Monday, November 29, 2010
Molding Your Own Carbon Fiber Components- DIY
MOLDING YOUR OWN CARBON FIBER COMPONENTS
Author: James Sparkes, Newcastle, Australia.
TOOLS / EQUIPMENT REQUIRED:
Small hand held rotary tool with cutting disks and sanding / grinding wheels (a Dremel
type tool with a flexible shaft is recommended),
Wet / Dry abrasive paper (240 grit, 400 grit and a polishing grit - say 1200),
Pane of glass (say 1.5 ft by 1 ft and thick enough to take reasonable handling loads
without breaking - I used my wife’s glass chopping board),
A few clothing vacuum bags (this is a must if you want to get a reasonable end product),
A powerful vacuum cleaner (I used my wife’s with the filters removed to improve the
A sharp pair of scissors (for cutting the glass and carbon cloth),
Hot water bottle and blanket (to speed up cure times),
A dust mask / respirator and eye protection (use when cutting / sanding).
Fiberglass cloth (6oz weight should be fine),
Carbon fiber cloth (I used a plain weave which was all the shop had - at $60 AU per roll
metre it’s not cheap),
Two part epoxy resin (I used WEST System epoxy which is a marine grade epoxy.
Don’t be tempted to use the cheaper polyester resin as this is not as strong as epoxy, does
not wet out carbon as well as epoxy and cannot be exposed to high temperatures.),
Mold release wax (a carnauba based wax specific for mold release - do not use car
Liquid PVA (for mold release - this is a specific PVA for mold release not the glue
Thin PVC plastic sheeting (to avoid having resin sticking to things you don’t want it to),
Roll of cling film (to use as a peel / release film),
Cotton cloth (to use as breather fabric),
Popsicle sticks (for mixing resin),
Some wax free plastic cups (for larger amounts of resin),
A small medicine cup (to measure out resin and hardener - I used a 50ml one and
usually only mixed up small batches of 30ml or less),
Acetone (for clean up of uncured resin),
Some short length bristle brushes (use some that will not loose all their bristles when
Latex gloves (to avoid a gooey mess all over your hands).
GENERAL SAFETY AND HEALTH PRECAUTIONS:
The reader of this article takes full responsibility for their own actions when following
these procedures. Uncured resin and the resulting dust from cured resin and glass /
carbon fibers may be toxic and have harmful effects when inhaled. Use common sense
and follow the manufacturers guidelines.
Notes on resin mixing. Always add the hardener to the resin, not resin to the hardener.
Use small quantities, i.e. only mix what you can use during the pot life (pot life is the
time taken for a standard volume of mixed resin to “gel” at a standard temperature).
Large volumes of mixed resin (say 100ml or more) generate excessive heat during the
chemical reaction. This heat build up will cause to resin to gel quicker, may cause the
mixing container to MELT and cause excessive resin vapors.
Notes on cured glass and carbon fibers: Take care when handling cured parts during
sanding and cleanup. Fine fibers with cured resin act as splinters and may break off
when imbedded in your skin. Carbon dust if left to sit on bare skin will cause a mild
irritation - wash off with soap and water.
Notes on sanding / grinding carbon fiber: Carbon fiber dust can conduct electricity.
Take precaution to prevent carbon dust from entering electrical equipment as this may
cause short circuits and expensive repair bills.
MOLDING BASICS - Plug Preparation
A warning on part molding. Mold only parts with a positive draft angle, i.e. the part
will not be locked into the mold due to it’s shape. For complex parts I suggest multiple
piece molds which can be disassembled for part release. These molds are beyond my
current experience. Also note that the clutch cover has a positive draft and can be
molded using a single piece mold. The original cover did prove to be difficult to remove
from the mold. The carbon part was also difficult remove and I ended up destroying the
mold in the process.
You can use you own original parts to create a mold. Start with smaller simple parts
which are flat or have small uncomplicated curves. The first part that I attempted to
make a mold from was the clutch cover and after three attempts I gave up and moved on
to the heel plates.
Once you have chosen a part to mold you need to decide whether you want a female or a
male mold. A female mold will give a smooth surface on the exterior side of the end
product. So with that in mind I assume you’ll use a female mold.
Take your chosen component and give it a good clean. The surfaces on both sides should
be spotless and free of nicks, gouges or blemishes as these will turn out on the mold.
If your part has any fastener holes, you can fill them with plasticine or a similar material.
This will prevent resin flowing through the hole and locking your part to the mold. It
also makes a nice impression in the mold and the final product so you know where to
drill any fastener holes.
Apply mold release wax to the part in accordance with the product instructions. It’s
generally wax on and allow to dry, polish off and then allow to dry for 10 to 20 mins then
apply another coat. Apply five to six coats and allow the final coat to dry for about one
Apply a coating of liquid PVA release agent to the part and allow to dry. This allows the
part to come away cleanly from the mold. It will wash off with soap and water or will
peel away like a layer of “cling wrap”.
MOLDING - Laying up and Vacuum Bagging
Before you mix any resin, ensure you have cut the required amount of glass cloth
(sufficient to cover the part with an overlap of about 1.5 inches), prepared an area to put
your vacuum bag where it can sit for a few hours and you have boiled the kettle (if you
want to use a hot water bottle for a faster cure).
Have your bristle brush ready and a cup of acetone to clean the mixing cup and brush
immediately after use.
The vacuum bag is required to hold the cloth in position and against the part / mold while
the resin cures. The application of the vacuum also draws any air bubbles out of the
layup ensuring a smooth mold surface. The vacuum also pulls out excessive resin and
compacts the layup which gives a lighter and stronger part.
A basic vacuum bag configuration is shown in the Figure 1 below.
Page 3 of 17
While I don’t expect you go to the effort of replicating the configuration shown in the
figure above, we can make do with our clothing vacuum bag, some cling film as peel ply
release film and some cotton cloth as a breather fabric ply.
Have your vacuum bag and vacuum cleaner (remove the filters to allow greater suction to
be applied to the bag) ready. Have a friend ready to help you seal the bag and hold the
vacuum cleaner to the bag port while you work the wrinkles out of the bag. I placed an
old towel on the bottom side of the bag to protect it from being pierced by the glass plate.
The towel will also prevent the bag from sealing within itself, i.e. it gives a route for the
inside air to escape to the vacuum, i.e. a breather fabric.
Place a layer of the PVC sheeting on the glass plate or you can use cling film if you wish.
Place your waxed part in the center of the plate.
Mix the required amount of resin for a single layer of glass cloth. Mix the resin well and
let it sit for a bit to allow any entrapped bubbles to rise to the surface.
Place a single layer of glass cloth over the part and apply some resin with the brush
(applying a single layer at a time allows the cloth to conform to the part better). Use a
stippling action (dabbing action) rather than a brushing action as a brushing action will
generally just move the cloth around. When the glass is completely wet out by the resin
(it is no longer white but transparent), and you are satisfied with the work, place a layer
of cling film (peel ply - see Figure 1 above) over the layup and then put a piece of cotton
fabric over the top (this acts as a breather fabric ply to help the air within the bag escape
to the vacuum port).
Place your part in the vacuum bag and seal. Apply the vacuum to the bag and slowly
draw the air out, as the bag closes in on the part manipulate the bag to conform to all the
curves and any tight radii of the part. Try to smooth out any wrinkles over the part as
these will create resin ridges and will need to be removed before the next layer of glass is
Once you are satisfied with the vacuum bag, let the resin cure overnight or if you prefer
you can use a hot water bottle a blanket to allow enough heat to cure the resin in about
1.5 to 2.0 hours. Periodically check on the bag to ensure that it has not lost its vacuum,
this is crucial in the first 30 mins of curing. Figure 2 shows a photograph of a vacuum
bagged heel plate molding. Note that the blue color is the dye in the PVA release agent.
The dye helps to show where you have applied the PVA.
Once the resin is cured, remove it from the vacuum bag and remove all traces of the cling
film. If any significant resin ridges are present remove them with abrasive paper. If the
resin has been allowed to cure for more than 24 hours, lightly abrade the external surface
and then wipe clean with acetone. This will expose a chemically active resin surface to
promote good bonding of the next cloth layer.
Apply successive layers of glass to the mold and vacuum bag cure as you go. After you
have at least two glass layers, you can apply more than one layer at a time. A total
thickness of about four or five layers should be strong enough for the mold. Apply more
glass around the edges to allow sanding back at a later stage.
Once the mold is thick enough and fully cured, remove the part from the mold. Be
patient and take care. Use plastic wedges (I used my wife’s plastic spatula) around the
edges of the part to pop the bond between the part and the mold. This is a tricky process
and can be frustrating. For a stubborn part try washing out the PVA layer with soapy
water. If this fails you can tap the mold (from the part side only to prevent damage to the
mold) with a wooden rolling pin or similar as this can provide the energy required to
break the bond between the part and the mold.
Once you have the part removed from the mold, trim the excess fiberglass from the
periphery leaving about 1.5 inches from the edge of the part outline. Smooth out any
sharp edges to prevent splinters occurring.
Clean the mold with warm soapy water and dry. Inspect the mold surface, it should be
smooth and free of surface voids or areas where the cloth did not conform to the part. If
the mold has significant areas of voiding then scrap it and try again. Small voids may be
filled with resin and sanded back. Smooth the mold surface after any sanding with a high
grit paper to polish out any sanding marks.
The mold should have a definite part outline a fraction of an inch high. Using a Dremel
type tool with a sanding wheel carefully grind back this line to a smooth profile while
leaving just the slightest ridge remaining (this will aid in defining the part outline for
trimming). The profile should have a smooth contour to allow the carbon cloth to easily
conform to the mold.
Clean the mold and allow to dry.
Apply molding release wax to the mold as per the instructions given above for plug
Apply PVA to the mold as per the instructions given above for plug preparation.
Figure 3 shows a photograph of a completed heel plate molding, waxed and with PVA
release agent applied. At this stage the mold is ready for layup of carbon fiber.
Figure 3: Completed Heel Plate Mold - Passenger, Right Hand Side
CARBON PART MOLDING - Layup and Vacuum Bagging
Using the process outlined above for laying up and vacuum bagging, cut a piece of
carbon cloth large enough to fill the mold. Prepare the required amount of epoxy resin
and apply the resin to the carbon cloth. Work the resin into the cloth and ensure that the
cloth is completely wet out and the cloth conforms to the mold as best as possible. Use a
stippling action with the brush rather than a brushing motion as a brushing motion will
tend to disturb the cloth weave.
Place the layup in the vacuum bag and apply a vacuum as per the instructions given
above for the mold vacuum bag process. Ensure that the bag conforms to the part with no
significant wrinkles present. Pay attention to any tight radius areas to ensure the bag
conforms to the radius instead of bridging across it.
Figure 4 shows a photograph of a vacuum bagged carbon fiber heel plate layup. Note
that I did not use a breather fabric ply in this instance.
Figure 4: Vacuum Bagged Carbon Fiber Heel Plate Layup
Cure the resin overnight or by using a hot water bottle for 1 to 2 hours.
Once the resin is cured, remove the part from the vacuum bag and apply successive layers
of carbon / epoxy. I used 6 layers for the heel plates and 5 layers for the clutch cover.
Alternate the angle of the cloth fibers for the layup between 0, 90, +45 and -45 degrees
and ensure that the layup is symmetrical. This will give a laminate that is strong in both
directions as well as resistant to twisting forces.
Once the resin is fully cured, remove the part from the mold. Be patient and take care.
Use plastic wedges around the edges of the part to pop the bond between the part and the
mold. This is a tricky process and can be frustrating. For a stubborn part try washing out
the PVA layer with soapy water. If this fails you can tap the mold (from the mold side
only to prevent damage to the carbon fiber part) with a wooden rolling pin or similar as
this can provide the energy required to break the bond between the part and the mold.
Wash the part in warm soapy water and inspect the exterior surface of the part.
Hopefully the surface is smooth and free of air bubbles in the resin. If this is not the case
then scrap the part and try again.
The carbon molding should have a nice visible line showing the original part outline. If
the part had fastener holes these should also be visible as circular depressions in the
Figure 5 shows a photograph of a cured carbon fiber heel plate layup, just removed from
Figure 5: Carbon Fiber Heel Plate - Prior to clean up
PART CLEANUP - Trimming and Hole Drilling
Using a Dremel type tool with a cut off disk trim around the part outline. Do not attempt
to cut to the line exactly but leave a gap and sand the final profile smooth with a sanding
wheel and abrasive paper.
Locate the center of any fastener holes using a small pilot drill (use the smallest you have
and use a high speed). Drill from the outside surface and use a piece of scrap wood on
the back side to prevent it from breaking away as you come through the surface. If you
are satisfied that the hole is in fact in the central location, proceed to a larger drill bit. If
the hole is not in the center, try to pull it to the center using the drill.
When drilling the hole to the final diameter use a slower speed (I used a cordless with a
very slow speed) and initially drill from both sides and then final drill completely through
from the outside of the part. This should give a clean hole with no break away on either
Using the Dremel with a sanding wheel sand the part to just off the edge outline. Take
care not to contact the outside surface of the part as this will obviously ruin the gloss
surface. Final sand the edges using 400 grit abrasive paper with water.
Wash the part in warm soapy water and inspect your handy work. At this stage the part
can be considered complete.
SURFACE FINISH - Gloss and Environmental Protection
If desired you can clear coat the part (I used Tectyl 501 made by Valvoline which is a
clear coat for aluminium to prevent corrosion) to give a glossy outside surface. Note that
this is recommended for numerous reasons:
a. The clear coat also gives a gloss finish. I applied three coats and sanded between
with 1200 grit paper.
b. The clear coating forms an environmental barrier for the part and prevents
moisture absorption by the resin.
c. The clear coat forms a barrier between the carbon fiber part and the aluminium or
steel components that it is attached to. The carbon, if allowed to contact these
metals will cause galvanic corrosion to occur to the metals.
d. The clear coat should have a UV filter additive (the Tectyl 501 coating claims to
have one). All epoxies suffer from degradation from UV light exposure, this
causes the epoxy to yellow. The UV filter in the clear coat should reduce this
effect. Some companies that market carbon fiber components claim that it’s the
clear coat that causes the yellowing and hence they don’t use any. This maybe so
but in any case, epoxy will degrade from UV light exposure if left unprotected.
The only way around this is to paint the component with an opaque coating.
WORKED EXAMPLES - Components made by the Author
996 Passenger Heel Plates:
The heel plates were relatively simple to make. Once the mold was made and prepared
actual manufacture of the part only took a few hours. Figure 6 shows a photograph of the
right hand side heel plate installed on the bike.
Figure 6: 996 Passenger Heel Plate - Right Hand Side
996 Rider Heel Plates:
Similar to the passenger heel plates, the rider heel plates were relatively simple to make.
The added curves did however present more difficulty. Both molds and components
were satisfactorily completed on the first attempt. Figures 7 and 8 show photographs of
the left and right hand side heel plates installed on the bike.
Figure 7: 996 Rider Heel Plate - Left Hand Side
Figure 8: 996 Rider Heel Plate - Right Hand Side
996 Clutch Cover:
I actually tried to begin molding the clutch cover first. I eventually gave up to try the
more simple heel plates. My first attempt was made too quickly. I used car wax as a
release agent and no vacuum bag. Consequently the cover was glued to the mold. In a
panic I used whatever I could find (a big screwdriver) to pry the cover from the mold. As
a result I damaged the paint on the cover. The scratch marks were not completely sanded
out and these turned out on my final product.
On my second attempt I used plaster of paris to make a mold. While the cover came
away from the mold cleanly, the surface was porous with lots of tiny air bubbles on the
surface. I attempted to make a glass part from this mold only to create a big mess of
glass epoxy and plaster which refused to part.
On my third attempt I used the glass cloth and vacuum bag molding method. This time I
used the vacuum bag but I did not use a breather fabric ply. The majority of the mold
turned out ok, but the cloth did not conform to the mold at the tight radius at it’s base.
This is where I gave up and began molding the heel plates and the exhaust shield (as
For my fourth attempt I used the vacuum bag with a breather fabric ply. I also filled the
fastener holes with plasticine and put a bead of plasticine around the lower rim of the part
to prevent resin getting drawn in between the underside of the part and the glass plate.
The mold turned out great and the resulting carbon part a success. Figure 9 shows a
photograph of the finished part. Figures 10 and 11 show photographs of the part installed
on the bike.
Figure 9: Clutch Cover - Finished Part