Been looking at some decent well known tandem manufacturers geometry diagrams and about tandems in general after not finding any decent bikes here, whether singles or tandems. I'm too big and my girlfriend is too small for 'em. LOL.

But the idea of building a frame fascinates me. One thing i've noticed with tandems is that both bottom brackets seem to be the same height off the ground : 11 to 11.5 inches ? Also the headset tube and seat angles are all pretty close on the touring tandem manufacturers, along with the bottom bracket drop measurements. The angles on these seem to be near what single touring bike frames have.

Also alot of the top touring frames have the two top tubes running in a straight line down the frame. Is that the strongest frame design?

Does all frame design and build start with the headset and forks, eg, angle and combined headset and fork length measurement and then work your way back, or on a tandem - could you start from the bottom brackets and seat tubes, and THEN adjust your front bottom bracket drop by different headset lengths??

I read that seat tube angles aren't really that important, but how bad would it be if you got a headset angle wrong by a few degrees?

Cheers