Titanium tandem frames
I know titanium frames can be made so light they ride like wet spaghetti, and I know design is important for stiffness, but what might be the minimum weight for a rideable frame. I'm finding some in the 2.5-3.5kg range...Thoughts?
Spend your time looking for builders with a good reputation, talk with them about what you're looking for and then talk to a couple of owners to see if the builder met their expectations. That's far more important than the weight of a frame, given most of the high-end tandem frames all fall in the 5.5 - 8 lb range, regardless of material, e.g., Carbon, titanium, Magnesium, aluminum and even a few steel frames. Put another way, it's the difference between a 26 lb tandem and a 28.5 lb tandem where four water bottles add nearly 6 lbs to the total bike weight.
A reference point is Seven cycles. Per web site below 7.7 lbs ave frame weight.
The Seven site lists the Ti tandem frame at 7.7 lbs. and the steel tandem frame at 8.9 lbs. As a frame gets larger and stiffer the weight difference becomes less because of the nature of the two metals.