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Hershey bar wing vs composite wing - how much drag?



 
 
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  #31  
Old March 29th 07, 06:59 PM posted to rec.aviation.owning
Montblack
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Posts: 972
Default Hershey bar wing vs composite wing - how much drag?

("cavelamb himself" wrote)
And a LOT of the drag is from cooling the engine!
There is an ideal place for big gains.



Ercoupe, Cessna 172, Piper Warrior:
How much drag would be eliminated it the prop was spun from, say, a
(hypothetically capable) electric motor - of the same weight as the engine?
An electric motor that needs little of the cooling air (drag) required by
the gas engines.

WAG, is a LOT ...33%?

Whatever the guesstimated drag number settled on, what then would that
number mean in cruise speeds, or fuel burn? 10% improvement? 20%
improvement? 30%?


Montblack


  #32  
Old March 29th 07, 11:20 PM posted to rec.aviation.owning,rec.aviation.homebuilt
Matt Whiting
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Posts: 2,232
Default Hershey bar wing vs composite wing - how much drag?

DR wrote:
Hi,

I don't see why a composite should be heavier:

For carbon composite, the Young's modulus is ~70GPa for a density of 1.3
g/cm3. Al has the same Young's modulus but twice the density (2.7
g/cm3). For glass the strength is about half but again the weight is
halved too -so it's not a gain over Al. I think the composites excel in
their lack of rivets and joining pieces tho...


Last I knew, Young's modulus was a measure of stiffness, not strength.

Matt
  #33  
Old March 30th 07, 01:20 AM posted to rec.aviation.owning
Kyle Boatright
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Posts: 578
Default Hershey bar wing vs composite wing - how much drag?


"Montblack" wrote in message
...
("cavelamb himself" wrote)
And a LOT of the drag is from cooling the engine!
There is an ideal place for big gains.



Ercoupe, Cessna 172, Piper Warrior:
How much drag would be eliminated it the prop was spun from, say, a
(hypothetically capable) electric motor - of the same weight as the
engine? An electric motor that needs little of the cooling air (drag)
required by the gas engines.

WAG, is a LOT ...33%?

Whatever the guesstimated drag number settled on, what then would that
number mean in cruise speeds, or fuel burn? 10% improvement? 20%
improvement? 30%?


Montblack


You're on the right track if you can work with a semi-trailer sized battery
or a 500 mile extension cord. ;-)

KB


  #34  
Old March 30th 07, 07:47 AM posted to rec.aviation.owning
Montblack
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Posts: 972
Default Hershey bar wing vs composite wing - how much drag?

("Kyle Boatright" wrote)
You're on the right track if you can work with a semi-trailer sized
battery...



I'm putting you down for 18%.


Montblack
I’m a little overweight and my log book’s way behind
Nothing bothers me tonight
I can dodge all them scales all right
Six days on the road and now I’m gonna make it home tonight


 




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