It is interesting to compare the specs on a Dyke Delta with
a BD4. Correct me if I get the numbers wrong Kelly.

.... Gross ..empty ..HP..rate cl..top spd..span..Wing area..stall
BD4  2000 ...1080...180...1400 .....183 ...26 ft..102....... 61
Dyke 1900 ... 960...180...2000 .....190 ...22 ft..183....... not listed

The span loading which is another way of saying aspect
ratio (sort of) is nearly the same.  The BD4 is the only 2000 
pound gross weight experimental airplane that I could find specs for.

The numbers are from Don Crawford's book A Practical
Guide to Airplane Performance and Design.

Most flying wings have surface area that does not provide lift.
In fact  some part of the rear part of the wing must provide down force
since the CG remains ahead of the center of lift. The loss of fuselage
drag is therefor made up to some extent by an increase in surface 
area of the wing.

The numbers are pretty close. The top speed difference may be significant
or may just be  experimental error. The BD4 is a real box with fixed gear
and the Dyke Delta is fairly clean with retractable gear. Same goes for 
rate of climb as the power loading of the BD4 is lower than the Dyke Delta.
It would be interesting to know what the best climb speeds were for
both airplanes. The over all efficiency is about the same.

The not listed stall speed for the Dyke Delta is another way
of saying "back side of the power curve".

Paul Lamar
 
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