Right everyone, will try to answer your questions:
Footflaps & DezB — the repair cost £50 all inclusive
pjm84 — I said 'must have' not because I think the rear mech twanged the frame, but because I know it did but at the time the crack wasn't huge! I.e. why I can only guess that this was the initial cause for the crack and it developed over time. Trust me, I really did know about it…snapped hanger and singlespeed ride home!
Spongebob — you would be surprised at how repairable carbon is! Steve buys broken carbon frames, repairs them and rides them himself. He has repaired road frames where the top tube was physically in two pieces. However, he broke an aluminium frame, and guess what? He had to chuck it. Non-repairable. So for me, carbon is the way to go. I'm not necessarily saying this On One frame is fantastic, but you can be sure I will never go back to a non-carbon frame, whether I have to buy it myself or not. And YES I am a racer, but I live on Dartmoor and only have one mountain bike, so this has to withstand pretty harsh terrain. I'm pretty happy that in the knowledge that if it does break again, I can get if fixed.
richmars & midlifecrashes — Steve worked out which way the fibres were running, stripped it down and rebuilt it exactly how it was but better (apparently the manufacturer's build quality was awful under the first few layers). If you want more detail, here's a compilation from the emails he sent:
In short the impact did more damage than was obvious. I've attatched the photo's hopefully which shows the extent of it, apart from the obvious crack what didn't show was that the opposite side of the tube delaminated internaly. When i ground away the filler (more on that later ) and started to go through the layers of carbon one area suddenly broke away leaving a hole. I've now put on a single thin layer of carbon to give a firm layer to work with when applying the rest of the plys.
Alot of the big name manafacturers use lots of ply's of carbon sheet in various orientation's to achieve the desired properties, when i ground the Race frame i took away the top layer of paint and then some white filler followed by a layer of biaxial carbon. This doesn't really contribute much to the tubes stength and is mostly for show, expecting to find lots of plys of different orientations underneath it i was suprised to find a few plys of unidirectional plys running along the seatstay only. If there had been lots of different plys in one orientation i would've thought nothing of it but there wasn't much there and the stay was very thin. Where the dropout was bonded to the carbon the manafacturers had put quite alot of filler to smooth out the area, they could've used more carbon plys just in that area instead of filler. It wouldn't have added much weight but could've added more strength to the area. I'll put the rest of the plys on next week and take more photo's as i go.
Right then, the laminatings all done and i'm sanding the excess resin off on monday morning. I'll then spray the black paint to blend in the back end again and laquer the repair along the seatstay. The green you see in the pictures doesn't stay on but is a disposable cloth called peel ply, this protects the surface from contamination and provides a keyed surface for subsequent layers.
andyl — You are quite right: the frame will probably be stronger than it was, so in terms of forces, the frame might not behave quite like it used to in terms of stiffness and flexibility. I am no expert about this though, so if you want to know more try emailing Steve directly.