What is the thickest airfoil ever used in an aeroplane wing for lift ?

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sotaro

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The Facetmobile airfoil is pretty thick, flies well.
View attachment 131887
I think the Facetmobile is 18%. Speaking of which, Barnaby Wainfan just announced that the replica is now covered, painted and assembled. It had previously done taxi tests. It is powered by a VW and it is being built by EAA 292.
 

Norman

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With such a huge rudder...that would make an ideal weather vane ?
Well... planes do turn into the wind, that's kind of the definition of directional stability. Stabilizer sizes are determined by wing area, wing span and the square of the lever arm. Shortening the tail arm a little bit increases required size of the surfaces a lot. The H-4 was already pretty big so he may have gone with a bigger empenage to gain a little maneuverability on the water. There's a drawing with several big airplanes overlapped for comparison on this page. The H-4's fins look normal. Not supersizing really, it wasn't Mr Hughes' first airplane and he also had and engineering staff.
 

Riggerrob

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Prolific small plane designer Chris Heintz recommended building wings 18 percent thick.

Since most of his kit planes carried two people with barely 100 horsepower, light-weight was critical, hence the deep, light-weight wing spar. All of Heintz's low wings were cantilever, making structural weight that much more important. His most poerful oow-wing Alarus only cruised at 114.

OTOH Heintz's 700 series and 800 series high-wings were primarily designed for "STOL operations, where the thick airfoil helped delay stall. Structural weight was less important on the high-wings, since their wings are strut-braced. With all those slats, Junkers flaps, wing struts, landing gear struts, etc. his high-wings struggle to cruise at much more than 85 miles per hour.
 

Norman

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With all those slats, Junkers flaps, wing struts, landing gear struts, etc. his high-wings struggle to cruise at much more than 85 miles per hour.
Yep, slots just make drag but the constructive interference of the pressure fields of the wing elements almost makes up for it. Still doesn't get you to an overall thickness of 50% though and the slots break up the internal volume that I think is the point of the OP.
 

Sraight'nlevel

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Prolific small plane designer Chris Heintz recommended building wings 18 percent thick.

Since most of his kit planes carried two people with barely 100 horsepower, light-weight was critical, hence the deep, light-weight wing spar. All of Heintz's low wings were cantilever, making structural weight that much more important. His most poerful oow-wing Alarus only cruised at 114.

OTOH Heintz's 700 series and 800 series high-wings were primarily designed for "STOL operations, where the thick airfoil helped delay stall. Structural weight was less important on the high-wings, since their wings are strut-braced. With all those slats, Junkers flaps, wing struts, landing gear struts, etc. his high-wings struggle to cruise at much more than 85 miles per hour.
I bet even 20-24% thick with some sweep would be very interesting.
 

Sraight'nlevel

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Well... planes do turn into the wind, that's kind of the definition of directional stability. Stabilizer sizes are determined by wing area, wing span and the square of the lever arm. Shortening the tail arm a little bit increases required size of the surfaces a lot. The H-4 was already pretty big so he may have gone with a bigger empenage to gain a little maneuverability on the water. There's a drawing with several big airplanes overlapped for comparison on this page. The H-4's fins look normal. Not supersizing really, it wasn't Mr Hughes' first airplane and he also had and engineering staff.
I have absolutely no quarrel against Mr Hughes H-4...I just like weather vanes and see here a splendid candidate for such...very elegant profile etc.
 
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