The good guys at Winged Shadow Systems were nice enough to send a sample of their How Fast Model Aircraft Airspeed Instrument to try out.

Key Features

• 15 – 500 mph / 24 – 800 km/h airspeed, 1 mph / km/h resolution
• Includes Pitot and Static Probes
• Plugs into your receiver or any 3.2v to 12v battery, draws 1.3 mA
• Light Emitting Diode (LED) used for communication
• Size 1.05″ x 0.65″ (26.7 x 16.5 mm); Total Weight 0.2 oz / 6 grams
• Optional See How display accessory, 9 in-flight speeds, resolution to 0.1 mph /
  km/h, 10 flight memory
• Instruction Manual

This diminutive package uses the same differential pressure sensing as on full-scale aircraft. Airspeed indicators measure the difference between ambient air pressure and total pressure in flight due to the plane’s forward motion (“ram air”) captured with the pitot tube. Obstructing the free flow of air of these tubes will compromise accuracy, as will off-center tube placement. The “How-Fast” captures the highest speed flown.

The Static Tube has four small holes drilled in it and is sealed on one end, the Pitot Tube is open on both ends:

The unit mounts in the wing

or on the wing for flat wings – the key is to make sure that the two tubes are NOT in the prop wash and that they extend at least ½” from the wing – the Static Tube’s small holes must extend at least ½” from the wing. You must ensure that they are parallel to the fuselage and level. The open parts of the tubes can be shortened if needed. Also note that you can shorten or lengthen the tubing between the instrument and the tubes – as long as they are not kinked, length should not be an issue.

Reading the unit requires that you wave your finger over the LED to trigger its read-out BEFORE you turn the power off. Once triggered, it flashes steady for about 4 seconds, then the LED flashes the speed – for example, for 123 mph you’ll see one flash, pause, two flashes, pause, then 3 flashes. Two digit speeds, eg 46, will report as four flashes, pause, then six flashes; zero is a quick double flash. Once you read this speed, it will be stored in memory and can be recalled later, even after powering down.

I found the finger waving requires some practice to get right. First you should have the LED pointing squarely at the sun or a light bulb – it’s triggered by the difference between light and shadow. I found one way to get a reading is to use a flashlight – hold it close to the LED and then wave; the waving cycle requires some experimentation – practice this before you mount it. I shot a video (blurry) of this process – the readout flashes 46 mph – HERE.

After getting the finger waving down, I tested the “How Fast” by mounting the unit on my car’s mirror and driving 60 mph on the highway. I found the unit recorded an average of 56 mph. This is within the accuracy range according to my query on this to Winged Shadow Systems:

“From our tests on a wide variety of installations, in the range of typical model flight speeds (30 MPH to 120 MPH) I’d say you can expect a peak reading well within 5 MPH of your true airspeed.”

Accurate mounting of the tubes is critical to accuracy:

“A unique (and potentially large) source of errors is the mounting of the Pitot and Static tubes. Careful alignment of the tubes directly into the direction of flight will give excellent results. Miss-pointed tubes or locating the tubes in the prop blast can create significant errors. Of course, clogged or pinched tubes can make the readings useless. Since the How Fast makes offset readings at power-up and again when the report is activated, strong winds into the sensor probes at these times can also cause minor errors.”

I mounted the How Fast on one of my foamies by taping the tubes to the flat wing and found it’s moving quite nicely with speeds in the high 30s.

Short of a radar gun (really expensive) or a measured course, measuring a plane’s speed anectdotally is not terribly accurate. The How Fast looks like a reasonable solution – while not cheap (what is in this hobby?) at $45, sharing it among a few flyers or buying it by a club to share among its members to determine plane speed with some accuracy could be one way to lower cost, although you can’t discount “bragging rights”.

Many thanks to Dave at Winged Shadow Systems for sending this our way to test out. Overall, a nice package!

I have been flying since March 2003 and have probably passed 2000 flights
between my parkflyers and gliders. During my pilot development, I learned
how hard it can be to find a plane that has landed in the woods, tall grass
and other places where you can't see it. Fortunately there are aids for
this kind of situation.

I lost my Aerobird when a huge gust of wind carried it over deep woods and I
was too inexperienced to deal with it. Even though I was certain I knew
where it went down, I could not find it. I bought another Aerobird and fly it
often.

When I moved on to gliders, I started flying a Great Planes Spirit 2
Meter. I got into trouble and it went down into heavy woods and brush. I
went into the woods to find it. Fifty feet into the woods, trying to decide
how to proceed since the area the plane went down could not be seen from a
trail, I heard Beep Beep Beep. The plane was about 150 feet away in heavy
tree growth. I had the plane located and out in 10 minutes. Believe me,
where it had landed I likely would not have found it.

The difference was a little device you put in the plane that gets attached
to the receiver. If you turn off the transmitter, the thing starts beeping
loudly and you can hear it from quite a distance.

This is what I use in my Spirit Sailplane and several of my other planes
HERE.

It hooks to any channel or it can share a channel with one of your servos.
It has the connector to pass through to the servo. This is the one I
recommend to everyone.

In addition to helping me find the planes, the Digi Alarm also monitors my
battery pack voltage and sounds an alarm if the pack voltage gets below a
safe level. This is especially valuable on my glider. If I catch a good
thermal, I could be in the air for over an hour, so a pack that tested good
on the ground could run low during the flight.

As a test to make sure no one is flying on your channel, turn on the
receiver only. If the device does not go into lost plane mode, then someone
else is on your frequency.

Here are some others I have not tried, but look interesting:

Lost Model Locator – $10

Does one job, but does it well – I hope.

SkyKing RC Lost Model Locator – $20

Review HERE.

RC Reporter – $24

A bunch of features.

The planes I fly most often now have a locator and battery monitor installed
Of course you only need one – you can move it from plane to plane,
but at $15-30 they are cheap enough you can put one in every plane and
forget it! It is helpful insurance to protect a $150 to $1000 investment.

The Plane Locator

This is a radio beacon/finder system. It does not connect to the receiver
but sends out a continuous signal that you can home on with their receiver.

From the maker's web site: About 1/2 mile range. Transmitter is less
than 1" diameter, 1/2" high, and has a weight of less than 1/3 ounce including
the battery. It is powered by a single CR2032 battery that will last for over 30
days of continuous operation and signals you when it needs replacing.
Factory programmed to any one of your choice of 50 channels.

The receiver is about $200 and the transmitter that goes in the plane is $50.

Many pilots don't know about these devices. Now you do!

This thread can be seen HERE.

"For those of you that are interested in seeing the inside of a 30 mm motor, here are a few photos that I shot. This motor is a 3026-8 that I pulled at random from my motor stock. First is a shot of the outside of the motor where can see how the back housing rises up and away from the back of the flux ring. This provides plenty of space for airflow, and allows plenty of room for mounting screws:

Here is a rather long mounting screw sitting next to the motor – a 3 mm screw with 9 mm of thread. This is actually a common size that is used to secure CD-ROM drives into computers, so it is readily available. As others have reported, when using longer screws like these on some motors, the extra length of the screw will poke through the back of the motor housing, hitting the stator windings inside, and cause a short.

Here is a close-up shot of the screw installed into the back of the motor. The rear motor housing is about 2.5 mm thick, and I ran the screw in so there was a 1.5 mm space between the head of the screw and the back of the motor. This is where the screw would end up if you had a 1/16" plywood firewall, and in this position there is 5 mm of screw thread poking inside the motor.

If you look closely, you can see the end of the screw at the top edge of the slot. Even with the screw this far into the back housing, there is still about 3 mm of clearance before the screw would hit the stator windings. This makes mounting the motor a very simple operation, without the worry of shorting out the windings with the end of the screw.

Now it is time to go inside the motor. Here is a view of the Stator from the 3026 series motors:

You can see how uniformly the stator plates are stacked and how nicely the stator windings are laid into the slots. The stator plates in the 22 mm and 30 mm Scorpion motors are only 0.2 mm thick for maximum efficiency and minimum eddy current losses. Because the stator plates are so thin, it takes 130 stator plates to make up a 26 mm stator assembly!

Here is a close-up view of the left side of the stator from the above photo:

In this photo you can see how neatly stacked the stator assembly is and you can see the green powder coat finish that is on the inside of the stator. This is done to prevent the wire from shorting out against the stator plates. If you look closely around the edges, you can see the thickness of the powder coat finish and how it creates a nice radiused corner on the stator. This helps the wire bend cleanly around the corners and virtually eliminates the chance for shorts with the stator windings. In this photo you can also get a sense of just how thin the stator plates actually are.

In the next photo you can see the end of the stator assembly, and how well the wires are wrapped onto the stator:

There are a few other things to take note of in this photo. Near the center of the stator, you can see just how thick the powder coat is applied at the end faces. This provides a nice radius for the wire to wrap around. Also, look closely down between the stator teeth – you won't see any daylight there. The stator slots are packed with just about as much copper as you can possibly fit inside. All of the stators in the Scorpion Motors are hand wound by people that take a lot of pride in their work, and I think that really shows.

Finally, here is a shot looking down inside of the flux ring can of the motor:

As you can see, Scorpion uses 14 curved magnets in the motor can and a generous amount of high temperature adhesive is used to make sure that the magnets stay put. The high level of machining extends inside the motor, and you can see on the inside surface that the holes are de-burred and the finish on the inside surface is every bit as good as the finish on the outside. Many motor companies leave this inside area unfinished, since you cannot see it, but Scorpion's attention to detail extends through the entire motor, even to the parts that you cannot even see in normal use.

So there you have it – a guided tour inside the new Scorpion 30 mm motors. Hopefully you can all see the level of quality, and the fit and finish of the internal parts of these fine motors. The owner of Scorpion is very serious about producing a quality product both inside and out, and the best part is that they run as good as they look!"

Lucien Miller

Balancing a prop is conceptually very simple – place the prop on a frictionless shaft, allow it to come to rest and if it's parallel to the ground, it's balanced. One product to do this is the DU-BRO Prop Balancer:

It comes unassembled – assembly is very simple; the only hard part is inserting the nuts for the rods into the plastic base – I had to use a vise to press them into their respective outlines.

Once assembled, you slip a prop onto the shaft and let it come to rest – it it's unbalanced, you'll see this:

Now take the prop and begin to remove material from the heavier tip – I used 400 grit carbide paper – and then try it again – eventually when the prop is parallel to the ground, it's balanced. Here's it almost balanced:

I can definitely attest that a balanced prop makes a noticeable difference – you can feel it when holding the plane under power – less vibration is a good thing.

As you begin to build your own models or retrofit an existing model with a new power setup, a wattmeter begins to make a LOT of sense – Ed Anderson's article "Who Needs a Wattmeter" sums it up very nicely – actually it's cheap insurance compared to burning out a motor or ESC.

One wattmeter that can meet your needs is the Super Whattmeter (Model 101)

The Whattmeter can be powered by the battery you're using or by a separate receiver battery if needed. The display will show Amps, Volts, Watts, AmpHours and WattHours (the latter two alternating every few seconds in the LED). The pic below shows the display with just a battery connected:

With a motor hooked up, it will display the following:

In the Astro Super Whattmeter, Model 101, User Guide, there are three diagrams which depict Whattmeter setups – to measure a motor setup requires the following:

The receiver battery is optional – as long as the source battery's voltage is 4.5 volts or more, a separate battery to power the meter is not required. I'm going to show this application in some detail in an upcoming article – it's a VERY powerful tool for optimizing the performance of a particular motor/prop/ESC/battery combination. You can use your transmitter and receiver rather than the servo controller if you don't have one, but I found it a lot easier to use the servo controller.

If your charger does not have an LED display, the Whattmeter can serve as your display:

And finally, you can also use it to display what happens as you discharge a battery:

Frankly if you mix and match your electric setup, how you can do this efficiently without measuring what's going on can be an expensive hit-or-miss game – a wattmeter such as AstroFlights's Super Whattmeter (Model 101) should be in your kit bag. I know it's opened my eyes to prop/motor combinations that I would not have considered before.

I enjoy electric planes. They are quiet, convenient, can be fast or
slow and are fairly inexpensive to fly.

A few months back I picked up a
Watts-up wattmeter.

I thought it would be a good investment as I was doing more in the area of
mixing and matching motors, props, and the like. It is small and simple to
use so I put it in my field box. It wasn't long before it started to show
its value.

We were flying one afternoon when one of the club members felt he was not getting
good performance from a new plane he had built. I put he wattmeter on the
plane and determined he was pulling about 9 amps. Turned out the pack he
was using really was not up to the load and the voltage was dropping off
excessively. As a result he was not getting the RPM out of the prop that he
expected. Problem discovered and cause identified in a few seconds. He
needed stronger battery packs.

A few weeks later we did the same thing with another plane. There was a
concern that the LiPo being used might be getting over worked. However the
Wattmeter showed that it was working well within its rated capacity. Flying
went on with confidence.

I recently purchased an Easy Glider Electric from another club member. He
had upgraded the motor from the stock speed 400 to a brushless, a 27 amp ESC
and was using 2 cell 2100 MAh LIPOs. I bought the whole package.

The plane flies very nicely on the 2 cell packs, but I had a 3 cell pack
that I thought I might add to the rotation and REALLY boost the power. The ESC could handle 3 cell LiPo so I did not see a problem. I assumed the system was probably running at about 18 amps which was within the rating of this pack. Should be a good fit.

Fortunately before I tried it in the plane I put the watt meter on the
system. I was surprised to see that the system was running at 26 amps on the 2 cell lipo packs. That was much higher than I had expected. It turned out that the 2 cell packs were an excellent match for the motor and speed control. The amp load was well within the specs of the 2 cell packs being used and the plane flew very nicely on this combo.

If I had blindly put a 3 cell pack in there I would have pushed well past
the ESC's 27 amp rating and probably burned out the speed controller. Or,
in the case of my 3 cell pack, it would probably have pushed over 30 amps
into the system due to the higher voltage, but it was not rated for that
high of an amperage and would probably have had a short life working at that
level. I would have thought it was just a crummy battery pack but in fact I
would have been over working it.

Operating in the blind I would have ruined the ESC, or the pack, or both. A
very expensive mistake. Certainly more than the cost of the watt meter. It
had just paid for itself.

A few days ago I pulled out my old Electrajet to prepare to sell it. I had
purchased it almost 3 years ago, but had never really been happy with the
plane and my interests have turned more toward gliders and slow flyers
rather than a pusher jet. When I purchased it I also bought some cells and
made up some 8 cell packs. However it really didn't seem to have the zip I
thought it should. I just attributed it to the speed 400 motor and the
plane being too heavy.

I put the watt meter on the motor/battery combo. The motor sounded about as
I had recalled. When I checked the meter, low and behold, those 8 cell
packs were duds! They were 9.6V 8 cell 1000 MAh packs rated for 10C. At
rest, fresh off the charger they were reading 11 volts, but when I hooked
them up they were both dropping to 7 volts while delivering 9 amps. That is
way too much drop! The problem was not the plane or the weight of the plane
but the quality of the cells I had used.

I tried one of my 15C Lipo packs and that held voltage well, delivering 13
amps. The motor screamed! Now that was more like what I had expected.
Hummm, maybe I won't sell it after all. I just need to put better battery
packs in it.

I also tried a 1000 MAh 2 cell lithium pack that is rated at 10 C. The
voltage sagged to 6.6 volts almost immediately. The motor ran but I was
clearly over stressing the pack. This pack would have been ruined in very
few flights if I had used it to fly the plane regularly.

I share this story only to help you understand that, without a watt meter,
or the use of a multi meter with knowledge and skill, we are working in the
blind. We really don't know what is happening in our power systems.

WHO NEEDS A WATT METER?

While the watt meter is a nice to have, some people don't need one. If you
are buying RTF planes, or ARF or kit planes and are using the manufacturer's
supplied motor and battery packs, I would say you can be pretty confident that all
is well.

However, if you start mixing and matching motors, gear boxes, props,
controllers, battery packs and the like, you are really working in the blind
if you are not measuring the energy flow in the system. In my case, I
started making my own battery packs but I was not measuring their
performance. Now I know the true results.

There are a variety of watt meters out there. This one is easy to use and
fits nicely in my field box, but there are other good ones. If you are
going to upgrade your power systems or make up your own packs, you need a
watt meter. You can perform many of the same tests with a millimeter if you
know how to work with shunts and the like, but if you want a simple to use
tool that does exactly what you need it to do, this is hard to beat. It has
other uses too, so read the instructions, but for this use alone it paid for
itself pretty quickly.

Clear Skies and Safe Flying
Ed Anderson 10/27/2006

Reprinted with permission from the author – The Original Thread on WattFlyer Forums

AstroFlight makes an interesting line of products and one that I recently purchased is AstroFlight's Li-Poly Charger. This unit caught my eye because it's a 12 volt model – it can be used at home with a 12 volt power supply and on the road with a 12 volt plug (shown above).

This charger not only charges but can discharge as well.

Once you change the plugs to fit your battery's configuration, using the charge is drop-dead simple. When first turned on, the cooling fan kicks in (noisy) and the charger beeps once to indicate it's in the first charging phase; the display shows this:

The "Amps Adjust" dial should be turned down to "0" when plugging in the battery – you'll see this:

The display indicates (top, left to right) that the charger is set to 0 amps charge, 3 cells in the battery, charging mode 1, the battery's voltage, the duration of the charge and the number of milliamp-hours of charge put into the battery pack – at this point, I have not turned the dial to match the battery's size – 2200 mah.

Matching the battery's capacity to the charge shows this:

There are three distinct charging phases:

• In Phase 1, the charger will charging the battery for three minutes regardless of the battery voltage;
• In Phase 2, the charging current will turn on and off at one minute intervals, continuing for 59 seconds then turning off for 1 second;
• In Phase 3, the charging current is turned on and off periodically; when the resting battery voltage reaches 4.2 volts per cell, the battery is declared charged and charging stops.