I have recently made a fibreglass + gelcoat mould, to reproduce a carbon frame guard for Yamaha YZ year '98.
I will fix a few cracks I had during the detachment of the plastic component with DAS, an italian modeling clay, reinforced with epoxy.
Apart from that, do you think I can use the mould as it is (applying only wax and/or PVA), or do you suggest to apply epoxy by brush, and then wax and PVA, to have a stiffer structure?
Depends on how you intend to build your part and what quality of finish you would like on final part. Is the mold only chop mat?
Yes, the moulds are made both in fiberglass MAT, you can see the finish in the attached pictures, after the original plastic components have been removed. I have already fixed a few cracks with the DAS clay
If you are happy with the surface then apply wax. Normally I apply 7-10 coats of wax on a “green” mold. On the flange I like to leave a heavy amount of wax to add some extra assurance that it will not bond to a uncoated surface (the area that was not gel coated.) Allow time between coats, 10-20 minutes. Always best to follow the wax manufacturers instructions. If you use wax there will be no need for PVA. My experience with PVA is that it will always release, but it can affect the parts final finish.
What is your resin system for the final part? Make sure you have plenty of pot life to be able to work into the texture groove areas.
What is your plan for the embossed areas?
Are you intending on having the carbon show, like an unpainted part?
What type of carbon reinforment are you going to use? i.e plain weave 3k, 8h satin, etc.
The areas on the flange that are cut/voids I would just fill with modeling clay. The part will not bond to the clay, but the clay usually leaves a sweated area that affects part finish.
In the end, on the embossed areas I have applied a few of DAS, as I said, a kind of clay that become hard and that can be smoothed with water.
The result was quite good, it was stiff enough to resist to the pressure of -1 bar.
On the mould’s surface I had previously applied more coats of wax and also PVA, but as you have suggested, on the second mould I will apply only wax, I think it will be enough.
The carbon fabric is Plain 3K 200gr/square m, it will be varnished
I post here what I got after making a new mould. I have vacuum bagged it to have the carbon accessories that you can see in the last two pictures.
Good job. The second mold looks much better. Are you happy with the parts?
Thank you.
Yes, I’m really happy with both components