As already stated on RC Universe, there are significant problems with the analogue incidence meter that comes as part of the Robart system. The main problem is that the reading can change, by anything up to a degree, if the meter is rotated through 180 degrees. In addition, the ‘bubble’ level that is built into the device is often out of calibration with the meter itself! These problems can be minimised by ignoring the ‘bubble’ level and ensuring that all the readings are taken with the face of the meter pointing the same way. However this can sometimes make it awkward to read the meter accurately, and without parallax error, especially when the meter is placed on one side of the tailplane with the face of the meter pointing inwards towards the fin. I have known some modellers who have gone to the expense of buying 4 different meters – one for each wing and one for each tailplane half – so that incidences can be set without the inconvenience of moving a single meter around between each of the 4 surfaces. Sadly, whilst this approach sounds good in theory, the lack of repeatability between individual meters does not justify the extra cost.

As Isaac says, the digital inclinometer that comes with the Hangar 9 Angle Pro is intrinsically more accurate and more repeatable. However the Angle Pro is not without its problems. The main issues lie not with the digital inclinometer itself, but with the mechanics of the mounting system. In particular, the plastic mouldings for the “V” notches are a very slack fit on the metal slide bar. Sliding the mouldings in and out to accommodate the different chords of wing and tailplane, can introduce unacceptable inaccuracies. The inclinometer itself is also a very slack fit in the plastic pocket in which it sits and this too can lead to problems. (Another quality issue with the Hangar 9 Inclinometer is the use of very flimsy buttons for Hold and Acquire switches and an equally flimsy On-Off switch. None of these components are designed to pass the test of time!)

I have had some success with mounting the Hangar 9 Inclinometer on the Robart slide bar and shimming the mounting bracket to ensure that it is a tight fit on the bar. However I find it disturbing - and frankly unacceptable – that both the Robart and Hangar 9 devices, neither of which is inexpensive, should be sold with major flaws.

For those interested in ultimate accuracy, I would have to agree with Troy Newman and recommend a good Laser level device coupled with some basic trigonometry. This approach would be more accurate and repeatable than either the Robart and Hangar 9 devices and would get the initial bench set up to an acceptable degree of accuracy – especially bearing in mind that the final set up can only be achieved through test flying and observation.

Bob Wasson

PS:
Great build thread on the Osmose!