Female Mold for Carbon Fiber Motorcycle Bodywork

I've taken up teaching myself how to build my own carbon-fiber/kevlar composite motorcycle fairings using some old fairings as my template. Originally I was just going to use the old fairings as my mold and layup directly on them but changed my mind and decided to do it right.. So I started building female molds out of plaster. I tried making a small mold out of fiber glass but after researching further decided to give the plaster a shot and it came out surprisingly well I think. The surface is not totally smooth but I was planning for that and will smooth it out with sandpaper and glaze. I'm just glad I separated the part without cracking the mold and the impression successfully got all of the edges.

I laid the plaster (100% plaster of paris - 1 large box from Home Depot) last night at about 6:30 finishing up at close to 8. I used cheese cloth soaked in plaster directly against the part and after fully covering it with cheesecloth, I mixed up the last bit of plaster (about half a bucket) and poured that over the top just to build up a base for the skin I'd layed down.

The next day I started around 3:30pm (having let it sit outside all night and all day up until then). In the middle of summer Los Angeles weather I was satisfied it was dry.

This is how it looked after wiggling it loose a little bit.

First thing to do is flip it over. You'll see I let the plaster wrap around the edges and covered the backside with papertape..

Flipping it over and removed the paper tape I had used to seal it off as you can see.. I had draped some of the plaster and cheesecloth up and around the part to ensure I got the edges.

I read somewhere that mixing wood glue or coating the plaster in wood glue would strengthen the plaster, so I flipped it over, coated it with wood glue and used a heat gun on it for about 10 minutes to cook in the glue and to comfort my nerves that the plaster was totally dry.

After that using a combination of scissors and a cordless Dremel I carefully trimmed away the excess plaster so I'd be able to lift out the part.

And positioned some scrap wood around the part to prevent sensitive edges from crumbling due to their own weight once the part was freed. I also positioned an assortment of clips, screwdrivers, a bondo squeegee and a plaster piece of junk I found in my tool bag around the part to act as my wedges.

I was concerned it might not come loose because I really didn't use much release prior to pouring the plaster and definitely didn't give it much time to dry but I was able to separate the part VERY easily in about 5-10 minutes being probably more careful than I needed to be.

After I got the part free, I did the same thing to the inside that I'd done to the outside.. Wood glue and heat gun for about 10 minutes.

Here you can see the comparison between the part and the mold. I think I will come back with a marker to draw out the edges just so it's totally clear since there are some cut away areas.

And last but not least.. the longest part of the process. I cleaned up and organized my work area because I'm OCD like that.
You see I used a pallet on top of a trash can as my work table and built a wooden bed lined with trash bag plaster to hold my work.. With a cardboard top and some string for peace of mind.

My buckets for mixing plaster. Off to the far right I have some more part in a large Rubbermaid container waiting to have plaster poured over them.

I just wrapped up and am going to take a break a bit longer and probably come back and work on smoothing it out so I can start the resin infusion / carbonfiber build up tomorrow