Hi
Im new at this, having made one uni-mould and one putty-mould before this.

i have a beaten plastic underside panel on my car that i was hoping to create a mould from.
As i have not been able to source a mint piece, this is what i have to work with.

Underside (facing away from the mould)





Side facing the mould



So i was thinking of taping and gluing it back together.
To cover the holes, where the plastic is gone i figured i could use some sort of backingplate, and fill it up with plasticine.

Any advice appreciated

That will work. It's the only way with plastic really, as it's pretty unfixable. If it's under the car and you don't care how it looks, just give it a REALLY good clean, tape up/fill the holes etc as you said, and make your mould off of it. 

You might also find that some selective use pieces of 3mm closed cell foam sheet and glue will be help to re-inforce the joins, rather than rely on tape alone

I would hot glue some signboard behind the holes and then fill them with plastercine.

If you treated yourself to some of the heatproof/release tape you could simply fill the hole with cardboard or what ever and then release tape over that, the mould will release from this no problem.

while your at it use the signboard to make flanges and seal any holt holes with the release tape.

Thanks guys.
I decided to start with another piece from the underside that is not broken, it got some damage, but its easily sorted.


Since the part has several large gaps i tried using expanding foam, has anyone tried this?


As you can see i have started cutting the foam and the plan is to use the uni-mould system.
I have ordered lots of stuff from EC, Flash tape included.
And i recon i can cover the "swiss cheese" with this tape and then cover the whole part with tooling gel.
The problem is that the EC package hasnt arrived yet, so the question is, is there anything else i can cover with?
I got

The reason i tried expanding foam is that i found it to be to much hassle with cutting polypropyleneboards to fit everywhere.
I got #8 mould release, and lots of plasticine, maybe a thin layer of plasticine to cover up the foam holes?
As you can see the part is in a bit of a rough condition, so i am prepared to sand and polish the mould once its done.

Any suggestions appreciated!

I think you will struggle getting anything to stick to the foam. Tape may work, but it won't stick nicely. Hopefully the foam just gives enough support to the tape to allow you to get the gelcoat and reinforcement on.

Yeah i recon.
Was hoping there was another way.
There is some regular packing tape where the film is polypropylene
http://adhesive-tape-converting.mbktape.com/viewitems/film-tape/polypropylene-pp-film-tapes?

If i put the adhesive side towards the part, then the tooling gel should not stick to this tape right?

btw. i work on a polypropylene board which keeps basically everything from sticking, including expanding foam.

Yeh PP packing tape will be fine, it is just the adhesive you don't want to expose to the resin.

Thanks.
Mould is on its way =)





Gel was applied last night, so it is now ready for the coupling coat.




I'll post the result as soon as im done.

looking good this far!

Matthieu Libeert
Founder MAT2 Composites X Sports
website: www.mat2composites.com