C bouts are in place. Since this is my first double bass build, this was something of a challenge. The books i am using suggesr bending thicknesses from 2.3 mm to 3 mm. I went with around 2.9 mm on the first attenpt, which resulted in some bad cracking at rhe corners. Since i had an extra piece of wood, i tried again, with a thickness of 2.5 mm tapering to around 2.1 mm at the corners. I ended up with a minor repairable split at one corner. For the second bout, i thinned to 2mm at the corners up to 2.3 mm toward the center. This resulred in a good bend. One observation is that the hardness and stiffness of the quartersawn sycamore i am using varied considerably across the width of the ribs, wirh all splitting occurring at the harder, stiffer, lighter colored edge.
initial thicknessing of ribs done with a homemade drum sander. Then worked to final thickness with this setup. Alternating lengthwise passes with toothed scraper plane and cross grain passes with fine set low angle block plane. Time consuming, but not terribly unpleasant on the relatively soft sycamore.
Homemade bending iron. 4 inch aluminum pipe, and an electric grill lighter. I have a fader switch on it to control heat level. one observation is that the 4 inch pipe is fine for most work, and even for the c bouts of this bass, but for future basses with violin like corners instead of the gamba corners of this one, a narrower diameter pipe will be needed.