HOW TO: Make a Carbon Fiber Part (Part 7: two part piece and final steps)

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)

So after a total of 12 hours the part seemed hard enough to turn off the vacuum and peel away the clay... you can re-use and re-use the clay... I just put it into gallon zip-lock bags and add about two cups of water in to re hydrate the clay again. (This obviously cured at room temperature in my garage.)

Got the part out of the bag and the breather cloth is still on the peel ply etc.

The perforated wax paper worked as a great alternative to peel ply

The little scraps of wax paper peel off no problem

Just for reference the part isn't fully cured yet and to show this I was able to cut some of the loose threads... the part is about as stiff as cardboard so don't take the risk of deforming your part to cut all the excess off or anything.

It's still in the mold 

and a trick to speed up the curing process and possibly make it even stronger than a full "room temperature cure" is by putting it in the oven. HOWEVER, be very careful as your resin or mold may be flammable or if your part is heated too much air bubbles can form in the faster curing set up. So I set my oven to the lowest temp possible of 170 degrees Fahrenheit and kept it cracked open. Turning the set up every couple minutes. 

When it reached about 125 degrees Fahrenheit with this candy thermometer resting on it I decided that was warm enough.

When it cooled back down to room temp (after about 15 minutes) It came out of the mold with little effort.

Here it is fresh out of the mold

After it was out for a couple hours it still felt slightly plyable so I decided to put it in the oven for another warming session... I have no idea if this makes it stronger than if I'd just left it alone for a few days to fully cure. I highly doubt it makes it weaker since I heated it up to only 125 ambient temp in the oven (not a core temp from inside the part). After this last heating, it felt fully cured.

Even in the rough state it was looking good

So to make the cowl be a working part that could attach to the existing hinges I first put a layer of plastic in the trunk (to avoid a mess). Then I piled in my clay and leveled it nice making sure it wasn't compressible in any areas.

For the bottom pan I used just two layers of 12K plain weave CF. And I placed a layer of Syrian wrap in between the clay and the carbon fiber pan I was making here. 

Having already gone over the whole bagging process I won't bore you with the details. Here I sealed the set up under a plastic sheet cut to fit and sealed with duct tape. Hind sight this was barely adequate, but since it's non-structural or even cosmetic I didn't mind. I was more/less just testing the idea of making the part this way. I taped down some tubing to get the CF to better comply with the details of the mold on the outside of the bag, but under the tape. 

Here it is right after about 14 hours of vacuum bagging. Pretty much fully cured.

As you can tell the mechanical compressing of the vacuum was enough to push the vacuum tube under suction into the clay and thus deforming the part. This is valuable info for me not to make a show or structural part on a clay mold.

So now you can measure and cut down your part with a cut off wheel since it's fully cured.

This was just the first rough cut... you can always cut off more. As you can see the flaw that was created from when I was trying to put my wetted out cloth in the mold into the vacuum bag... Again, having some wax paper or plastic over the edges that are tacky and can get pulled away from the mold easily is a good idea. You can also see I completely gave up trying to save my paint job.

Measure, Measure, Measure... here's a second cut down. Just showing you all this in case you can learn at all from my process.

Getting there

Cutting the pan down, using a file for the minor adjustments

Still rough

Almost

Good:

Pan inside cowl, good to go to bond

Since The Max clear 1618 is meant for vacuum bagging it was too thin of viscosity to bond the two parts (think the viscosity of honey or warm ketchup)... it's just going to run down into the crack. This two part epoxy from the hardware store is more like the viscosity of craft clue like "elmer's glue" that has chemicals in it that quickly evaporate within minutes to get progressively thicker until hard. 

While bonding I secured it down

After it was bonded it didn't look that much different

After the two were joined together I added more epoxy to the seam

Great fit underneath when I took the back of my bike off.

I taped off and spray painted the graphics I wanted on the part... hindsight this was a HUGE waste of time, effort and resources... it would be far more appropriate to have just got vinyl decals made and clear coat over them.... on the top left you can see how "orange peel" the surface of the part was when I applied a coat of Max Clear 1618 epoxy on the top of the part. Max Clear HP epoxy resin may have provided the "clear coat" effect I was looking for... instead I just used rattle can clear coat that I had been happy with the results to get the final product seen here.

Sanded down the paint job I ruined on my tail

Now to make a Carbon Fiber tail out of a two piece mold... I tried outlining the areas I was to cut out with Elmer's glue to prevent fraying of the fiber matrix after cutting... It seemed to work. I of course let this glue dry overnight so the bead of glue would hold the cut out and the remnant matrix together. Today I don't use the glue technique I simply cut the excess off in manageable squares and stack them up for use in small projects.

You can also see I was repeating the process of using a piece of fleece as a template (the tan fleece)... It's also nice to keep if you ever want to make another part.

The little 3cfm vacuum pump had enough power to do two parts at once

Using carnuaba wax mold release allowed the parts to pop out clean and with a much more smooth finished look.. the chalky appearance is due to the carnuaba wax that isn't wiped off yet.

Before I bonded the two pieces together.

After they're bonded together and before any paint.

Put together on my CBR 929.... now to do the subframe.

(see part one of series to see the picture of the subframe)

"So what's the point?" people ask. Dropping half the weight of your fairings isn't a bad deal is it? (This is a fiberglass cowl I made but never finished... it's a wall hanger just because I ended up getting it signed by Jason Britton and Tony Carbajal

Best of luck on your project!

-Matt Behning