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Bell Aircraft's twin-boom fighter projects (XP-52, XP-59, etc.)

TomcatViP

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@blackkite : greap pics!

Haven't read all post at the moment but someone asked about coolant air exhaust: look at the propeller spinner. We can see that it is surrounded by a large slot where I suppose hot air was ejected (low pressure and suction from prop wash and spinner rotation). Injecting hot air here makes sense since it will be have a propulsive effect like on the P-51.

My 2 cents (and sorry if this has been debated earlier already).
 

blackkite

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Hi! Model 20 and Model 22.
 

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blackkite

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Hi! XP-59, Senden, Ki-98 and Shinden.
 

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riggerrob

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Yes, these Bell proposals do remind us of contemporary Japanese proposals.
Bell understood balance better than Senden designers (e.g. swept wings).
Unfortunately, Shinden was a "dog's breakfast" of aerodynamic problems flying in loose formation!
 

blackkite

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windswords

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What is the aerodynamic problems of Shinden? Yawing?
I remember reading about a guy who created a scale RC model of the Shinden and found that the torque of the 6 blade propeller pulled the model to one side. He did something (can't remember the details) - like off-setting the engine or drive line to counter act the torque - I think. Maybe that is why the Japanese thought about using a more traditional 4 blade prop on the production version.
 

blackkite

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The tests showed that the biggest problem was the pull to the right on the fuselage caused by the
large torque. Various counter-measure were applied; for example, the attachment angle of the
front wings was raised 3 degrees, and as the tendency was strongest at low gear and when the
flaps were down, the lowered flap angle was raised 35 degrees. And so for the time being, steps
had been taken to fix the problem.
 

riggerrob

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Japanese Shinden suffered many of the same problems as the contemporary Curtiss Ascender.
First, the propeller worked in turbulent air coming off the fuselage.
Secondly, lowering flaps meant even more turbulent air hitting the propeller.
Thirdly, both air planes suffered balance problems, compounded by canards that were too small.
Fourthly, rudders were too small and mounted on moments that were too short.
Fivethly, designers failed to compensate for P-factor, which means the the descending propeller blade hits the air at a steeper angle of attack, creating more thrust on one side and trying to turn the airplane. P-factor is worst while climbing. Since Shinden's propeller rotated counter-clockwise (as seen from the rear), it imparted a right-turning tendency.
Shinden had difficulty raising its nose for take-off because the canard was too small and at too shallow an angle of attack.
P-factor (asymmetric thrust) soon over-whelmed rudder authority and aileron authority, giving Shinden a difficult, right-turning tendency.

During the 1970s, Burt Rutan solved those problems by shifting centre of gravity forward to load the (larger) canard more heavily. Rutan also mounted rudders farther aft on swept wings or long tail booms. The end result was Rutan canards that cruised very efficiently, but were not extremely maneuverable.
 
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blackkite

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Thanks a lot.
According to the wind tunnel test picture, I feel that the Shinden air flow around the fuselage is not so bad.
Perhaps engine cooling air intake inhales part of the boundary layer.
View: https://www.youtube.com/watch?v=AH62KXgyQnc
 

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TomcatViP

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It's not the same power/surface ratio!

(if this thing is ~1:5 scaled, it should have 200hp++ to be comparable) ;)
 

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