J7W1 Shinden

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Laurelix

Laurelix

Airman 1st Class
253
139
Jun 13, 2016
J7W1:
Empty Weight: 3525kg
Loaded Weight: 4950kg
Wing Area: 20.49m2
Wing Loading: 241.6kg/m2
Engine: Ha-43 MK9D
Take Off: 2130hp (WEP)
1730hp @ SL / 1850hp @ 2000m / 1660hp @ 8400m (Military Power)
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Max Speed: (Military Power)
593km/h at SL
741km/h at 8400m
750km/h at 8700m
[I wish I knew the top speed of WEP was applied]
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Rate of Climb: (Military Power)
Time to 3000m: 4:05
Time to 8000m: 10:40
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Turn Time:
(I'm not gonna even going to try calculate a turn rate of a canard design aircraft especially if it has wing slats also) - That being said it's turn rate was probably not terrible but just little bad.
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Armament:
4x 30mm Type 5 (66 Rounds per gun)
2x 7.92mm Type 1 (75 rounds per gun

Vintage Footage of J7W1


72-D72-FB9-6-FBA-46-BE-AF02-32466-FF78-C16.jpg



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Conventional theory has it that the elevator is either powerful enough to give you a good turn rate but give uncertain handling or weak enough to stay safe but not turn well. Canards before fly-by-wire were likely to have bad stall characteristics and horrible spin problems. MAYBE the Shiden could just get it right, but nobody else could.
 
The Curtiss Assender kinda demonstrated near impossibility of a practical military application of this theoretically cool idea. The relationship between the Center of Gravity and the Center of Lift would be critical on a theoretical WW2 combat capable canard but in practice both Centers are dynamic and conspire to work against the designer. I've looked the Shinden over in detail (notable corrosion) at Silver Hill years ago, it's one of my favorite planes but it would've been very far from a warwinner if ever delivered in numbers.
 
Rutan wasn't building a fighter when he first made a canard. The eze types have a very benign stall but that is by making the canard stall before the wing at all times. Which means you can never get maximum lift out of the main wing.
 
K5083 said:
Conventional theory has it that the elevator is either powerful enough to give you a good turn rate but give uncertain handling or weak enough to stay safe but not turn well. Canards before fly-by-wire were likely to have bad stall characteristics and horrible spin problems. MAYBE the Shiden could just get it right, but nobody else could.
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Well, from what I remember: The problem has to do with the fact that the canard should stall before the wing. If it doesn't, the wing drops, the canard keeps on lifting and the plane backflips. If you have an all-moving service, this is basically inevitable as the canard has to operate at a higher AoA than the wing for that to work out.

If you're using the canard flap as a trimmer, it shouldn't be a problem (it wasn't for the XB-70), as a direct pitch control device, I'm not sure if it's an intrinsic problem if the canard flap is used as an elevator only.
 
Considering that the designers apparently started by working with gliders, and the planned role for the Shinden was to intercept high flying bombers, rather than close in fighter vs fighter engagements, I would assume that the Shinden would er on the side of high stability, low control, rather than low stability, high control. The twin rudders also seem too small to be particularly effective as an anti-spin measure. Or rather, they don't seem like they were deliberately designed to counteract a spin prone arrange. Also, as a pusher prop, high angles of attack at takeoff or landing would be dangerous anyway, due to risk of propeller strike.

Also, we can get a crude estimate of sea level WEP speed (not a value we can put down on paper, but at least a nice assumption) by taking the cube root of (Takeoff power / military power sea level), and multiplying by the military power top speed, as power required increases proportional to speed cubed.

2130/1730 is roughly 1.23, and the cube root is roughly 1.07. Multiply that by 593, and we get 635km/h. Of course, this doesn't account for the reduction in prop efficiency with increasing airspeed, and I don't know what the formula for that is, but it should still be reasonable to assume that with War Emergency Power, the Shinden should be able to achieve at least 620km/h.

For a quick gut check, a water injection equipped F4U-1, 1A, or 1D Corsair could reach around 350mph on military (no Injection), and 365 on WEP (with injection), a difference of around 1.04 times. That's 564km/h and 588km/h, respectively. If the Shinden is "clean" enough to hit 593 at 1,730 rather than 588 at roughly 2,200hp, 620km/h should be achievable. For another example to compare against, the P-51H, at 67" Hg (roughly 1,500hp, noticeably less than the Shinden's Sea Level 1,730), could reach near the same speeds as a WEP Corsair (358mph, so technically smack dab middle). At 90" (around 2,200hp), it could reach more than 410mph, or 660kph. The J7W on equal power being around 40km/h slower than the P-51H seems entirely possible, and I probably didn't even need to add such a large correction factor, as being only 25km/h behind is still a reasonable value.

Again, this isn't a primary source, not even a tertiary one. It's just a random guess based on power numbers and known speed/power combinations.

And yes, I'm aware this is an old thread, but I think the issue is unresolved enough that there's no harm in starting it up again.
 
There is no inherent reason why the J7W design would not work. Using a canard rather than a conventional tail configuration would only require that the fuselage/main-wing be inherently over stable (think dart) without the canard. To prevent instability when the canard is used you just make sure that the pitch-up forces generated by the canard never exceed the inherent stability of the fuselage-main wing/CoG range combination. As mentioned above, designing the canard to stall before the main wing will ensure a minimum pitch control/stability under any reasonable flight condition. It would even be possible to design the effects of the canard and main-wing flaps to reduce the possibility of stall vs a conventional configuration, or effectively make the plane un-stallble. At high speeds the nose/AOA would not have to be as high for a given rate of turn as for a conventional design. At low speeds the sink rate would simply increase dramatically (think Lysander or Storch). It might be difficult to create a neutrally stable/twitchy aircraft capable of very high pitch rate (high instantaneous g), but something with the pitch control/authority and sustained turn rate similar to most WWII higher speed fighters (P-47, P-51, Fw190, etc) would be doable.
 
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To be fair, the Gripen is inherently unstable and uses fly-by-wire to maintain pitch control. I am not sure what WWII tech/methodology could approach the control allowed by modern fly-by-wire. I am not saying it could not be approximated to a more limited degree - just not sure how they would go about it.

Canard and flap interlink?
 
ThomasP said:
There is no inherent reason why the J7W design would not work. Using a canard rather than a conventional tail configuration would only require that the fuselage/main-wing be inherently over stable (think dart) without the canard. To prevent instability when the canard is used you just make sure that the pitch-up forces generated by the canard never exceed the inherent stability of the fuselage-main wing/CoG range combination. As mentioned above, designing the canard to stall before the main wing will ensure a minimum pitch control/stability under any reasonable flight condition. It would even be possible to design the effects of the canard and main-wing flaps to reduce the possibility of stall vs a conventional configuration, or effectively make the plane un-stallble. At high speeds the nose/AOA would not have to be as high for a given rate of turn as for a conventional design. At low speeds the sink rate would simply increase dramatically (think Lysander or Storch). It might be difficult to create a neutrally stable/twitchy aircraft capable of very high pitch rate (high instantaneous g), but something with the pitch control/authority and sustained turn rate similar to most WWII higher speed fighters (P-47, P-51, Fw190, etc) would be doable.
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Yeah, I don't expect it to fly like a total lawn dart, just that limit to achievable angle of attack would result in a relatively wide turning radius, at least compared to what the wing loading and airfoil section (whatever that may be) would suggest as possible. Since this really only limits how hard the pilot can pull in a turn, it should still have good Maneuvering Energy Retention. Also, while it's probably just my bias from having played games of dubious accuracy which have the Shinden in it…. I feel like it should have a responsive rate of roll. I have ZERO supporting evidence for this, so I don't really know why I'm even saying it, but it doesn't seem like there would be too much restricting intentional sharp rolling moments

On the additional upside, I believe this arrangement should mean that compressibility shouldn't impose as significant of a Mach tuck effect as in a conventional aircraft, or at least when compared to the authority available at lower speeds. I might be very wrong, however, and it could actually be the inverse: that the canard will actually have the elevator response lock up almost entirely during transonic flight



I should just go to bed now. No good ever came from trying to aerodynamics on low sleep…
 
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