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KevinCG

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

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G'day again Large scalers,

Its been a reasonable interval since my last post. This does not reflect a lack of time at the bench but rather the complex bast that is scratchbuilding. If you ever hear anyone suggest that they should build a large scale P-38 and then skin in it in Al sheet, suggest that they should perhaps have a clinical test for madness! Not only is it complex but 2x so because of the twin booms.

Anyway on with the build.

This post covers the fairings between the wings and booms and the supercharger intakes.

This took many hours to do not only because of the complex shapes but also in scouring hundreds of photos and drawings in order to ascertain the correct layout of the skins.This was particularly difficult for the inner fairings as there were very few pics available and certainly nothing of any accuracy from drawings.

As it transpired they were comprised of many pieces of which the tiny trailing edge fairing at the boom/wing joint was th emost difficult. For each of these 4 pieces I probably made 5-6 to get the correct one, and this despite multiple annealing to shape the piece.

The following pic shows this YPFsXbp.jpg

The gap that is not skinned will be completed once the u/c is fitted.

This has been omitted at this stage for ease of handling.

There is still the panel beneath the engine to add- the area under the green padded tape. Again this has been omitted until after the u/c has been added, to prevent damage.

ztNhZAO.jpg

 

Once these fairings were completed it was on to the supercharger intakes.

To make these a plastic pattern was made from formers and epoxy putty. Once shaped this pattern was used to cast a mould. Th efinal pieces were then vast in epoxy resin. The rationale here was that an epoxy component would be stronger than plastic when it came to forming the metal skin.

S6ZKb45.jpg

 

The picture shows the component and the skin shell that was shaped over the epoxy piece. Th epic below shows the reverse side. The dark colour of the al is from the annealing process

 

 

c7OI206.jpg

 

The actual intakes were comprised of 4 skin elements; upper, lower, front rim and inside fairing.

The rim was turned from Al tube.

To make the elliptical fairings that sit between the intake and booms another pattern had to be made. This was then glued to the original fuselage master and Al sheet shaped accordingly.

The next pic should illustrate what I am trying to convey.

G0wEHOt.jpg

 

Th efinal result for the two intakes is shown next.

nKx6wst.jpg

 

I must apologise for the camera work. I only have an iphone so the depth of field etc is not the best.

I hope however that the gist of what I'm trying to convey is reasonably clear. If not please ask.

 

My next post will cover the top of the booms and the fitting of suprechargers and the various vents inlets etc.

 

Until then all the best

Kevin

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Kevin,

   That is an epic you're doing.  I admire your progress.and your ability to shape those complex pieces.

 

Gaz

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Wonderful stuff, just seen it for the first time. I shall soak it all up like a sponge.

I have a modest F-E5/XP-38 build going on over at BritModeller and I expect to pick up more than a few tips from you.

Also, thanks for mentioning the Alcorn book. It's now on the list.

Cheers

 

Dennis

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Thanks very much to all those who posted it is much appreciated.

This post as promised will cover the rear empennage.

As those who have followed this post will know both fins broke off the model due to my clumsiness and the fact that they have a thin and hence frail attachment to the booms. The boom at attachment is less than 10mm deep and the fins and tailplane are both only 4mm thick at their thickest point.

 Consequently when I dropped the model at one stage they both broke off. The result being inevitable especially considering the weight of lead inside the nacelles to prevent it being a tail sitter.

This necessitated constructing new fins and tailplane that would withstand my hamfistedness when at the desk ie accidental knocks etc.

 

To do this I constructed the tailplane in two halves split horizontally and with brass tube inserted to provide horizontal strength but also into which a vertical piece could be inserted so that the fins would be both vertical and also rigid enough to with stand the odd knock.

The top and bottom halves of the tailplane were affixed together using double sided sellotape and sanded to the correct aerofoil shape. A span wise channel was cut into which the brass tube was inserted to provide rigidity and also an attachment for the square tube shown in the following pic. This tube will act as the key attachment point for both the booms and also the fins

Hopefully the pic that shows the tailplane and the brass square tube into which the vertical piece will be inserted and also how this same tube serves as the attachment into the booms.

 

BQvvPcJ.jpg?1

 

 

The next pic hopefully conveys what I mean. It shows a similar slot for a vertical tube in the fins.

The tricky bit is that all this has to be built so that it can be attached to the model after I have plated the fins and tailplane and added rivet fastener detail etc. It being very difficult to do this on the aircraft once assembled. I also have to leave the space for the fairings around the fins once it is fixed in place. Further more it also has to fit prefectly so that the empennage is both correct in the horizontal and vertical plane.

OibRun6.jpg?1

 

Note also the annoying lockheed trailing edge which requires a thin piece of metal sheet onto which the skins are attached. On the real aircraft the skins were riveted onto this peice.

 

The fins were made in the same manner as the tailplane being composites of layered styrene shaped to the correct aerofoil.

Both the fins and tailplane were covered in lithoplate and to shape the leading edge piece for the fins a blank was made that would be able to withstand some strenuous pressure as it has quite a difficult compound curve. Several 'annealings' were required to get the piece correct.

The next pic shows the blank and the fin element.

uOjUZ9O.jpg?2

 

The slot for the fin to fit over the leading part of the tailplane can also be seen. The entire tailplane and fin were plated except the area with the arrow on it which will be attached once the fin and tailplane are in place on the model.

This was a somewhat tedious task as each fin has 25 individual panels and took approximately 6 hours to skin. I'm not sorry its finished especially as I had already done this once before!!

It is unfortunately true that for scratchbuilders such as myself we only have one completed model to show for our efforts as generally speaking with the number of parts constructed that don't quite live up to expectations we have probably constructed the equivalent of 2-3 models by the time we are finished.

The next picture shows the pieces skinned and polished ready for detailing. The pre-cut panels for attaching after assembly to the booms are also illustrated.

mVvwsKX.jpg?2

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oh boy that is beautiful..

 

 

great recovery too - it can sap energy redoing things, but I generally find my second try is always better than my first - I guess because you learn things first time around & put them into practice when you do it again..

 

this is building up to be one stunning model :)

Peter

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On 9/1/2018 at 8:50 PM, airscale said:

oh boy that is beautiful..

 

 

great recovery too - it can sap energy redoing things, but I generally find my second try is always better than my first - I guess because you learn things first time around & put them into practice when you do it again..

 

this is building up to be one stunning model :)

Peter

Thanks very much  Peter,  your efforts aren't too shabby either:)

 

Time for another update.

The previous post showed the plan behind re-attaching the fins and tailplane in order to obtain a strong joint. I am happy to report it worked.

One of the advantages of using metal is that it is possible to get good fits and handling does not erode initial slots and gaps as can happen with plastic.

The tailplane was first attached as per the post above and then after many checks that they were vertical the fins were permanently fixed in place the slots filled in with epoxy putty and the last panel which had been pre-cut affixed into place.  

The next task was to fit the fairings around the fins. This was another task to which I was not particularly enthused. I had made spare vacformed fuselages so cut pieces off the end and used these to fit around the fin and tailplane as per white inserts in the picture below. These were done in two parts, upper and lower.

 

a0ApscD.jpg?1

 

Once glued in place they were faired in with epoxy putty and primer taking care to mask off the previously applied lithoplate.

For this task i got out my trusty lazy susan. This was a product I bought from an Aldi special buy some years ago. I think it cost about $12.  it is glass so I then made a silicon rubber 'plate' that sits on top which stops models from sliding about and also protects their finish. It greatly aids modelling when painting and also where one has to continually move the model about to obtain different orientations in order to get the best access.

 

0KyGq90.jpg

 

The next step was to make the lithoplate fairing that covers these. Fortunately on the real aircraft they are in four pieces.

these were shaped over the plastic using annealed lithoplate. The initial shape was derived from sticking masking tape onto the model and then drawing on masking tape around the existing outline of the lithoplate already attached to the model.

DnSGsEp.jpg?1

 

Although a complex shape the method of using tape to provide the initial two dimensional cut on lithoplate worked well. Nonetheless each piece took about 1hr on average to fit accurately. The beauty of it was that as the piece fitted snugly it was relatively easy to ensure it fitted correctly in place when it came to gluing. lucky as one mistake meant starting all over again. I only had to do this once fortunately.

 

oRBvTcs.jpg?1

 

Once in place they looked like rather smart if I may so myself.

wNvcTMj.jpg?1

 

The slightly larger gap between this fairing element and the other one on the boom is intentional as this was also the case on the original due to changes made to empennage incidence after the first set of jigs were made. This was to help avoid issues relating to compressibility and pulling out of high speed dives.

 

On the same note the mass balances were also made using Aluminium rod. The mass weights were turned up on a lathe

pzSFnr4.jpg?1

 

The support strut was also filed out of rod and the pieces assembled as per below. For strength a 0.7mm hole was drilled into both the mass weight and end of the strut into which brass rod was inserted ensuring that the weight and strut remain united.

lV7Iir1.jpg?1

 

These will be attached once the model is almost finished. I don't want to push my luck too much with the attachment rods!

 

The next step will be inserting approximately 2-300 rivets around the empennage/boom join as per the actual aircraft and then joy oh joy I can move onto the fuselage pod.

Thank you for looking.

 

Cheers

kevin

 

Edited by KevinCG

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Awesome Job you are doing on this Kevin!

There's some very talented people on this site!

You must be retired Kevin, to put in the hours here... no way you have a job and do this?

Pip

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