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KevinCG

1/24 Scratchbuilt P-38L A retrospective to the present

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Kevin, I see your section in the Alcorn book, a text I've been taking to bedtime reading most nights this year as I learn the methods and stories of the masters. Those are fantastic models.  I certainly respect the Corsair P&W engine work having faced this challenge myself. I hope you enjoy showing your work and building with us here. I find it very motivating to build in a community. 

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G'day again,

The saga rolls on.

Having made several copies of the boom (in case I muck some up and a practice that I have learnt from past experience). It was on to the various appendages that adorn said booms. It was at this point that I began to appreciate what I had let myself in for. It is a truism that although the results of a scratchbuilt project usually result in only one model the amount of reworking etc means that by the time it is finished one has for all practical purposes built several!

The P-38 has several intakes on the booms and of course the fins. Usually I have made the fin as part of the original fuselage pattern. The reason i did not do so are somewhat lost in the mists of time but I think it was due to a desire to get a perfect cruciform between the fin and horizontal stabiliser. There are a lot of angles to line up on a P-38 and a mistake in any will render a rather sad looking object.

I made patterns of the fins and vacformed then only to decide a solid one would be better.

there were also patterns for the intakes on either side of the booms and the supercharger intake. The latter was made from card and epoxy and then cast in resin to produce the final result.

The photo shows the various components.

I did not mould the boom intakes on the booms as the curves at where it attaches to the boom are subtle and a vacform in 1mm card would have lost this subtlety.

nLKd3CL.jpg?1

 

The wooden pattern with no piece beside it was for the internal ducts of the radiators and the shape could be made by heating small pieces of card over a candle and pulling to shape. It was necessary to make a pattern and do this as it is a compound curve curving in both the horizontal and vertical plane. - Gotta love this hobby!

What I have not shown is that initially made a set of radiators that were split horizontally but cutting out the slot in which to fit them weakened the vacform shell of the boom to the point that it broke - first of many  many expletives and see note above about making spare copies.

It also became clear at this stage that a jig was going to be required. The first of several jigs was constructed and will be covered next post.

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G'day 

Many thanks for the compliments from everyone

In this post I want to briefly cover the stage of beginning to add detail to the vacform components. It was also about now that I realised how complex this model was to become. Previous projects had started from the "ground-up" adding pieces to the model as they were built. The size and difficulty of access to many parts of a partially assembled model meant that components would need to be fitted and then removed again to enable easier construction. As an example I could only envisage many trouble and frustration in trying to work on the inside of a boom with the other one in the way. Damage also seemed a likely result.

Thus it was inevitable that i would need a jig(s). As mentioned earlier so far I have constructed 4. I hope that will be all that I need.

 

After gluing the two vacformed boom halves together it was time to get serious.

The key reference for this model apart from the datum line was the main spar to which the booms and fuselage are attached. I thus built 2 jigs to enable me to work on the booms and ensure the undercarriage locations were the same on both sides of each boom and also the same on each boom.

Had I looked at the complexity of the undercarriage in more detail before I started i may not have! 

The picture below shows a small segment of the many pieces that go into making up the main undercarriage. It only gets worse when you see more.

PKnGciQ.jpg

 

I confess it took me hours of studying countless photos plus the manuals to work out how all the pieces fit together. However I digress.

In order to ensure that this mass of components was the same I built these two jigs. One for working on the booms inverted as below

Bd2O3Cx.jpg?1

 

The metal tube slides through the plastic tube and through the same diameter square plastic tube attached to the former that will attach to the wing main spar. This jig held the boom upside down and vertical and enabled the accurate detailing of the wheel wells and the correct alignment of the front radiator intake segments. I found this jig indispensable.

A second jig was also constructed to enable the booms to be worked on for the upper portion and again this was held in place by the holes drilled for the main pivot points for the undercarriage.

aClgiwu.jpg?1

 

The boom in this instance was also fixed at the front with a screw into the centre of the circular backplate for the spinner.

sPtOv5P.jpg?1

 

I trust i have not made this too confusing???!!!

 

At this point it was clear that I needed the wing to be constructed before I went any further to ensure i was not getting ahead of myself.

I will leave this to another post.

Thanks for looking

Cheers

kevin

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G'ady Guys,

Making the wing

To my mind the most important part of model making is capturing the character of the original. The wing is an important aspect of this process.

For the P-38 I first obtained a dead flat piece of board on which to mark out wing stations/ribs main and rear spar and other key attachment points such as the boom centrelines and fuselage.

On a P-38 the wing is comprised of a centre section and an outboard section attached on the outside of the booms. There is a central carry through box going through the booms and to which the booms are attached.

This is shown in the following pic from the Erection and Maintenance Manual.

4vBeMUU.jpg

I elected to make the wing as a single structure for strength but allowing for the boom cutouts.

 

The first stage was to make the wing out with location of spars, wing ribs, and centre line of booms etc.

 

Unfortunately i have no pics of this however the remains can be seen on the white board underneath the alignment jig in the photo below.

I3Ifdx0.jpg?1

 

I then cut out a plan form of the port and starboard wing from plastic card and marked this out as per the wing plan form on the base board.

The next stage was making a main and rear spar. The rear spar is shown in the above diagram. These were cut from 2mm plastic card and then cut into an upper and lower spar  pieces (allowing for thickness of the wing plan form) and glued perpendicular to the wing plan form.

This created a single wing as shown

l64Y3nu.jpg?1

 

 

The space for the boom attachment was then cutout.

Although a considerable amount of work is shown in this picture it reveals the boom cutout in the wing

NrybH3l.jpg

A very distinctive feature of the P-38 is the upsweep at the wing tips combined with its washout. This has to be replicated to get the characteristic sit of the aircraft. 

The wing ribs were cut from 1mm card and split through the wing datum. The ribs were attached to the port and starboard halves with wing affixed to the base board.

This ensued that the washout was captured. This is difficult to describe but hopefully can be seen in the following images.

PEM5zUW.jpg?1

 

 VN720Qz.jpg?1

 

Thanks for looking

Kevin

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The Wings (Continued)

However first a reply.

Thanks for the positive comments guys Its a pity this work was done before i thought of posting so photos are somewhat limited

 

Just awesome! Has Rutman seen this?

Thanks for the compliment but this is the the first time i have aired any of this so the answer would be no unless he is looking at this forum.

 

Last post covered getting the wing ready for covering. The rest was fairly straightforward until it came to the trailing edge.

The main part of the wing was skinned in 1mm plasticard except for the wingtips which were solid pieces sanded to shape and the leading edges. These were filled with epoxy as per fuselage pattern and sanded to shape.

The problem with the trailing edge is the Lockheed construction in which the upper and lower wing skins are fixed to t a metal insert as shown in the photo below

ugBRp0e.jpg

 

This insert is on the wings outboard of the flaps, the tailplane and the fins.  Note also on the pic above how the upper wingtip skin overlaps the lower.

Unfortunately lithoplate was too soft for this and would have been too easily damaged so a thin metal insert was made from tin sheet as per the photo below.

This seemed to work well and so far has been stiff enough to survive the constant handling.

Where the fin and wing tips were solid the gap on the inner part of the wing had a thin sheet of 0.125mm card inserted so as to keep wing contour. Thus the fin and wing tips were a 3 piece lamination sanded to shape and the tin trailing edge inserted after sanding to shape had been completed.

TuoAJ3G.jpg?1

The picture shows this on the tailplane before final cleaning up.

Ailerons, rudders and elevators were marked out but not removed as on the real aircraft they were a tight fit and connected to their respective components by piano hinges. This will be covered in more detail once I get to the skinning stage.

 

This  completes the basic wing structure and the fun can really start.

Cheers

and thanks for looking 

Kevin

Edited by KevinCG

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