I’ve cut, drilled and notched the seat-post sleeve and epoxied it into the seat-tube. Hopefully the carbon fibre will arrive tomorrow and I’ll start the mega-sisal-carbon-bamboo composite process!
I’ve completed the wrapping of the drop-outs with sisal. I’ve also added stay support bars near the bottom bracket and seat-post to give the frame more stiffness. Here’s some pics:
The clearance between the last cog and the chainstay wasn’t something I thought about that much. Luckily for me there’s about a 3mm gap to spare. This will be a single speed bike, so there will be plenty of room anyway.
The chain tension screws were also a very close fit. I actually had to cut away at the joins a bit to make them screw in properly.
Started wrapping the sisal twine around the joints tonight. Here’s the process for the seat-tube. I’ve done it in two layers. The first using lengths that run lengthwise down each pole, following the curves of each filleted corner. The second layer then holds these strands in place by wrapping around and around them. I finish it off with a few diagonal turns across the main joint and give it a haircut to neaten it up.
There’s no epoxy on any of this. I’m mainly practicing the wrapping process but am also considering making some sort of mould that I could then inject the epoxy into the sisal and joint as it is now. I’ve tried brushing and drizzling epoxy into twine like this before and then wrapping it in PVC tape to set and it sort of works, but due to the tightness of the wrap and the double layer it might need more pressure than what PVC can provide in order to make its way to the bamboo and not have any air bubbles in it.
Today I’m sanding back the tack epoxy to a smooth finish. I figured I probably shouldn’t have used as much epoxy for this stage as it’s not very strong, due to the micro-fibre filler that’s added to make it more paste-like. The final wraps will use undiluted epoxy along with sisal twine and should be the main force-bearing layers.
It’s messy work sanding this stuff back. You need to wear a mask as the un-cured epoxy is still toxic. Only after it’s properly cured, which takes 4-5 days is it harmless.