If you’ve followed any of our hot tub antics in the past, then you already know about the inflatable hot tub party on Ocean Beach in San Francisco. A few years ago we built a heat exchanger that would use a bonfire to heat up salty ocean water.

This winter I’m taking on a new project, following our work on Carbon Garden: to build a hot tub entirely out of carbon fiber.  Since fiberglass hot tubs are common, the same techniques should apply to building the carbon fiber tub.  Step one is to come up with a pleasing design, and for this I’m using Rhino, a CAD software tool.

The 3D shape is sliced into multiple flat pieces along the black lines, which are then cut out of 1/2″ plywood on a shopbot CNC router.  I’ve decided it will be easier to build the positive shape, so the mold will be more  of a hump than a dish.

Here’s a video of the shopbot going at it too

Next the mold stays are assembled by cutting correct length support pieces (according to the CAD model) and screwing the whole thing together. Here’s an image of the mold partially assembled.  In this shot the mold is upside down since it’s easier to put together that way.  Eventually it gets flipped over and it will look more like a hump.

Once the mold stays are assembled, I’ll lay sheets of paperboard across it to complete the bowl shape, then like drywall, apply plaster and sand it perfectly smooth (don’t want any bumps on the interior of the hot tub of course).  When the mold is complete it will be time to lay up the carbon fiber.  But that’s for another rainy winter day…

This entry was posted on Saturday, January 16th, 2010 at 7:29 pm and is filed under Models, Side Project, Video, Workshop.