High/Low Wing a different question

AdamZ

AdamZ

Touchdown! Greaser!
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Adam Zucker
Was reading an article on the High Wing Sirius LSA in Plane and Pilot. It discussed how the strut was angled back so it was afixed to the fuselage behind the front seat.
It got me thanking about the Cessna highwings and I wondered why it was that Piper went to low wings from their orginal highwings. I don't mean for this to be the highwing /low wing debate. But wondering why a given manufacturer chose to stay high and another go low after they made highwings. I'd think you go with what you know and avoid as much retooling as you can. But are there other reasons? Is one cheaper to manufacture? And why would cessna make their twins low wings? Different design team?
 
AdamZ said:
I'd think you go with what you know and avoid as much retooling as you can. But are there other reasons? Is one cheaper to manufacture? And why would cessna make their twins low wings? Different design team?
Click to expand...

Well, since they went from tube and fabric to all metal construction, the retooling thing isn't even a player. As for the rest, who knows?
 
According to

http://flightopedia.com/piper-pa-24-comanche.htm

It is reported that Pug Piper made many of his design choices based on existing aircraft. The laminar flow wing was a feature found on the P-51 Mustang fighter. The swept tail was evocative of the current fighter aircraft, and the stabilator (flying tail) was a prominent feature of the Bell X-1, the first aircraft to break the sound barrier. The Comanche was a popular model and is still appreciated for its attractive lines.

The Comanche preceded the Cherokee line. Piper had Fred Weick to come up with a cheaper plane and he came up with the Cherokee (in collaboration with others).
 
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They hired a different designer, Al Mooney if I recall correctly.
 
It's mostly the question of what you want the wing box to intersect, which depends on the mission. In the low bottom, ramp equipped transport it goes on top of the cabin in order not to create a bump like in Tu-104. In a generic passenger transport it goes underneath the floor, through the baggage compartment deck. In common GA planes there's basically no difference. Keep in mind that ground and undercarriage are always below, so there is always a structure there. In low wing you can unify it with the wing, save mass. In high wing you can use a brace, again save mass by using lighter spars. It's up to designer to make tradeoff. Often comes down to preference.
-- Pete

P.S. Note that in a canard GA plane you can use midwing for best aerodynamics by passing the wingbox between passengers and engines, with canard providing the necessary balance. LongEZ and Avanti are that way. In high or low wing you need a fairing that creates the 90 degree meet-up. In a Cessna usually the top of cabin serves as a fairing. In most low-wings these days there's a noticeable buldge. Some small jets positively began to look pregnant when the size of the advantage became realized thanks to CFD.
 
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