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Author Topic: Boeing JAST / JSF / X-32 projects  (Read 112997 times)

Offline kcran567

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Re: Boeing JAST / JSF / X-32 projects
« Reply #225 on: December 06, 2017, 09:32:41 pm »
Very nice!

And a question for any aero guys out there---the sharp chine that starts at the nose curves upwards along the front edge of the wing, and then back down again, is this done for aerodynamic reasons or for stealth reasons. why not just a straight chine where the nose to wing chine flows?

does it help prevent airflow seperation at high AOA?
« Last Edit: December 06, 2017, 09:37:51 pm by kcran567 »

Offline ScrutorAudax

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Re: Boeing JAST / JSF / X-32 projects
« Reply #226 on: December 07, 2017, 09:11:30 am »
It is likely not straight because they were experimental planes and not prototype planes.  The money and time of the design team was better spent in the system as a whole, rather than designing the plane to be stealthy.  Of course, overall stealth shaping, such as edge alignment, needed to be demonstrated, but the minute details of panel and chine shaping was likely not a priority, as the aircraft selected would see major changes.  If you look at the X-35 panels, they are not saw-toothed at all.  The PWSC X-32, among other differences, has a straight chine.

Offline flateric

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Re: Boeing JAST / JSF / X-32 projects
« Reply #227 on: December 07, 2017, 09:19:53 am »
is this done for aerodynamic reasons or for stealth reasons.
obviously aerodynamics
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Offline flateric

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Re: Boeing JAST / JSF / X-32 projects
« Reply #228 on: December 07, 2017, 09:20:51 am »
It is likely not straight because they were experimental planes and not prototype planes. The money and time of the design team was better spent in the system as a whole, rather than designing the plane to be stealthy.
sorry, this is plain BS
« Last Edit: December 07, 2017, 09:26:56 am by flateric »
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stealth, more than a few of them truly technically ignorant and proud of it." Sherm Mullin, Skunk Works

Offline ScrutorAudax

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Re: Boeing JAST / JSF / X-32 projects
« Reply #229 on: December 07, 2017, 06:15:55 pm »
Flateric, I have no doubt that RCS tests were performed.  I am talking about further refinement of the chine shape.

Quote
Of course, overall stealth shaping, such as edge alignment, needed to be demonstrated, but the minute details of panel and chine shaping was likely not a priority, as the aircraft selected would see major changes.

The differences between the X-35 and F-35 (included below) chine shape shows what I was trying to convey.

Offline SpudmanWP

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Re: Boeing JAST / JSF / X-32 projects
« Reply #230 on: December 07, 2017, 07:50:21 pm »
X-35 did not have a weapons bay
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Offline flateric

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Re: Boeing JAST / JSF / X-32 projects
« Reply #231 on: December 07, 2017, 11:48:19 pm »
Chine shape _evolution_ while moving from tailless delta to four-poster PWSC doesn't mean that designers were giving a low priority to LO at CDP stage as you suggest.
_Flying prototypes_ were never intended for RCS tests (just like ATF contenders) - tests were performed on high fidelity RCS models, including full size ones.
Read the question once more.
« Last Edit: December 07, 2017, 11:51:42 pm by flateric »
"There are many disbelievers in
stealth, more than a few of them truly technically ignorant and proud of it." Sherm Mullin, Skunk Works

Offline AeroFranz

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Re: Boeing JAST / JSF / X-32 projects
« Reply #232 on: December 08, 2017, 06:11:38 am »
I think demonstrating the objective OML should be a goal of the flying prototype. Now, details of the panel edges don't affect aerodynamics, so there would be no problem using non-representative ones.
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Offline kcran567

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Re: Boeing JAST / JSF / X-32 projects
« Reply #233 on: December 08, 2017, 09:41:32 pm »
There were a lot of "directional changes (up, down, X-Y) of the continuous chine that runs through on the fore body and the wing.

Just wanted to know the intention, to keep air attached to the top of wing at AOA?

 As Flateric says for Aerodynamic reasons mainly? but not necessarily for stealth.

Offline Dragon029

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Re: Boeing JAST / JSF / X-32 projects
« Reply #234 on: December 08, 2017, 11:11:08 pm »
I would expect that it's for aerodynamic and weight reasons; stealth-wise I don't see much disadvantage with straightening the chine (imagining that the cockpit canopy was properly designed for stealth and that the geometry changed to match the upper surface of the fuselage).

Aerodynamically on the other hand, if you straighten the chine (while maintaining the lower fuselage surface angles) you end up with a slightly wider fuselage beneath the cockpit, which means more supersonic drag and more weight, plus you might have to change the geometry of the nose to match the chine, which could cause intake issues, plus for cockpit visibility you'd probably have to raise the canopy higher which leads to more drag.

Offline Harrier

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Re: Boeing JAST / JSF / X-32 projects
« Reply #235 on: December 09, 2017, 12:20:24 am »
The chine was shaped to enhance its good looks.  ;D
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Offline sienar

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Re: Boeing JAST / JSF / X-32 projects
« Reply #236 on: December 09, 2017, 01:29:05 am »
I would guess that the chine does much the same role as a lex, generating a vortex over the wing at high aoa

Offline ScrutorAudax

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Re: Boeing JAST / JSF / X-32 projects
« Reply #237 on: December 12, 2017, 05:27:08 pm »
Chines typically produce vortices farther inward, but with the wide body of the X-32, it may function in that way to a limited extent. 
 
On a side note, does anyone know why some images of the PWSC X-32 have clipped wingtips and others (most of the images and the full-scale mock-up) have sharply pointed wingtips with the airfoil section showing at the wingtip?

Offline TomS

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Re: Boeing JAST / JSF / X-32 projects
« Reply #238 on: December 12, 2017, 07:29:27 pm »
Just a guess, but possibly these are different variants.  The STOVL was going to need a smaller wing, so perhaps that's the clipped version?

Offline flateric

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Re: Boeing JAST / JSF / X-32 projects
« Reply #239 on: December 12, 2017, 08:01:28 pm »
On a side note, does anyone know why some images of the PWSC X-32 have clipped wingtips and others (most of the images and the full-scale mock-up) have sharply pointed wingtips with the airfoil section showing at the wingtip?
Because PWSC was evolving. Clipped wingtip was at the early iterations.
« Last Edit: December 12, 2017, 08:04:25 pm by flateric »
"There are many disbelievers in
stealth, more than a few of them truly technically ignorant and proud of it." Sherm Mullin, Skunk Works