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Old Apr 27, 2014, 05:56 PM
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Does anybody have a good, clean 3-view of the P-51H that comes with formers? Thanks for the help

Adam
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Old Apr 27, 2014, 11:45 PM
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Adam,

Sorry--been a bit busy with some other issues.

Yes, I got it all. Hopefully you will too, very soon. Got your last PM.
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Old Apr 27, 2014, 11:57 PM
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Thank you for this very informative discussion Charles. It's nice to have all this information in one place!
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Old Apr 28, 2014, 01:19 PM
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Thanks Chad,

All the information isn't here. In fact I'm trying desparateley to keep to essentials only, without going into too much detail. I figure if anyone really wants "chapter and verse" they can ask, or contact me or, better yet, actively join the P-51SIG discussion. As always, all are free to question anything I've shown or promoted. Not wishing to argue with anyone and will READILY adopt corrections and new documented information as part of my ever changing "current understanding".

"Thought I was wrong once, but I was mistaken."
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Old Apr 29, 2014, 11:34 AM
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Allison Mustangs had two slightly different diameter Curtiss Electric types. 10'-6" up til A-36 and P-51A, IIRC. Later, more powerfull engines, had 10'-9" "fan".

Adaptation of Packard RR V 1650-3 saw four blade Hamilton Standard "cuffed" type fit to P-51B. Diameter is oft given as 11'-2", but is not quite 1/10 " bigger (IIRC, 11'-2.98"). Early examples of this type had anti-icing system plumbing and a "tit" fairing over fluid orifice, located at extreme inbord root of the cuff, at leading edge, next to spinner. AFAIK, no actual de-icing was ever a standard production item on a Mustang. Suggests HS may have had an existing prop on hand, when NAA came calling, or, that de-icing was a consideration, at one time.

Later cuffs on P-51B/C/D's deleted the orifice fairing. It should be noted blade shank under the cuff is NOT a standard type shank, with a cuff added.

Hamilton Standard 11'-2" diameter "square-tipped "blades were introduced late in P-51D production at Inglwood and later, at Dallas. These have a normal shank and no cuff was ever fitted. These fit the same hub as the cuffed type. Wt. also unchanged from cuffed type, although full pitch angle slightly diverent between the two.

After some 800 P-51D's (cuffed HS) Dallas production introduced the 11'-0" Aeroproducts propeller version, known as P-51K. 1,500 K's were made during second and third Texas production blocks. Line reverted to P-51D manufacture.
The Aeroproducts featured a hollow steel blade , no cuff and as a complete blade /hub unit, was 30lbs lighter than the HS units. A lead ballast ring was fitted to compensate. These units proved a bit unsatisfactory, due to vibration and service issues.

special blade shank of cuffed HS type were also of special section and outline. Section transitioned more quickly than normal, from round at the hub, to "square" (rectangular actualy). There are four distinct facets, with relatively flat surfaces. It is believed this shape not only accommodated an efficient airfoil, closer in, it also aided in retaining the molded on plastic cuff.

Suspected myths: Cuff does not appear to be spcifically needed to increase ram effect of either the carburetor intake (at chin) or augment airflow through the radiator during ground running. Both no doubt did enjoy some benefit. However both became void when the "square tipped" and or Aerproducts units were utilized.
Reason for the switch to Aeroproducts and the later HS units has been attributed to production shortages of th e cuffed type. However, it is more likely NAA was looking to move away from the cuff. If there was a shortage, it probable it was of the "square tipped" type, notbeing up to full production. Possibly related, NAA engineers may have bowed to preassure from parent General Motors,to use more "in house" suppliers, such as Aeroproducts.

We'll get to why the cuff was being phased out, next time.
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Old Apr 30, 2014, 01:16 PM
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Why the switch from 'cuff" to "no cuff"

During extensive testing of late P_51B/C/D airframes, at ever higher operating combat air speeds, the cuffs, which had once been viewed as a large part of an overall package of forward thinking Mustang features, began to be seen as detrimental to both top speed and stability. When in high pitch, the cuff root was only some 15 deg off the line of flight. This was felt to represent too much side area forward of the CG. At these High angles of attack , diminished lift/thrust efficiency was occurring in the shank portion of the blade and producing considerable drag. There was also a huge spiraling flow of heavily disturbed air mushing outward . This was seen as an additional cause for spiral instability. It was decided to trade high end prop benefits, for for those gained at climb and at cruise.
Kind of ironic, if you think about it.

Last prop myth, for now. In recent years it has become common to refer to the "Square-tipped "HS blade as the "paddle blade". Even among aircraft owners, operators, and enthusiasts of the Mustang. However, they (you?) may want to read the Maintainance manual (1944, '46, '54 etc.), which discusses all three props as fit to Merlin P-51's. There in, it it specifically refers to the "cuffed type" as "the paddle blade". Hmmmmmm.....
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Old May 04, 2014, 02:19 PM
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Cowls from Spinner(s) to Canted Firewall

Mustang I thru P-51A: AFAIK. basic shapes and dimensions identical.
The carburetor intake of the prototype was about a foot back from the spinner. Same on the first production Mustang I. On the latter, a simple scoop had given way to a raised type, which appears to be a nod toward boundary layer avoidance. With the second production example, the scoop had been moved forward and raised away from the surrounding surfaces even more. This seems to have successfully addressed the intake issue. The scoop, in its new position actually overhangs the spinner rear, by about an inch.

At first, the scoop was rather straight sided, width constant and parallel, when viewed from above. However, desert operating conditions saw a filter added, introducing a wide flowing bulge at the sides. This, IMHO, made a marked improvement in the Allison Mustang's plain jane look.

On models with nose guns, at the sides below the engine, The starboard gun was much farther forward than port gun. Probably to stagger the ammo canisters (??).

There is a visual unpleasantness observable in the cowl sections, from just in front of the engine, to just aft of the engine. Cowl sides appear near vertical for the length of the engine, and then taper back into the original sloping lines, farther aft. According to Ed Horkey, this was done to accommodate exhaust shrouds of the initial shipment of engines to NAA, by Allison. A production mod had, apparently, been made by the engine manufacturer, but NAA had not been informed.

The canted firewall is inclined to a very specific angle. This remained the same throughout evolved Mustang production. It is also the mount for the cockpit front armor plates. The thrust line was parallel to Fuselage Ref. Line. There was no side thrust.

The Allison variants have never really interested me. However that is changing and i hope to learn a great deal more very soon. There may be scale drawings. A few years back I provided a great deal of information to Jerry Bates. He did in fact produce a couple sets of scale drawings depicting various types, to go with his 1/5 scale plans. They are quite decent, and used to be available on-line.

IIRC , one of my old newletters, MM&E, has all of the NAA former drawings superimposed upon one another, showing correct sections from spinner to firewall. Sorry I cant recall which issue. They are linked to, earlier in this thread .
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Old May 05, 2014, 12:27 PM
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packardpursuit,

Did any of the Mustang versions have engine down-thrust? If so, measured to what datum?

Jim R.
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Old May 05, 2014, 12:52 PM
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YES
All Merlin variants had 1.75 deg. down thrust. P-51B/C/D/K Thrust line - Fuselage Reference Line intersection occurred at Fuse. Sta. 41.600.
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Old May 05, 2014, 11:52 PM
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This is great stuff Charles, keep it coming! I just returned from the annual Planes of Fame airshow which included flying examples of the P-51A, P-51C, P-51D (8 of them!), and P-51K. If only Mike Coutches had attended with the P-51H it would have been Mustang nirvana!




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Old May 06, 2014, 07:55 AM
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Chad Veich,

Nice work on the photos. I note the exhaust plugs on the P-51C, but on none of the other Mustangs. In one of the Folkerts threads the subject of exhaust plugs first came up, re reducing exhaust valve warping after shut-down by slowing cooling. Some folks use plugs, some don't.

Jim R.
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Old May 06, 2014, 01:08 PM
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Chad
thanks for adding the photos!
In the "line up" photo, first two aircraft are P-51D's showing both styles of production Hamiton Standard props. A/c closest o camera is HS "Square tipped " blade. Second is more familiar "cuffed" and or"paddle blade" types. Many probably already knew this, but a good side by shot for comparison is always good!

"Miss Virginia" has what appears to be proper Curtiss Electric. Compare root blade thickness to that of later HS types. I'm wondering if the HS 's could be considered 2nd or 3rd generation of prop designs?

Any chance you got inside "Planes of Fame Museum"? The Gee Bee R-1 on display was built by us, for the 2003 LA County Fair. It is a 4x enlargement of 1/4 scale R/C plan!
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Old May 06, 2014, 06:15 PM
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Attached you will find a 3 view drawing of a P-51D-5-NA drawn in 1990 by Packard Pursuit (Charles L. Neely). It appears here for uploads by permission of the artist.

I'm sure that PP can do a finer job than I relating history and technical tidbits of this a/c.

This will print out fine as an 8x11 doucment, but it was scaned in its 2' X 3' form and should print out well at that size.

Thanks PP!
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Old May 06, 2014, 09:18 PM
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Many thanks to TedD60 for helping me get this posted!

The drawing may look familiar, as it appeared in Ray Wagner's book "Mustang Designer -Edgar Schmued and the P-51". Orian Books 1990. Reprinted by Smithsonian Press (no date given).

Wagner's book is excellent narrative of war years from Schmued's prospective. Indeed it it is Ray's compilation of Edgar's personal notes for his auto-biography. Lot's of eye opening Mustang history. Edgar's wife Chrystal, was also intrumental in getting her husband's story told. Both were absolute joys to work with.

The drawing is of P-51D-5-NA, as a production standard. It has no Dorsal Fin Fillet and features a -2 style canopy blister. The drawing itself was 1/24 Xerox reduction of my 1/16 scale D side view work-ups , traced in pencil, onto vellum. New wings and tail outlines were drawn to reduce distortion at the extremities.

As a modeler, I tend to wish draftsmen used thinner lines. Thickening of the line when "blowing up" is greatly reduced. For photographic and or digital reproduction purposes, thicker bolder lines make for better visual definition, as not evidenced here. The book versions are a bit better in that regard, however. This one is twice removed from the original. Thin lines are a general drawing habit (flaw?) of mine. Not making excuses, just letting you know.
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Old May 07, 2014, 09:50 AM
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I agree that thicker lines when enlarged to model size make it difficult for the builder to determine where to make cuts on wood--inside the line? outside? in the middle? And how will such parts fit together?

Problem with thinner lines is that higher res is needed when scanning, along with careful exposure. Otherwise, thin lines will disappear either altogether or in parts. Higher res means bigger files, which slows downloading and increases storage needs.

Jim R.
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