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Old school incidence measuring?

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Old 10-05-2012, 10:11 AM
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vertical grimmace
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Default Old school incidence measuring?

I was wondering what tools they used back in WW1 to measure incidence when rigging/assembling these aircraft in the field? If you look at a Fokker DVII, there is a datum line painted on the side of the fuse. Also, the wings have angle numbers at various rib locations.
I am just curious if they had a specific tool for completing this task.
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Old 10-05-2012, 10:16 AM
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Default RE: Old school incidence measuring?

I'd expect that a spirit level would do the job... Combined with a couple of straight lengths of timber, some string and a tiny bit of ingenuity. And the Mark One eyeball.
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Old 10-05-2012, 11:30 AM
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Default RE: Old school incidence measuring?

I think you will find that they were a little more sophisticated than that. Rigging boards were supplied that fit the wing at marked stations, and the fuselage was similar, the rigging line on the fuselage would have been used to level the airplane, then the rigging ('incidence') boards used to adjust the wings to the manual angles. And quite accurately too, within a 1/4 of a degree. We tend to forget that, even back then, much more time was spent maintaining these things, than actually flying them. There are still Riggers manuals available from the time that tell you just how it was done.
Evan, WB #12.
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Old 10-05-2012, 02:56 PM
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Default RE: Old school incidence measuring?

Occasionally you will hear of "rigger's incidence" This is the relative incidence measured using a stick on the underside of a wing. It will invariably be less than the actual aerodynamic incidence which is from the farthest point forward of the airfoil to the trailing edge. For instance at 0 degrees rigger incidence, a Fokker wing is flat on the table, but the leading edge centre is much higher and the actual aerodynamic incidence is 5 or 6 degrees. That's the reason for what may appear as a lot of incidence in the stab.

Clear as mud?

Martin
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Old 10-08-2012, 11:49 AM
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Default RE: Old school incidence measuring?

See for example this for an SE5a
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Old 10-08-2012, 12:08 PM
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Default RE: Old school incidence measuring?

If you look at my pic, the Fokker DVII had the rigging manual slid into a sleeve on the side of the fuselage. That white rectangle.
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Old 10-08-2012, 01:54 PM
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Default RE: Old school incidence measuring?

With the Babylonians and Greeks doing trig and dividing circles into 360 deg and the Egyptians using protractors with basic marks, angular measurement has been around a long time. Just like we do I am sure. I am more impressed that someone got it right in the design department.
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Old 10-15-2012, 08:18 PM
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Default RE: Old school incidence measuring?

Part of my practical test for Airframe and Powerplant licence was a Stearman with rigging board and prop protractor. if I remember correctly, we had a crate of rigging boards for each section of wing and you flipped them over for the top or bottom wing as required. I had to check wing tip incidence. Same protractor for the prop angle and by the way, check the timing on a Jacobs 985 while you are at the nose. Mostly show and tell that you understood the concept. To my new 1st AIRLINE job, Nord 262a with fabric rear flight controls. Rig boards for those as well. My chief inspector at the time had his ticket hand signed by Orville Wright. Older than dirt but knew everything!
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