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I'm on the brink of ordering some materials:
3mm rod https://www.easycomposites.co.uk/3mm-carbon-fibre-rod for the tent poles, which will double as the major struts of the rack. I have no idea whether this rod is strong enough or agreeably bendy. It's 22 grams per metre. Is that too conservative? Should I try 2mm rod first? https://www.easycomposites.co.uk/2mm-carbon-fibre-rod It's only 4.5 grams per metre. I'm tempted.
if I get the 3mm rod I'll get a bit of 5mm tube, which has an inside diameter of 3mm, to make ferrules. https://www.easycomposites.co.uk/5mm-pultruded-carbon-fibre-tube If I get the 2mm rod I'll get a bit of 3mm tube https://www.easycomposites.co.uk/3mm-pultruded-carbon-fibre-tube
I can test the poles by using them with my current tent. It's a single skinned freestanding thing and the fabric weighs about 800 grams. It has 2 poles which cross each other diagonally and fit into little pockets.
To join the rack struts to each other and to attach them to the bike, I'm thinking pieces of rubber hose and Sugru.
nick_h.-
I'm on the brink of ordering some materials:
Been having fun thinking about this rack.
I think you gain very little by using such thin tubes. I would probably use 10mm outer diameter (OD) carbon tubes for making a rack, or 8mm if I was feeling WW. I've no calcs to back that up, but it feels risky to just use 2-3mm tube without doing the calcs. And think of abuse loads, like someone stepping on the rack.
As for the brackets which connect the tubes at corners, you have many options.
Hose might make things a bit flexy depending on geometry - a cube would flex but a pyramid would be fine, so use many diagonal tubes. Triangles good, squares bad. If you took two short sections of hose, drilled at the middle and nut/bolted across each other into an X, you'd have a cheap weather proof 4-way connector. I'd use clear, bendy PVC tube for this.
You could also just drill holes into wooden blocks (or some other material), using ever increasing drill bits - i.e. in 0.5mm increments - to achieve an interference fit (push fit).
Or take fatter sections of rigid tube with ID matching main tube OD (like your ferrules). Join these using epoxy-soaked carbon tow. You'd want to do this with the tubes assembled into a mock rack, with some awkward jig involving tape and swearing.
You can also google "3 way PVC pipe fitting" if you don't mind 90 degree corners. Then spec your carbon tubes to match the sizes to achieve push fit.
With all of these solutions though, you'd need to hold (compress) the assembly under tension so that it doesn't dismantle during use. Like how tent fabric tension holds the poles into connectors. So one or two bungee cords would be an idea, perhaps made from inner tubes (can fasten these using buckles from an old rucksack).
Ndeipi
Any updates on the tent pole rear rack?