Recently being inspired by the Performance Tuning DVD I decided to go back through my fleet and check them all for CG and incidence.

When you have had a model for a while and it is flying fine ? you usually assume that you have managed to get it to the right setup ? well it may be ok, but could it be better?

Going through the flock, I started to realise that the old Robart incidence meter I had was a little clumsy for the amount of work I was asking it to do.

Being a sucker for gadgets, I had a look to see what was available in digital incidence meters. And basically there are two:

The Hangar 9 Angle Pro 4-in-1 Digital Throw/Incidence Meter

Or the top of the range:

AeroPerfect Digital Incidence and Control Throw Meter

That trusty old faithful robart meter<FONT class=captions>That trusty old faithful robart meter</FONT>

So, what is so wrong with the old Robart Model incidence meter?

Well nothing really - it is just that the new digital meters allow for a much easier, faster and more accurate measurement and setup of our models.

There fundamentally is three drawbacks to the Robart Meter:

Firstly, because it is a jewelled movement pendulum, it is sensitive to the fact that it is not held perfectly vertical.

Second, because it is an analogue display, it means that the ?readout? of the angle can be offset by simple things like the viewing angle? thus getting accurate readings time and again can be difficult.

and last, to do proper setups, you need to set the reference wing surface (usually the main wing) to 0 degrees first so the corresponding angles can be set. Not always an easy thing to do on the various shapes our fuselages take!

With that said ? it is the benchmark by which we have worked for at least the past 15 years.

Putting them to the test

Fundamentally, both the digital meters have the same basic functions ? a digital readout and a ?zeroing? function. The later allows you to start with a 0 degree angle no matter what angle the wing is set at. And that is where the comparisons end.

From that point the two devices are vastly different ? The Angle Pro is a small very light plastic case and the AeroPerfect is dual unit device with a fairly heavy measuring unit and a digital readout head unit connected by a cable. The Angle Pro is accurate to 0.1(1/10th) of a degree whereas the AeroPerfect is accurate to 0.05 (1/20th).

Initially, before actually using them, I thought that the weight and size of the Angle Pro would be far more suitable than the AeroPerfect. Actually, I found quite the opposite.

There are a few problems with the Angle Pro. Although you would think that the lightweight design is great, lack of accuracy in the manufacturing of the plastic casing has created ?slop? in the mounting system making the mounting on the incidence bar virtually useless. The unit was able to move inside its holder by up to 1.6 degrees on my unit (and I would imagine it would get worse with wear). This meant that it had to be used freehand only.

The poorly fitting bracket on the rear of the Angle Pro unit

This and the next picture showing the amount of slop in the mounting on the incidence clamp

...the Angle Pro mounted on the supplied incidence bar gives a discrepancy of almost 2 degrees.

Using this unit freehand, the buttons were too small making them awkward to use while trying to hold the unit steady on the incidence bar. Setting zero was a bit or a hit and miss affair, as the unit would move while trying to get at the zero button.

Using the Angle Pro freehand

The on/off switch can also be a bit of a pain ? the unit does not have a timer-off circuit? so if you leave the unit on, the battery will drain ? and the mini 6v 11a battery it uses are rather hard to get.

Using the AeroPerfect makes for easier ergonomics and more accurate measurements

As mentioned previously, I initially thought that the twin unit of the AeroPerfect would be cumbersome, and with the measuring head weighing in at 230grams. It is a little weighty and I would not recommend this for very lightweight models when testing control throws, but surprisingly, I found this not only easier to use, but much more accurate. The split unit allows for better ergonomics of testing the angles and easier viewing and control of the readout.

Switching the unit on and off is easy and resetting zero is a dream for thumbs like mine and the readout makes it all easy to see? even having a backlit readout.

AeroPerfect readout and backlight

Although it does not come with an incidence clamp, it is not hard to make one or use one of the commercially available ones? or use the one from your old Robart meter.

aero_battery.jpg

I would recommend that you make a battery pack plug for the unit (Note: you need to ensure that you have the polarity correct to avoid any damage to the unit. - check the AeroPerfect site for proper specs) ? having it plugged into mains is a bit of a drag with the extra cables. I used an old 11.1v LiPoly pack with an adaptor for the unit (this would last a while as the unit only draws 18 micro Amps (.018 milliamps) at 12v). This, with a bit of Velcro, made it really neat? and usable in any place at any time. The cable I made up makes it easy to use virtually any pack I have lying around.

Close up of the battery connector

The clamp units supplied with the AeroPerfect allow for lots of variations of use for measuring throw, rigging angles and even checking for squareness when building. The AeroPerfect site has many examples you can reference.

Testing control throw

Conclusion:

In this sport, we often pay a premium for items. And I do not mind when the item has been designed properly and to last as was the original Robart Incidence Meter.

Using the Robart meter as the benchmark, the Angle Pro is a disappointment! It had all the potential of being a great device and it is let down by bad design and cheap manufacturing giving it a ?toy? feel? and not at a ?toy? price.

The AeroPerfect is also not inexpensive, but you can see and feel a quality product that has the potential of being a professional tool in the workshop for the next ten years, just like the Robart meter has been up till now. The added benefit is that this tool will be much more useful across the board.

The Hangar 9 Angle Pro 4-in-1 Digital Throw/Incidence Meter
Price		$149au, plus delivery
Value for money		3.0/10
Quality		3.5/10
Usefulness		7.0/10
In Australia available from:		Model Flight
Manufacturer:		Hanger 9

AeroPerfect Digital Incidence and Control Throw Meter
Price		$317au approx, plus delivery
Value for money		6.0/10
Quality		8.5/10
Usefulness		8.0/10
In Australia available from:		Not currently available locally
Manufacturer and available directly from:		Bell Electronic Technologies