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How accurate are the Mushroom Models aircraft plan booklets

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That's sort of like asking "how long is a piece of string?". The term "accurate" in the context of plans we modelers think of is actually a highly subjective notion (contrary to popular belief). The kind of orthographic projections we think of are generally not produced by aircraft manufacturers, or if they are, they're pretty small, low detail things used to illustrate things like operating manuals, maintenance manuals, etc. They are not usually intended to be "accurate" scale plans of the real thing.

The only way to determine if a set of plans is "accurate" is to dissect them piece by piece and compare the dimensions and shapes they contain to known dimensions (from manuals produced by the manufacturer) and photographs. Since almost no one is equipped to do that, to say this or that set of plans is definitively "accurate" is bascially hogwash.

Consider: If I were theoretically able to produce a set of four-view drawings of the Mumblypudge B.Mk.VI, where every single dimension, shape, proportion, and relationship of parts was 100% exactly to scale with the real article, but in doing it, I accidentally moved the left hand Dzus fastener on the battery access hatch 0.00003mm too far to the right, would the plans still be "accurate"? Nope, by definition, they wouldn't be. Would you notice it? Nope, but they still wouldn't be accurate. Now, if I drew the same plans, but didn't bother to actually do any scale conversions of any measurements from known dimensions, and I just "winged it", could the plans possibly be "accurate"? Nope. And then there's all the territory in between. So is any set of plans "accurate"? Ask any draftsman, and the answer you'll get 100% of the time is (or should be) "NO!". Are some better than others? Absolutely. Is there any reliable way to know which is which? Not really. Do the plans "look" like the real thing? If you study them closely and compare them to photos of the real thing, does your eye tell you something does or doesn't look right? That's the real test...

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:D, And then there are tolerances in the production of any real aeroplane, car, truck tank or wigwam for a goose's bridle so it doesn't matter how "accurate" the drawings are the real thing might not conform exactly to the specified dimensions. In a drawing an edge may have a length of say 100mm +/- 0.05mm. I once borrowed a book on the Lancaster from a mate and in it was a story of a brand new Lanc that from memory crashed on its initial service test flight killing all on board.

What happened apparently was that during a hard left turn as the aircraft was straightened up again the dinghy panel on the starboard wing about 2'6" forward of the trailing edge and about 1' outboard of the fuselage opened uncommanded and the dinghy suddenly streamed out over the trailing edge causing more drag on that side. The dinghy caught on some part of the structure of the dinghy compartment and continued to cause drag which caused the aircraft to yaw to starboard and then roll to starboard (further effect of yaw) and before the pilot could correct this the aircraft had flipped onto its back and because of a high power setting and its low altitude at the time, it plunged into the ground. The investigation found that the panel opening was caused by a build up of tolerances in both the panel itself and the surrounding structure allowing the panel to flutter during the turn thus weakening the fasteners which failed allowing the panel to open, the dinghy to stream and catch on the surrounding structure and it was all over red rover.

Was there anything wrong with the drawings in this case? No. Was there anything wrong with the dimensons of the parts of the aircraft? No. They were all found to be within tolerances. But a build up of those tolerances cost 7 young men their lives. Was anyone in particular to blame? No. Not really. That's just the imperfect world we live in.



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