ELIPPSE wrote:
pTooner wrote:
Firstly, I am new here although I've been reading for a few days. For
anyone with more knowledge than I, I keep considering building a small 4
wing aircraft. Not stacked, but two up front and two in the rear. I have
read frequently of problems supposedly resulting from interference of the
airflow between wings, but I can't seem to find anything very specific. I'm
fairly confident that interference between the front wings (or rear) can be
minimized by reasonable spacing and differing dihedral. I'm not sure what
the effect of the airflow coming off the front wings will have on the rear
set. I don't know whether I could remove most of the problem by having one
set considerably higher (how much?) than the other set or if it is
reasonable to have them on more or less the same height. The reason for
the concept is trying to get a wingspan small enough to fit into a normal
garage and conceivably take off and land from streets and highways. I
visualise something in a two place plane that would fall into something of
the appeal category of a motorcycle or small sports car. Any thoughts would
be appreciated.

Gerry
Hi, Gerry! Just remember this: if you take someone's word that
something won't work, you've only learned to pass that off as fact in
the future, and thus contribute to possible anti-knowledge and myths.
However, if you read as much as you can about a subject, then try it
yourself, even if it doesn't work, you'll know why. Go to www.mbda.net
and click on one of the little symbols in the lower left to get
"search", then put in Diamond back". A very interesting joined-wing,
extendable-wing concept!

Gerry,
Try NASA CR-178163 'Weight estimation techniques for composite
airplanes in general aviation industry'. Published 1986. While the title
says that it is for weight estimation, the report goes into pretty great
detail about various wing configurations, straight, canard, biplane/dual
wing, and swept forward/rearward and joined wing. In fact, it is the
first report that I can recall ever seeing that did any actual analysis
on joined wings. Lots of graphs showing the relative performance of
differing staggers and separations. Sounds like it's just what you are
looking for.