Hi guys,

I am almost finished with my pattern and I have ordered materials for high temperature mould that will be used for pre preg. I cannot find some answers so I hope you can help me.

First thing is, since I still don't have oven and won't finish it in next 1 or 1 and a half month, can I make mould and post cure it when I finish oven, or I need to post cure it as soon as possible?

My plan was to brush approx. 1mm of gelcoat, brush some resin afterwards and add chopped carbon on sharp angles and reinforce everything with 12 layers of 200g black stuff twill. In total, mould should have thickness around 4-5mm for each part of mould. Is that enough? I am not comfortable using thicker fabrics due to complexity of pattern.

Also, is it maybe possible to "level" some curves with mix of high temp epoxy and milled carbon fiber and pour it as next layer after gelcoat and before fabric? That would greatly reduce amount of work needed for laying fabric reinforcements.

Unfortunately my pattern is routed from MDF and I am not really comfortable going above room temperature because I am afraid of warping it. 

When talking about torsional rigidity, I am considering placing steel ribs across length or something similar if possible but model is quite complex with couple long grooves so as you said, it's very likely that it will be stiff enough on it's own. Also, I don't think I will be able to use roller because grooves are 10mm wide so I guess I would need 5mm diameter roller at least so brush is my only option..

I use MDF for patterns all the time, it can go to 50-60 quite happily and not cause any issues.

Steel ribs on a pre-preg tool are another iffy situation. The difference in CTE means they can end up warping your mould or printing through onto the surface. Personally, I prefer to just make moulds monolithic and rigid enough to be free-standing. I still feel that at the size you are doing, 4-5mm carbon is going to be very rigid, especially on a complex part. It generally isn't something you need to worry too much about unless your mould is oddly flat.

Not being able to use a roller could be an issue, I have not managed to make one single successful wet-laid epoxy mould without using a roller. You can get very small diameter rollers, I think I have a 3mm one here. If you can't roll it, I would suggest casting those grooves solid may be a better option than just trying to do it with a brush. Woven reinforcements just trap voids like nothing else, and with carbon you can't see them so you need to be very methodical about getting them out.