lead once cast and bed it in thickened epoxy.
If you coat the removed lead with several coats of epoxy and then also bed the lead into the cavity with thickened epoxy you will both eliminate any gaps and seperate the lead electrically from the stainless steel. The pre-coat will ensure the electrical barrier is thick enough where it might otherwise create a contact point between the metals when reassembled.

Thanks Alan for your kind comment. My intension is to leave the lead in the stainless steel frame which will be used as such. As we have only 0,5% salt water i do not regard the corrosion as a risk. Thgus I do not see there is a need for electric barrier. Keel bolts will be stainless as well. My only consern is how the shrinkage could be avoided, can it? or would it be possible to fill up the gap between the mould and the fabricated/welded frame later with some new lead melted in afterwords?
Mozart

[TeddyDiver]

There won't be any gap to fill. Possible shrinkage comes unevitably on the top (free) surface. Instead even if you try to take the cast out of a steel mould you need some serious hammering and end up busting the mould..

[mozart]

There won't be any gap to fill. Possible shrinkage comes unevitably on the top (free) surface. Instead even if you try to take the cast out of a steel mould you need some serious hammering and end up busting the mould..

Thanks Teddy this is nice.
an other question is: what about leakage, from how small wholes would the lead leak out when pouring the melted lead into the stainless steel mould?
My welded keel is not purfect so there might be some small wholes along the weldings....

[alan white]

Thanks Alan for your kind comment. My intension is to leave the lead in the stainless steel frame which will be used as such. As we have only 0,5% salt water i do not regard the corrosion as a risk. Thgus I do not see there is a need for electric barrier. Keel bolts will be stainless as well. My only consern is how the shrinkage could be avoided, can it? or would it be possible to fill up the gap between the mould and the fabricated/welded frame later with some new lead melted in afterwords?
Mozart

I am aware you want to encase the lead in a stainless shell. In any case, I would never do it because it is doubtful you'll have a perfect bond between the lead and the stainless even if no shrinkage occurs (adding antimony), since any slight grounding can loosen that poor bond.
Now you have the possability of crevice corrosion inside the thin stainless shell.
I realize you don't intend to sail in salt water. However, if it were me, I'd assume someone who bought the boat from me might sail it wherever they liked. Also, I'm not sure that corrosion couldn't happen due to other factors such as minerals or pollutants in the water.
The real issue, to me, would be whether the expensive and essentially unneeded stainless shell was worth the risks. My immediate answer would be no, based on hundreds of years of boatbuilding history where simple lead keels without anything over them have been completely practical.
I've seen few plain lead keels that didn't at one time or another had their forward end mashed in from a grounding. If that forward end has a stainless shell over it, there has to be an inner gap formed. In addition, the resultant gap will be nearly impossible to fix except by filling outside only with thiickened epoxy---- but if it had been plain lead, a half hour with a hammer would have the lead as good as new.

[Fanie]

The only way to get lead to adhere to SS is to have protrusions on the SS.

Although lead is soft, if it is in a thicker piece it becomes progressively difficult to bend. I would go the way Alan suggested. I can see the SS is not going to be the right thing to use.

If you haven't closed all the holes while pouring the lead is going to pour out of them. Lead is heavy and the pressure is much greater as a liquid than water would be. I build solder pots, the smallest hole will leak like you won't believe. No, you cannot block it with your finger :D

[gonzo]

We used to make molds out of wood. We whitewashed the inside to keep it from burning and as demolding agent.

[Submarine Tom]

What a project. Any pictures Sam?

Tom

[mozart]

I am aware you want to encase the lead in a stainless shell. In any case, I would never do it because it is doubtful you'll have a perfect bond between the lead and the stainless even if no shrinkage occurs (adding antimony), since any slight grounding can loosen that poor bond.
Now you have the possability of crevice corrosion inside the thin stainless shell.
I realize you don't intend to sail in salt water. However, if it were me, I'd assume someone who bought the boat from me might sail it wherever they liked. Also, I'm not sure that corrosion couldn't happen due to other factors such as minerals or pollutants in the water.
The real issue, to me, would be whether the expensive and essentially unneeded stainless shell was worth the risks. My immediate answer would be no, based on hundreds of years of boatbuilding history where simple lead keels without anything over them have been completely practical.
I've seen few plain lead keels that didn't at one time or another had their forward end mashed in from a grounding. If that forward end has a stainless shell over it, there has to be an inner gap formed. In addition, the resultant gap will be nearly impossible to fix except by filling outside only with thiickened epoxy---- but if it had been plain lead, a half hour with a hammer would have the lead as good as new.

Thanks everybody for many pieces of good advice. I scrapped the stainless mold idea and went for a wooden mold made of plank with dimensions 8 by 2 inches and 6 foot long. Howard I. Cahapell tells me to paint the mold inside with waterglass. How should this be done? What will it look like? Where to get? Has anyone done it?

[gonzo]

Sodium silicate Na2SiO3 in a water solution. It is the same stuff they make muffler repair paste with

[Submarine Tom]

Sam III & mozart (two birds with one stone on this thread),

I am most interested in pictures of your projects.

How about it?

Tom

[mozart]

Have a lot of pics but you would need to tell me how to send them, born in 1756, I am not that good with computers.

[Sam III]

Sam III & mozart (two birds with one stone on this thread),

I am most interested in pictures of your projects.

How about it?

Tom

Tom,

Go to http://www.thirdcoastcomposites.com/coppermine/index.php for project photo's.

Sam

[Submarine Tom]

mozart,

I hear 'ya. I was born 200 years before you, I can't make it happen either.


SamIII,

You're going to have to be a little more specific as there are 100's, perhaps

thousands of photos there.

Tom

[mark775]

You're already going traditional, good, but another factor in why it is better is that lead absorbs some grounding or container shock and hard and fast things transmit it. Perhaps one of the guys that knows how much harder antimony/lead alloy is can tell me if we lose the "container cushion" of soft lead by the addition of too much antimony.

[apex1]

You're already going traditional, good, but another factor in why it is better is that lead absorbs some grounding or container shock and hard and fast things transmit it. Perhaps one of the guys that knows how much harder antimony/lead alloy is can tell me if we lose the "container cushion" of soft lead by the addition of too much antimony.

About 3% Mark.
And the lead does not get so hard that the main properties are lost. (but noticeable harder)
For a "home made pour" you need to make a pre pour alloy. Use 28% antimon in 10% of the total amount of lead, let it cool down, cut according to the fractions of material you melt in one go.

Regards
Richard

[Sam III]

Tom,

I looked and there are very few pictures of the lead bulb,

http://www.thirdcoastcomposites.com/coppermine/thumbnails.php?album=8&page=7

and the next page.

I guess I was to busy with the pour to take pictures.

Sam

[Fanie]

Wow ! You went to a lot of troubles for a mould there. I was just thinking, if you make a former and use paper pulp to make a mould to pour in, won't it be cheaper and easier ? You can make the mould four parts and seal the paper with silicone on flanges.


The mounting flange to the boat looks a bit narrow to me. If you are hit by a wave side on I can see you can run into troubles there.

[mozart]

Have a lot of pics but you would need to tell me how to send them, born in 1756, I am not that good with computers.

My 6 foot long 2" wide 7" high lead keel came from the foundry.
Looks great mut seface rough due to the glasswater treatment.
What would be a good way to treat the surface before mounting/attaching the keel under the boat?

[Submarine Tom]

SamIII,

Nice pics, thanks. Great job on the bulb, I hope it stays on!!!!

Tom

[gonzo]

Use a planer. It is the easiest and fastest way to remove lead. You can also pound on it with a big hammer.

[mozart]

Use a planer. It is the easiest and fastest way to remove lead. You can also pound on it with a big hammer.

Ok fine, do you meen an electric one?
Why not put some putty or glass fibre on the surface to avoid hard job?

[gonzo]

If you have voids, fill them with epoxy. However, you can use an electric planer to take down the bumps, specially on the top. Hammering also works well

[Sam III]

SamIII,

Nice pics, thanks. Great job on the bulb, I hope it stays on!!!!

Tom

Tom,

It has stayed on with no problems. It has taken one serious grounding that lasted 6 hours in the mild waves and hit a rock with only minor damage to the leading edge of the glass shell on the keel. We have removed some keel bolts after the major grounding and there was no damage to the structure in the bottom of the boat or to the keel bolts themselves.

With a 200 mm x 660 mm flange on the top of the keel the 12 x 12 mm keel bolts will keep it in place.

Plus we used the designer's design and he has had several hundred's of his boats successfully built and sailed in the Mini Transat, 4200 miles offshore.

Sam

[Submarine Tom]

Sam,

Good to hear. Sleep well.

Tom