een bi-delta-plane?

[lespinoy]

hey,

ik heb hier toevallig nog 2 delta vleugels liggen (piep, +-zelfde span)
en kreeg vanavond het idee om een bi-delta-plane te maken, maar ik ben dit eigenlijk nog nergens tegen gekomen, is daar een goede reden voor?
ik vermoed dat het zwaartepunt moeilijk goed te krijgen zal zijn, maar is het onmogelijk om 1 of andere goede reden?
kmoet er iets anders niet-vliegklaar voor maken dus daarom dat ik het eerst even vraag..

grtz

 

[prop-er]

http://www.djaerotech.com/dj_askjd/dj_questions/biplane.html

Biplanes have lower induced drag than monoplanes, but higher parasite drag. The flow fields from the two lifting surfaces fight with each other, causing something called "interference drag". In addition, there is extra parasite drag from the supporting structure required to keep those two wings in proper formation. More gap between the wings will improve the interference drag, but the extra structure required will increase the parasite drag. It's your basic "no-win situation".

De rolwerking rond een vleugel, en zeker een delta, heeft ruimte nodig. Wanneer je twee delta vleugels boven elkaar zou zetten, maak je het vrijwel onmogelijk voor de luchtwervelingen om rond de vleugel te draaien.

Werkt alleen als je de afstand tussen de vleugels groot genoeg maakt.

http://forums.radiocontrolzone.com/showpost.php?p=503294&postcount=14

Getting back to bipes, many of them tend to glide like bricks, and slow down very rapidly in tight turns. This is largely due to mutual wing interference. Away back in the 'teens, it was determined that the cross section of air influenced by a wing is nearly all contained within the smallest diameter circle that can be circumscribed by the wing tips. If a bipe had its wings separated by a distance equal to its span, its wings would perform almost exactly like those of a monoplane. Move the wings closer together, and they begin to interfere with each other very seriously.

Wind tunnel tests that were conducted in the 1920s established that mutual wing interference had exactly the same effect as lowering the aspect ratio. A bipe with an aspect ratio of 6.0 may suffer as much induced drag as a monoplane with a wing aspect ratio of about 3.5 to 4.0. To combat this, I like to use higher than normal aspect ratios on my own design bipes, and with an aspect ratio of about 8.0, they glide about as well as a monoplane with an aspect ratio of about 5.5 - typical of many of today's competition aerobatic monoplanes. Regardless of wing chord, a bipe with typical inter-wing gap needs about 90% of the wingspan of a monoplane to achieve the monoplane's induced drag numbers.