HOW TO: Make a Carbon Fiber Part (Part 3: making a fiberglass mold)

HOW TO: Vacuum formed Carbon Fiber Part for $200 (Part 1)
HOW TO: Make a Carbon Fiber Part (Part 2: making a clay mold)
HOW TO: Make a Carbon Fiber Part (Part 3: making a fiberglass mold)
HOW TO: Make a Carbon Fiber Part (Part 4: making the budget vacuum bag)
HOW TO: Make a Carbon Fiber Part (Part 5: mold prep and cutting CF)

HOW TO: Make a Carbon Fiber Part (Part 6: vacuum bagging CF in mold)
HOW TO: Make a Carbon Fiber Part (Part 7: two part piece and final steps)

It took tons of time getting the clay angles equal as I could... come to find out I should have spent even more time getting them exact down to the millimeter because what's not so noticeable on the clay mold is VERY noticeable on a final product. More on that later.

Also, if you need a break until the next day or anything all you have to do is place a layer of damp paper towel over the clay and then put plastic (like a trash bag or cling wrap) over the wet paper towel to prevent it from drying out... Every 24 hours simply lift up the plastic and spritz water onto the paper towel... you can postpone your project as long as you want doing that everyday... assuming you're not working outside in the sun in which case you'd need to bring it inside.

Once you have your final shape you like you can lay out your sheet of twill fiberglass cloth on the mold to cut the excess off the cloth before you get out the resin... Also make sure you cut relief cuts for the sharp angles (see red dotted line in picture)

After you cut out the shape you like you can put whatever type of mold release you want on the clay mold that you like... or none at all, but the clay might stick to the fiberglass making a mess to clean out your fiberglass mold.

Here I used dawn dish soap (hence the green color in later picks) However now I use simple cling wrap you can buy at the grocery store to create a barrier between the piece I'm copying and the mold I'm creating. It's clean separation and there is no mess to wash out. Or you can use carnauba wax in the method I show later to form a wax barrier that functions as a great mold release when several built up layers dry (more later).

Really make sure your dry cloth is conformed to every contour of the mold after you put down your mold release (cling wrap, carnauba wax or whatever you choose).

You can use the cheap poly resin... I usually use about double the amount of liquid hardener they recommend for a small piece like this just so I don't have to wait 12+ hours for the mold to cure. You still have about 5 minutes before the resin starts to congeal and harden... If you're not comfortable with that than follow the box. It's not essential to follow the recommendations because it's only a mold, not a functioning part that will be used. (I do follow the CF resin instructions)

I mixed up 5 ounces of resin to wet out just the one layer of fiber glass here plus a second layer in spots with scrap cloth...

My dawn dish soap mold release was working but it turned out to be a mess... stick with carnuba wax (more later)

I waited an hour for my twill cloth to harden before moving on to strengthen the mold with the thick fiberglass cloth. But you don't have to wait until the first layer cures, but you should only mix up enough resin at a time to do small sections or one layer in this case with this small part. But that's me using double the amount of hardener so I don't have to sit around.

Both the twill cloth and the thick fiberglass matte are the same price per package; however the thick cloth is nice to quickly bulk up a piece like this.

I used two layers of the thick matte and I used about 18 ounces of resin to wet out this... I mix up 9 ounces with double the recommended amount of hardener at a time just because it sets up so fast... but that's just how I do it... you can discover your own preferences. When it comes to the resin for the Carbon Fiber, I follow the directions strictly. 

You'll also notice I put a plastic bag over the wetted out fiberglass and that's because it's easier and cleaner to work out the air bubbles AND it's a clean way to completely eliminate the annoying cured strands of glass that can form when you don't put plastic over. And Don't worry, resin does not need air in order to cure. 

poly and exopy resin does not stick to any plastic

I waited a day before popping the mold off the clay, but I could have done it in just a couple hours.

Had to wash the gunky soap and clay out of mold... that's why I switched to just cling wrap, but you can use carnuba car wax (more later).

I cut the excess off with tin snips but you can use a cut off wheel if you have one... Make sure to leave extra on the sides that way you have a cutting reference when your carbon fiber part comes out of the mold.

Sanded with 80 grit sand paper on the flip side for any extra slivers of glass.

Sanded the inside of the mold too in prep for spot filler. You can use whatever type of filler you like if you didn't make your clay model precise enough (like I did). Learn from me, Clay is MUCH easier to perfect a good shape out of than fixing your fiberglass mold after the fact. I won't bore you with how to use body filler... see google if you need instructions on that

Needless to say it was time consuming and you can again, learn from my mistake. Here's a pic by pic of each step in the process. 

You may notice towards the end of the steps the mold is painted with a black layer... That was also a massive waste of time. 

The plan worked in theory. That is, resin doesn't stick to plastic and it releases from it. True. However, the method of dissolving the ABS plastic in acetone and painting it on without it causing defects in the layer below was nearly impossible. 

Lol, I even went the extra mile and polished the plastic layer I eventually got laid down.... Again, don't waste your time doing this step.

It's FAR easier to avoid all these mistakes by:

1.) making your clay positive (or negative) mold perfect as you want your final part to be so then you don't have to do body work to fix it.

2.) Simply use carnauba wax on whatever surface you want to mold release from (more on that later).