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New 1/72 Airfix Typhoon


Johnson

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I'm familiar with the later builds, where we were talking about gaps 20-30thou on smaller parts fitting to larger ones.  It was certainly acknowledged that non-interchangeable parts came without holes for fasteners predrilled because variation meant that pre-drilled holes in different parts wouldn't align.  Interchangeable parts were required to be exact, but were also in a minority.   Some of the single metal skins on a Spitfire run for a considerable length - for example the fairing over wing fillet or indeed sections of the upper wing skin, or rear fuselage.  Fuselage longerons?  Or indeed a wing spar, which was a very complicated structure which ran for a almost the semi-span.   I think you'd have problems fitting such parts if there hadn't been a high consistency of standards.  The production lines were not filled with skilled fitters.  

 

As for the variation in a fuselage length when made in a jig, these jigs are serious metal constructions set in concrete.  Not that this avoids all problems - we did have trouble when trying to set up production of one jig at Warton in a hangar by the estuary.  The solid concrete 1944 floor was moving with the tides.  But expansion in summer vs winter?  No.

 

If you wanted - as you did - a smooth wing skin, very smooth at the leading edge, then you couldn't have wing ribs that were coming out in different sizes, or picking up at different points along the wing.

 

This was a lesson learnt by RR when they approached the motor industry to set up the shadow factories.   They were told that the motor companies couldn't build engines to RR drawings because of the tolerances.  Too tight?  No - too loose.  Prewar the aircraft industry dealt with such small numbers that skilled fitters were employed to fettle individual parts to fit and each engine was bespoke - for wartime production runs such people didn't exist in the required numbers and the process would have been too slow anyway.

 

As for something like 2 inches on a modern metal aircraft - would that be a Cherokee or a B747?  I think that I'd like to see that in context, and if the context is after something that has caused you to wonder if it is bent, then I don't think that it is appropriate for build standards of a high performance fighter.

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1 hour ago, Graham Boak said:

As for something like 2 inches on a modern metal aircraft - would that be a Cherokee or a B747?  I think that I'd like to see that in context, and if the context is after something that has caused you to wonder if it is bent, then I don't think that it is appropriate for build standards of a high performance fighter. 

 

Confession time:  I was thinking of the comparison from port to starboard, which I now realize does not directly relate to aircraft dimensional specifics.  But I looked at the Hurricane Manual and it was, indeed, 2 inches.  The text also said that this wasn't a hard-and-fast limit, but gave the rather obvious advice that if it's more than this you might want to look at the structure as a whole and figure out why!  The Typhoon is also 2 inches, with similar text to Hurri but without the proviso I elaborated on above.  The Spitfire gives 1 inch for these diagonals (wingtip to nose or tail).

 

My point remains that even with a rather extreme amount of variance from a short (not "Short") Spitfire to a long one, when we scale it down it becomes a rather miniscule potential difference.  And I heartily agree with Graham about the jigs.

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I've no argument about a 2 inch stretch overall not being anything to be concerned about in model scale.  Should it appear locally over what is a short distance anyway...clearly another matter.

 

The measurement is wingtip to tailplane tip?  Interesting.   I was just thinking about dihedral boards, that it wouldn't take more than a very small change in the position of a wing to throw out the very precise angles these were built to.

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I'd suggest that worrying that even a 1/72 kit is 1/2mm to 1mm, even 2mm too short is largely entirely redundant and verging on the ridiculous, for the simple fact that 99.99% of even knowledgeable observers will probably not discern such small discrepancies, and unless you are an almost flawless modeller, those with such eagle eyes will no doubt be drawn to flaws in build quality far more than such infinitesimal inaccuracies of scale.

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One little issue I've noticed with the Airfix kit is that the shape of the gun bay hatches is slightly off. The front set of panels should be rectangular, but they're not. The panel line between the front and rear set of hatches can be filled and rescribed to correct this though. A bit nit-picky I know...

 

Justin

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On ‎4‎/‎26‎/‎2019 at 2:47 PM, gingerbob said:

Well, I remember on those diagrams about checking the rigging (on a "modern" metal airplane, that basically means "see if it is bent or not") that it usually says something on the order of "maximum variation 2 inches"- that's from wingtip to tail, for example, so a longer distance than fuselage front-to-back.  2 inches in 1/72 is .028, or about .7 mm.  I don't think that's an "error" that I'd be worrying over, nor is it a variance that would allow me, in good conscience, to shrug and say, "Well, you know, aircraft can vary one from another..."

 

Is that "allowable" variation against aircraft dimensions or between port and starboard measurements of the same aircraft to identify whether it is bent or not?

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