1/12 Kremer K3 Porsche 935

[capri-schorsch]

Next step was the master model preparation.
I used some nitro putty for the fine details and started with the plate for casting.





Nest was closing all holes and windows.I used some plastic card for it.





On the inside i used some way sheets to get an thicker wall for casting and more stability.Its always hard to find the best solution for a light body and a good flow for the resin.
Will see how this works at the end.





Thats all right now.
regards Christian

[gp-models]

It will be very interesting to see if you can do it with a 1 piece mold or have to switch on a 2 or 3 parted mold, such hugh intakes and holes ( Hinterschneidungen ) will be hard to take out of the mold without damaging the mold.
From my experience in casting 1:43 metal bodywork it is not possible, but i know from experience with resin that the silicon for resin is much much softer, but i think it will be on the limit at this bodywork. Fingers crosses that you have success cause i want to see the result!

[capri-schorsch]

I don't see a big problem releasing the casted car from the mold.
Or maybe I wish there is not a problem.

I got that support case around the silicone mold while I cast the model.
After the resin is hard enough I will remove the silicone mold from the support mold.
Than will start with the front of the car and carefully remove the front of the car. When I am at the back I could bend the mold to release the deeper areas.
Hope that works?

My silicone is round about 35 shore hard. It's more a middle hard one which works fine in the past.
But every mold is different. Just ordered 10 kg of silicone. Should be enough for this mold.

Regards Christian

[capri-schorsch]

The "interior " is ready for casting now.
I got some massive edges at the rear wheel arches.I need them for the casting.But at the end they have to be removed from the resin model.Donk know how i could make it better.Cant find a better solution.
Anybody got a idea to avoid this?
Otherwise i want to cast it this weekend.Silicon and Vaseline is here.Only need to find some hours time for it.



Here you can see the massive part which is closed with blue plasticine.



Somebody could help with these problem?

regards Christian

[gp-models]

I`ll send you a pm, better to discuss this in our native language cause my english is not good enough for it, but maybe a two parted inner core as mold yould be a solution

[daniel]

I would simply cut those two inner parts from the rear fenders off. I think there is no problem with a "multipart" body.

[capri-schorsch]

Thanks to both of you.
Yes,a two part inner core will be the solution.Only think about how to make it easy.
But that something i could make after the outside was made.
Thanks for the input.

[JamesB]

Thanks to both of you.
Yes,a two part inner core will be the solution.Only think about how to make it easy.

It depends... if the split is front/rear, a provisory wall would do the trick. But I also have a rick I have used in these complicated inner mould cases. A hollow inner part.
the thing would be like that:

Though probably that was what you meant with "two part inner core" now I think it!!
Well, the thing is that once you release the inner cre of the inner core, the main inner core becomes hollow and "squizable" so it comes out easier...

[capri-schorsch]

It's not exactly that what I mean.
The problem with your solution would be that the silicone inner part would not stick together with the harder inner part if it's once removed.
That what I learned from my first experience with the Capri mold long time ago.
I removed the inner silicone part and it went out very well. But for the second cast it did not stick together very well.
Couldn't find a solution for that couple of years ago.

Now I would go for a two part hard resin core.
It's hard to explain that in English for me.
First step is to cast the inner core like it is.
When the master gets broken I got a core who is ready for copies.
If the master is not destroyed I will cut the core a bit and use a small guidance for the smaller core part. I must make it in the right shape to remove the bigger part first. Than I got room to remove the smaller part into the place where the bigger part was.
Hope you can follow my thoughts?

In my mind it works perfectly.

Will post pictures of it. If it works or not.
Regards Christian

[JamesB]

Hope you can follow my thoughts?

In my mind it works perfectly.

Hmmm.... I think I get it: the inner part of the mould would be then a resin main part with a skin of sillicone? roughly explained!!!
About the problem of the two parts of the silicone core not sticking, I don't see the problem while the inner-inner has some tabs to fit the inner-outer: enough to hold em together, weak enough to easily take it off. Also maybe eeping them together with some needles?
I also see it well in my mind!!!
Maybe your/mine silicones differ in terms of softness to the extent of allowing quite different performances...
Whatever, moulding/casting these sizes is pure bravery...