Sanding and coating

Only one picture now, more will follow. Look for the sneak preview below.

Sanding is the job that I hate most on carbon fibre constructions. The carbon dust is irritating to your skin and itches. So sanding is done in long sleeves, long trousers and with gloves. Not really fun when it is 30 degrees centrigrade.

First I do the rough work using file, sanding paper and a Stanly shaper. I remove most of the ridges and other small defects.

Next step is sanding the entire surface. Tjalling is a good friend of mine with a wood workshop. And in this workshop he has a professional Festo sanding machine connected to a Festo vacuum cleaner. I have asked him to use his workshop in the hope that the carbon dust will be less of a problem. It works like a charm. The sanding dust simply disappears. In stead of a black workshop and an itching skin I just end up with a nice smooth frame and nothing else.

In the weekend I go for a ride with Levia in the cargobike and buy a pot of dubbel D UV coating. This is a polyester based coating that is very tough, UV resistant and it is an UV filter. The epoxy of the frame can not tolerate UV very well, so this coating is like sunscreen for my bike.

After 2 layers of the coating the frame looks like this:

I probably will add one extra layer off coating, lightly thinned got get a smoother finish.

After that I will paint the rear triangle in glossy black.

And off with the peelply

No pictures this time.
The resin has cured, and the frame must be freed of its second skin of peelply. We put the peelply all around the frame (on both sides). This makes it extremely difficult to get off the stuff. An hour of really hard work yields sore fingers and a nice clean frame. A really nice clean frame.

To be honest, this frame exeeds my expectations and it is by far the most beautifull that I build up to now. Again some ridges, but only near the edge of the new layer. This means that I can sand those off without losing strength or stiffness.

Next step: sanding.

And now the other side

After the nice results of the first work I look forward to the other side.
The procedure is largely identical. This time we need to get the cloth really tight around the edges of the frame, because it is the last layer. After this there is no way to cover up ridges and other mistakes.

At 8 pm we start work. The first session took 5 hours, so we hope to use a bit less time and to be ready at midnight.

This time we make the first 5 layers in all directions 1 cm smaller. The last layer has the normal size. In this way we hope that we get e nice edge on the new laminate.

So first we start out with reducing the size of the template.

After this we cut all layers and stack them on a bourd in the correct order.

And now it is time for the real work. Again Andries works on the front of the frame and I on the rear. The exercise of the first session helps, and we need less effort and less small cuts to get the laminate around the edges of the frame. A trick to avoid fibre pull out on locg strainght edges is to make a few tiny cuts in the edge. This helps to get a cleaner edge on the laminate.



We take a lot of care to avoid lose fibres on top of the existing carbon. For the last layer we also try to avoid this, so we take new brushes and gloves for this layer.

The team

And again


Adding an extra layer

Next job is peelply. This time we put peelply all around the frame, and try to avoid any areas without peelply. Last time the peelply fell off when we tried this, so now we decide to use some extra resin to stick the peelply onto the laminate. This helps a lot. The bleeder will take care of the extra resin anyway, so for the weight it should have no serious impact.

What to do....

Bleeder on the frame

The last job again is the vacuum bag. And here the problems begin.
Error number 1: I forgot to buy new silicone. I think we have enough, but not plenty.
Error number 2: we start out with kitting the bag before we have measured the lenght properly. The result is that the top side of the bag is to short. Usually I would discard the bag and make a new one, but the lack of silicone forces us to go on with this bag. We patch up the short topside with an extra piece, but this results in a silicone seal that has to go over the frame in stead of along the edge of the bag.

Sealing the bag

Lots of silicone

The difficults parts: joints in the bag

Result: it takes us two hours to get the bag resonably well sealed. The pump maintains around -0.7 bar pressure at a dutycycle of 50 % (10 seconds on, 10 seconds off). This should be good enough. At 1.45 AM we call it a day.