Context: By "slow-flying" I refer to ultralights that can be classed as "motorfloaters" - similar wing loading to a hang-glider, stall speed below 40km/h, cruise speed not much above.
I'm interested in designing something of similar capabilities to M. Sandlin's Bloop ( http://m-sandlin.info/bloop/bloop.htm ) where the plan is to get into the air as cheaply as possible and then "fly too slowly/lightly to really be able to hurt yourself". (See also Ron Wheeler's Skyscout, more traditional ultralight design but manages an empty weight of 55kg, MTOW 135kg and a stalling speed of 32km/h, and and first flew in 1974 - http://all-aero.com/index.php/54-planes-p-q-e-r-s/9873-skycraft-scout- .)
The Bloop's designer chose a biplane layout as an easy way to achieve high wing area and structural strength for a given span, with cheap/light materials. The wings are approx 9m^2 each, with a span of 7.6m. (Due to diminishing aerodynamic returns on additional wings, I'm not sure whether to treat this as a total wing area of 18m^2m, or less - I have seen some sites suggest *1.5 instead of *2 as a good estimator.)
Given deltas also offer a large wing area and good structural strength, I am curious: Assuming similar wing construction - rigid metal frame, foam LE supports, stiff fabric covering - what differences in flight performance could be expected if an otherwise-similar craft flew with a single delta wing, of equal total area but lesser span? For example's sake, let's say a span of 5m.
Off the bat, I would expect induced drag to be much higher due to vastly lower aspect ratio, but I'm unsure to what degree that may be balanced by the removal of an extra wing's worth of profile drag, interference between the two wings, and parasite drag from struts and bracing wires etc. Plus, possible improvements in lift coefficient for same AoA range as I would think the wing would operate at much higher Reynolds numbers due to greater average chord length.