The inner frame parts need hollowing. Set up your router for this shaping operation. Refer to our video for this step.
Once hollowed, make the block that will connect the main triangle part to the top of the top tube part. This is done by placing those parts over the main triange template, and drawing the block between. The block is made from lightweight poplar plywood, which adds little weight, but provides some structure during the skeleton building process. The poplar also assists with the deck bonding later.
When you bond these three parts together, set them up vertically on a bench so that the area that will house the seat tube post is horizontal, and will run straight. After the epoxy cures, flaten this face, the route it to house the seat post.