[NSRCA-discussion] Biplanes

[JEREMY CHINN]

I just answered this same question by another person in another forum..... This is what I wrote...... and while 3D and Precision Aerobatics seem very different, the truth is the are some very strong similiarties between the two when considering their needs aerodynamically.
 
 




I think to understand bipes, you have to understand aviation history a bit.... (I won't pretend to say I understand them, but I've tried really hard) First, Bipes were built to get more wing area while 'boxing' the structure and making it stronger with the available technology.... and they were also made to be ultra stable...... hence the stagger. Couple correct stagger with appropriate incidences and you have a super stable platform to deliver the mail. The stagger also helped with ingress/egress to the cockpit..... Then Curtis jumped in and put up his first Pitts biplane. The two wings were designed different from each other to make the airplane less stable than the aerobatic airplanes from before - but only to a point. Then the Ultimate came on and it was essentially an extension of the Pitts. The real one even had flaperons to make the dern thing snap (would'nt snap right without them). So now we get to 3D'ing....... People keep trying to design Pitts and Ultimates that will 3D well. Unfortunately, the real ones were never designed for performance in the realm 3d of or even model aerobatics. So by trying to design an model airplane to 3D that is based on an airplane that would never 3D given all the power in the world is trying to make a silk purse out of a sow's ear. I really love foamies, because many of the early designers of foamys (George Hicks for example) felt pretty unconstrained in their designs. "Doesn't look like an airplane? Who cares, it flys right" they would say. I've wanted a bunch of times to build a full on performance at all costs 3d profile bipe, but I don't want to truck the thing around. A Boxxer fits very neatly in the bed of any pickup truck and can go down the highway without a problem. The bipe of my dreams could only get to the field in a trailer. Stagger is useless in 3D. Our goal in 3D is perfectly balanced areas, moments, forces in all directions.... Stagger biases one wing against the other. Therefore with the Boxxer, it harriers better than just about any other profile when upright, but inverted is not nearly as good (doable, but not as comfy as a ChinnYak or MoJo). Upright, its probably one of the better upright harrier trainers you could fly. Tapered wings are no problem, but they have to be designed right. Space between the wings becomes even more critical when 3D'ing, show me a good performing 3D'able bipe that does not have the correct wing spacing and I'll eat my hat. One of the best airplanes at the ETOC this weekend was the Blender Bipe that Jesky made famous. Look at its symmetricality and its balance and it becomes obvious why it does things so well...... Nothing beats a bipe in the character realm. They have panache......






Date: Fri, 30 May 2008 11:06:51 -0700From: cahochhalter at yahoo.comTo: nsrca-discussion at lists.nsrca.orgSubject: [NSRCA-discussion] Biplanes
What is the aerodynamic advantage to putting the top wing forward on a biplane as opposed to the Beech Saggerwing design? 
 
Just curious... looking for some good discussion.
 
 
Chuck
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