Discussion:
Was the SR-71 are ruled?
(too old to reply)
hoarse with no name
2004-10-24 22:44:56 UTC
Permalink
The SR-71 does not appear to me to have been designed with the area rule
in mind. Was it area ruled and I just can't tell? Was it not area ruled
for some interesting reason? Will I be stumping Mary with this one?
Peter Stickney
2004-10-25 02:31:37 UTC
Permalink
Post by hoarse with no name
The SR-71 does not appear to me to have been designed with the area rule
in mind. Was it area ruled and I just can't tell? Was it not area ruled
for some interesting reason? Will I be stumping Mary with this one?
The short answers: Yes.
That seems to be the case.
No.
Not in the least.

The long answer.
The Area Rule is that the lowest drag shape for an airplane is one
where the plot of the cross-sectional area of the entire
fuselage/wing/nacelle/external stuff system equals that of a
Sears-Haake body - pointy nose, a maximum thickness 1/12th of the
length, and a tapered tail. (Think .30 cal or .50 cal bullet.)
If you can't make it match exactly, you try not to have any rapid
changes inthe cross-sectional area.

There are some variations for very high Mach Numbers that involve the
cross-sections being taken at an angle to the centerline, rather than
perpendicul;ar, but that's not really important, here.

Making an airframe conform to the Area Rule doesn't have to mean
bulging thing here, & squshing them there. If you're clever about it,
you can arrange things so that the cross-sectional area curve is of a
good shape without being obvious about it.
If you look at a plan view (From above or below) of an
A-11/F-12/SR-71, you'll note that the fuselage is tapering back where
the engine nacelles are. A head-on view shows that the wing is razor
thin (A t/c of around 2.5%, IIRC) and doesn't add much to the
cross-section. There's the chine along the outside of the engine
nacelles that help the cross-section distibution as well.

When you're good, you don't have to be obvious.
--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster
hoarse with no name
2004-10-25 05:22:32 UTC
Permalink
Post by Peter Stickney
A head-on view shows that the wing is razor
thin (A t/c of around 2.5%, IIRC) and doesn't add much to the
cross-section.
Is fuel stored in the wings? I would imagine that with that looong
fuselage there would be enough storage space elsewhere.
Peter Stickney
2004-10-25 14:13:17 UTC
Permalink
Post by hoarse with no name
Post by Peter Stickney
A head-on view shows that the wing is razor
thin (A t/c of around 2.5%, IIRC) and doesn't add much to the
cross-section.
Is fuel stored in the wings? I would imagine that with that looong
fuselage there would be enough storage space elsewhere.
There are two tanks in each inner wing section. The majority of the
fuel is carried in the fuselage. Don't forget that the fuel is also
used as a heat sink. The inner wing fuel helps carry heat away from
the landing gear bays, a fair chunk of the hydraulic pumps &
actuators and stuff like that.
--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster
David Lednicer
2004-10-26 16:07:40 UTC
Permalink
Post by Peter Stickney
The Area Rule is that the lowest drag shape for an airplane is one
where the plot of the cross-sectional area of the entire
fuselage/wing/nacelle/external stuff system equals that of a
Sears-Haake body - pointy nose, a maximum thickness 1/12th of the
length, and a tapered tail. (Think .30 cal or .50 cal bullet.)
If you can't make it match exactly, you try not to have any rapid
changes inthe cross-sectional area.
What the Transonic Area Rule says is: "Within the limitations of small
perturbation theory, at a given transonic Mach number, aircraft with the
same longitudinal distribution of cross-sectional area, including
fuselage, wings and all appendages, will at zero lift have the same wave
drag." The Sears-Haack body has the minimum wave drag for transonic
Mach numbers and hence is considered the optimum. The Sears-Haack body
does not have maximum thickness at 1/12th of length - its at 50% of
length.

At supersonic Mach numbers, the Hayes Area Rule can be used to give
quantitative values for wave drag. I'm not real familiar with how this
works, so I won't comment further on it.
Peter Stickney
2004-10-26 18:33:59 UTC
Permalink
Post by David Lednicer
Post by Peter Stickney
The Area Rule is that the lowest drag shape for an airplane is one
where the plot of the cross-sectional area of the entire
fuselage/wing/nacelle/external stuff system equals that of a
Sears-Haake body - pointy nose, a maximum thickness 1/12th of the
length, and a tapered tail. (Think .30 cal or .50 cal bullet.)
If you can't make it match exactly, you try not to have any rapid
changes inthe cross-sectional area.
What the Transonic Area Rule says is: "Within the limitations of small
perturbation theory, at a given transonic Mach number, aircraft with the
same longitudinal distribution of cross-sectional area, including
fuselage, wings and all appendages, will at zero lift have the same wave
drag." The Sears-Haack body has the minimum wave drag for transonic
Mach numbers and hence is considered the optimum. The Sears-Haack body
does not have maximum thickness at 1/12th of length - its at 50% of
length.
You're right - I should have explained that a bit better. The Max
thickness isn't _at_ 1/12th the length, as you say, but shoul be 1/12th
the length. (That's the trouble when you're trying to simplicate. I
hate when that happens)
--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster
Gord Beaman
2004-10-27 01:45:16 UTC
Permalink
***@Mineshaft.local (Peter Stickney) wrote:
snip
Post by Peter Stickney
If you look at a plan view (From above or below) of an
A-11/F-12/SR-71, you'll note that the fuselage is tapering back where
the engine nacelles are. A head-on view shows that the wing is razor
thin (A t/c of around 2.5%, IIRC) and doesn't add much to the
cross-section. There's the chine along the outside of the engine
nacelles that help the cross-section distibution as well.
When you're good, you don't have to be obvious.
Thank you Peter, again I learned something from you (although why
a 'big iron' man needs to understand 'area rule' I don't know) :)
--

-Gord.
(use gordon in email)
Kevin Brooks
2004-10-27 02:42:22 UTC
Permalink
Post by Gord Beaman
snip
Post by Peter Stickney
If you look at a plan view (From above or below) of an
A-11/F-12/SR-71, you'll note that the fuselage is tapering back where
the engine nacelles are. A head-on view shows that the wing is razor
thin (A t/c of around 2.5%, IIRC) and doesn't add much to the
cross-section. There's the chine along the outside of the engine
nacelles that help the cross-section distibution as well.
When you're good, you don't have to be obvious.
Thank you Peter, again I learned something from you (although why
a 'big iron' man needs to understand 'area rule' I don't know) :)
Why, so you can discuss US presidential politics (the *real* purpose of this
group), of course! Remember, the original F-102 prototype lacked area
rule...until, of course, we rediscovered the ancient sanskrit writings on
the subject, no doubt from ancient Germanic researchers, which had been
hidden away at a secret Antarctic R&D base... :-)

Brooks
Post by Gord Beaman
--
-Gord.
(use gordon in email)
The Enlightenment
2004-10-27 14:38:04 UTC
Permalink
Post by Kevin Brooks
Post by Gord Beaman
snip
Post by Peter Stickney
If you look at a plan view (From above or below) of an
A-11/F-12/SR-71, you'll note that the fuselage is tapering back where
the engine nacelles are. A head-on view shows that the wing is razor
thin (A t/c of around 2.5%, IIRC) and doesn't add much to the
cross-section. There's the chine along the outside of the engine
nacelles that help the cross-section distibution as well.
When you're good, you don't have to be obvious.
Thank you Peter, again I learned something from you (although why
a 'big iron' man needs to understand 'area rule' I don't know) :)
Why, so you can discuss US presidential politics (the *real* purpose of this
group), of course! Remember, the original F-102 prototype lacked area
rule...until, of course, we rediscovered the ancient sanskrit writings on
the subject, no doubt from ancient Germanic researchers, which had been
hidden away at a secret Antarctic R&D base... :-)
Brooks
Actualy the Americans seem to have not realised the importance of 'area
ruling' when it was presented to them in the form of Dietrich Kuchmanns work
and had to rediscover it for themselves albeit from more developed work of
Whitcombe rather than the work Kuchmann had done as head of research at the
wind tunnel at Brushwick where he was studying swept wing fueselage
interaction.

Dietrich Kuchmann actualy moved to Farmborough in England where he worked
at the research establishment and became a British citizen making important
contributions to Concord.

One of Kuchmann's mach 0.95 designes is shown here:

http://www.luft46.com/fw/fw1000a.html
Peter Stickney
2004-10-27 17:22:41 UTC
Permalink
Post by The Enlightenment
Post by Kevin Brooks
Post by Gord Beaman
snip
Post by Peter Stickney
If you look at a plan view (From above or below) of an
A-11/F-12/SR-71, you'll note that the fuselage is tapering back where
the engine nacelles are. A head-on view shows that the wing is razor
thin (A t/c of around 2.5%, IIRC) and doesn't add much to the
cross-section. There's the chine along the outside of the engine
nacelles that help the cross-section distibution as well.
When you're good, you don't have to be obvious.
Thank you Peter, again I learned something from you (although why
a 'big iron' man needs to understand 'area rule' I don't know) :)
Why, so you can discuss US presidential politics (the *real* purpose of
this
Post by Kevin Brooks
group), of course! Remember, the original F-102 prototype lacked area
rule...until, of course, we rediscovered the ancient sanskrit writings on
the subject, no doubt from ancient Germanic researchers, which had been
hidden away at a secret Antarctic R&D base... :-)
Brooks
Actualy the Americans seem to have not realised the importance of 'area
ruling' when it was presented to them in the form of Dietrich Kuchmanns work
and had to rediscover it for themselves albeit from more developed work of
Whitcombe rather than the work Kuchmann had done as head of research at the
wind tunnel at Brushwick where he was studying swept wing fueselage
interaction.
Kuchemann didn't have anything to do with the Area Rule. The
"Kuchemann Coke Bottle" came from n attempt tpo have the fuselage
contours of his swept-wing model match the local flowfield - not the
same thing at all. The idea that overall cross-section distribution
should as closely as possible conform to an ideal shape didn't occur
to him.

So, I'd have ot count home out. There was a theoretician (Hale, or
Haley, I think it was) who also had done some work which could have
led to hte propunding of the Area Rule. But neither man was able to
make the conceptual leap that Whitcombe did to develop teh full
principle.

Kuchemann did make a further contribution to tranonic aerodynamics -
the "anti-shock body" or "Kuchemann carrot" - a large canoe shaped bdy
at the trailing edge of the wing, which was supposed to delay shock
formation. Indeed, it did do that, but the drag reduction that it
produced was more than offset by the increased wetted area of the
carrot. Example of the Kuchemann Carrot are teh trailing edge pods of
the Tu-16 and itd derivatives, the pods on the wing of the
H.P. Victor, and the Convair 990 airliner. If, like Tupolev, you had
to have the volume to stick something else in - like the Standard Issue
Soviet Era rough-field landing gear), it wasn't too bad, but it didn't
pay off in practice.
--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster
The Enlightenment
2004-10-28 11:33:38 UTC
Permalink
Post by Peter Stickney
Post by The Enlightenment
Post by Kevin Brooks
Post by Gord Beaman
snip
Post by Peter Stickney
If you look at a plan view (From above or below) of an
A-11/F-12/SR-71, you'll note that the fuselage is tapering back where
the engine nacelles are. A head-on view shows that the wing is razor
thin (A t/c of around 2.5%, IIRC) and doesn't add much to the
cross-section. There's the chine along the outside of the engine
nacelles that help the cross-section distibution as well.
When you're good, you don't have to be obvious.
Thank you Peter, again I learned something from you (although why
a 'big iron' man needs to understand 'area rule' I don't know) :)
Why, so you can discuss US presidential politics (the *real* purpose of
this
Post by Kevin Brooks
group), of course! Remember, the original F-102 prototype lacked area
rule...until, of course, we rediscovered the ancient sanskrit writings on
the subject, no doubt from ancient Germanic researchers, which had been
hidden away at a secret Antarctic R&D base... :-)
Brooks
Actualy the Americans seem to have not realised the importance of 'area
ruling' when it was presented to them in the form of Dietrich Kuchmanns work
and had to rediscover it for themselves albeit from more developed work of
Whitcombe rather than the work Kuchmann had done as head of research at the
wind tunnel at Brushwick where he was studying swept wing fueselage
interaction.
Kuchemann didn't have anything to do with the Area Rule. The
"Kuchemann Coke Bottle" came from n attempt tpo have the fuselage
contours of his swept-wing model match the local flowfield - not the
same thing at all. The idea that overall cross-section distribution
should as closely as possible conform to an ideal shape didn't occur
to him.
I don't see how you could say "its not the same thing at all".

Kuechmann came up with a coke bottle shape, the same solution as Whitecombes
area Rule, and it had the same effect.

It was comming from a different 'perspective' but it produced the same
solution albeit with a lower level of understanding.

At least two German designes used this primitive flow field area rule which
admitedly wasn't as well elucidated.

I came across this:
<http://www.all-science-fair-projects.com/science_fair_projects_encyclopedia
/Wave_drag>

"Fuselage shaping was similarly changed with the introduction of the
Whitcomb area rule. Whitcomb had been working on testing various airframe
shapes for transonic drag when, after watching a presentation by a German
researcher in 1952, he realized that the Sears-Haack body had to apply to
the entire aircraft. This meant that the fuselage needed to be made
considerably skinnier where the wings met it, so that the cross-section of
the entire aircraft matched the Sears-Haack body, not just the fuselage
itself. "

(don't know who the German researcher was)

Dietrich Küchemann arrived at the solution by studying airflow, notably
spanwise flow, over a swept wing but even he later commented (now working at
the British RAE at Farnborough) that Whitcomb's statement of the problem,
and solution, was considerably more clear and decisive than his own.
Post by Peter Stickney
So, I'd have ot count home out. There was a theoretician (Hale, or
Haley, I think it was) who also had done some work which could have
led to hte propunding of the Area Rule. But neither man was able to
make the conceptual leap that Whitcombe did to develop teh full
principle.
Possibly it could have been Dipl.-Ing. H. von Halem who was Küchemann's
partner?
Post by Peter Stickney
Kuchemann did make a further contribution to tranonic aerodynamics -
the "anti-shock body" or "Kuchemann carrot" - a large canoe shaped bdy
at the trailing edge of the wing, which was supposed to delay shock
formation. Indeed, it did do that, but the drag reduction that it
produced was more than offset by the increased wetted area of the
carrot. Example of the Kuchemann Carrot are teh trailing edge pods of
the Tu-16 and itd derivatives, the pods on the wing of the
H.P. Victor, and the Convair 990 airliner. If, like Tupolev, you had
to have the volume to stick something else in - like the Standard Issue
Soviet Era rough-field landing gear), it wasn't too bad, but it didn't
pay off in practice.
All these aircraft were quite succesfull. These 'carrots' are in fact a
form of the 'area rule' as is the swept wing itself which also leads to a
gradual increase in cross sectional area.

The Tu 95 Bear used them and is still the fastest seving Truboprop (as fast
and high flying as a B52 in some of its versions)

The Convair 990 is still faster than any other airliner.

Only the B747 comes close and that is because the famous jumbo 'hump' was
in fact a form of deliberately introduced area ruling. Rather than waisting
the fueselage the designer bulges the fueselage ahead of the wing.
Post by Peter Stickney
--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster
Keith Willshaw
2004-10-28 13:25:32 UTC
Permalink
Post by The Enlightenment
The Convair 990 is still faster than any other airliner.
I can think of at least 2 that are faster and while they arent
currently flying neither is the Convair 990

Keith
The Enlightenment
2004-10-28 23:28:30 UTC
Permalink
Post by Keith Willshaw
Post by The Enlightenment
The Convair 990 is still faster than any other airliner.
I can think of at least 2 that are faster and while they arent
currently flying neither is the Convair 990
Smartypants.

Concord & Tu 144?
Post by Keith Willshaw
Keith
The Enlightenment
2004-10-30 14:56:00 UTC
Permalink
Post by The Enlightenment
Post by Keith Willshaw
Post by The Enlightenment
The Convair 990 is still faster than any other airliner.
I can think of at least 2 that are faster and while they arent
currently flying neither is the Convair 990
Smartypants.
Concord & Tu 144?
Possibly the B727 was as fast as the Convair 880. The problem with the
Convair 880 & 990 however was their small 5 seat across size compared to the
larger DC8 and 707: this limited their per seat economy.

Accounts of the Convair 880 & 990 indicate that it had rocket ship like
performance.

Peter Stickney
2004-10-29 03:35:56 UTC
Permalink
Post by The Enlightenment
Post by Peter Stickney
Kuchemann didn't have anything to do with the Area Rule. The
"Kuchemann Coke Bottle" came from n attempt tpo have the fuselage
contours of his swept-wing model match the local flowfield - not the
same thing at all. The idea that overall cross-section distribution
should as closely as possible conform to an ideal shape didn't occur
to him.
I don't see how you could say "its not the same thing at all".
It's quite simple, really, What Kuchemann was doing didn't have
anything to do with the Area Rule.
Post by The Enlightenment
Kuechmann came up with a coke bottle shape, the same solution as Whitecombes
area Rule, and it had the same effect.
You lack understanding. The Area Rule has nothing to do with a "Coke
Bottle" shape, per se. The way that it works is that you get the
minimum amount of drag if the overall cross section of your aircraft
approxiates the ideal shape. That doesn't mean "Coke Bottle", but
that's one way of doing it. The F-102A's Area Rule application, btw,
wasn't just waiisting the fuselage. The airframe was dramatically
lengthened, and the Yellow Canary extensions - those pointed fairings
on the aft dside besire the afterburner nozzle, were added at the aft
end. (The Yellow Canary extensions, btwm, were resonsible for the
"Marylin Monroe" apellation for the restrung F-102. It wasn't a
reference to her waist measurement, but to other uh, pointed ogivial
fairings.)
Many aircraft, especially those designed after the early 1960s conform
to the Area Rule without any obvious "waisting".
Post by The Enlightenment
It was comming from a different 'perspective' but it produced the same
solution albeit with a lower level of understanding.
No, it was an attempt to reduce the interfernece drag between the wing
and the fuselage. That's not the same thing at all. The form drag
doesn't become a factor until up around Mach 0.9 - faster than either
Kuchemann's drawing or any tunnel that existed before 1948-49. (The
Germans did have at least one "bump" tunnel, which allowed a transonic
section without incredibly (And for the Germans after 1943,
impossibly) high power consumption, but they didn't have slotted-wall
tunnels, which prevented choking.
Post by The Enlightenment
At least two German designes used this primitive flow field area rule which
admitedly wasn't as well elucidated.
Again, that wasn't the Area Rule.
Post by The Enlightenment
<http://www.all-science-fair-projects.com/science_fair_projects_encyclopedia
/Wave_drag>
"Fuselage shaping was similarly changed with the introduction of the
Whitcomb area rule. Whitcomb had been working on testing various airframe
shapes for transonic drag when, after watching a presentation by a German
researcher in 1952, he realized that the Sears-Haack body had to apply to
the entire aircraft. This meant that the fuselage needed to be made
considerably skinnier where the wings met it, so that the cross-section of
the entire aircraft matched the Sears-Haack body, not just the fuselage
itself. "
(don't know who the German researcher was)
Adolph Busemann, as a matter of fact. (Busemann, BTW, didn't come up
with the idea of the swept wing - he was a bug un using biplane wings
to cancel the shock wwaves. The swept wing was the idea of a Redia
Aeronautica Gerneral who attended the High Speed FLight conference
where Busemann presented his paper.) Busemann's point, that jogged
Whitcomb, was that at subsonic speeds, the airpflow could be
considereed as a series of tubes with varying cross sections, the
cross section changine with airspeed adn pressure. At sonic speeds,
these "streamtubes" had a constant cross section.

This, combined with the new tools available - the slotted transonic
tunnel built by Whitcombe and John Stack, adn the Schlieren photos that
it could produce, were what allowe Whitcombe to see what was
happening, and dedice the phenomenon. Without that visual reference,
nobody had picked up on what has happening. Not Whitcombe, up to that
point, or Stack, Hayes, Busemann, or Kuchemann.
check out:
http://history.nasa.gov/SP-4219/Chapter5.html
(It helps if you spell Kuchemann's name right.)
Post by The Enlightenment
Dietrich Küchemann arrived at the solution by studying airflow, notably
spanwise flow, over a swept wing but even he later commented (now working at
the British RAE at Farnborough) that Whitcomb's statement of the problem,
and solution, was considerably more clear and decisive than his own.
Post by Peter Stickney
So, I'd have ot count home out. There was a theoretician (Hale, or
Haley, I think it was) who also had done some work which could have
led to hte propunding of the Area Rule. But neither man was able to
make the conceptual leap that Whitcombe did to develop teh full
principle.
Possibly it could have been Dipl.-Ing. H. von Halem who was Küchemann's
partner?
No, Wallace D. Hayes, in fact.
Post by The Enlightenment
Post by Peter Stickney
Kuchemann did make a further contribution to tranonic aerodynamics -
the "anti-shock body" or "Kuchemann carrot" - a large canoe shaped bdy
at the trailing edge of the wing, which was supposed to delay shock
formation. Indeed, it did do that, but the drag reduction that it
produced was more than offset by the increased wetted area of the
carrot. Example of the Kuchemann Carrot are teh trailing edge pods of
the Tu-16 and itd derivatives, the pods on the wing of the
H.P. Victor, and the Convair 990 airliner. If, like Tupolev, you had
to have the volume to stick something else in - like the Standard Issue
Soviet Era rough-field landing gear), it wasn't too bad, but it didn't
pay off in practice.
All these aircraft were quite succesfull. These 'carrots' are in fact a
form of the 'area rule' as is the swept wing itself which also leads to a
gradual increase in cross sectional area.
The Tu 95 Bear used them and is still the fastest seving Truboprop (as fast
and high flying as a B52 in some of its versions)
The Yu-95 owes its performance more to the unique and very clever
NK-12 variable-pressure ratio "supercharged" turboprops, which can deliver
sea level power at 40,000', an astonishing reduction gearbox which
turns those props at 750 rpm, keeping the tip speeds manageable, and
crews that don't ming going deaf from the "contra-clatter". The
"carrots" are more thaere to hold the landing gear, I'd say - the
cruiise L/D is much worse than that of a B-52 (More drag), and,
compared with its contemporary Buff, it's down about 100 mph (160 kph)
in speed, and 3,00 miles (5,000 km) in range.
Post by The Enlightenment
The Convair 990 is still faster than any other airliner.
Not even close - and not even among its contemporaries. The 990
exhibited no measurable performance advantage over the earlier CV-880
(Convair model 22), and was out-run by the Boeing 720 and 727. The
747 was also able ot show it a clean pair of heels. The CV-880 and
990 series were quite uneconomical to run. They had no speed
advantage over their contemporaries, and were small and short-ranged to
boot.
Post by The Enlightenment
Only the B747 comes close and that is because the famous jumbo 'hump' was
in fact a form of deliberately introduced area ruling. Rather than waisting
the fueselage the designer bulges the fueselage ahead of the wing.
Which would move the maximum thickness distribution too far forward,
and make the nose too "blunt". I'd say tht the 747's hump owes more
to its origins as a C-5 competitor, where the disire was to have a
large, unobstructed cargo hold.
--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster
John Keeney
2004-10-25 08:32:53 UTC
Permalink
Post by hoarse with no name
The SR-71 does not appear to me to have been designed with the area rule
in mind. Was it area ruled and I just can't tell? Was it not area ruled
for some interesting reason? Will I be stumping Mary with this one?
Area ruling is important in the transonic region, the Blackbirds are
decidedly supersonic.
hoarse with no name
2004-10-25 17:00:45 UTC
Permalink
Post by hoarse with no name
The SR-71 does not appear to me to have been designed with the area rule
in mind. Was it area ruled and I just can't tell? Was it not area ruled
for some interesting reason? Will I be stumping Mary with this one?
Loading Image...

I found a pic I had not seen before and in this view one can see
evidence of area ruling in the coke bottle pinch.
Scott Ferrin
2004-10-28 03:49:02 UTC
Permalink
Post by hoarse with no name
Post by hoarse with no name
The SR-71 does not appear to me to have been designed with the area rule
in mind. Was it area ruled and I just can't tell? Was it not area ruled
for some interesting reason? Will I be stumping Mary with this one?
http://www.fas.org/irp/program/collect/sr-71-00000003.jpg
I found a pic I had not seen before and in this view one can see
evidence of area ruling in the coke bottle pinch.
You're not seeing a "coke bottle" fuselage. That's a wet area from
fuel. And "aera-ruled" doesn't mean "it's got a coke-bottle
fuselage".
The Enlightenment
2004-10-26 23:23:24 UTC
Permalink
Post by John Keeney
Post by hoarse with no name
The SR-71 does not appear to me to have been designed with the area rule
in mind. Was it area ruled and I just can't tell? Was it not area ruled
for some interesting reason? Will I be stumping Mary with this one?
Area ruling is important in the transonic region, the Blackbirds are
decidedly supersonic.
I recall reading that SR71 opperationaly break the sound barrier by using a
shallow dive: it's apparently much easier.
The Enlightenment
2004-10-26 23:19:58 UTC
Permalink
Post by hoarse with no name
The SR-71 does not appear to me to have been designed with the area rule
in mind. Was it area ruled and I just can't tell? Was it not area ruled
for some interesting reason? Will I be stumping Mary with this one?
If you have a look at Boeings now aborted 'sonic cruiser' you will not that
it is a mild canard with a double delta wing. The area rule is applied but
through the use of the delta (double delta) pushes the 'waist' back to the
tail where it is easier to construct. I think Concord used this as well.

There have been many attempts at producing near super sonic ie transonic
(mach 0.975) jet airliners all have foundered to some degree on the cost of
the structural complexities of 'waisting' the fueselage in the middle. By
using a highly swept double delta they seem to be able to shift it to the
rear. Myabe the comming world of plastics airliners will provide new
material and structural ways of achieving this. (It still doesn't get rid
of the loss of seats)

As early as 1944, German aerodynamacist Dietrich Kuchemann (Junkers I think)
had designed a tapered fuselage fighter plane that was dubbed the "Kuchemann
Coke Bottle" by American intelligence personnel predating Whitecombs area
rule. Kuchemann's design was not aimed at smoothing the curve of the cross
sectional area to displace the air less violently, however. He had simply
observed the direction of air flow over a swept-wing design and was
trying to design a fuselage that would follow the contours of that flow.
It was much the same thing. As I recall the "Luftwaffe Secret Projects"
Series of books has one or two of these crude "area ruled" type designe
studies.
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