Talk Composites - The Forum for Advanced Composites

dent problem

http://www.talkcomposites.com/Topic11908.aspx

By kidpaint - 6/18/2014 11:09:47 PM

I am wanting to start making some molds of my audi rs4 rear doors to eventually make in carbon. The drivers door is in perfect shape, but the pass. door has a very shallow indent from a door ding or the like. I am not afraid or new to doing body work as thats what I use to do for a living. My question is this. Is it better to do the body work ahead of time and get it all smooth or can I make the mold and then sand the raised area of the mold that is the reverse of the dent. I think it would be easier to block it down than to fill it up on the actual door. 

The dent is like 1 inch by .25 inch by .125 deep


Also, I have read a lot about mold making and most posts I read about what weight glass to use is in metric measurements. What type of glass and how many layers should I use for making these molds, if I plan on making more than one copy out of them?

I was thinking this 

Tooling gel coat
Epoxy resin
(tearing some strands of fg out and laying those down in the one 90 degree edge where the front door overlaps)
1.5 oz chopped mat for the first 2 layers
4 layers of 4 oz woven or 2 layers 4 oz followed by 2 of 6 oz

Adding some sort of reinforcement of wood or something

I have made molds of smaller one time use parts before so Im not entirely new to the process, but this will be my first larger reusable mold so to speak. 

Does this sound right, overkill, or not enough?
By Hanaldo - 6/30/2014 4:43:28 AM

It's hard to recommend anything, as availability is always going to vary from place to place. Personally I don't actually have any off-the-shelf epoxy tooling systems available to me here in Aus, not in useable quantities anyway. So when I need an epoxy tooling gel, I blend my own using laminating resin and a variety of additives and pigments. Works very well. Not as nice to work with as the Airtech stuff I've got here, but still good. And doesn't cost the Earth.

Point being, if it's an epoxy tooling gelcoat, it's likely going to be decent. If you're using a semi-perm release agent as well, then I'm sure you'll get an easy 5 pulls from the tool. Build the reinforcement to be about 7mm thick, the thing will last virtually a lifetime if you treat it nice.