One shot moulds

[The Wooksta!]

Had a brainwave earlier but thought I'd float it first.  I have to stress that I have not tried this - yet!

I want to do the Attacker two seat trainer that was proposed.  I have a two seat canopy which is close but isn't quite right.  I don't want to carve it up but only want one resin plug to play with so I'd like a single copy.

Fill the interior with plasticine/playdoh/blue tack and then, after adding mould release agent of choice, coat the exterior very liberally with maskol.  Whilst that's still wet, cover with dry builder's sand (so it'll soak in) and then dump a load of wet builders sand on top.  Allow to harden and then invert before carefully removing the canopy.  Pour resin in, allow to cure and then pull it out.

Will it work?

[Martin H]

only one way to find out............................good luck.

[Hobbes]

Builder's sand? Is that the stuff they use for sand casting?

[The Wooksta!]

Don't know.  I do remember from when I used to play with it as a kit that it's retains it's shape when it dries.

[Steel Penguin]

probably not exactly the same ( and from my time in a Al casting foundry) it had oil not water in the mix, but sounds like it may work, and it wont ruin the origanal so its open to refinement,,
try and see

[TsrJoe]

sounds similar to latex moulding, altho the sand might weaken the mix, try 'maskol/copydex soaked tissue instead as a binder, another route would be to just plunge cast it in plasticene taking a resin copy from the imprint mould and using that as an acetate plug?, the latter technique is quick and definately works

cheers, Joe

[rickshaw]

It'll work, as that is the same basic technique used in casting metal.  However, you might need, because of the size of the mould to put some sort of better binder into the sand mixture.  I'd suggest watered down PVA glue.  Once you remove the canopy, put it into a slightly warm oven for a period to speed up the PVA drying but don't actually put in any heat. 

This will off course give you a positive cast of the canopy, which I assume you'd then use for vacuforming/plunge moulding?

[The Wooksta!]

More so I've something the right size/shape to sand to size.