Originally Posted by MidLandOne
I would be very interested in some more comment (and photos
) as to the background to your use of carbon fibre for the bench tops and how they will be finished.
Photos to come, but here is the skinny...
The bench tops are for a vanity and a cupboard in our refitted head area.
We made the bench tops from 10mm marine
ply, cut to the appropriate shape. They had to be made in conjunction with the main structure of the cuboards, so they ended up with lots of drilled holes from the building process, which we have subsequently filled and sanded flat
On the leading edges we added a double thinkness of ply (glue & screw with epoxy/glue fibres, with screws subsequently removed and holes filled) to make it look more solid, and then rounded the duble thickness with a router to give a rolled edge. (with hindsight, it might have looked even better with a triple thickness to give a bigger round, or perhaps 2 x 12mm ply instead of 2 x 10mm, but it looks good anyway). The glue/screw process did put a slight bow in the benchtop, so we probably should have clamped the whole thing to a bench at the time, rather than just clamping the 2 pieces of ply, but we fixed it laster (read on).
We laid biaxial fibreglass on the underside of the benchtops, for added stiffness and to straighten the aforementioned slight bow. Because the underside of the benchtops are inside cupboards and are therefore pretty much invisible, they will probably just get a coat of high build primer and a coat of top coat. If it were somewhere visible, we would probably fair it with epoxy/microballoons, but it ain't so we didn't.
We coated up the surface with a coat of expoxy resin. Normally we would coat with Everdure (or the Wattyl equivalent - just as good, 1/2 the price), but Everdure soaks in so much but we wanted a good smooth surface so that the carbon cloth wouldn't get caught as we laid it. With hindsight, it might not have been too necessary, although you would want some sort of pre-coat to stop your epoxy
getting sucked into the wood, rather than the cloth.
We cut the carbon out to shape, with a small amount extra right around. We actually laid masking tape onto the cloth and cut it through the middle of the masking tape, but this may have been overkill and we had to cut the masking tape of later anyway wherever we were rolling around an edge. You need very sharp scissors
We wetted-out the surfaces for teh carbon with a good coat of resin (don't put any extra catalyst in at this stage... chances are you are going to be messing around a fair bit, so you don't want your resin to go off in a hurry)
We floated the carbon cloth down by holding the corners. With hindsight, this was probably sup optimal... even the weight of the cloth will make it sag and distort the weave. When we next to this we propose to roll the cloth onto a pice of PVC tube and then rollthe tube over the job to get the cloth to fall onto the surface with the weft and warp perfectly straight. In fact, you have to look very very carefully at our job to see that the warp and weft are a little bit off-straight, and Lisa & I will probably be the only people that notice it. Note, also, if when you get the cloth down, you are not happy with it, you can easily pick it up again and re-lay it, although the extra resin it will have absorbed does make it want to sag more. We ended up lifting and repositioning the cloth on the biggest bench top about 3 times before we were happy (hence the idea to use a PVC tube next time).
Once you have the cloth down and you are happy with it, wet it out thoroughly - do not skimp on the resion... remember this is for aesthetics, not for weight / strength, so the resin/cloth ratio is irrelevant. Don't worry if you can see plywood
through the weave, as you wet out the cloth, it will swell and close the gaps. We used 1.5" disposable brushes
and a steel roller, which seemed to work out fine.
The tricky bit is rolling the cloth around the corners; do it gently or you will disort the weave - use your fingers if necessary. Once you have got the cloth rolled around to your satisfaction, carefully trim off enough as much excess as you can, because excess cloth will tend to want to make the cloth sag or fall off the underneath of your rolled area. Once you have trimmed it, you just have to keep an eye on it and keep pusing it back up if it starts to sag until the resin goes off sufficiently to hold it in place - that was, for us, about every 10-15 minutes, for about an hour, after which we could leave it alone.
That is about all I can tell you for now. We are still deciding whether to add an additional coat of epoxy
, or go straight to 2-pack varnish
. We will have to let the resin cure for a couple of days before trimming the excess cloth at the edges back hard (probably with a grinder, because I reckon the stanley knife will struggle).
Thats all I can tell you at this stage, but I can assure that the results end up looking spectacular. A friend used it for benchtops on the refit
of his 50 footer... just awesome. Photos soon...