First Aircraft to Use a Symmetrical Airfoil

[mike-wsm]

BobM2
"No P-51 either Allison or Merlin ever had turbocharging"
Jane-DoH
"Really, I was always under the impression that the Merlin version did... if you're right, you learn something new every day"

Bob is right. The Merlin was supercharged, not turbocharged. And no, I'm not going to explain the difference. Go and look it up. Or have a good look at this pic.

[Jane-DoH]

mike-wsm

Bob is right. The Merlin was supercharged, not turbocharged.

So they managed to retain good performance by using a dual-staged supercharger with twin-speeds?

And no, I'm not going to explain the difference. Go and look it up. Or have a good look at this pic.

I do know the difference between a turbocharger and a supercharger....

[mike-wsm]

Originally Posted by Jane-DoH

So they managed to retain good performance by using a dual-staged supercharger with twin-speeds?

Read the book.

[Jane-DoH]

mike-msm

What book are you even talking about?

[bearfoil]

JaneDoH

How could you not know "JANES, all the world's aircraft"

[ChristiaanJ]

Jane-DoH,

I would think Mike was referring to "Not Much of an Engineer" by Stanley Hooker... which has most of the story.

CJ

[mike-wsm]

Originally Posted by bearfoil

The F-104 is an odd duck. When looking down the wing tip, Tank removed, the wing shows a definite symmetry top/bottom. the deal is, it is shaped like a noodle. It is "S" shaped, a cuff-like (droop) leading edge, an up swoop, a down, then straight at the TE.

All thanks to ChristiaanJ for some pics of F-104 wingtips with ancilliary hardware removed. I've cropped and enhanced a bit but the geometry is as original photo.
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[Turbine D]

Merlin Engines

JaneDoH

There are some great sources of information for questions you have posed regarding the Rolls Royce Merlin. Just "Google" Merlin engine and this is what you get, Page 1:

Rolls-Royce Merlin Engine - Great Britain

Rolls-Royce Merlin - Wikipedia, the free encyclopedia

Regards,

Turbine D

[bearfoil]

mike-wsm

Yo, dassit. One can see a very supercritical aspect, and obviously, not symmetrical. You can also understand why when I was ten, and a Starfighter pilot told me the wing was carved from billet, I believed him. Thin to win. Now, can we discuss the "anhedral"?

bear

[PBL]

Let me put in my vote for this as a fine thread. I am learning a bunch of stuff, all of which I don't really have the time to look up, but which I am glad I now know. For example, that the Merlin had dual superchargers and how they were configured; the exact shape of an F104 wing; the list of airfoils on the U.Ill WWW site (which apparently one of my guys knows about because he designs airfoils for X-Plane as a hobby); the name of a book which contains details of Merlins; the names of lots of airplanes with symmetrical airfoils, a feature of which I was not aware they had (I had thought symmetrics were for aerobatics, for all the usual reasons). (I even sent a note off to Boeing about the XB-15, which was acknowledged but remains unanswered. It's hard to believe that Boeing doesn't have a company historian.) In particular, many thanks to Jane for originating the thread and asking all the questions that the rest of us would like to ask but don't get around to.

PBL

[HazelNuts39]

Originally Posted by PBL

It's hard to believe that Boeing doesn't have a company historian.

The Boeing Company is mainly interested in 'Shareholder Value'. I believe there is an association of (ex)Boeing employees interested in history, which also keeps a small museum going, with some support from the Company. Unfortunately I don't know if they can be reached on the WWW.

[Brian Abraham]

One can see a very supercritical aspect

Not supercritical Bear.

the Merlin had dual superchargers

The Merlin came in a variety of versions.

Single stage, one speed
Single stage, two speed
Two stage, two speed

[barit1]

Company historians

Pratt & Whitney had an informal historian for many years (50s-90s), Harvey Lippincott. GE had a cadre of men who had worked on the first GE I-A engine, the Jet Pioneers Associaton. I'm sure the tin-knockers have similar adjunct functions.

I've found that the retirees and informal archivists manage to present a more honest and balanced picture, than do the ones subject to current corporate whims.

[bearfoil]

Brian

Are you sure? I figured the chord was "flat on top" to escape the need for area ruling.
Was the wing thin enough to produce little Waist drag? The fuselage is rather 'unassuming' in section?? Also, the "inverted planform" of the wings, added to anhedral, made the a/c very "manouverable" ('unstable'). This I believed to be the Deal with the Devil that killed so many Germans. IE, a natural tendency to the Roll, requiring little if any draggy aileron input. The 104 could ill afford to kill any of its lift just to turn.

[mike-wsm]

Originally Posted by PBL

It's hard to believe that Boeing doesn't have a company historian.

I had this problem with Bell when researching for a book many decades ago. They kept sending printed cards telling me to "contact my local library". This was a bit pointless, a library in the uk wouldn't know a lot about Bell designs. After a bit of though I wrote to their local library in Buffalo. The result was soooo surprising, a kind letter from the librarian with a whole stack of reference material and past company newsletters for the era I was interested in. She also said she had looked up the then President in the phone book and gave me his address. I wrote to him, explained what my interest and he went back into work, he still had an office there, and dug out all sorts of research material and photos. He converted a gap in the book into a really interesting section. So keep trying, in particular Seattle Public Library and the local Museum of Flight, they may have volunteers who will be happy to look through their archives and make copies for you.

[HazelNuts39]

mike-wsm;

thanks for the link to The Museum of Flight, which I was referring to because remembering a visit some years ago when it was still in the Red Barn. (Look it up in 'About the Museum', History).

regards,
HN39

[Annex14]

addition

bearfoil

quote:
This I believed to be the Deal with the Devil that killed so many Germans. IE, a natural tendency to the Roll, requiring little if any draggy aileron input.

Hi Bear, please allow for a small addition. The "Deal with the Devil" was not that much the wing but the additions made to the original VMC interceptor desighn. It added about 2000 lbs to the weight without adequate improvements to engine performance. Some critics called the plane later " the egglayingsheepwoolbreedingmilkpig". Fact is it was very fast, stable weapons platform in normal flight envelope. The mentioned instability came in play on slow speed envelopes. During approach - app.speed 185kts - the plane became very soft through all axis. A frequent problem was "open nozzle", I only remember one attempt of landing in these condition that didnīt end in bail out.

Though I was civil, I worked a while dep. and app. control for a F-104 base. Later, when I held a "Red Card" for 8 years, because of other activities in my carreer, I applied for and was approved a low level mission on a TF 104. I must admit, even after more than 30 years still a milestone in my aviation life.
Jo

[BobM2]

Jane-DoH

So they managed to retain good performance by using a dual-staged supercharger with twin-speeds?

As I recall, the 2-stage 60 series Merlin was introduced in the Mk 9 Spitfire. This was necessary in 1941 to counter the threat of the new FW-190 which completely outperformed the Mk-5 Spit with its single-stage Merlin.

It should be noted that the first 2-stage supercharger was on the P & W R-1830 in the F4F-3 Wildcat. Unlike the AAC, the US Navy didn't pursue turbochargers or V12 engines ("we'll buy liquid-cooled aircraft engines when we convert to air-cooled submarine engines"). Ironically, the Navy found their lower altitude pacific war didn't require the two-stage blowers & later FM Wildcats (built by GM) used single stage Wright 1820's. They were lighter, cheaper, simpler & developed more sea level power to get the FM Wildcats off the short decks of escort carriers.

[Brian Abraham]

Brian

Are you sure?

Certainly am Bear. The supercritical airfoil was invented by NASA scientist Richard T. Whitcomb during the 1960's, and was first tested on a modified F-8 in 1971. Is designed for high subsonic and transonic, not supersonic, performance. It's use is confined to airliners, business jets and transports (C-17).

[Jane-DoH]

mike-wsm

All thanks to ChristiaanJ for some pics of F-104 wingtips with ancilliary hardware removed. I've cropped and enhanced a bit but the geometry is as original photo.

That looks very supercritical in nature, especially in the second picture you can see a definite inverse camber and due to the particular curvature, it looks like it would do very well supersonic. It would appear that the small curvature to the top was to compensate for the inverse camber on the bottom.


bearfoil

Now, can we discuss the "anhedral"?

Sure, as I understand it was added to deal with the size of the T-tail and something called a "wing-on-rudder" effect which, as I understand it was either a form of dutch-roll, or a tendency for rudder-application to roll the airplane. Adding some anhedral would fix the problem.

Interestingly, I have speculated that the anhedral could have also had an additional benefit (whether realized or an unintended consequence) of producing some kind of compression-lift effect. My reasoning was based on the fact that a wing with no sweep would have a shockwave along the whole leading-edge, and with it a pressure gain on any convex portion of the top and bottom of the wing; if you canted the wing down 10-degrees you'd have more pressure confined to the bottom.

This had to do with a curiosity of mine as to how the aircraft still retained a good degree of agility when supersonic. Straight wings experience large shifts in the center of pressure when transitioning from subsonic to supersonic speeds, which often results in high trim-drag. My guess is that the high-thrust available, the large tail, and the fact that the overall drag of the plane was low got around that. Still, L/D ratios drop when supersonic which affects sustained-agility. To some degree, ram-compression helps drive up thrust at supersonic speeds, but I figured the anhedral actually helped drive up the L/D ratio when supersonic and produced an overall better L/D ratio allowing improved sustained maneuvering performance.

Regardless, with the inverse-camber of the wing, it's L/D ratio would be good at supersonic speeds because inverse-camber works well when supersonic, and if the anhedral did actually produce a compression-lift effect by confining the pressure gain on the bottom that would explain a lot.


PBL

Let me put in my vote for this as a fine thread. I am learning a bunch of stuff, all of which I don't really have the time to look up, but which I am glad I now know.

I'm glad we're all of help

I even sent a note off to Boeing about the XB-15

The XB-15 had a symmetrical airfoil?


Brian Abraham

Not supercritical Bear.

True enough. It does have an inverse camber though


bearfoil

Are you sure? I figured the chord was "flat on top" to escape the need for area ruling.

I thought the F-104's fuselage shape did incorporate some area-ruling to it


BobM2

It should be noted that the first 2-stage supercharger was on the P & W R-1830 in the F4F-3 Wildcat. Unlike the AAC, the US Navy didn't pursue turbochargers

I'm surprised they didn't pursue turbochargers earlier. If I recall the F6F and F4U had them though...