I have been doing some research into alternative configurations for my project, a single seat, 500 mile range, 150mph runabout. I have done sketches for the normal low-wing monoplane layout (taildragger and tri-gear) and even a rough high wing layout. I would like to explore some other options, namely the joined wing concept. What attracts me to the joined wing is an increase in span efficiency and structural efficiency. Raymer suggests that wing weight savings of up to 30% are possible with this configuration. Having lower weight AND lower induced drag is appealing, since the engine sizing constraint is for the climb, where induced drag is dominant. Smaller engine means cheaper airplane. My questions are these:
1)What is the lift distribution among the wings? Is the front wing like a canard, requiring a higher Cl in order to stall earlier? Is the rear wing instead lifting DOWN in reaction to the wing's pitching moment.
2)What sort of structural issues would be expected? What are the moments involved? Where would flutter be an issue?
3)Is this effort to get low induced drag going to end up costing in higher parasitic and interference drag, basically negating any gains (especially on the top end)?
Advice, comments, and opinions are welcome, as are references. I am just exploring various configurations looking at different ways to arrive at the same design goal.