North American P-51A Mustang

Accurate Miniatures 1/48 part-1

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Drawings

 Prior to the construction, I made drawings of Alison Mustang Series using a set of factory drawings and the Structural Repair Instructions manual of A-36 and P-51. I carefully read factory drawings and manual, checked photos of actual aircfart, then I translated them into my drawings.



P-51A, A-36A Sideview

  • The thrust line is 1.5" below the fuselage ref. line. The length of the spinner is 26". The front edge of the engine cowl is sta-8, thus the leading edge of the spinner is sta-34. The total length of P-51A/ A-36A is 32'2-7/8" = 386.875".

  • The radiator of P-51A is different from A-36A and former models. In the result of this difference, panel lines rearward of the wing filet and the length of the radiator flap are different. As for P-51A, the panel line is diagonal and the flap is long. On the other hand, A-36A and former models have the horizontal panel line and short flap.

  • The height of the elevator hinge is 12.42" from fuselage ref. line.

  • The nose gun of A-36A is located 12-5/16" alongside from the center line and 14-1/8" lower than thrust line. The starboard gun is located rearward.

  • There are two or three variations of the glare shield of the instrument panel. The early style (e.c. P-51) is diagonal rear edge and the late one is vertical.

  • The small parallelogram door rearward of exhaust is for gun heating system. Some aircraft don't have this door.

  • The bypass door of engine intake is in the photo of Walk Around p.27. This door is described in factory drawings as well. Restored P-51As don't have this door.

  • According to the SRI manual, there is a large circle shaped access panel and a small hole of the signal ejector on the top of the rear fuselage of A-36A and former models. And there is no square access panel on the port fuselage. This circle access panel can be confirmed in documentary photographs of A-36As. On the other hand, P-51A style square panel can be seen in the other documentary photographs of A-36A. So I think that it might be the later production model of A-36A.




P-51A, A-36A Top/Bottom view

  • Panel lines and rivet lines of the wing are drawn as projected figure on the wing reference plane. Each rib of the actual wing is orthogonal to the wing ref plane. See the figure below.

  • The 25% chord line is orthogonal to the fuselage ref. line. This line is located at sta99.

  • The cross section of the main spar is "[" shape (the left is the front). The reference line of the main spar is defined as the front face of its web. Thus panel and rivet line are located rearward of main spar ref. line. This main spar has angle of advance approx. 1 degree.

  • According to the SRI manual, there are three-color navigation lights under the radiator cowl of A-36A. But I haven't seen them in photos of actual aircraft. A restored A-36A has these lights on the lower wing tip.

  • The lower side of radiator is not included in factory drawings. So rivet lines are unknown.

  • I counted numbers of wing fuel tank panel bolts in factory drawings. Yes, I'm paranoiac. The front side is 56, outer side is 35 and rear side is 47 (corner bolt are double counted).

  • The number of stringers from sta135.5 to 190.5 is different between restored aircraft and factory drawings. Restored A/C have one more stringer. My drawing shows the former.



  • The gun camera of A-36A is located at the lower engine cowl center. On the other hand, P-51A's one is at the leading edge of port wing root.

  • The size of upper and lower dive brake is different.



P-51A, A-36A Cross Section, front view




  • The diameter of the spinner is 27-11/16". A numerical value of 13-5/32 is described in factory drawings. But this value does not mean the radius of the spinner but the radius of stepped nose cowl front edge. (The cowl front edge laps inside of the spinner end.)

  • Fuselage frames (section E to S of the drawings) are traced from factory drawings.

  • The side and upper shape of the firewall is the same as P-51B/C and D.

  • The leading edge line of the wing is shown in thin black line. This line is bent at the bulge.

  • The engine cowl side is almost straight (see section B to D). Accurate Miniature's kit is not correct.

  • The port and starboard bomb / drop-tank rack is exactly identical. This rack is attached orthogonal to the lower surface of the wing. Accurate Miniature and Tamiya B model are inaccurate.







Mustang I, P-51 side view

 Mustang I is the very first Mustang and was only used by RAF. The next model is P-51 (same as Mustang IA).



  • There are two variations of Mustang I's nose gun. The early model has bulged cowl.

  • The exhaust of Mustang I is straight type. Some Mustang I have large size fish tail type. The most of P-51 have P-51A type fish tail exhaust.

  • The small ventilation window on the port wind screen is not introduced Mustang I and P-51.




Mustang I top/bottom view

  • The engine intake duct on the upper cowl is straight type. The aileron tab rod located at the outer end.

  • The small window on the port leading edge near the wing tip is for the gun camera. The rectangle panel rearward of this window is the gun camera access door.

  • There may be a navigation light on the lower rear fuselage.




P-51 top/bottom view

  • Two 20mm wing canons are located sta82.75 and 94.3125.

  • The length and thickness of wing guns are shown in factory drawings. Each size of the inner and outer gun is different.

  • Both landing lights are shown in factory drawings as well. Wing stringers are described in factory drawings. Panel lines are in SRI manuals.

  • Some aircraft has wide engine air intake duct. (Details & Scales p.17)B

  • Tricolor lights are shown in P-51 factory drawings of radiator front flap. Thus they are described in my drawings with light blue line. But I couldn't confirm in photo of P-51. At least, I can confirm that RAF Mustang Is don't have these light.




P-51B cross section

  • Factory drawings contain contour figures of B model nose cowl. So I made B model cross section drawings by tracing them.

  • The thin line in section A shows the leading edge.




Kit review

 Accurate miniature's Alison Mustang is basically good. Especially, the shape of its rear fuselage is accurate. However, there are a few minor mistakes. See the following figure. The engine cowl and wind screen are not so correct. The diameter of the spinner is small and the cowl is slim. The cross section shape of the cowl is a little roundish. The front window of the wind screen is wide and the angle is a little shallow. The vertical fin is tall. See following figure. Red lines show the kit (minor differences of panel lines are not described). Blue lines are actual aircraft.


Construction


The spinner

 The first step was the aluminum lathe work. I bought an aluminum cone. A 2mm (0.08") brass rod was inserted into the center of the cone. The cone was turned by hand router and was grinded with a metal file. It took almost three hours to be the spinner shape. Finally, the surface was roughly polished with sand paper. The latter half of the spinner was made of resin block. The kit spinner is a little small. So the shape was adjusted to my drawings.







The nose

 The kit nose cowl is not accurate. Its shape was corrected according to my drawings. The kit side shape of the cowl and spinner is thin. And the air intake is high. Then the total height is not so wrong. Another important point is the lower outline of the cowl. The actual aircraft has straight line leading to the wing, and this line is parallel to the thrust line. On the other hand, the kit line is not strait but curves upward.



The kit cross section shape is roundish. The upper air intake was cut off.
The bulkhead was cut out from 0.5mm (.02") plastic sheet.

The kit nose cowl was cut at panel lines. Each piece was bent to correct shape and glued on the bulkhead.
The bent portion changed whitish. Bulkheads have a role of reinforcement. They keep the shape rigidly.

The outer surface was sanded to the correct shape. The air intake was rejoined.
Plastic sheet was glued on the inside for reinforcement. Mortise joints were installed. They kept left and right fuselage position at the time of sanding.



The cockpit

 At first, the rear quarter window was glued on the fuselage with CA glue and the surface was sanded to flat. The cockpit side wall was Aires's resin for P-51B. The upper edge of the resin part was thick. So the upper portion was cut and replaced with kit inner parts.



Kit cockpit parts.
Aires resin parts.

They were glued on the fuselage inside.
The cockpit was painted and weathered.

The seat and bullet proof plate were from Aires. The floor (to be exact, the upper wing surface) was from the kit.
The left two parts are kit parts. The right is Aires.



The wing

 The gear bay was from Aires's resin for B model as well. But, this resin parts was not fit to the Accurate Miniature's wing. The gear bay was smaller than the kit opening.



The front side wall and ribs were deleted in order to fit the kit wing.
The carbon fiber rods were glued for reinforcement.

The upper parts were glued with care for wing specs. The dihedral is 5(wing ref.line) or 6.2(lower surface). The incidence is 1.05 (root) and -0.85(tip).
The leading edge of the wing bulge is droop down. So, the bulge looks small in the front lower view.


The leading edge line is bent at the bulge in front view. The kit wing is insufficient regarding this bent.


The fuselage



The propeller axis was held with two pieces of plastic sheet. These were glued slowly with liquid cement. This method enables exact positioning of the axis.
The corner of the lower fuselage was too squarish (blue arrow). So the edge was sanded to be roundish. The shape of radiator outlet side end was corrected (red arrow).

The nose correction works had been insufficient. Plastic sheet (gray portion) and CA glue with plastic powder (white portion) were put on.
The side view was checked. See the straight line of the lower side.

The fitting of the wing and filet was adjusted with CA glue and plastic powder.
The overall shape appeared. The fin tip was cut by 2mm (.08").



Engraving panel line

 Panel lines were engraved with photo etching saw. Templates were cut with a household use cutting machine. Cutting data were already made as drawings.



Cutting sheet was used as template.



Wing assembly



Ribs of the gear bay were made of plastic sheet.
The wheel door was glued.

I couldn't satisfy the position of the wing. I found that the kit wing position was a little low.
Then the wing position was raised by 0.5mm (.02"). The gap between the filet and wing was filled with CA glue and plastic powder.



The horizontal fin

 The kit horizontal fin is not accurate in top view. The sweepback of the leading edge is shallow. Also the elevator is thin. The actual elevator is thicker than the stab end. So I use Tamiya kit. The Tamiya is almost perfect but the front corner of the tip is a little squarish.



The left is Tamiya, the right is Accurate Miniature.
The joint line was adjusted with plastic sheet (gray).



The wind screen

 The kit wind screen is not correct. The kit front window is too wide. So it was to be replaced with heat formed clear plastic sheet. Please see my P-51A cross section drawings. There are flat layouts of windows drawn with blue-green lines. Thin strait lines show that the window surface is strait along these lines. These lines are drawn in North American factory drawings.



Then I made wooden mold of chemical wood.
This is the kit wind screen. The silver sheet is correct shape of the window. See the kit window side frame located outward.


The demarcation line of the kit wind screen and fuselage is just the edge of window glass. So the glue line might be seen through the clear window. In order to prevent from such situation, the glue line of the fuselage was cut by 1mm (.04").



This is the kit fuselage glue line. The pencil marked portion is to be cut.
The glue portion was cut.


Tamiya 0.4mm (.02") Plaban (clear plastic sheet) was cut as 20 x 20cm (8 x 8"). Sheet was held by hands with thick heatproof gloves and was heated over a small flame of the kitchen stove. Melted clear plastic shrinks and thickens. Then press it on the wooden mold. Cut out and sand the inside and outside surfaces.



The wood mold is fixed on a wood rod.
The heat formed wind screen was sanded together with kit center canopy portion.

Template for the wind screen was cut by cutting machine.
Window frames were engraved with a custom made double needle.



The instrument panel

 The Accurate Miniature's instrument panel is not so accurate. So I chose Aires one for B model. The actual panel of A model and B model were not so different.



The left is Aires, the center is Accurate, the right is Tamiya.
The left is Aires, the right is Accurate. Aires's resin portion had shrunk so I had to trim the photo etch panel.



Aluminum works

 Aluminum sheet was glued on natural metal portions of the wing tip and fin tip. The surface of the plastic part was cut down with a chisel. 0.3mm(.01" for the wing tip) and 0.2mm(.008" for the fin tip) aluminum sheet were annealed, formed, cut and trimmed. Next, each aluminum piece was glued on the wing and fin tip with epoxy glue. Then the aluminum surface was sanded and polished. Further information of aluminum works is described on my F-86F article.



The plastic surface of the fin tip was peeled off by 0.3mm (.01").
0.2mm (.008") thick aluminum sheet was anealed, formed, trimmed and glued with epoxy glue.


The top view shape of the kit wing tip was corrected before aluminum works. The front curve was to be roundish. Then 0.3mm (.01") aluminum sheet was applied.



This is the original kit wing before correction.
Here is the starboard upper wing. The aluminum portion was cut down. Aluminum sheet was formed. Small holes were for eduction of excess glue.

Here is the port lower wing. The edge of upper side aluminum sheet can be seen.
Lower aluminum sheet was glued.

The surface was sanded with #600 to #1000 grit sand paper.
Aluminum works were finished.





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