Hi,

With great difficulty, I got the mould to release from the front bumper. I am happy with the outcome. Just a few questions:

1. Is there an alternative to mould cleaner I can use to clean away the wax?

2. Is there a trick to touching up any imperfections with additional gelcoat?

Most of the wax will scrape off plus warm soap and water will help too.  

There is no special trick to repairs.  Sand the effected area then use a small amount of gel to touch up.  Solution MW will help avoid a tacky surface.  Once filled, flat level with surrounding area then polish back to a gloss.

You can see the repair process on our bonnet mould video at 17min 39Sec.

How to Make a Mould for a Carbon Fibre Bonnet

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Thanks Warren. 

I have read on this forum that its extremely difficult to get a perfect finish when building up gelcoat and then sanding it flat.

Is this true? The only reason I ask is so I can gauge how much persevere with making it perfect.

Nah vinyl gelcoat is pretty forgiving, you CAN get it back to perfect - depends a lot on your skills and technique, as well as the complexity of the area you are repairing. If you build up too much, you're going to have a hell of a lot of flatting back to do and likely won't get there. If you dont build up enough, you will have a low spot. 

As you mentioned, the problem I have had before is that gelcoat is super hard and takes forever to sand. I have use a fine file to flatten and that works better.

You shouldn't be using anything as rough as a file, you'll certainly never get that back to a good finish. If I'm compounding anything, whether it is gelcoat or clear coat or resin or whatever - if I have to start rougher than 800 grit then I know I'm not going to be able to compound it up to a true full gloss without applying more material to fill the rougher scratches. 

Tooling gelcoat is tough and hard wearing and difficult to sand, so you want to be getting your repair job as close to flat as you can without having to do any sanding at all. Sometimes that means doing an initial fill that is a bit low, and allowing that to cure. Then do another smaller fill that just takes you slightly proud of the surface, so that all you need to flat it back is a few minutes with 800 grit paper on a block. If you try to do it all in one application, you will likely get some bits that are high and some bits that are low and it won't work properly. 

Another trick I do often for less complex areas is to use flash tape or release film to shape the repair. That works very well for flatter areas and outside radii, but not so well for compound curves or inside radii. You just want to be careful not to wrinkle the tape/release film or trap air bubbles as this will give you even more repair work to do. 

As with all hand work - it really just comes down to technique and practise. You won't learn the techniques without trying them, and sometimes you will make things worse. But give it a go and see how you get on. Be patient, don't try to do too much at once. If you need to, multiple fills are often better than one for larger repairs. Take your time sanding, it isn't a 2 minute job. 

That's some really useful information especially choosing 800 grit as the coarsest of sand paper. That's a mistake I made on project two. 

I can imagine the trick with the tape being effective. I will use that and see how I get on.

Thanks, making carbon fibre parts must be your profession?!