Flying Remote Control

Big Day Out at Murrumbateman

noreply@blogger.com (Oz RC Boy) — Sun, 02 Nov 2008 21:58:00 +0000

Well, joined some flying buddies at Murrumbateman this past weekend, and we had a great day.

Tons of aircraft, most of which got a really good workout. We didn't even let the wind get in our way.

Youtube evidence below - see ya later.

Timmy and the TREX

noreply@blogger.com (Oz RC Boy) — Sun, 19 Oct 2008 06:45:00 +0000

Well, it's been a while since a post and there ain't much to this one I'm afraid, but I did want to share this youtube vid I shot of Canberra Heli Pilot Timmy Tron - I've seen this stuff on the Interweb thingy but have never seen anything like this in person. Enjoy:

GUANLI Me109 Review

noreply@blogger.com (Oz RC Boy) — Sun, 25 May 2008 11:01:00 +0000

Summary:

Wingspan: 900mm
AUW (as built): 470g (16.8 oz)
Power Setup: 3s 1250mAh, 200w TP 2409-12T Outrunner, ASSAN 25A ESC.
Avionics: Guanli 36MHz RX, 3 x 9g Guanli Servos

Pros:

Great looks.
Fast assembly with neat features and handy included tools.
Surprisingly good hardware.
Flys well provided you keep the energy up.

Cons:

Tricky flying envelope (see scale note above).
Legacy of NiMH design (battery compartment to thin, and gearbox setup).

Introduction:

When Richard Wood (Woodsy) from AussiEFlight announced he was looking for people to review a new range of small foam warbirds he was planning to import I thought I may as well jump in.

I'm a big fan of foam warbirds - a little bit of history come to life. I've had a great deal of success with my GWS Zero, and even though the Ultrafly P51 wasn't half the plane the Zero was, I've still found a niche to fly it in.

The plane that was coming to me was the GUANLI Me109 (aka Bf109). Along with the plane itself was a full avionics pack including servos, RX, ESC and brushless gearbox/motor.

Before we get into the review it's probably worth going over what the review is about. The review's purpose was to let Woodsy get some honest feedback about this new range of models. As such you may be surprised about the candor of this review. Don't take it as a bad sign about AussiEFlight -the entire purpose of this exercise from Woodsy's perspective is to make sure he doesn't send a pup to any of his customers.

Build:

I'm going to spare you the box photo - the plane was well packed and arrived without a mark.

At first look the standard of completion was very high. The fuselage comes fully assembled and all control surfaces are pre-hinged and secured. That was great news for a fast build. The foam is well finished and painted. As scale models go, it quite looked the part.

Construction is foam around a central ply skeleton which is common to many of these foamies. Seems like a smart way to save some weight, and add some strength to the model.

If you look at the photo on the right you can see the two servo holes for the elevator and rudder servo at the right of the photo. From taking a look you may be able to see the small notch, which provides a nice convenient place for the servo lead to run.

This photo of the wing servo hold shows the same slot. It may not seem like a big thing, but it shows a surprising amount of forethought for a budget Chinese model.

Before installing the supplied servos I tested them all on the bench with a flight pack. Always a good idea with new servos - test before installation.

Another surprising feature was this neat little bag of tools, including even a roll of sticky tape (uneeded I might add) and magnetised screw driver.
This might seem like strange little things to stress but I was impressed - and optimistic. These little things showed a lot more thought than I would have expected.

As I started putting the model together I was impressed by the quality of fit. For example - how well the wing fit the wing saddle on the fuselage. And how well the battery cover/cockpit fit the fuselage.

Hardware with the model was surprisingly high quality too. Collars for the wheels, even a nice wide tail wheel.

The plane uses a single servo for the aileron. The last model I built with this kind of setup was the GWS Zero. For that one I had to put the 90 degree bends in the wire so that I could "trim" the ailerons to line up with each other.

No such problem with this plane - it includes threaded rods.

The one thing I did add to the build was some quick link connectors for the rudder and elevator horns. Seemed a shame not to use them when so much effort had gone into making the build very quick and slick otherwise.

Power System
Like lots of little foamies the GUANLI still seem to be obsessed with provide a motor stick setup built around the idea of using a gearbox. In an age where cheap outrunners are the fastest and most reliable way to power park flyers the throwback to NiMH/Brushed motor days is, to be honest, unwelcome.

However, Woodsy provided a little brushless inrunner gearbox rig for the plane. This seemed like the perfect solution, and with the plane itself he was seeking feedback.

Most motors are going to need some extension leads made up so that the motor leads can reach the battery compartment. I used some speaker wire for mine.

The gearbox was a 5.33:1 reduction, and the included props with the model were 10x8 slow flyer props. To be honest - a 10x8 prop on this plane would have been a mission - the undercarriage aren't that long - getting the plane to even rotate without prop striking would be a challenge.

Once again - this throwback to the NiMH stuff is a bit unwelcome.

Okay - so static testing the motor pulled about 15A with the included prop on a 3s - for about 15 seconds, and then began the tail of woe. When the prop spun the prop shaft shifted forwards just a little, which meant that the engine cog was only making contact with about a quarter of the prop cog. The result was that the metal engine cog stripped the plastic prop cog very quickly.

I've seen this exact problem on a mate's brushless gearbox motor (that came as part of an RTF plane). The problem is these cheap brushed speed 400 gearboxes are just not up to handling the power put out by a brushless motor. My mate's plane lost power in flight, and spun in (of course it sounds like it is working, and the prop is spinning, but you aren't actually getting any power).

So, I adjusted the motor cog, and spun up again this time making sure that the remaining 3/4 of the prop cog's teeth was in good contact. It took a little longer - maybe 45 seconds this time, but once again the prop cog was stripped.

Now - a static load test is the most demanding environment for the gearbox. There is no potential to unload, but nevertheless, the gearbox really should have stood up to more punishment than that. I would predict any plane running this setup on 3s can probably expect less than 10 flights before losing power in flight..., which won't be fun.

So, I decided to take a different tack and install simple, reliable brushless outrunner. Of course, the biggest problem here is that the motor mount is really built for a gearbox. I ordered a Towerpro 2409-12T (200W, 1600kv) for the plane. When it arrived I mounted it "high style" on the gearbox mount and then cut away the excess so that the gearbox could fit inside the nose.

Of course, because the plane is designed for the gearbox, even though the high mount of the outrunner puts the prop shaft in the right alignment, there is still an issue with the motor sticking out to far.

A little bit of dremmel surgery got the engine stick cut down, and enough foam cleared up to allow the motor to be mounted to emerge approximately flush from the end of the nose.

With the motor mounted successfully it was time to turn to power options. Once again, the lack of design work since the NiMH days left limited choices. The battery compartment is not very high. While there are plenty of 3s battery packs that will fit the space, none of them are the $25 type. For example, a 3s 1200Flightpower will fit the space quite happily - but it will cost more than the rest of the plane combined.

I have a 3s 1250mAh Multiplex battery that is quite thin that I use with the GWS Zero. When I checked her with the Multiplex battery installed she was perfectly balanced.

Flying

With the plane and power system sorted it was time for the test flight.

I lined her up with my other warbirds for a bit of a group photo. I'd bought my other warbirds to the field so I could fly them all back to back, so as to get an immediate comparision between them.

It was quite a windy day but I was confident the sleek lines of the me109 would handle it okay, and after giving both the zero and the mustang a go, I opened the throttle on the Me109.

Apart from need about 3 clicks of up trim she flew almost dead straight from take off, which is always a nice sign for a straight aircraft.

Having flown all 3 of my warbirds back to back I did get a sense of her very quickly.

Comparing her to my floaty/aerobatic GWS Zero (smaller wing span, almost exactly the same weight), and my porky fly on the wing Mustang the Me109 was, surprisingly, much more like the Mustang than the Zero.

She is certainly a capable flyer, but she demands your attention, and has quite a nasty tip stall. It is also possible, unless you are careful or running at WOT, to put her into a spin in a high banked corner quite easily if you aren't careful with the elevator.

This probably isn't a particularly good starter warbird - her small wing span means she lacks effeiciency and she is twitchy, and her typical warbird cut means she needs to be flown with some care, but I'm confident she will be a lot of fun.

Well - here's the youtube of the maiden video:

Avionics:

I haven't had any problems with the provided servos. They seem to be doing their job well. The Guanli RX hasn't been super solid. A few twitches in flights since the initial maiden have caused a little concern.

Conclusion:

This is a neat little plane, cheap, and fast to build. It flys like a warbird - it flys nicely on the wing, but it is unforgiving and has a real tip stall. Keep the energy up and learn how to fly her and you will have a lot of fun.

The lack of modernisation of the design (which is still built for NiMH) is a bit of a shame, although it can all be modded around without too much difficulty.

Indoor "Easybox II" from NQRC

noreply@blogger.com (Oz RC Boy) — Sat, 26 Apr 2008 22:40:00 +0000

Flying a bit of indoor recently has made me keen to try and find new and interesting aircraft which can fly slowly and predictably. Although I've had some limited success with flying a Stevens Aero 'lil squirt I was always concerned she was a bit heavy for the duty, and thought to myself something with a little more wing area, and attention paid to keeping her light might work out okay.

Enter the Easybox II, designed by Paul Daniels from North Queensland Radio Control. At first glance this neat build yourself balsa parkflyer looked like it might be just the ticket. And the price - $50 bucks for the whole kit including *all* hardware and covering. Combined with some cheap electronics from UnitedHobbies.com (including a tiny 16g outrunner) the inkling of an idea for a new slowflyer for indoor was taking shape.

So, I ordered the EBII from Paul, and some bits from UH. The total parts list in the end was:

EBII (from NQRC)
16g Hextronics Outrunner (from UH)
EM 3.7g Servo x 2 (from UH)
Towerpro 12A ESC 9g (from UH)
Hitec HFS05MS RX (from Nitrodude)
2s 850 LiPo (from NQRC - not stocked anymore unfortunately)

Construction:

Construction was breeze. Even with only a plan sheet (rather than instructions) this plane went together very quickly. As per the name, the fuse is a box with two the two fuselage sides running the length of the aircraft with shorter pieces used to brace top and bottom to allow for the various bends.

I was using my flash bulbs and being a miser with thin CA to keep the weight down as much as possible. Even for a slow builder like me the main fuse only took about an hour to put together.

The wings were a straight forward affairs with a smart approach by Paul to the main wing spar. Rather than one solid continuous main spar (the more standard approach) two thinner pieces locked the ribs in - one from above and one from below. A third and fourth piece was then CAed across the "front" and "back" of the two wing spars making a "box" configuration which would be extremely strong for weight. Given I was after every weight saving I could achieve, after consulting with the designer (yes Paul is one of those guys that answers your emails and does his best to help you out) rather than building the spar up to the full box I only glued one of the braces in place between each set of ribs, alternating between bracing the front, and bracing the back of the spars. Hopefully the photo explains what I'm on about.

One tip I would say for the wing is sand the trailing edge pieces to shape before you glue them to the ribs. Once installed, it is a tiresome job to delicately sand the trailing edge without catching/splintering/breaking the wing ribs.

To try and reduce weight even more the whole model was given a really good sand. I think everyone detests one part of building models. For a lot of guys it's covering. For me it's sanding. Nevertheless, I carefully hand sanded her back, and managed to achieve a saving of around 4g through sanding the fuse - not bad when the fuse weighted in at about 32g before the sanding.

The wing was sanded to shape - not without some cursing I might note. Check my tip above about shaping the TE before glueing it in place. After that came the covering. I had contemplated covering only the top of the wing (to create an under camber affect, and to reduce the weight of covering). However, after discussion with the designer by email the decision to fully skin the wing was made because: 1) The laminate covering is an important part of the strength of the wing, 2) The airfoil isn't designed to be an undercamber wing and 3) the main spare arrangement would likely disrupt good airflow.

The laminate is easy to work with, and with the EBII wing being a constant chord wing covering is a breeze. The whole wing was covered in two pieces, doing one wing half at a time, and getting a nice smooth finish was easy. If you haven't worked with laminate for covering before, Paul has some notes on his site. By and large, very similar to other covering. Only thing from my perspective is that a heat gun is essential - the hair dryer wont cut it.

In the end, covering the whole wing probably added about 4g over covering just the top half of the wing. The weight of the wing and the airframe was coming to around 70g at this stage (I made a note at the time - do you think I can find it now).

Avionics and Power System

I started by installing the 16g outrunner to the front firewall. Paul's original design has a brushed can motor sitting behind the firewall direct driving a prop. However, I was worried about weight being to far back, and the outrunner was really only made to base mount.

The ESC was installed, and a 2s450mAh (which I was to later find out was dead) was used to check the balance, and give me positions for the RX and servos which live under the wing. The whole fuse (but without the wing) was test balanced like this to help me determine the right spots for the RX and the servos so that I was within cooee of getting the Centre of Gravity.

Just quickly on power system - I had calculated I should easily be able to get 40watts out of this system, giving her a power loading of about 100w/lb - more than adequate for what I had in mind.

The included control linkages and horns (yes - *all* hardware included) were installed into the fuse and tail feathers without fuss. I used double sided tape to secure my servos in place (they live in the space under the wing). Just a word of caution here - make sure the inner wall of the fuse is free from balsa dust so that the double sided tape gets a good hold on the wall of the aircraft. The control surfaces on the tail were hinged using magic tape. Also, because the aircraft was going to be operating at slow speeds I set her up for maximum control throw (furthest hole at the servo, closest hole at the control surface).

With all the gear in I tried powering up the motor, and found out the 2s450 I planned to use was dead. Switch of plan - rifled through the battery box and found a 2s850 - a little heavier than I would have liked, but had the advantage of being available, and without needing to give an explanation to Mrs Oz about why more parts were needed.

This did affect the CoG unfortunately, and I ended up having to put a small amount of plasticine on the tail to get her to balance. Not much. This was just attached with sticky tape (it's very important you don't over engineer on indoor models ;-).

AUW with flight pack - 172g (6.14oz). Works out to a wing loading of 4.4oz/sq ft. That was a little higher than I was hoping, and having to change the flight pack at the last moment probably robbed me of my target of sub 4oz/sq ft.

Maiden

I maidened the EBII (or EBIII as I was calling her by now after my customisations ;-) down at my local oval on a pretty calm day (maybe 2-3 km/hr winds). From the hand she took just one click of trim to fly level. She felt solid in the air and easy to fly. I slowed her down quite a lot and before I knew it was tooling around at 1-2 metres - the sort of altitude is not the way I normally approach maidens. However, the plane felt solid, and I was happy with her there.

I did some loops and stuff, and had an easy landing to finish - all up a very satisfactory maiden.

The next flight gave me an unscheduled chance to test the robustness of the aircraft courtesy of a receiver failure (or maybe it was the double sided tape slipping of the balsa - I think RX though - the one before the Hitec). So here's the situation. From about 5 metres up running I started her into a turn to the left which she continued after I released the stick. She turned over and went into a stall turn. I gave her power and tried to pull up but she didn't answer elevator and I cut the power a moment before she nosed in.

Fearing the worst I walked over. Damage - broken firewall, and just a little glue needed around the nose. Back at home I cut a square of balsa to replace the firewall, and CAed the nose back up - took about 20 minutes including time to reinstall the motor. From nose in to flight ready in 20 minutes. The aircraft had inadvertently passed another of the indoor flying criteria - robustness, and ease of repair (you don't take precious models to indoor - you just don't).

Her next flight was out at Murrumbateman with my mate, The Mongrel. On this day I really started to make an effort to see what was required to fly her low and slow, and we got some video (first plane in this youtube vid so take a look). Although not on the vid, as I pushed myself for lower and slower I had another "incident" with this plane. She stalled while in a banked turn, went in touching a wing tip onto gravel. I closed the throttle before impact - no damage.

After a bit of practice in the wide opens I was happy this plane could give indoor a go. One thing I had learnt from flying her low and slow outside was that although she was steady, and relatively easy to fly slow, I just needed a little more finesse on the throttle than I was used to. More power was required for turns to stop her stalling, which needed to be throttle back in straight level flight to stop too much speed being gathered. Thinking back to how aircraft fly there is nothing too surprising here, except that many of us probably don't build this into our flying when we are on the wing because we are so far above stall speed.

The Indoor Night

Well, the big night finally came, and with my past record of fixed wing at Indoor (it isn't exactly confidence inspiring) it was with some trepidation that I launched the EBIII off.

She completed her first circuit quite easily. Although I was in a bit of hurry (you always are with indoor) nothing was happening to fast for me to keep up. I was throttling up for corners, and back for straights. In the straights a little bit of up elevator was giving me a slight positive angle of attack and letting me fly just a little bit slower.

However - the table they had stuck out on the floor for landing helis on earlier, which had been looking at me evilly all night, did finally strike. I tried to enter a turn a bit slow and a bit too close to the ground - it was all okay with extra power, if the table hadn't jumped in front of my aircraft. Realising things were perilous I went full noise to try and get over the table - bang - into the table I went, and the floor a moment after. A few gasps from the crowd.

I went out, grabbed the model. One minute with the thin CA, and a borrowed rubber band, and she was flying again (almost no damage).

On her second flight of the night my landing was just a little rough and partially cracked the sheeting of the forward lower nose - CA - fixed. Otherwise a good flight.

On her third flight of the night, everything went just perfectly. Although there were some moments when she almost seemed to be in formation with other models (3 models, seemingly flying in formation, indoors - it is crazier than it might even seem).

Conclusion

About the EasyBox II - a great fun little plane. Easy to build, cheap, durable. If you've never built with balsa before, it's a nice place to start. I think she would even make a half decent trainer, particularly if the beginner has someone to help them over those first few flights so you don't end every flight with repairs.

About the EasyBox II as an indoor model - it was a lot of fun getting her to this point, and I will keep on flying her at indoor. Her airfoil means she has to fly a little quick compared to her contemporaries, but she has a grace of her own. She is very robust and repairable (critical for indoor).

What we really need is an EBIII, using 1.5mm balsa for the fuse to save weight, and a more appropriate airfoil with undercamber wing - what about it Paul? ;-)

Other Weight Saving Ideas to Pursue Your EBIII (Indoor Easybox)

Here's some ideas that Paul and I came up with that didn't make it into this model, but seem like decent ideas:

Use Carbon Fibre rods rather than dowl for wing retainers.
Drill some holes in the airframe - this very strong airframe can lose some rigidity and not really suffer.
Use lighter batteries - this build showed, surprisingly enough, that this model comes out pretty neutral even when built with ultralight components. Mounting the outrunner in front of the firewall is clearly a critical step here, but it should be possible to step down to a 2s350mAh and still get the model to balance.

What's happened to the blog

noreply@blogger.com (Oz RC Boy) — Sat, 05 Apr 2008 21:20:00 +0000

Well - it's still going - kind of. Simple answer is I'm finding the record keeping on flights/etc a pain - so I'm stopping that, and that's sort of lead me to fall out of a few other things I was planning to put on here.

However, watch this space for a future review of the PLD Easybox II as an indoor model, me finally getting that SU27 airborne, and possibly some other interesting developments here at ozrcflying.

Thanks for visiting - watch this space for some more stuff over the next couple of weeks.

Good (Bad) Day at the office

noreply@blogger.com (Oz RC Boy) — Tue, 19 Feb 2008 08:09:00 +0000

Well I'm not going to say much cept the Zero had a nasty spill on the weekend, in what was otherwise a brilliant day of flying.

Enjoy the youtube vids...

A day in the life of an easystar

Fun at Kambah on Sunday

And from the Mongrel:

and

Electric Magic Numbers

noreply@blogger.com (Oz RC Boy) — Tue, 19 Feb 2008 07:35:00 +0000

One of my buddies from rcuniverse (you should check out the BBQ and Beers thread - very friendly guys - yours truly is normally nearby) has found an outstanding piece discussing many "magic numbers" for electrics. He didn't write it (he's more of a "try it, if smoke doesn't come out then increase the power and repeat" type) - so this is someone else's work but they posted it on wattflyer so obviously wanted to share it. If you are the owner, drop me a line and I'll put a credit up here for you.

This isn't an article on electrics for beginners - if that's where you are then take a look at:
http://www.ozrcflying.com/2007/01/electrics-of-electric-flight.html

If you are a nitro head thinking about electrics take a look at:
http://www.ozrcflying.com/2007/09/guide-to-electrics-for-nitroglow-heads.html

So, without further ado:

Magic numbers for modelers...

Schoolboys (and girls) know Watts, Ohms and Amperes. Modelers speak of props, lipos and BESC's. Not to forget the mysterious ‘KV’ and the famous ‘C’, which is not the speed of light... But what hides behind these cabbalistic concepts? And how do they relate to the everyday business of flying RC machines? Follow the magic numbers...

Today's pilots understand that you get more from a good electric setup than an average IC engine. Cheap sources of equipment have dramatically changed the price tag on brushless motors, ESC's and batteries. But it is still something akin to the dark arts to select the right combination of these three items in order to fly well. The best way to success is to follow the secret recipe of electrical gurus, based on kilometers of burned windings, and the third law of universal common sense. Enter the hidden side of real-life quantum physics, the one that mixes weight and mass, translates temperature in 'seconds-of-finger-on-the

-motor-bell' and flying times in burned amperes... Who cares for the Science, as long as we can punch holes in the sky

Buy your watts by the kilo (or Pound)

The first magical number tells you how much watts you need to fly your plane. Of course, it works only for decently matched systems. A GWS parkflyer won't fly with a 300gr motor,
however powerful it is...

Foamie, motorglider, Piper Cub: 100watt per kilogram (2lbs)
Trainer: 150 watts per kilo
Warbird, 'sport' aerobat: 200 watts per kilo
Racer, 3D: 300 watts per kilo
EDF Jet: 400 watts per kilo

Examples: a 3kg (6lbs) 150cm (60") Hurricane will fly on a 600watts setup. A 2.5kg Calmato will require 375 watts, etc.

Watt is pushing us forward?

The second magical number gives an idea of how much static thrust you can expect from a good setup. Once again, this is only true for a propulsion system that is performing normally.
These values give a good indication of what is possible... and what is not.

Brushless outrunner: 4gr per watt
EDF: 2gr per watt
Brushless 'inline': 2gr per watt
Brushless 'inline' with gearbox: 5gr per watt

Examples: A warbird with a 1000 watt brushless outrunner will have 4kg static thrust. An EDF jet having a 600 watts power system gives 1200gr thrust on the ground.

Powerful horses...

The third magic number is in fact a magic formula, one that most of us forgot after school...

Watts = Volts x Amperes
Volts = Watts / Amperes
Amperes = Watts / Volts

How does that relate to horses? Easy: you can convert watts to horsepower with the following rule: 1000 watts = 1.34 HP or 1HP = 750 watts.
Example: a Trainer aircraft with a 12 volt battery delivering 40Amps gives 480 watts (or 0.65HP). Note that the same plane having the same performance in IC would use a .40ci engine providing 1HP, which is 750watts... This is because electrics have a better efficiency, with more power at lower rpms. A similar phenomenon applies to diesel vs. petrol cars. The diesel drives better even if both cars have the same 95HP.

One Hot Minute!

E=Mc2 and the planet is warming up, everyone knows that. Electric motors also get warm. To know how much too warm the windings should not glow, here is a rule of thumb that is nothing short of magical...

Prop aircraft: motor weight in grams x 3 = max. watts.
EDF: motor weight in grams x 5 = max. watts.

Example: a 235gr brushless outrunner can dissipate 705 watts for a minute without meltdown.
A 200gr inrunner on an EDF will not die even at 1000watts.
Of course, this is assuming the motor is correctly used and cooled by adequate airflow.
This rule is only true for brushless motors. Old 'can-style' brushed motors like the Speed 600 don't survive more than their weight in watts...

Resistance is useless...

Gold is a fantastic metal when it comes to moving currents. Unfortunately it is also very heavy. That is the main reason for us to use copper in electrical wires. But then copper transforms some of the current into heat. Not only does it fuel global warming, but it reduces the available in-flight power, which is a real catastrophe!
To avoid this dramatic event, one should always use large enough wires:

Up to 25A: 1.5mm² wire section (15 AWG)
Up to 60A: 2.5mm² wire section (13 AWG)
Up to 100A: 4mm² wire section (11AWG)

Not only wires, but connectors and soldering must be able to handle the current. In this field like in others, bigger is also better...

Round and round

You always wanted to know what the famous 'KV' stands for? This indicates the number of revolutions per volt provided by an electrical motor. It gives us the 'nominal' rpm of a motor on a plane.

rpm = KV x volts x 3/4

Examples: a 1200KV brushless outrunner connected to a 10 volts source will turn at 9000rpm. A 4200KV inrunner on 10 volts will spin at 31500rpm.

Full or empty, that is the question...

The voltage of NiMh cells is said to be 1.2 volts and lipos are sold for 3.7 volts. These 'nominal' values are confusing at best. The real figures depend on what you need. For instance, to know the wattage of a power system, you need to take into account the voltage of the battery at full throttle. But when you need to know if a battery is full, you measure the 'idle' voltage. The values written here give you an idea of typical 'real life' cell voltage.

Lipo in flight (motor full power): 3,3 volts
Lipo fully charged (idle): 4.1 volts
Lipo empty (idle): 3.7 volts

NiMh in flight (motor full power): 1.1 volts
NiMh fully charged (idle): 1.4 volts
NiMh empty (idle): 1.2 volts

Example: In order to get 300watts from a power system, you will need a 3-cell LiPo or a 9-cell NiMh battery and a motor loaded to about 30A.
Here are the (rounded) 'in flight' voltages of typical lipos:
2S = 7 volts, 3S = 10 volts, 4S = 13 volts, 6S = 20 volts, 10S = 33 volts.

Need for speed? Get some serious pitch!

Chosing a prop is not easy. Most people select the right diameter so that the motor doesn't soak too much current . But the pich is often disregarded. Nothing replaces the test flight, but here are some magic numbers to guide you when choosing the pitch of a prop.

Airspeed in kph = pitch (in inches) x rpm / 800
Airspeed in kph = pitch (in cm) x rpm / 2.000

Example: On a big trainer aircraft, a large 14x4" prop spinning at 8000 rpm will get you 40 kph of speed, which is marginal.But a 11x8" at 11000 rpm gives 110 kph which you don't need. The best choice will probably be a 13x6" spinning at 9600 rpm and providing a top speed of 72 kph. This is true for all planes, not only electrics.

Masters of the 'C'

The label on your brand new lipos reads '15-20C', but there is also a '1C' somewhere else on the sticker... WTH???
The '1C' in small letters means the maximum charge current is 1 time the cell's capacity (all lipos charge at '1C'). On the other hand, the '15-20C' note promises you can discharge the battery at 15 times the capacity and even push it briefly to 20 times the capacity without damage. The truth is that most manufacturers are too optimistic, so forget the second number and try to keep the 'peak' discharge current under the first number. A 'realistic' discharge current can be calculated like this:

Max discharge current on the ground = (first number) C x capacity / 1250
Max discharge current during 1 minute = (first number) C x capacity / 1500
Max continuous discharge = (first number) C x capacity / 2000

Example: A 3000mah '20/30C' battery should be able to discharge at 60A during a few seconds. It will survive a take-off at 48A. A whole flight alternating slow passes and full throttle at 40A will be OK. And it could be discharged at 30A continuous without degrading.
Whatever the 'C', remember to provide adequate airflow to cool the battery.

The heat is on!

To cool down an IC engine, you just cut some holes in the motor cowl. For an electric aircraft, you also have to provide cooling for the ESC and batteries. The warm air has to find it's way out of the plane so there have to be additional holes at the rear... But what size of holes do you need to drill?

Air entry surface (cm²) = number of watts / 40
Air exit surface (cm²) = number of watts / 30

Example: a warbird using 1000 watts needs 1000 / 40 = 25cm² of cooling air intake and 33cm² of opening behind the battery to let the warm air exit. The exit MUST be larger than the entry to avoid warm air stagnation which is even worse than too small an air intake.

Check the internal resistance

Modern batteries provide tremendous performance thanks to a very low internal resistance ('Ri'). But all batteries are not equal. To compare two brands or to know if an older pack is still fit-to-fly, you must measure the Ri. All you need is a voltmeter and an (cl)amp meter (or a wattmeter that combines both functions).

Measure the voltage 'V1' during a discharge at a current 'A1' corresponding to ±1C
Measure the voltage 'V2' during a discharge at a current 'A2' corresponding to ±10C

Ri = (V1 - V2) / (A2 - A1)

Example: on a brand new 3-cell 2200mAh lipo you measure 11.4 volts at 2.2A discharge and 10.5 volts at 22A discharge. The Ri of the pack is (11.4 - 10.5) / (22 - 2.2) = 0.045Ω. This means a single cell Ri of 0.015Ω.
Several month later, your plane doesn't fly like it used to do. You measure Ri again with 11.2 volts at 2.2A and 9.5 volts at 22A, which gives 0,086Ω. This means that the battery has lost half its performance...
To be meaningful, Ri must be measured in 'standard' conditions. Ambient temperature, cells temperature and state of discharge have a direct impact on the results. The easiest is to always measure Ri on a freshly charged pack at ambient temp.

What goes up...
...Must come down. But when? Follow these magic formulas to estimate how long you can fly using a specific battery:

Contest or 'full throttle': Seconds = capacity (mAh) x 4.2 / max current on the ground
Aerobatics: Seconds = capacity (mAh) x 7 / max current on the ground
'No-stress' flight: Seconds = capacity (mAh) x 11 / max current on the ground

Examples:
FunJet race using a 2.400mAh battery discharging at 42A Max: 2400 x 4.2 / 42 = 240 seconds, or 4 minutes.
F3A aerobatics using a 4100mAh battery discharging at 52A Max: 4100 x 7 / 52 = 552 seconds, or 9 minutes.
Piper Cub flight using a 3000mAh pack at 34A Max: 3000 x 11 / 34 = 970 seconds, or 16 minutes.

Fly longer: add a cell!
The last magical number gives you an estimate of how much energy a battery stores:

E = capacity (in Ah) x voltage

For instance, did you know you can fly longer with a 3S 1000mAh lipo than with a 2S 1300mAh...? Indeed, to get the same flying style, the 2S at 7.4volts needs to discharge at 13.5A for 100 watts of power. The 3S needs giving only 9A for the same power. Using the time formula, we get a 'No Stress' flying time of 20 minutes for the 3S vs 18 minutes for the 2S. As a bonus, the lower discharge 'C' rate on the 3S battery means it will last longer.
The magic number tells the same story:

Energy in the 2S: 1.3 x 7.4 = 9.62
Energy in the 3S: 1 x 11.1 = 11.1

Some will say that a lower voltage usually means a larger prop and better efficiency. True, but the higher 'C' discharge and current on the motor cause losses that cancel the expected benefits.

Demonstration on my P-40 Svenson (170cm span, 4kg AUW, Motor HXT50-55)
The motor uses 51A Max current on a 6S lipo. The voltage magic number predicts ±20 volts so we can estimate the power: 20v x 51A = 1020watts or 1.36HP. This plane has more than 250 watts per kilogram, it is powerful and climbs vertically, just like the magic formula says: 4gr x 1020 = 4080gr thrust. But beware of the excess heat buildup because the motor weights only 320gr! In theory, it should not be used above 320 x 3 = 960watts. However, on this plane the 26 cm² air intake and 34 cm² air exit provide optimal cooling.
2.5mm² power cables are used for efficient current transfer. The motor has a KV of 500, it runs at 20 x 500 x 3/4 = ±7500 rpm. The prop is a 15x8", which gives a max speed of 8 x 7500 / 800 = 75kph, which is ideal for this warbird. I use a 4400mAh battery, So I can fly for 4.400mAh x 11 / 51A = 949 seconds or about 16 minutes of cruising 'No Stress' performance.
the battery is sold for '20/30C' and could deliver a maximum of 20 x 4400 / 1250 = 70.4A peak and 20 x 4400 / 1500 = 58A during one minute. I must avoid flying continuously at full throttle because I would discharge the pack above its safety limit: 20 x 4400 / 2000 = 44A...

Aerodynamics Basics to Improve Your Flying

noreply@blogger.com (Oz RC Boy) — Fri, 01 Feb 2008 21:41:00 +0000

This short piece is to explain some of the aerodynamic forces that affect your flying and what they mean. Yes - it is theory but I think it will be worthwhile anyway.

Turning

Why does an aircraft turned when it is banked? Why does an aircraft lose altitude when it is banked?

The answer to both of these questions is the same and the diagram on the right illustrates it.

When the wing is parallel to the ground all the lift acts directly against gravity. However, when the plane is banked the lift doesn't fight gravity directly. It pulls up perpendicular to the wing, but that is no longer straight up.

We can think of this lifting force as acting in two directions. Some acts against gravity (less however, than when in level flight, so the plane may lose altitude). Some of the lift acts in the direction of the horizontal, pulling the aircraft into the turn.

Stalling

Many of us think of stalling as simply that speed where we lose lift and the plane noses down. Of coures, the whole story is a little more complicated.

Stalls happen when the wind stream striking the wing passes the critical angle of attack (see wikipedia for more detail if you want). This is normally 14-16 degrees.

The picture on the right tries to illustrate this (click on it to see a blown up version).

As you pass the critical angle of attack you get what is called a separated air stream (go and look at wikipedia if you want more details). This separated air stream (where air passing over the top of the wing doesn't meet air going under the wing) causes turbulence, and destroys the low pressure system above the wing that normally gives lift. That's why you stall.

Given how difficult it is to measure true airspeed in our models anyway, the more reliable indicator of stalling is to watch the way the aircraft behaves in the air. If at neutral attitude she can't maintain altitude then you are potentially heading for a stall (of course you may also be descending to land under power...).

Adverse Yaw

There's a pretty good explanation of this one on wikipedia which is worth a look which explains the forces involved. I'm going to put it slightly differently because I've never seen adverse yaw that prevents an aircraft entering a bank (I'm not saying it doesn't exist) - adverse yaw is a yawing force (so a force that rotates the plane around its CoG on an axis drawn from the top to the bottom of the plane {what the hell do I mean? Think of your plane cartwheeling - that's the axis of rotation "yaw" describes}) that causes the nose of the aircraft to fail to track true when you bank the aircraft using the ailerons.

So if you roll the aircraft and it tends to go nose high or nose low (so if you from level flight you roll to perpendicular and the fuse is not parallel to the horizon) you are getting some adverse yaw.

Now - if you've never really noticed this before chances are you don't get it, or don't get it enough to make a difference.

The correct way to fix adverse yaw is with differential ailerons as the first option (so the aileron that comes up comes up further than the one that goes down goes down - there's a good pic on the wikipedia page - check it out). If you've got a computer radio and your ailerons on different channels then chances are you have a differential function you can use. If you don't the same thing can be achieved by carefully adjusting the neutral position of the servo arm (assuming ailerons are on different servos).

Although your servos hopefully throw the same arc by changing the neutral position in that arc you can make the push/pull motion in one direction larger than the other. Set them up so that in the direction you want the most throw the servo travels through the point perpendicular to the servo. Hopefully the picture on the right makes this all clear.

If you only have one servo to control both ailerons then I guess you are going to learn how to use the rudder to compensate - have fun with that.

Induced Lift and Aerodynamic Lift

Aerodynamic lift is the low pressure system created above an airfoil as a result of the Bernoulli Principle. You need something shaped like an airfoil to produce it. Just as an interesting aside, it's the same effect which allows sailing boats to sail into the wind. While they are sailing into the wind the sails take a shape similar to an airfoil. However, rather than trying to create a low pressure system on the outside of the surface of the sail, the goal is to create a low pressure system just in front of the leading edge of the sail, to pull the boat forward. Just like an airfoil they also have a critical angle of attack which if you exceed (by trying to sail too close to the wind) you will take away the "lift" and the wind will spill from the sales.

Aerodynamic lift is the one that fails when you stall. However, you get more lift for less drag from aerodynamic lift than from induced lift.

Induced lift is the equal and opposite reaction when an airstream strikes an object and bounces off. A simple cross kite is kept in the sky by induced lift - the airstem hits the kite and bounces down. As a result an equal an opposite force pushes the kite up.

Flatties (models made from depron etc with flat wings) fly only on induced lift. They are light enough that they do not need much lift (and half the time they have their nose in the air hovering anyway, so who needs a wing?).

Planes with a "built up" wing (an airfoil) use a combination of aerodynamic and induced lift to fly. For example, when a powered plane approaches to lands with its nose slightly up it is using induced lift (as well as aerodynamic lift) to achieve a very slow but very stable flight. However, the amount of thrust required to hold the aircraft in this attitude is surprisingly high (given how low its airspeed is). That's because the induced lift comes at the expense of large induced drag. Likewise when the aircraft climbs out. It is getting lift from both aerodynamic and induced sources. However, as the plane transitions to stable level flight the induced lift all but dissapears (as does the drag it creates) and the aircraft enters its most effecient flight mode.

The Good Ship Easystar and other adventures

noreply@blogger.com (Oz RC Boy) — Sat, 26 Jan 2008 07:13:00 +0000

Been a while since a post so there's a bit of ground to cover.

On the rotary front I have now had two successful nose in hovers with the TREX - the altitude was pretty higher (5 metres or so) so I was giving myself some margin for error, but I've done it, and the second time was easier than the first, and hopefully it will keep on getting easier.

In other news I now have a Minium Cessna. These cute little 16g RC planes are amazing. Having done a bit of indoor flying now I would have thought getting a scale model that looks this good, and fly this well would be impossible. Bit pricey but it does include everything.

On the topic of indoor flying, it was almost the end of the Cessna. I took her down to nitrodude's indoor night last Saturday having purpose bought her that afternoon. Having had a go on Ground Dancer's I was happy I could handle her, and taxied out. She completed a half circuit before finding the one environment which the superlight plane doesn't automatically survive without problem - the spinning blades of a rotary aircraft. She was brought down with some massive gashes in her wings, busted prop and for a few moments I though she was busted for good. But with a bit of tape, and a prop from another model (thanks Jan) was able to have a number of good circuits indoors with her.

I've also been able to fly her in the street outside which is kind of mad. I just step outside and launch her. If she gets into trouble I just cut the power. She landed on top of one of the bushes out the front the other night.

Have a number of new RC projects on the way. Have grabbed some stuff from Richard Woods at Aussieflight including a Cow warbird (Corsair) which I'm looking forward to seeing. I've also got an Easybox coming from Paul Daniels at NQRC. I'm planning to set that up for indoor flight - hopefully I can build it light enough to make that practical. Finally I've also grabbed a new flycameone 2 from The Mongrel. However, here's the thing - all of these purchases failed to arrive by the end of the week. What happened next was not my fault - you know what they say - the Devil makes work for idle hands...

Here's a hint:

Yes - for some time I have been thinking about how to set the easystar up for amphibious operations. The big long smooth bottom fuselage seems perfect to float in the water (notwithstanding the holes I drilled in the fuse for cooling).

So - I used some duct tape to seal the bottom of the fuselage, and built some really dodgy floats to hold the wing tips out of the water. I wasn't really interested in a particulalry challenging engineering operation, and just wanted to quickly trial the ideal, and decided to velcro the supports to the wing.

So after flying down at Kambah this morning the crew that were about went down to Lake Tuggeranong to try out the amphibious easy star.

Looked good from the start - she floated at almost eactly the height I had planned for and the floats were beautifully holding the wing tips level above the water. The Mongrel (who was flying with me today) was shaking his head about the float supports (they were certainly dodgy but I thought they would make it for a trial.

Here's the youtube of the mornings flying - the Amphibious Easystar is at the end.

So after the flooding you see at the end of the vid there was some speculation that the ESC or RX was fried, but it seemed to get better once it dried off - I haven't retested, but I think they are okay. I'm glad I have the video of the failed take off. Hopefully it will help me figure out what went wrong.

Here's another vid with some flying buddies including ground dancer with his Minimum Cessna (he's the one that convinced me to buy one).

Okay - gotta go.

I've got Friday on my mind...

noreply@blogger.com (Oz RC Boy) — Mon, 14 Jan 2008 23:24:00 +0000

Pretty busy with work (yuck) ATM, so don't have long to post. But I though I would quickly share these videos that the Mongrel shot of our flying over the weekend.

The Mongrel had a new Eflite P47 Thunderbolt model to maiden. I gave him a push in this direction, but he did plenty of independent research too and the P47, or "Jug" came up trumps according to all accounts. He had a very successful maiden, and the plane just slows down beautifully to land.

The zero had a bit more footage shot of her..., this is nice to have of course. With so many flights under her belt you figure her time has to be close to up. BTW I switched from an APC style 8x6 to GWS Hyper Drive 8x6 prop, and man - what a difference.

The Mongrel also strapped his FlyCamOne2 to the top of his Ultrafly ViVi for a bit of a pilots eye view of a flight.

Finally, we also tried to capture our warbirds in flight (from the air using the easystar as the camera platform) with Nathan as the pilot in the first instance, and then tried to catch Nathan's Cessna in flight with myself as the pilot - it's harder than you might think - here's what 15 minutes footage yielded:

Not great perhaps, but we had fun.

The Mongrel is selling those Flycamone2. His blog is linked on the left, although I'm not sure the shop part of it is open yet. For mine I would say the flycam's are impressive little units. Light, very high resolution capture (as always youtube mangles it). As for the Easystar - a good camera platform for the most part, although lacking the rudder authority to maneuver at low speeds. Must get round to doing that rudder mod. Okay - I have to do some work - Ciao.

The Weekend

noreply@blogger.com (Oz RC Boy) — Sun, 06 Jan 2008 21:03:00 +0000

Well, a bit more flying this weekend - heh - what else would I be doing.

I also finally got a successful flight and landing with the Mustang yesterday. I've also found out why I've been having a great deal of trouble flying her. Made to spec she has a wingloading of 18.14 oz/sq ft, or 48g/sq dm - that is massive. To give you some comparisons - the Zero has a wing loading of around 11 oz/sq ft, and the Parkzone Mustang has a w/l of around 14.5 oz/sq ft.

Anyway, after the failed landing attempt with her on Saturday (yes there's a youtube vid of it at the end of this post) she went on a diet on Saturday night. After the landing on "Saturday" the flap servo had broken - so, ditched that plus linkages, and taped up the flaps - including using tape to make close the gaps between the flaps and the wing (so hopefully extracting every bit of lift from that wing) That saved about 12 grams (almost half an ounce). Then I flew her on a 3s 1500mAh rather than a 2200mAh which saved another 46g. The 3s1500 isn't the best battery in the world. It's already done 100+ cycles, so its voltage tends to be a bit average under load, but I just wanted to test what a difference being ligher made.

So, having saved 58g (about 2 oz) I flew her on Sunday. I wouldn't say she was a different aircraft by any means - still pretty portly, but at least she didn't just stall when the power came off, and the difference on landing was noticeable.

Anyway, with a slight breeze on Sunday the first successful landing of the P51 on retracts was pulled off - yeah.

Flew with a big mixture of people on the weekend. The Saturday flying (including the stang er..., landing) is on this vid - check it out.

See yas.

Cheers,
Oz.

Ultrafly P51 Mustang Maiden/Review

noreply@blogger.com (Oz RC Boy) — Sun, 30 Dec 2007 04:55:00 +0000

Well, after having her sit in the stable for almost 12 months, and after a fair few nights finishing off little details the P51 Mustang had her maiden today at Kambah. It was a bright sunny day, with the only real concern being almost the complete absence of any wind - why would that worry me - we will come back to it.

The Plane

The Ultrafly Mustang is a parkflying P51 replica which includes micro retracts, flaps and a 160w FRIO brushless motor. Mrs Oz bought this one for me almost 12 months ago now, so I have taken my time getting round to getting her together.

The Build

Build Strengths:

Good quality foam with positive lock together feel.
Straightforward motor mounting for included motor.
Instructions are straight foward and clear (provided you read the errata as well).

Build Weak Points:

Heavy - as you put the plane together you just can just feel the weight building up.
Hardware for flaps not correct (there are no pushrods that work).
Threaded rods don't fit inside included control sleeves for rudder/elevator (I ended up using thin wire which fit).
Decals not very sticky.
Build takes a long time.

Calling this an ARF is stretching the definition beyond breaking point. I wouldn't know exactly how many hours I've put into it, and although I've done it in fits and starts I doubt it is that much less than my Stevens Aero RV4.

The Flight Pack

With a 6 servo set up the thing that is probably most unusual about this plane is that you must have a standalone Battery eliminator if you want to run flaps and gear (which I did).

So I used one of these Phoenix Hobbywing 25A with separate switching BEC. Receiver was an MKS 8 channel. Servos were a mixture of cheapies and hitech HS55.

Given the modest power requirements (160W) the battery was a 12C 2200mAh Elegance LiPo. I gave serious thought to using a lighter battery given the manual tells you to stay below an all up weight of 650g.

The Flight

As I said, the wind was very light - too light really (because warbirds land better with a nice head wind). Took off into the breeze. With no steerable tail wheel you are at the mercy of the gods as to where the plane turns as it accelerates. Of course the undercarriage is a delicate affair, and the method for locking in the direction of the main wheels leaves a little to be desired.

After takeoff I spent a few minutes trimming the plane. Once trimmed she flew very steadily, although, at an AUW of 660g she felt a little heavy in the air at all times.

Large loops even with full power were out, and even with aileron deflection set 50% higher than recommended (that was my high rates setup) the planes roll performance was not outstanding.

However, when she was riding along at mid throttle in the air, with her wings level, she looked the part, particularly as she passed overhead showing you her tucked in wheels underneath.

When it came time to land I was in a bit of a bind. The wind was coming from the South, but my time at the North end of the field had convinced me it was quite glitchy up there. I didn't want to temp fate with an approach from the North. The wind was almost non existent, so I decided to come from the South. However, this did mean a hottish landing would be compounded with just a little tail wind. Nevertheless, on approach it all seemed doable.

The plane began losing altitude alarmingly quickly as I reduced throttle, and I found she need to fly quite quickly to avoid a stall. I brought her in to land, flaring her nicely to touch her down - she still had quite a lot of velocity, but she made nice 3 point contact (showing she had no lift left to speak off). Then she rolled out for 5 metres, and hit a tuft of grass growing through the asphalt strip, no higher than 1/4 an inch above the surface. Not even enough to make the plane nose over, but enough to make the hopeless hopeless Ultrafly retracts collapse.

I can only say my experiences seem to line up with others with this plane. The power is a little disappointing, and the retracts are a joke.

Here is the youtube vid of my flight including the landing, so you can judge for yourself whether you thought I was too hot, made a mess of it, whatever.

I'm going to be trying a pair of GWS ultralight retracts on this plane. The seem to lock properly, which seemed to be a critical weakness in the other model. I'll let you know how it goes.

Summary

Without the retracts this model is a kind of expensive, hard to steer warbird, but it does fly pretty well (not withstanding power caveats). With the retracts/flaps it would be a nice to fly warbird with a great scale touch for the park..., if you didn't need to pull off not just a good landing, but a perfect landing every single time.

Holiday RC

noreply@blogger.com (Oz RC Boy) — Fri, 28 Dec 2007 22:07:00 +0000

A few notes on what I've been up to...

A week ago I nuked the motor on my elebee. I had a brand new 4s 2200 LiPo. Unfortunately, the slight voltage and current delivery differences between the old 4s and new 4s was enough to nuke the motor. When she came down I touched the battery - nice and cool, touched the speedie, warm but just fine, touched the motor and burnt my finger (ouch!).

Was actually flying her head to head (kind off) with another elebee - this one on 3s. So I need to source another motor - that align one stood up to a lot of punishment, and I was certainly happy with it, but I'm thinking if I can get something cheaper in the 2000kv range from UH that is probably where I will go.

The Tucano had a close call on boxing day morning. I'd just put here up, she was running about nicely when suddenly she started rolling to her right. At first I messed with trim before realising there was no way trim could account for that roll rate. It took almost full left aileron to keep her flying straight and level, and she was very sluggish in the air.

An emergency landing saw her on the ground in one piece. When I got closer it became obvious the right wing servo had failed, and failed in an upward deflected position, leading to the roll. And of course, when you counter the roll you end up with two airbrakes! Oh well, a reasonably straight forward repair I guess.

Have been giving my TREX a few tentative hovers. I'm not real impressed by the MKS gyro which is installed at the moment. Having come from a faulty, but more expensive gyro, which didn't need trimming and held the nose proprely, having to trim the MKS everytime the heli takes off is a real drag (frightening in some situations). Yesterday the MKS gyro was so out of trim I was hesitant to take my fingers off the rudder for long enough to trim the heli.

Some news on my Ultrafly P51, which has been sitting round since my last birthday. She is almost ready for her maiden. I've installed the works - retracts, flaps plus those other kind of essential controls like rudder, elevator and aileron. Hopefully maiden her tomorrow (should have had her ready today but for slackness).

My 45 minutes to disaster post and my learning to fly course seem to be getting a fair amount of attention - no doubt lots of Christmas presents have already had their maidens. Welcome to the blog to the new readers - I was where you are about 14 months ago.

45 Minutes to Disaster

noreply@blogger.com (Oz RC Boy) — Fri, 21 Dec 2007 12:36:00 +0000

It's Christmas morning and you have finished opening the presents. Someone has an RTF plane and is just itching to get it down the oval and have a fly.

Timeline - 45 Minutes to disaster:

45 minutes to disaster - You quickly pull the battery and charger out of the box and hook them up. Sorted
43 minutes to disaster - You start flicking throught the instructions - seems straight forward.
40 minutes to disaster - You take your first attempt at attaching the tail. But how do you get that control rod into place.
30 minutes to disaster - You begin the final assembly of the tail.
25 minutes to disaster - You put the main wing on - there that was easy.
20 minutes to disaster - The prop is now on. You fumble around for the batteries for the transmitter. Turn it on - it lights up - looks good.
17 minutes to disaster - You start flicking through the "how to fly" section of the manual - okay this stick left/right bank, up/down here, this one makes it go faster. Don't fly when it's windy. Get someone experienced to help you - peh - who has time for that.
12 minutes to disaster - So for landing, just turn it into the wind and cut the power - how simple is that.
10 minutes to disaster - The battery is charged - you chuck the plane, battery and transmitter into the car and head to the local school yard.
5 minutes to disaster - You arrive at the school yard. It's not windy at all really. You can barely notice the wind, and the odd bits of litter are only flying two or three feet at a time when the wind gets underneath them and lifts them away from the ground.
3 minutes to disaster - You plug in the battery and turn on the Transmitter (in that order).
2 minutes 45 seconds to disaster - You do a radio check - the manual seemed to think that was really important, but you aren't sure what the big deal is.
2 minutes 15 seconds to disaster - You push the turn control - aw - that's how that works - neat. You wonder if it should be in the middle - it seems pretty close - surely that little bit wont matter.
1 minute 40 seconds to disaster - You fiddle with the up/down control. That's easy isn't it - just remember to pull back to make the nose come up. You look carefully at the transmitter while you play with it.
1 minutes 15 second to disaster - You realise the wind is not coming straight to you across the field. Rather than walking 50 metres for a clean take off you figure you can take off into the wind parrallel to that row of trees at the edge of the field.
45 seconds to disaster - You put the motor on full bore - sounds okay. You wiggle the controls again. You're still not sure about that control that doesn't seem to line up, but you figure you'll fix it after the first flight.
11 seconds to disaster - You give the motor full power and throw the plane.
9 seconds to disaster - The plane is banking to the right straight towards that line of trees you didn't want to walk away from.
7 seconds to disaster - For two full seconds you do nothing. Then you push the left right stick to the left. Your plane is getting perilously close to the ground.
5 seconds to disaster - why isn't the plane responding. You look down at the transmitter to try and get your bearings on which control is which.
3 seconds to disaster - You try telling the plane to climb with the up/down thing. The plane seems to be losing altitude, not gaining it, and you are almost at the trees.
2 seconds to disaster - The plane flys between a gap in the trees and is now headed across the street at someones house. You glance desperately at the controls to try and figure out which control you need. You try to use the up/down thing to ditch the plane into the ground, but rather than diving it starts to accelerate.
1 second to disaster - You watch in horror as you realise the plane is headed at someones lounge room window and that you have no idea how to stop it. You don't know what to do. Something deep inside your mind is telling you to drop the transmitter and run like crazy in the opposite direction.
0 seconds to disaster - the wing tip catches on a railing, cartwheeling the plane into the cement balcony and it then collides harmlessly (for the house) with the wall just to the side of and below the window.
5 seconds after disaster - You realise the motor is still running. You look down at the controls and realise the throttle is on full. It dawns on you that when you were trying to tell the plane to climb of dive you were actually playing the with the throttle and the entire time you were trying to tell the plane to turn you were playing with the stick that seems to do nothing.
17 seconds after disaster - The people inside the house have emerged to see what the thud was. You are greatful they've had a couple of drinks, seems like good people, and see the funny side. You collect your wreckage and head for home.

Okay - so a bit of poetic licence there but seriously - many first flights go an awful lot like that one.

I hope if you are reading this on Christmas day, you are doing it just before you go out to fly that new model, not just after.

Now I've written a whole series of notes on how to learn to fly - they are over on the right hand side at the top but I'm not sure you will have that much patience - so I'm going to give you the 30 minute version - you've read this far. What I'm going to ask you to do will take another 30 minutes in preparation and this will increase your chance of a successful flight enormously.

Appropriate Model

Do you have an appropriate model? An electric trainer will be three channels (Rudder, Elevator, Throttle) and will look pretty ugly, but tough (the HZ Supercub is an exception - it looks nice but tough). If the well meaning other half bought you a spitfire/mustang/corsair/F15 etc if you try to fly it today you will end up with bits.

So - only read on if you have an electric trainer. I guess you could read on if you had the other type of model but I'd recommend against flying it.

Trimmed

The control surfaces need to line up almost exactly with the thing they are attached to. Use the trim tabs on the transmitter. If you can't get it to line up even with the tab pushed full over you need to make a mechanical adjustment - don't fly with it like this - you will crash.

Familiarising Yourself with the Controls

Here is the most important thing - when you are flying you should never take your eyes off your model, and things happen too fast to rely on looking at the controller to figure out what to do. Spend 20 minutes, with the battery in the model in the lounge room grooving which stick does what into your brain. Don't look at the transmitter while you do it - look at the plane.

Disconnect the battery from the plane, and now build the throttle into your practice as well. Make sure you can set the throttle at full, half and off without looking at it. If you have someone to help you get them to quiz you for 3 or 4 minutes - nose up, turn right, etc - afterwards check the input you made and make sure it was the the right one (include throttle too, provided the plane isn't "on").

Practice doing small as well as big inputs to the controls.

Go to the big field

Spend the extra 10 minutes in the car to get to the really big sports field (you know - the one with 4 football fields etc).

Use a Ribbon to Test the Wind

If it deflects more than 45 degrees from straight down when you let it hang out of your hand then it is too windy..

Takeoff from the downwind edge of the field

Walk as far as you have to take off directly into the wind out across the centre of your field.

Takeoff at Full Power - be ready to correct the model immediately with a small input

The model will almost certainly not fly out straight and level - even though you trimmed it on the ground subtle misalignments mean you will need to trim it in the air. From the moment it leaves your hand it will start to turn one way or the other - you need to correct this immediately, but with only a small input.

Likewise, as you climb out you want to use a little up elevator - not too much otherwise the model will stall.

Do nothing except keep the plane wings level, nose slightly up for the first 50 metres - you want to put on as much altitude as you can.

Set your throttle at half

After the initial climb out set your throttle at half - this will stop stuff happening so fast.

Always turn left

For your first flight make all your corners left handers, 90 degrees and just try and fly a big box. If you turn both ways you may disorient yourself.

Remember, small smooth inputs building up as you get a feel for how the aircraft responds.

Regain altitude between each corner

When you aren't in a corner try and put on some altitude. You may need more throttle for this.

Landing

Close the throttle. After that you have two jobs - keep the wings level, and put her on the deck before you run out of runway.

You will probably find it easiest to land going away from yourself so you don't get an orientation mistake (where you get your left, and the plane's left confused).

That's it - that's what you can get through in 30 minutes. If you must fly then fly - good luck. Afterwards come back and read the full course notes. Oh, and of course, all the best for the Holidays... 8-)

Oz.

Flying at Murrumbateman

noreply@blogger.com (Oz RC Boy) — Mon, 03 Dec 2007 12:39:00 +0000

Went flying with a buddy from RC Universe out at the Murrumbateman fair ground last Saturday.

Had a nice little fly on some quite challenging "run ways" and conditions were a little cloudy, but overall was magical.

Here's the vid he shot - great to have some more video of my birds flying - particularly my old favs - the Zero and the RV4. Thanks Mongrel...

It's all fun until someone loses a TREX

noreply@blogger.com (Oz RC Boy) — Thu, 29 Nov 2007 22:46:00 +0000

Just moments ago, while hovering in the front yard I had what I think can be fairly described as my first serious heli smash.

It didn't seem like a big impact, but it sure has done some damage.

I'll let the photos speak for themselves.

I'm pretty cool about the whole thing.

As always seems to be the way, I was having a pretty good flight, I'd done a pirouette, tried a nose in hover (shortly before flicking her back to nose out before I lost her) and was happily flying around 1.5-2.5 metres.

As I was thinking about finishing up the battery at about 2.5 meteres she took a hit that brought the tail round and started going to her right - definitely not a control input (perhaps the gyro just gave up for a moment). I didn't think I could get her back (a tree was getting very close), closed the throttle and hoped for the best - looks like I could have saved myself the effort.

Oh well - repairing helis is part of flying them.

Big Weekend Flying

noreply@blogger.com (Oz RC Boy) — Sun, 25 Nov 2007 09:36:00 +0000

Spent a fair bit of time on RC flying this weekend, with flying both mornings, and indoor night last night at Erindale College, and going out to take a look at the Namadgi Club open day today.

Not sure how much of what has gone on seems blogworthy but here's an attempt.

I installed some rare earth magnets in the wings of my easystar. A couple of times after high speed runs I was finding, even after a perfect landing that one of the wings had started to come away in the air. Needless to say that could get bad easily. The rare earth magnets are installed about an inch forward of the CF spar holes in the wings. Had a test fly with it today. Works good. Even after much gliding punctuated by high speed stupidity the wings were exactly where I left them (an unsurprisingly comforting thing for an aircraft).

The one incident of the weekend involved stalling the RV4 on approach on Saturday morning. She was just coming down a bit short (with me trying to perfect the positive AOA landing technique) and I gave her a click of throttle and some more up elevator - should have have just given her more throttle. She is a little hard to get in correctly, not cause the technique is wrong, but she is flying so well on that 8x6HD GWS prop, and there just isn't enough granularity between those low throttle positions to get quite what you want (or that's my excuse anyway). She was barely moving when she stalled, and damage was quite light - snapped the over wing stringer on the right hand side - glued up with CA this morning and she flew like a trooper this morning.

Elebee got some stick time after a bit of an absence - still just as she was.

Put a few more batteries through the TREX. Even did a pirouette today - first one ever in a real heli, and recovered to a nice stable hover at the end. Moving towards nose in hover gradually.

Speaking of helis the indoor night at Erindale had the normal amount of carnage and destruction. My Squirt was let down by her speedie and so didn't fly, but the Blackhawk had a good stretch of her legs. Was great to fly the counter rotating ship in such a nice large space, and see some of it's flight characteristics.

I did learn one thing - it is possible to bring down counter rotating helis - get enough speed in them, rudder them round to 90 degrees and give full cyclic role - blades touch, lose all energy and the thing falls to the floor like a feather. No real damage but a broken undercarriage strut (and I had a spare) - I spose this counts as an incident too, but let's face it - indoor night - it's gonna happen.

Close Call For T-Rex

noreply@blogger.com (Oz RC Boy) — Fri, 16 Nov 2007 13:28:00 +0000

After messing about with the T-Rex out in the front yard yesterday I had a couple of moments where she started yawing to the left and seemed to stop answering rudder. It wasn't like a complete failure - the heli didn't pirouette, but it was not controllable.

This was easily handled out the front - I only had her 3 feet off the ground so just close throttle and land.

Anyway, popped back down to nitrodude to get Paul to take a look at it. He had a fly, we played with the gain on the gyro a bit, and then I had another fly. We hadn't been able to replicate my problem and were thinking maybe interference.

I had her up and flying about quite well when she stopped answering the tail again - she was much higher this time and she started turning to the left. I fought with her for a few moments but she got back over my head, and then over the roof of the verandah outside Nitrodude.

Given I was about to lose visual on her I just tried to slow her down as much as possible and shut the throttle. There was an all mightly bang as it hit the sloping tin roof. We all walked away from the building looking up onto the roof expecting to see debris. And there was the T-Rex sitting happily on the roof with her blades gradually slowing down and pointed directly out from the building. Paul flew her down from the roof, and at this stage let me know that he thought he might have had a moment where the tail stopped responding but my flight had confirmed it. Bad gyro. It's been replaced now.

Oh - the TRex didn't quite escaped unscathed. She broke one of her landing skid supports - but let's face it - that's nothing. I'm trying to epoxy it while I wait for new parts.

One other thing I wanted to mention. Over the last two weeks I've been helping a nice guy called Richard Wood (Woodsy) set up his RC shop. He was trying to run the site with html etc - I just helped him out by setting up a basic ecommerce site for him - which I think is great cause now he can focus on what he does well - customer service - rather than battling with Microsoft Frontpage and HTML. Anyway you can find his shop here: http://www.aussieflight.com.au - He's got some quite unusual stuff there as well as a great collection of other models and things.

In Other News

noreply@blogger.com (Oz RC Boy) — Wed, 14 Nov 2007 21:40:00 +0000

Few interesting things to share.

First, Mrs Oz helped me snap a few photos of the twister hawk (Australian Army livery) on patrol around the lounge room.

If you click on the photos in the title bar it will take you to the images directory, giving you a thumbnail of all the images on the site. But I've put a couple here to give you a taste.

This little guy is quite a lot of fun to push around inside. To be honest it wanders a little more than you might expect, but with a little practice and it is definitely possible to fly around safely indoors.

Although I might get there eventually with My little GWS mini-dragonfly there is no way I could attempt that at the moment. That being said, having flown the MDF at nitrodudes recent indoor night I'm aware how much easier things get when you have no wind.

By the way, I've tried the "Blackhawk" outdoors - when they say no wind, they mean NO wind. Even in a 2-3 km/hr gentle as you like breeze the blackhawk couldn't hold position against the wind.

Other news - my TREX is finished (with thanks to Paul @ Nitrodude for helping me with finishing the setup of pitch and throttle curves) and I even had a brief hover of it yesterday. This is such a different machine to the MDF. In it's own ground effect it still achieves a fairly stable hover with very little input. Six inches of the ground I am still making only minute adjustments to keep it hovering compared to the MDF. Now don't get me wrong - I'm glad I started with the MDF (thanks grounddancer) - there's no way I would have had the confidence to try and hover the TREX, let alone the skills to actually do it without the many sessions I've put in on the MDF. So, onwards and upwards in that direction.

Embarrassingly, I've actually figured out how to land aircraft - I used to think I knew, but now I know I didn't. I'll be re-writing advanced landing at some stage in the future. Keep an eye out for it.

Finally, having the RV4 back in the sky has been a delight. I'm not going to pretend she is a challenging plane to fly, but she flys beautifully, is fun, and I did build her, and it is just great to see her crusiing around the sky again.

With the RV4 and the Zero out on the tarmac together the other day I realised that I had choosen to only bring my two oldest planes to the park - nostalgia eh (it ain't what it used to be I hear). See you next time.

Cheers,
Oz.

Some Updates

noreply@blogger.com (Oz RC Boy) — Fri, 09 Nov 2007 14:46:00 +0000

Hmm, given it is late I wont spend long but here is some stuff to bring readers up to speed.

I've bought myself a little hawk twister counter rotating heli. I wanted something I could fly inside and I don't have enough ability with the dragonfly yet to get close to that point. From nitrodude for $199.

Have had quite a few plays with it. I'm currently hovering above a card table (its helipad) wedged between a walking machine and fish tank. The space seems tight but no doubt a bit more talent would help.

Anyway, Paul at Nitro helped me out with a few adjustments this evening getting cyclic roll and pitch properly trimmed and she now approximately hovers at neutral control inputs. She keeps on yawing to the left (mostly - very occasionally to the right). Suggestions are that as the motor wear in a bit that might improve.

Okay, other bits of exciting news - depending on weather tomorrow I will be re-maidening my RV4. Pretty exciting. Even with badly bashed up balsa it is so often worth putting it to the side and coming back to it when the pain of the crash has passed.

Although the repairs are done I have some concerns about some of the wing forming stringers - also a little worried about the strength of the fuse over the wing given how many times I have repaired the stringers there. No snap rolls okay ozzie?

Now, the last bit of exciting news - tomorrow I pick up my new T-REX 450S fully built. Ground Dancer won it in an auction a few months ago, just before realising he didn't have room for another heli so he sent it my way at a good price.

So, several weeks ago I opened the T-REX box while at the PC, planning to thumb through the instructions (the box says 80% complete) figuring there wont be much to assembly... WRONG! The first page talks about joining individual nuts and bolts together to assemble the head, and it didn't look like it got better from there - so, I spoke to paul@nitro who arranged for their heli repair service to build my chopper - fantastic - expert assembly for a pretty good price.

Now, as for that 80% figure - the only way I can see they can defensibly say that is they are including mining, smelting and milling of the aluminium. In an industry full of exaggerations about completeness it stands out as an even more unrealistic claim than usual. Anyway - it's late - I'll try and keep the blog a bit more up to date.

The Roll of Honour

noreply@blogger.com (Oz RC Boy) — Fri, 09 Nov 2007 13:52:00 +0000

Sweet Dreams and Flying Machines in Pieces on the Ground - Fire and Rain (James Taylor)

Here is where I remember those planes that have passed on pursuit of the freedom of flight.

In the line of duty

Eflite Mini-Pulse XT

Type: 4 channel low wing balsa ARF.
Engine: Eflite 480 Brushles with 11x7 prop.
Battery: 3s 2200mAh.
Avionics: 4 x Esky Servos, MKS Narrowband Receiver, Align 35A Brushless ESC
Built Time: 5-6 hours (really!).
Pros: Nice wide flight envelope between cruising and high speed with the eflite 480. Seems to be capable of many aerobatics - particularly at 75%+ throttle Can even do a knife edge. Goes together really quickly. I'm also a big flan of the tail mounting servo setup in this model.
Cons: No so sure about the landing gear on this model. I bent one of the wheel axles under quite low load. Plane also has higher flying speed than you might think (it seems slow in scale terms how fast it has to fly to maintain altitude).
Built Tips: Don't plan to go past an 11 inch prop - she wont rotate. I'm not sure the CoG from the plane is right. You can come a little forward of the recommended CoG and she still flys well. If you are using the Eflite 480 (and you should - for a few bucks it is much more fun than the 450) then use washers between the X mount and motor (and locktite in the screws) to give just a little more clearance for the bolts, and preferably, go and buy some Dubro 4-40 1.25 inch bolts (they have a much lower profile head with a flat head screwdriver) which will fit the space far better.

Service Life: 51
Accident Cause: Three glitches in a row from a starting altitude of 6 metres.
Accident Site: Kambah
On Reflection: A great plane. A moderately capable aerobat, but gentle flyer.
Career Highlight: The knife edge circuit she did the morning she crashed.

Honourable Retirees

Electrafun XP

Type: 3 Channel Trainer, Pusher Prop
Engine: 400 Class Electric
Battery: Mixture of stock (8.4v 650mAh Ni-Cds) and aftermarket (8.4/9.6v 1100mAh NiMH)
Avionics: Included
Built Time: 15 minutes
Pros: Cheap, flys well, flys fast. Can perform basic tricks. Very robust will stand up to a lot of punishment. Very forgiving. Like the energizer bunny - just keeps going and going and going.
Cons: Avionics are rubbish - don't put them in any model you value. Batteries don't give great flight time.
Service Life: 145 flights with me.
Retirement Reason: Outgrown
On Reflection: A great plane that I owe much of my passion for model flight to.