I am to the stage of casting the keel for my project. Please comment
on my proposed method of making the mold:

--make a male plug out of styrofoam with a thin coat of bondo for
fairing and smoothing.

--coat the plug with half a dozen thin coats of no texture drywall
mud.

--suspend the coated plug in the mold box and surround with cement.

--burn out the styrofoam and bondo, leaving a smooth female mold for
pouring the lead into.

note: I have never cast with sand and have no desire to learn
another new skill.

TIA mm

wrote:
I am to the stage of casting the keel for my project. Please comment
on my proposed method of making the mold:

--make a male plug out of styrofoam with a thin coat of bondo for
fairing and smoothing.

--coat the plug with half a dozen thin coats of no texture drywall
mud.
Better do some tests on what happens to the set plaster mix when you
heat it to casting temperatures. Its not a refractory and will probably
crumble.

--suspend the coated plug in the mold box and surround with cement.
Sounds like a recipe for either a *large* steam explosion or a bad
casting. Ordinary cement retains too much moisture and will spall
violently in contact with molten metal. If you heat it enough to make
it safe to cast into it will probably crumble.


--burn out the styrofoam and bondo, leaving a smooth female mold for
pouring the lead into.
Doesn't Bondo contain talc as a filler? that *wont* burn out cleanly!
Try wax for fairing.

note: I have never cast with sand and have no desire to learn
another new skill.
Have you *ever* done a large metal casting? If not, stick to a tried and
tested method of keel casting and find some help that knows what they
are doing.


TIA mm


--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
[at]=@, [dash]=- & [dot]=. *Warning* HTML & 32K emails -- NUL:

wrote:
I am to the stage of casting the keel for my project. Please comment
on my proposed method of making the mold:

--make a male plug out of styrofoam with a thin coat of bondo for
fairing and smoothing.

--coat the plug with half a dozen thin coats of no texture drywall
mud.

--suspend the coated plug in the mold box and surround with cement.

--burn out the styrofoam and bondo, leaving a smooth female mold for
pouring the lead into.

note: I have never cast with sand and have no desire to learn
another new skill.

TIA mm
You are setting yourself up for a disaster that includes violent steam
explosions and running streams of molten lead.

Sand and molasses because it could be baked dry.
For a keel mold, the mold box work has to be extremely strong as the
molten lead (~600*F) will exert approximately 11 times the hydraulic
pressure of water.

Look up a magazine article that was about a decade ago in either Wooden
Boat or Good Old Boat about the well meaning guy that tried to recast
his keel.

Good Luck Guy

Matt Colie
Third Generation Boat Builder, Lifelong Waterman, Licensed Mariner

This an extremely dangerous thing to do. It is a field of mines to the
inexperienced and most of them can kill you or worse, make you an invalid.
Your plan will not work. There is no shortcut. You must do this correctly,
using the correct materials and tried and true processes. Lets forget about
the mold for just a moment. Just consider the task of melting the
appropriate amount lead and pouring it into the mold and the required
machinery. Pure lead is 11.7 metric tonnes per cubic meter. Do the math.
Think how much heat is required to raise your melt to 600 F. Then think how
long this will take to cool to room temperature. A 6 ton plug takes about a
week to cool. There are no shortcuts. There is a legitimate reason why you
contract this out. How do you justify the one time expense to build the
tools and machinery? Think about the volume of poisonous gases you will
generate. There is absolutely no way this can be done in a residential area.
Just for your information, creating your ballast will one of most expensive
parts of a boat project and for very good reasons.
Steve

wrote in message
...
I am to the stage of casting the keel for my project. Please comment
on my proposed method of making the mold:

--make a male plug out of styrofoam with a thin coat of bondo for
fairing and smoothing.

--coat the plug with half a dozen thin coats of no texture drywall
mud.

--suspend the coated plug in the mold box and surround with cement.

--burn out the styrofoam and bondo, leaving a smooth female mold for
pouring the lead into.

note: I have never cast with sand and have no desire to learn
another new skill.

TIA mm

wrote:
I'm to the stage of casting the keel for my project. Please comment
on my proposed method of making the mold:

--make a male plug out of styrofoam with a thin coat of bondo for
fairing and smoothing.

--coat the plug with half a dozen thin coats of no texture drywall
mud.

--suspend the coated plug in the mold box and surround with cement.

--burn out the styrofoam and bondo, leaving a smooth female mold for
pouring the lead into.

note: I have never cast with sand and have no desire to learn
another new skill.

TIA mm

First of all, you don't burn Styrofoam, you melt it with solvents.

Lead melts around 700F.

How big is the ballast?

How big is your melting pot?

What kind of material handling equipment do you have to handle 700+F
lead and keep it molten during the pour?

How many 1,000,000 BTU burners do you plan on using? You will need
several that can operate for several hours.

How long do you think this project will take?

It will be a long day, at best.

How long do you plan on allowing for cooling this ballast?

It will take several days.

IMHO, you are a disaster waiting to happen.

SFWIW, poured a 20,000 lb INTERNAL ballast.

Did it safely, but wouldn't even consider pouring an external ballast.


Lew
..

wrote in message
...
I am to the stage of casting the keel for my project. Please comment
on my proposed method of making the mold:

--make a male plug out of styrofoam with a thin coat of bondo for
fairing and smoothing.

--coat the plug with half a dozen thin coats of no texture drywall
mud.

--suspend the coated plug in the mold box and surround with cement.

--burn out the styrofoam and bondo, leaving a smooth female mold for
pouring the lead into.

note: I have never cast with sand and have no desire to learn
another new skill.

TIA mm

You've obviously put a lot of thought into your plan and have gotten an
earfull with the responses. Please don't let the attitudes exhibited by some
responders chase you off- these guys are very experienced, if not civil.

I have no idea where you are, since you have not created a profile.
But anyway I use www.dogpile.com, and find interesting stuff. There is
a weight calculator, and lots of information at this Lake Ontario
site.
http://www.alchemyextrusions.com/projects/default.asp They did
NOT list keels. They seem to be close to a railroad spur, If I had the
stones I think I would dig a mold in the ground. A bulb keel would be
problematic. I think you have an idea that this is extremely
dangerous. Can you post information re your project? Pics? Vessel
dimensions, etc. ? That way we can surmize, ooh and aw and such.
Den 48Ft YF EAGLE

It can and has been done for 'smaller' sized boats. The description
of the process in this link seems reasonable:

http://www.glen-l.com/misc/lead-keel-2.html

MW

wrote:
I am to the stage of casting the keel for my project. Please comment
on my proposed method of making the mold:

--make a male plug out of styrofoam with a thin coat of bondo for
fairing and smoothing.

--coat the plug with half a dozen thin coats of no texture drywall
mud.

--suspend the coated plug in the mold box and surround with cement.

--burn out the styrofoam and bondo, leaving a smooth female mold for
pouring the lead into.

note: I have never cast with sand and have no desire to learn
another new skill.

TIA mm
*
*
Burning out Bondo seems problematical. Some other fairing skin might be
more practical??

Brian W