Carbon Fiber Versus 7075 Aluminum in Alite Mantis ?

Not sure about 'tube over post.' Those look like hubs, and you don't have to be an engineer to see that enormous force will be placed on the very short lengths of tubing that project into the hubs, especially when the sitter inevitably rocks back and forth. Given the crush strength issues with even the best carbon tubes, and the fact that they don't bend like metal before breaking, IMO your chair would not be a good application for them. There are similar chairs without the four short pegged feet, but with a couple of struts projecting downward from the front lip of the seat to hold it up. If you were going to convert to carbon, that design might work better. But the cost of filament wound carbon tubes can be very high. For hoop or dome tent poles, we have just been lucky to find a couple of brands of arrow shafts that are high strength filament wound, but at a lower cost due to mass production for archers. I would expect you would need larger diameter tubes for the chair, and am not sure where you'd find a mass produced product with such tubes. For another approach resulting in a 1# 5 oz chair that has been in service for over a couple years now, you might find the following thread to be of interest: http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?id=AP9WqfoL&forum_thread_id=81152&skip_to_post=690746#690746

Not an expert by any means in this area, but inclined to agree with Sam about carbon fiber for this application. However, sometimes you don't really know until you actually try something. Edit: On second thought, don't think that bamboo would save any weight over Al.

I have the same chair and have pondered the same thing, including making the seat portion from cuben. I think Sam's points above make sense, and wonder if the 1-2" inserts in the carbon tube ends would alleviate this. From experience I have had some carbon fibre failure with trekking poles and tried to use the remnant tubes for other MYOG projects. Each time I tried to saw the cuben tubes (fine tooth hack saw) the tubes invariably splintered and cracked. I was shocked by how weak the tubes were once a crack develops. They just collapse. Due to collapsed disks in my lumbar spine a chair is a necessity for me to keep my back properly aligned, and the Mantis is the chair I have settled on, but always look at it and think that carbon and cuben would make it much better. Derrick

Derrick, When you cut the carbon tubes did you wrap tape around the area you were cutting? I've always taped and either used pipe cutters or a flush saw and have never had any issues. This has been done with both CF cycling parts (seatpost, steering tube…etc) and CF poles (the .340 ones from quest)

https://www.bigagnes.com/Products/Detail/Helinox/groundchair Lists at 22oz and it looks like there's a lot less bending moment on the tubes so perhaps more conducive to carbon. The plastic hubs on an the Helinox line look friendlier for carbon in general. You might be stuck w/ those 2 bent pieces in alu., though.

I once tried to make a chair with carbon legs in a criss-cross pattern. bought some thicker carbon tubes from Josh at Ruta Locura and made a quick seat from tyvek. Promptly snapped one of the tubes, which were not cheap, first time I sat on it. Haven't bothered trying it again.