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KevinCG

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

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G'day Guys,

Been interstate past few days and a quick post before off again.

Before I start many thanks to all for the compliments.

 

Tail plane.

 Another minor saga. I initially made one that was from vacformed plastic over a wooden pattern in order to save weight to reduce counterweight required. Unfortunately this approach failed as when doing the skinning the underlying surface did not have enough support and hence a very uneven rivet, fastener pattern resulted so to junk heap!

The second attempt was from two solid pieces of 2mm card sanded to correct profile. Fortunately it is a constant chord structure.

The first pic shows the inside of the upper and lower components. The grooves that have been routed out will be for brass tube to ensure a square structure on either side of fins when viewed from above and head on.

iY0x49p.jpg?2

 

The second picture shows the structure prior to skinning.

ww3HryF.jpg?2

This will be done once the booms have been attached to the wing and the structure trial fitted in place. Once the tailplane/empennage has been fitted it will be skinned prior to final assembly.

 

There has been and will continue to be a lot of trial assembly and disassembly in this model to ensure component alignment.

 

Next post will cover detailing the booms. and whee wells - my least favourute activity.

 

Once again thanks for looking

Kevin 

Edited by KevinCG

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Two pieces. Brilliant! I think I may do my Bearcat wings in two pieces and take advantage of easy access to the internals. Thanks for posting, again. It's like Alcorn's book in action! 

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Two pieces. Brilliant! I think I may do my Bearcat wings in two pieces and take advantage of easy access to the internals. Thanks for posting, again. It's like Alcorn's book in action!

 

Thanks Jim for your kind words. Its a pity I didn't take more photos during the buildib gbpgases to date. I always forget until after inhave completed the piece.

Cheers

Kevin

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G'Day Again Everyone from a lovely late spring day in Tassie

 

Main Wheel Wells

This is my least favourite part of modelling heaps of detail and no-one ever sees it. Unfortunately the P-38 seems to have an U/C that is unbelievably complicated and a helluva lot of detail as well as a multi-level upper surface that is variously part of the main spar, the base of the turbochargers and the upper skin the booms.

The wells were boxed in with 2mm card over which was laid an embossed skin of 0.05mm card. As the wheel wells are painted I saw no need to use litho plate.

the following pic shows the wells at this stage.

rEmPIak.jpg

 

Then the fun began!

I will cover the U?C separately as it is a topic in itself. However the location holes for the drag struts, main gear and forward struts all needed to be accurately marked out and drilled at this stage, using a jig i illustrated earlier.

The gap between the wheel well wall and the external skin was filled with epoxy filler to provide some additional weight to help prevent tail sitting. It also provided a substrate for locating screws using the technique described below.

For this purpose holes were drilled in the wing surface, as shown in an earlier photo and repeated below;

NrybH3l.jpg

 

Screws were then placed in these holes and then liberally coated in vaseline. Using another jig the booms were located in their correct positions, the gap between the wheel well walls and the outer skin filled with slow setting epoxy, cling wrap was attached to the under surface of the wing and the whole upper wing structure lowered into its correct position on the booms. This was allowed to sit for 24hr to cure and then the screws removed and - presto we now have an accurate and reproducible way of attaching and removing the wing for the rest of construction.

The detailing of the wheel well could now proceed.

This was performed with brass rods, aluminium bits and of course various items of plastic card, tube etc.

The next photo shows the rear of the wheel well 

9XBoUTZ.jpg

 

Whilst the one below is of the forward portion

BZu0rLe.jpg

 

The photo also reveals a considerable amount of the undercarriage detail that needed to be placed into the well. These portions could be included at this stage as they do not protrude below the booms so are in no danger of being knocked off.

Also visible in the pictures are the turbocharger intake, various electrical lines, piping and the pulleys for the undercarriage actuating lines and inspection hatches, made  from lithoplate over a male pattern.

I am not sure if i have explained this very well but i hope it is understandable.

Again thanks for looking 

Kevin

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excellent work, P-38 Main gear bays are a nightmare of pipes, cables, wiring, pulleys etc

Never was a truer word said Shawn and I hope the pic below tries shows some of this complexity in its entirety although the cabling will not be added until the undercarriage is installed. The whole construction took about 8-12 mths for both main wheel wells.

 

gjndh9L.jpg

The round hole about 1/3 distance from firewall on the outside of the boom is the metal tube into which the undercarriage fulcrum will fit. These were drilled out using the jig mentioned earlier and a metal tube inserted for strength..

Undercarriage.

This was made from metal as the finished model will be rather heavy due to the amount of lead which is required to prevent a tail sitter.

I can only speculate upon why it was necessary to make the undercarriage so complex but i confess it took hours of looking at photos and diagrams to work out how all the various struts etc were connected and worked.

The following diagram from the maintenance manual may give some sense as to this problem.

NQrOPI7.jpg?1

 

The rest of the bracing and struts were pre-affixed into the wheel well as described earlier and can be seen in the pics above. To make the nuts i used brass pins which were then made into hexagonal nuts using an indexing head to create the six sided nuts from the circular pin head.

 

The main issue of difficulty was creating the main undercarriage fulcrum which was a machined piece of steel that was both tapered and of rectangular section.  Recognizing that fitting the u/c would require some jostling into position and that I will not want it fully extended until the model is complete, it was necessary to make all the parts able to be able to be pivoted as on the real thing - talk about making a rod for ones back!

To make the fulcrum i constructed the out piece from rectangular tube stock which was then slit to produce a taper. Into this was inserted a piece of brass tube that will locate the whole assembly into brass inserts that 

The complete set of part in various forms of assembly is shown below. 

lUVJncu.jpg?1

 

Pins are used to hold pieces together until final assembly.

One item which was invaluable in this exercise was paintable solder. This material can be painted upon brass and copper and when heat is applied it fluxes and creates a solid and very neat joint. It comes in a range of heat sensitive grades. Makes soldering much neater and i wish i had found about about this stuff years ago.

 

Other pieces were largely fashioned out of brass stock, the torque arms being made from I-Beam which was slotted to induce the taper and then had the central area filed out at either end in order to create the pieces into which the bolts (pins) were inserted as shown.

The top piece is the cover which is attached at the back of the wheel well for covering the actuating mechanisms. It fell off and needs to be re-attached. The strengthening horizontal indentations were made by first making a plastic card female piece into which were cut the slots for forming the final lithoplate structure the was formed around the card pattern.

 

To make sure that the aircraft would sit level and square the undercarriage was fitted onto the trial assembled aircraft using the screws mentioned earlier. The painstaking work of building jigs and continual trial fitting of components etc paid off and the model sat correctly -  a relief I can say.

 

Once again thanks for looking and the nice comments

Kevin

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Lovely work going on here Kev! I haven't yet had the chance but I'm going to have to go back and having a look at the Alcorn Books again. I like your oldschool methods and clearly a lot is going on in the back ground. I'd never heard of paintable solder until I just read your post.... Interesting! Going to have to look it up.

 

I also only just realised you were from Penguin.... cute little place. I passed through last Christmas :)

 

Cheers,

 

Craig

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G'day Again guys,

Thanks for the comments guys.Amazing to learn that you had passed through Penguin brahman 104. Actually we are not in Penguin itself but just put of town. Agree though it is a quaint little place and long may it remain so.

Skinning

I like to skin my models and use two materials. If the model is to be painted I prefer to use clear plastic sheet heat formed over the various components and then cut to size. Peter Cooke used this method on his patterns and describes it in the Book 'Scratchbuilt'. This produces a beautiful surface on which to apply paint.

However I wanted my lightning to be natural metal finish and then the only recourse is lithoplate. The lightning is an elegant design which is enhanced when in metal finish.

Whilst i admire the beautiful finishes that many modellers achieve on this forum and elsewhere with Alclad and similar p[roducts, to my mind it still does not get quite the right patina and dare I say it looks too perfect for the hand built aircraft of the 1940s.

The most difficult areas to skin on the lightning were the intakes on the booms as the leading edges of each were single pressings on the original. These were then made first as of I could not get this right then there was little point doing the rest of the model

To enable this to be done without breaking the delicate areas on the model i cast some epoxy patterns which i could then employ as male moulds around which to shape the lithoplate.

 

These patterns are shown below

9epwIAa.jpg?1

 

These then meant that the necessary force for shaping metal could be applied without damaging the model.

The rest was then just patience, annealing, a bit of shaping, more annealing etc. Each piece took about 1/2hr to make and there were several that did not make it.

In making the centre orifice it is important when cutting the lithoplate not to have any corners but have all holes etc with rounded corners. If this is not done the plate will invariably tear and ruin the piece.

After a few hours I had the pieces shaped and was particularly pleased to have the entire front piece of the radiators including the two vertical dividers as a single (albeit fragile) piece..

The following two photos show the end result and i was reasonably happy with the final result. Consequently we could now get on with the rest of the skinning which whilst tricky was a piece of cake compared with making these components.

 

RlMjCML.jpg?1

 

XZfzYjs.jpg?1

 

Once again thanks for looking.

Kevin

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Wow!  I love the imperfection of your perfect aluminum pieces!

 

How is litho plate different from plain sheet aluminum?

 

Gaz

Edited by Gazzas

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Thanks Gazzas

As far as i am aware lithoplate is an Al alloy albeit mostly Al (99%). It is also grained so its surface is very uniform. It is also very thin (approx 7 thou or 0.12mm) and cheap. I get mine from local printers who have been happy to give it away from their recycling bins.

The finish will be polished so that it looks beter than in the pics, nonetheless it will have small imperfections in it as the anealing process makes it quite soft. It also needs protecting once on the model to prevent damage during the rest of construction.

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