Welcome to the final instalment in our video tutorial on how to make a carbon fibre bonnet.
In this instalment we're going to be looking at trimming these two outer and inner skins
that we made in the two previous videos, and we'll be fixing the fasteners and bonding
these two skins together and then putting the final touches to our finished component.
First thing to do is trim this inner moulding.
To do that we're going to be using a Dremel, like this, and we're going to be rough trimming
around the edge following the original line of the bonnet and then taking out this inside
section as well.
Now some obvious points that we've got to make before we start the trim is safety precautions.
We're going to be using a good quality dust mask, eye protection because we're working
with high speed tools, and we've got our localised extraction that's going to be taking away
all of the carbon dust.
Now with that out of the way we can get on with the trim.
Now that we've done the rough trim using the Dremel, the next step is to use a Perma Grit
file like this to tidy up these edges considerably.
So we just do that, go all around the edge making this flat and consistent all the way
around.
The
next thing we're going to do is drill the holes for the hinge fasteners.
To do this we've marked out the position for the two holes which we've measured off the
original bonnet, and we're just going to use a normal drill bit ensuring that it's quite
sharp.
We're going to use a high speed and we're going to use steady pressure.
We're going to put a block underneath to prevent the carbon fibre from bursting as we get through.
We've marked out the area at the front for the catch mechanism and we're just going to
cut this out, again using the Dremel and then use a file to finish the edges.
We're looking now at the fasteners.
We're going to be using these special bonding fasteners which are designed for composites
use and we're going to be gluing these in place and that's going to be the studs for
the hinge pick up, and we've also fabricated this keep mechanism for the latch and we've
just keyed this up with the grinder so we've got a good bonding surface.
For bonding the fasteners we're going to be using a structural epoxy adhesive this is
from our Perma Bond range, it's the ET500.
Now we're using an epoxy because that offers excellent bond strength to both the metal
and the composite material which is obviously perfect for bonding fasteners.
So apply the adhesive through a static mixer nozzle which actually mixes the two parts
to the epoxy as it goes.
And we put plenty of adhesive all around the area to be bonded.
the peel ply finish of course on the underside of this laminate is ideal for bonding to already.
And then we just push the fastener down into the adhesive and what we're looking for with
a boding fastener ideally is for some of the adhesive to squeeze up through the holes in
the bonding fastener and actually out on top of the fastener creating a mechanical lock
to hold that fastener in place.
And then the same again with the latch mechanism just bond that to hold it firmly in place.
To bond the two halves of the bonnet together, we're going to use the upper mould to hold
the parts stable and secure whilst we do the bond itself.
So we take the upper skin and drop it back into the mould that we used to make it in
the first place, and then we can take the inside skin.
Now it's only about ten minutes after we've bonded these fasteners but you can see they're
already incredibly secure, no danger of those moving, and so we're actually ready to bond
these two skins together.
For this bond we're going to use a different adhesive to the one that we used for the metal
fixings and that's because epoxy adhesives are recommended where you're bonding between
plastic and metal but for a plastic to plastic bond such as this then the ideal adhesive
is a polyurethane.
So we're using the Perma Bond PT326 from our range and we're going to be putting a large
bead of the adhesive all the way around the perimeter, both this edge and the inside edge.
So it's a twenty minute adhesive it's not too much of a panic, again we're using a static
mixer nozzle.
So the adhesive will be thoroughly mixed by the time it makes it to the part.
It will have some gap filling to do so we don't want to be too short with the adhesive.
We've just got a small amount of spring in this inner moulding that's holding it off
the outer skin so we're just going to pull some vacuum bagging film over this to protect
it and then weight these down with some bricks.
This adhesive is about twenty minutes to tack so we're going to leave this around about
forty to forty five minutes before we come back to it but before we go we'll make sure
that we've got good contact all the way around the edge.
Now that the adhesive has cured we're going to remove the weights and take the part out
of the mould. and you can see here where this excess adhesive has actually spilled over
onto the upper moulding and that's the reason why we didn't trim this upper moulding earlier
we've just left this so we can trim it now and that's prevented any of this excess adhesive
from going onto our mould.
We're now onto the final trim.
This is of course the most important because when this bonnet is fitted to a vehicle this
is going to be clearly seen.
So what we're going to do is trim it again using a Dremel, and we're going to do that
a few millimetres wide of where we can see that the original bonnet ended, and then we're
going to rub the edge back using a sanding block.
After we've finished with the Dremel a Perma Grit block like this is absolutely fantastic
for rubbing back to the line.
So we can see clearly where the bonnet should end and that's just a slightly over run that
we've been left with from the Dremel.
And then we just finish these edges by hand using abrasive papers, probably going for
a 120 and then finishing up with a 240.
That now concludes this video tutorial.
We've made an extremely light visually perfect carbon fibre vehicle panel, and with the information
that we've given you in this tutorial so can you.
So as ever all of the materials, the supplies and the equipment that you've seen in this
video are available from our website easycomposites.co.uk and if you want to discuss this project we
hope to see you on the forum talkcomposites.com.