P51 1/48 scale nose.

[gingerbob]

53 minutes ago, Mick_Gannon said:

...I want to model a Merlin engined F82 aircraft as I don't thing the makers will be making a new tool any time soon of the early aircraft, I have the P51H and the F82 twin allison engined kits

 

Right, my concern was that discussion started turning to P-51H Merlin vs F-82 Merlin, but yet you were measuring an Allison-engined kit, and comparing to a station drawing that might have been one or the other, and I just wanted to make sure we (I?) didn't start mixing up different "facts".

[Mick_Gannon]

1 hour ago, FinnAndersen said:

 

 

 

But why are you doing this? I thought that you wanted to stick a pair of merlins to the front of the P-82. If the Merlin and the Allison happens to have the same length from back of spinner to firewall, then you're done.

 

Trying to adjust the length of a kit is much more work

 

/Finn 

Well if you read what I have said, I was Measuring from the drawing gave me an error, using the station drawing which gave me dimensions gave me a fact of true overall length, no I am not trying to adjust the length of the kit but determine that what I am stating with is a true scale length(which is good practice), also note there is no evidence that either engined aircraft where different length's, so an assumption for modelling purpose's has to be made that they are the same.

Using the P51H nose and grafting it to the P82 using the firewall engraved lines would make the overall length of the finished model too short, as stated above only 3 % of the P51H parts were used in the P82 and that the nose(s) would have had to be extended to ensure the CG would be in the correct place.

Now if I just stick a pair of merlin nose's onto the front of the P82 kit, yes I would have a Merlin engined P82, then everyone that looked at the model would say " it looks too short in the nose area ", so please excuse me for asking questions before I start cutting up kits to make my proposed model, also note that I do not have access to vast amounts of drawings from North American Aircraft Corporation unlike aircraft restoration companies or contact details for them, hence asking questions from modellers that know their aircraft.

 

Regards

[FinnAndersen]

11 minutes ago, Mick_Gannon said:

... Using the P51H nose and grafting it to the P82 using the firewall engraved lines would make the overall length of the finished model too short...

Fine, things are moving forward. Now you only need to determine how much you need to lengthen the Merlins. The rest is basic modelling skills.

 

Just for the record, I dont have access to P-82 works drawings either. I would be very surprised if anyone here on BM did. Those that did the fullsize restauration of a XP-82 in the US might. 

 

https://warbirdsnews.com/warbirds-news/tom-reillys-xp-82-twin-mustang-is-for-sale.html

 

/Finn

[sharkmouth]

Well, this is for future reference since so many are so kind to spend their time answering.

 

Many of the references needed are available... at a price.  In this case, the Air Corps Library (which supports the warbird community) has an original aircraft checker's report for F-82B-1-NA 44-65162

 

... and of much better use, as one can see the structure of both Merlin and Allison powered twin mustangs, the Structural Repair Instructions for P-82B, P-82E, P-82F, and P-82G:

 

If unwilling to spend the membership (about $6USD a month), then modelers can search for what others before them have done.  Here is an excellent one:

 

Building the XP-82 Twin Mustang in 1/32 Scale | Large Scale Planes

 

NOTE: There are active links embedded.

 

Regards, 

Edited February 2, 2022 by sharkmouth
Spellcheck Police, only warning this time.

[sharkmouth]

Since Finn mentioned the restoration of (actually two) P-82, a simple search resulted in a few useful links (to help get the Merlin engine geometry in the nose correct).

 

Air Wing Media - North American XP-82 Twin Mustang Restoration

 

World War II Aircraft - XP-82 Almost Ready to Fly

 

Factory photographs

 

Video in Flight from Cockpit

 

Regards,

[Mick_Gannon]

Thank you for the info, I live in the UK and yes the info would be useful but getting it is the hard part.

 

[gingerbob]

Well, I thought (or acted) to search my files for dimensions.  I found one identified with a type (or whatever) number "123", which means P-82B - that is, Merlin engined.  Unfortunately, I then found a similar drawing for F-82G [Allison] which gave the same dimensions.  So... do they in fact HAVE the same dimensions, or is this a case of a manufacturer re-using existing drawings and forgetting (or not bothering) to correct the numbers?

 

I do remember that when I compared Modelcraft F-82 (yeah, I know) and P-51H (Classic Airframes) noses, the former was significantly bigger than the latter, a bit to my surprise.  Not worth much, but at least it agrees with your own observations.

 

IF we could find a photo or drawings of what things look like inside the cowling, that might give further evidence of an obvious dimensional difference, or perhaps even give some hint as to why the two are different.

 

Now, maybe all of the above is just tedious "discovery" of stuff you already have found for yourself, but you got me curious and I'm just trying to help.

 

bob

[sharkmouth]

9 minutes ago, gingerbob said:

IF we could find a photo or drawings of what things look like inside the cowling, that might give further evidence of an obvious dimensional difference, or perhaps even give some hint as to why the two are different.

 

Aside from two of the links I posted which show the nose without cowling (Ready to Fly and Factory Photos), Tom Reilly did chronicle his restoration saga online.

 

Tom Reilly's F-82B Restoration

 

Regards,

Edited February 2, 2022 by sharkmouth
Spellcheck Police, only warning this time.

[72modeler]

2 hours ago, sharkmouth said:

Since Finn mentioned the restoration of (actually two) P-82, a simple search resulted in a few useful links (to help get the Merlin engine geometry in the nose correct).

 

Air Wing Media - North American XP-82 Twin Mustang Restoration

 

World War II Aircraft - XP-82 Almost Ready to Fly

 

Factory photographs

 

Video in Flight from Cockpit

 

Regards,

Looking at the two factory photos that show the uncowled engines on a P-82B, there is quite a bit of space between the firewall. which has the oil tank, and the rear of the engine, on top of which you can see the intercooler. I don't recall seeing that much space between the firewall/oil tank, and the intercooler on the P-51B/C/D. Perhaps this is evidence that the engine  was shifted forward to maintain the cg because of the Twin Mustang's  extended rear fuselage. Might be why the 1/72 kits have noses/cowlings that are too short, and corrected as shown in Russell's build article.

Mike

Edited February 2, 2022 by 72modeler
corrected text

[Mick_Gannon]

My thinking is this, A, cast the P51H nose just past the start of the cockpit, B, calculate the length of the nose from cockpit to back of spinner, of note I measured the F82 kit fuselage and spinner and got a length of 253.74 mm, from the D&S book the drawing showing STO 0 position, when calculated to 48th scale comes out at 247.729 mm, from the above statement by gingerbob from his drawings both engine type aircraft share the same length so the kit is 6mm too long or 288 mm inreal life or 11.338 inch's.

So if I make the assumption that the new nose when fitted must equal the overall kit length with spinner it should look correct in proportion. Does this seem a good start point?

[silberpferd]

I had totally forgotten I had an incomplete F-82 parts catalog, and the engine cowlings page confirms that most of the panels for the P-82B are the same than those used on the P-51H. All the panels with the part number starting with "117" were both used on P-82B and P-51H.

 

 

Using the 3 view drawings from P-51H and P-82b manual, there is a difference in length of the nose of about 49 centimeters between the wing leading edge and the firewall, the P-82B being longer.

 

 

HTH,

 

Laurent

[Mick_Gannon]

Well that buggers up a lot, the P51H and P82 kits are not the same at all from the same maker same scale, but it does show that the previous comment that the nose was made longer to put the CG in the correct position has a valid point.

[sharkmouth]

1 hour ago, Mick_Gannon said:

 it does show that the previous comment that the nose was made longer to put the CG in the correct position has a valid point.

 

Nose made longer, or wings moved further back on the elongated fuselage?  The cockpit being in the same station position, relative to the cowling , on both.

 

Your clues are:

1. The statement that there is longer space in front of the wing
2. The cowlings (part numbers starting with 117) are the same
3. The distance from the windscreen to the cowling seems the same.  (Moving the wing back also shifts the Center of Gravity.)

 

Regards,

Edited February 3, 2022 by sharkmouth
Spellcheck Police, only warning this time.

[FinnAndersen]

5 hours ago, Mick_Gannon said:

My thinking is this, A, cast the P51H nose just past the start of the cockpit, B, calculate the length of the nose from cockpit to back of spinner, of note I measured the F82 kit fuselage and spinner and got a length of 253.74 mm, from the D&S book the drawing showing STO 0 position, when calculated to 48th scale comes out at 247.729 mm, from the above statement by gingerbob from his drawings both engine type aircraft share the same length so the kit is 6mm too long or 288 mm inreal life or 11.338 inch's.

So if I make the assumption that the new nose when fitted must equal the overall kit length with spinner it should look correct in proportion. Does this seem a good start point?

Using Laurents (@silberpferd) input, I would make the join on the firewall as the wing is not in the same position, being higher on the P-82. Not the best of places, I admit, but what can you do. 

 

/Finn

[sharkmouth]

56 minutes ago, FinnAndersen said:

... as the wing is not in the same position, being higher on the P-82.

Finn, I'm not sure what you meant by the wing being higher on the P-82.  Of course, Laurent's input is valued (he and I have discussed many things on a manufacturer's reference and assistance group on FB which I run).  I'm simply trying to understand what was meant by that phrase.

 

Regards,

Edited February 3, 2022 by sharkmouth
Spellcheck Police, only a warning... this time!

[silberpferd]

26 minutes ago, sharkmouth said:

 Of course, Laurent's input is valued (he and I have discussed many things on a manufacturer's reference and assistance group on FB which I run).

That was someone else, I'm not on FB.

[sharkmouth]

5 minutes ago, silberpferd said:

That was someone else, I'm not on FB.

Ah, you're not Laurent Stern then.  My apologies.

 

Regards,

[FinnAndersen]

39 minutes ago, sharkmouth said:

Finn, I'm not sure what you meant by the wing being higher on the P-82.  Of course, Laurent's input is valued (he and I have discussed many things on a manufacturer's reference and assistance group on FB which I run).  I'm simply trying to understand what was meant by that phrase.

 

Regards,

When I look at the picture in Laurents post, and draw a horisontal line from the wing leading edge, it seems that the wing is moved upwards on the P-82. Not much, but noticeable.

 

/Finn

[silberpferd]

7 minutes ago, sharkmouth said:

Ah, you're not Laurent Stern then.  My apologies.

 

Regards,

No problem.👍

[sharkmouth]

3 minutes ago, FinnAndersen said:

When I look at the picture in Laurents post, and draw a horisontal line from the wing leading edge, it seems that the wing is moved upwards on the P-82. 

 I see it now, thanks.  

 

Regards,

[Mick_Gannon]

Thank you everyone for all the photo's thoughts and input, think I know where I am going now, so off to cast the nose sections off a P51H.

 

Regards

 

[sharkmouth]

5 hours ago, Mick_Gannon said:

Thank you everyone for all the photo's thoughts and input, think I know where I am going now, so off to cast the nose sections off a P51H.

 Hopefully, you will share your build here as that is the best "thank you" which can be provided to those that assisted.  Waiting patiently here.

 

Regards,

[Mick_Gannon]

I found an old F82B modelcraft kit in my collection the nose on that nearly is the same as the New kit for size, so now have 2 options.

Edited February 4, 2022 by Mick_Gannon

[72modeler]

On 2/3/2022 at 11:10 AM, Mick_Gannon said:

Well that buggers up a lot, the P51H and P82 kits are not the same at all from the same maker same scale, but it does show that the previous comment that the nose was made longer to put the CG in the correct position has a valid point.

I have attached links to two photos; one is a factory photo of the P-82B on the assembly line- the other is a photo of the XP-51F that used the same Merlin as the P-82B and the same basic engine mount, firewall and accessories, In the P-82B photo, note the space between the intercooler on top of the engine at the back and the oil tank mounted on the firewall; note also the diagonal motor mount  bearer goes from the firewall and attaches to the lower bearer at the 2nd exhaust stack from the rear. In the XP-51F photo, note the much smaller distance between the intercooler and oil tank; also note that the diagonal engine bearer attaches to the lower bearer at the third exhaust stack from the rear, which would indicate to me that the engine on the P-82B is mounted further forward than the engine on the lightweight/F-51H Mustangs. Maybe why the Monogram kit nose is  short?  In the two photos Mick commented upon, you can also see that the nose on the P-82B photo was extended,- look at the distance from the wing root fillet faring to the  angled panel line on the cowling in the two photos. (If I can get access to Lackland AB again, I will measure the nose on the F-82G there- should be the same for all variants.)

Mike

 

https://ww2aircraft.net/forum/threads/north-american-p-82-f-82-twin-mustang.40081/#post-1492114

 

https://www.key.aero/article/mustang-might-have-been

 

Dunno if this helps, but I have a set of 1/72 Scale Aviation News  drawings of the F-82G that also has a profile drawing of the P-82B fuselage.  I also have the Detail &  Scale P-82B/F-82G drawings. I have no idea if either set  of drawings is accurate. I also have the Monogram F-82G kit, and the published overall length  and span dimensions for the P-82B/G. For what it's worth, what I found is listed below. In a nutshell, the figures were all over the place! I make no claims as to the accuracy  of my findings, as the published printed figures and the drawings do not agree, nor can I claim that the build article and corrections within that I posted above are accurate, I think each modeler can refer to his/her references and the information posted here on BM and draw their own conclusions- mine being we need an accurate and state of the art kit in 1/72 and 1/48 scale! I think this is as far as I can go with the references I have; if somebody can measure either of the P-82B's at the Air Force Museum, the mystery could be solved!

Mike

 

Aviation News drawing, P-82B (BTW, these were also in the Norm Avery NAA book and were drawn by Ian Huntley.)

length: 38.9 feet

span: 51.9 feet

center section wing chord: 9.0 feet

height of fin at rudder post: 7.0 feet

 

Detail & Scale drawings, P-82B

length: 38 feet, 9 inches

span: 51 feet, 3 inches

center section chord: 9 feet, 9 inches

height of fin at rudder post: 8 feet, 3 inches (on the F-82E/G drawing, the height is 9.0 feet)

 

Monogram F-82G kit

length: 37 feet, 9 inches

span: 50 feet, 9 inches (Probably more than this, because of measuring from tip to tip across both outer wings, which have dihedral.)

center section chord: 9 feet, 3 inches

height of fin at rudder post: 8.0 feet

 

Detail & Scale NAA factory drawings with dimensions listed in inches from station to station; I took the measurement from station to station and divided by  12 to convert into feet; I hope I got them right!, but here  is what I came up with:

 

length: 38.25 feet

span: 51.2 feet

center section chord: 9.7 feet

Height of fin at rudder post: 7.6 feet

 

Published length for the P-82B is 38 feet, 1 inch

Published span for the P-82B is 51 feet, 3 inches

 

This just in!

I remembered I had a copy of North American Aircraft, 1934-1998, Volume 1, by noted aviation author Norm Avery, and I examined the section on the Twin Mustang. here is the pertinent info taken from pp 144-153:

 

'No parts were interchangeable with the Mustang except for the engine and cowl installations, which were shared with the  P-51H. Wing chord at the root was increased from 104 inches for the P-51H to 112 inches (9.3 feet!)  for the P-82. Overall length for the P-82B/C/D (Merlin) was 38 feet, 3 inches; for the F-82E/F/G/H 39 feet, 1 inch. The second P-82 prototype was fitted with Allison V-1710 -119  engines that rotated in the same direction; NAA preferred the Merlin, but with the war over, the British were charging a substantial royalty for each Packard-built Merlin engine  produced.' (Plus the Air Corps had sunk a ton of money into General Motors' Allison engine division during the war, so  the USAF required Allisons after the P-82D. 'They demanded that Allison produce a  V-1710 that could operate continuously at 90 inches of MAP and produce at least the same 1,600 hp as the Merlin, which it never did. When operated at more than 60 inches of manifold pressure, chronic backfiring, surging, and plug fouling occurred.' (The author commented that he witnessed many Allison powered F-82's coming back to land at Mines Field with sick engines.)

 

Very interesting!

 

Edited February 5, 2022 by 72modeler
added text, corrected spelling

[FinnAndersen]

22 minutes ago, 72modeler said:

look at the distance from the wing root fillet faring to the  angled panel line on the cowling in the two photos.

Who says that the wing was not moved backwards? If you look at the picture Laurent (@silberpferd) posted, the distance from the cockpit to the firewall seems the same.

 

There was also this:

 

On 03/02/2022 at 17:38, silberpferd said:

I had totally forgotten I had an incomplete F-82 parts catalog, and the engine cowlings page confirms that most of the panels for the P-82B are the same than those used on the P-51H. All the panels with the part number starting with "117" were both used on P-82B and P-51H.

 

I'd say that the nose of a P-51H and the P-82B was the same...

 

Besides, Mick found a P-82B in his stash, so you might want to hold your horses.

 

/Finn