Prototype DIY Carbon Fiber rack (seat post mounted)

Folks.

Thought I would what started as a bit of a crazy "what if?" idea for a seat post mounted carbon fiber rack to carry any form of dry sac. I just did 600K's on mix of gravel and sealed roads and it worked an absolute treat with a standard 20L sea to summit dry sac.

Cost $15 ($10 bucks for a cheap eBay seat post mounted rack + $5 for assorted buckles). I managed to scrounge from a local fabricator enough carbon fiber offcuts to do a reasonable job. I did have some epoxy in the shed and would estimate that it would probably be another $20 or so to buy that in the small quantity required. If you can find a business making, repairing Kayaks etc, they are throwing away a LOT of CF which is usable. They simply cannot afford for imperfections to be present so will have a lot of good quality waste in sizes that are really useful for fabricating components. Take adequate care with the stuff and you can give almost anything a go.

Pictures tell a thousand words but I basically threw away the existing short rack component off of the seat post rack so as to be left with just the main mounting section. IN most cases this is a cylindrical aluminium tube. I really wanted a seat post mount with a quick release but those were outside my super cheap price range. And before anyone asks, "why not just tie stuff onto the intact seat post mount?" Well then I would not have had the fun of splashing some resin around. I also wanted a rack that slightly wrapped the bag to avoid any sideways waggle or movement. I achieved that. Weight was less than the shipped aluminium rack and provides a far more supportive holder for the dry sac (Cradles the dry sac and is longer than the shipped rack). The weight is supported at the seat post mount plus I put an adjustable strap around the rack to loop through the seat post rails to distribute some of that load, although in hindsight I think this is overkill.

Happy to discuss fabrication in more detail but essentially made this is two parts.

1. with liberal use of mold release (Mr's Palmer's Surf Wax) I layed up carbon fiber directly onto the cylindrical post itself. When cured this then creates a mounting system that slides on and off the seat post mount. I actually used a Dremel to cut length ways to enable me to ease this off the tube. That cut would help later on.
2. Created a cardboard template in the form of a tube (diameter approximating that of the planned dry sac) and layed up carbon fiber to form the main support structure of the rack.
3. Bonded 2 pieces together with some simple supporting CF and then shaped to final result with jigsaw and ceramic blade. In future models I would not do such big side supporting wings - it could have been much lower profile. That length ways cut that I used to get the CF off of the tube allowed me to create just a little wiggle room otherwise this would never slide on and off the tube.

As I said, hopefully pics will tell the story