What to use to make a mold?

On Mar 23, 8:28*am, wrote:
On Mar 22, 5:23*pm, AK wrote:

I want to make a small mold I would later use to create a fiberglass
container to hold lead weight. It would be nice if *mold material can
withstand 500 degrees Fahrenheit so I can pour lead into it and then
cover it by fiberglass. Alternatively I would use the mold to create a
fiberglass container first and fill it up with lead pellets. So my
question is what do I use to make a mold, gypsum if so what kind,
anything else?

Andrzej

sand

http://en.wikipedia.org/wiki/Sand_casting not quite that simple in
practice and would also req the purchasing of some specific setup
materials which are not found at Home Depot etc...

You should go the wood or plaster route.Wood is dead simple if your
shape is not to complex. I saw that Steve quite rightly mention of
worry of plaster and residual water/steam being an issue... hence
the very specific directions I layed out for preheating/drying your
plaster mold BEFORE lead is poured in. If it survives the 4 hr
incremental ramp up to 400deg, it will not break from the pour since
all the water will have been evacuated by then. If in doubt, leave it
in the oven for an extra hr or 2 at 400ish...

I dabble in investment casting, and the same methodology applies for
pouring 1700-2100 deg metal (bronze, slver, gold, etc) into a plaster
mold, except the heatup/dryout process brings it up to 1000deg over a
5, 7, or 12 hour ramp up (usually spending some an hr or 2 at 1300deg
to vaporize out the wax remnants before ramping back down to
1000ish).

-Paul

On Mar 23, 12:12*pm, sisu1a wrote:
On Mar 23, 8:28*am, wrote:

On Mar 22, 5:23*pm, AK wrote:

I want to make a small mold I would later use to create a fiberglass
container to hold lead weight. It would be nice if *mold material can
withstand 500 degrees Fahrenheit so I can pour lead into it and then
cover it by fiberglass. Alternatively I would use the mold to create a
fiberglass container first and fill it up with lead pellets. So my
question is what do I use to make a mold, gypsum if so what kind,
anything else?

Andrzej

sand

http://en.wikipedia.org/wiki/Sand_casting* not quite that simple in
practice and would also req the purchasing of some specific setup
materials which are not found at Home Depot etc...

You should go the wood or plaster route.Wood is dead simple if your
shape is not to complex. * I saw that Steve quite rightly mention of
worry of plaster and residual water/steam being an issue... * *hence
the very specific directions I layed out for preheating/drying your
plaster mold BEFORE lead is poured in. If it survives the 4 hr
incremental ramp up to 400deg, it will not break from the pour since
all the water will have been evacuated by then. *If in doubt, leave it
in the oven for an extra hr or 2 at 400ish...

I dabble in investment casting, and the same methodology applies for
pouring 1700-2100 deg metal (bronze, slver, gold, etc) into a plaster
mold, except the heatup/dryout process brings it up to 1000deg over a
5, 7, or 12 hour ramp up (usually spending some an hr or 2 at 1300deg
to vaporize out the wax remnants before ramping back down to
1000ish).

-Paul

Thank you a lot to all who responded, especially to Paul for the
details he provided and Steve for the safety warning.
I was already aware of safety issue, but I appreciate you mentioned
it.

For safety in an accident I would use the lead pellets
and make a containter.

Plus you will be able to make adjustments to your weight if you use
pellets in a containter.

A big chunk of lead could become a very dangerous projectile in a hard
landing or crash.

Ray

On Mar 24, 10:53*am, jb92563 wrote:
For safety in an accident I would use the lead pellets
and make a containter.

Plus you will be able to make adjustments to your weight if you use
pellets in a containter.

A big chunk of lead could become a very dangerous projectile in a hard
landing or crash.

Ray

Good point, that is why the lead weight is going to be under my rear
end and it will be properly secured. Obviously I want the lead weight
as small as possible (vertically) so I don’t loose much of head room.

On 23 Mar, 00:23, AK wrote:
I want to make a small mold I would later use to create a fiberglass
container to hold lead weight. It would be nice if *mold material can
withstand 500 degrees Fahrenheit so I can pour lead into it and then
cover it by fiberglass.

I'm a little puzzled here. When you have filled the mould with lead
and covered it with fibreglass, won't the mould still be in there. Is
that OK?

How big is this thing? How complicated is the shape?

Ian

On Mar 24, 12:26*pm, The Real Doctor
wrote:
On 23 Mar, 00:23, AK wrote:

I want to make a small mold I would later use to create a fiberglass
container to hold lead weight. It would be nice if *mold material can
withstand 500 degrees Fahrenheit so I can pour lead into it and then
cover it by fiberglass.

I'm a little puzzled here. When you have filled the mould with lead
and covered it with fibreglass, won't the mould still be in there. Is
that OK?

How big is this thing? How complicated is the shape?

Ian

Ian, I create a mold first then I pour lead into the mold. Later I
break the mold up and I use fiberglass to cover the lead so it is
trapped and I am not exposed to lead dust.

On Mar 24, 4:05*pm, AK wrote:
On Mar 24, 12:26*pm, The Real Doctor
wrote:

On 23 Mar, 00:23, AK wrote:

I want to make a small mold I would later use to create a fiberglass
container to hold lead weight. It would be nice if *mold material can
withstand 500 degrees Fahrenheit so I can pour lead into it and then
cover it by fiberglass.

I'm a little puzzled here. When you have filled the mould with lead
and covered it with fibreglass, won't the mould still be in there. Is
that OK?

How big is this thing? How complicated is the shape?

Ian

Ian, I create a mold first then I pour lead into the mold. Later I
break the mold up and I use fiberglass to cover the lead so it is
trapped and I am not exposed to lead dust.

Sheet lead is usually available from a good hardware store or from a
roofing supply place. I picked up a roll approx. 300 mm wide by 4mm
thick. You can easily cut it with tin snips and some judicious
forming with a mallet against a sand bag will get it to whatever shape
you want. Multiple layers can be kept together with double stick
carpet tape.
Craig

On Mar 24, 7:56*pm, Craig wrote:
On Mar 24, 4:05*pm, AK wrote:



On Mar 24, 12:26*pm, The Real Doctor
wrote:

On 23 Mar, 00:23, AK wrote:

I want to make a small mold I would later use to create a fiberglass
container to hold lead weight. It would be nice if *mold material can
withstand 500 degrees Fahrenheit so I can pour lead into it and then
cover it by fiberglass.

I'm a little puzzled here. When you have filled the mould with lead
and covered it with fibreglass, won't the mould still be in there. Is
that OK?

How big is this thing? How complicated is the shape?

Ian

Ian, I create a mold first then I pour lead into the mold. Later I
break the mold up and I use fiberglass to cover the lead so it is
trapped and I am not exposed to lead dust.

Sheet lead is usually available from a good hardware store or from a
roofing supply place. *I picked up a roll approx. 300 mm wide by 4mm
thick. *You can easily cut it with tin snips and some judicious
forming with a mallet against a sand bag will get it to whatever shape
you want. *Multiple layers can be kept together with double stick
carpet tape.
Craig

Good idea, I guess this is another way of doing it.

On Tue, 24 Mar 2009 19:20:32 -0700, AK wrote:

Is this for a private glider of for use in a club glider?

IOW, what are your options for placing the weight and for securing it?

- if you have to sit on it then sheet bent to match the seat pan
would minimize its effect on your headroom, but securing it
properly could be difficult.

- putting a block of lead in the nose is safest (its on the scene of
the crash before you get there), and securing it may be somewhat easier,
particularly if you use sheet lead and the securing bolts also hold
the sheets together. Last but not least the forces you need to
anchor it against would be less (launch acceleration, sliding back
during a winch launch)


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

On Mar 24, 4:05*pm, AK wrote:
On Mar 24, 12:26*pm, The Real Doctor
wrote:

On 23 Mar, 00:23, AK wrote:

I want to make a small mold I would later use to create a fiberglass
container to hold lead weight. It would be nice if *mold material can
withstand 500 degrees Fahrenheit so I can pour lead into it and then
cover it by fiberglass.

I'm a little puzzled here. When you have filled the mould with lead
and covered it with fibreglass, won't the mould still be in there. Is
that OK?

How big is this thing? How complicated is the shape?

Ian

Ian, I create a mold first then I pour lead into the mold. Later I
break the mold up and I use fiberglass to cover the lead so it is
trapped and I am not exposed to lead dust.

Unless you are planning on eating you lunch off the lead I would not
be too worried by the minuscule exposure. Is this a club ship where
people are going to be moving the weights in and out all day long,
without washing their hands etc? If you are worried by lead exposure,
be careful in venting the area when you cast the lead. And the
exposure to chemicals and fiberglass fibers while encapsulating the
lead in fiberglass may be a larger minuscule health risk than the
small miniscule lead exposure :-) (says man who is hypersensitive to
epoxy).


Darryl