Thank you for the detail response including the formulas. When comparing steel double butted tubes I usually just calculate the stiffness of the thinner center section and ignore the butted ends. This is of course an oversimplification but has worked pretty well in predicting the stiffness when compared to the seat of the pants feel when riding the bikes. I can see that the complexity of the carbon tubing structure make such estimations very difficult.
For comparison to your bike, I think that many Calfee tandems use a 2 inch diameter top tube but other than that I have no idea of its construction. Possibly some Calfee owners or someone from Calfee can chime in with some more data. Your top tube diameter of 34.8mm is much smaller. The smaller diameter would indicate a much more flexible tube but without more data on the Calfee tube I am not sure if a valid comparison can be made. Personally I like the look of thinner tubes but beauty is in the eye of the beholder.
As you may know from my previous posts I like wide tires and the idea of a carbon tandem that allows for big tires is very interesting to me. I look forward to watching your build continue. Please keep us posted with as much information as time allows.
Wayne
Last edited by waynesulak; 01-17-13 at 07:30 AM.