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Friday, December 30, 2011

Z8RC Finishes 2011 With Our Best Day, Ever

Happy New Year, honesty lovers!

Now with 300-600 readers per day, Z8RC has established itself as a premier RC review site and the world's only mainstream source of expert, impartial and down-to-Earth RC aircraft and helicopter reviews.
In 2012, I pledge to Z8RC readers our continued refusal to take any money, products, sponsorship, or any form of compensation from the manufacturers or resellers of the products under review.

That is in stark contrast to all other mainstream review sites, RC groups, forums and magazines who are on the take.  Unlike Z8RC, they are compensated by manufacturers of the very products they pretend to "review" (= paid advertisement) in exchange for positive commentary (= sleezy salesmanship).   Yes, their petty business model is to systematically rip off the entire RC loving world just to pocket a few peanuts.

Not here.  No way. 

Keep the Faith and enjoy the end of days!

Tuesday, December 20, 2011

E-Flite Cessna 150 Aerobat 250 - Build & Flight Review

This will be a complete build post, including a flight review.
Yes, the wingtips are orange, not red as shown on the box.
The plane comes in one of the original, but rather 
odd, two tone red/orange paint scheme..
I bought this Cessna based on the strength of the real airplane.  With relatively recent challenges from more flashy designs like the Diamond DA-20, and previously Piper's Tomahawk, the little 150 continues to grow in stature.  

The Diamond, well, it looks great but flies like a POS by comparison.  And although I got my civilian wings in a Tomahawk, I never felt it flew particularly well even as a beginning Student Pilot.  Yet, every time I hop in a 150 or 172 I'm treated to a "better than I expected" flying experience.  These aircraft have endured because they fly better than anything else in their class.
The Tomahawk posed a brief challenge to the 150 in the 
early 80s, but it had too little excess power.  Although 
Piper creatively branded the plane "spinnable" 
for training purposes, it is simply not as stable 
or as joyful to fly as a 150.
The little Diamond DA-20 is a charmer, but jeezus those 
seats are rocks, and the bubble canopy with no A/C 
can be a joke.  The wheel pants look nice, too bad 
the nose gear doesn't steer and there is very little room 
to differential brake in the foot-wells. Flying this
underpowered plane is, well, a bit of a chore.
With the strength of the core design not in doubt, $119 minus 20% in illegal store-based coupons sealed the deal.  Horizon Hobby does not permit price competition among it's resellers, apparently not realizing that American retailers will find creative ways around their European socialist nonsense business model seven ways to Sunday.  Without the store discount, probably not, but for under $100 the heavily discounted E-Flite mini Cessna seemed promising enough to try.

I would like this little guy to be a relaxing evening flyer.  Relaxing, to me, means mostly hands-off manners, decent float, plenty of power for sport aerobatics, excellent flight times, and spot land-able for quarters.  To accomplish that, my plan is to disregard E-Flite's instructions entirely and build the plane as it's Chinese designers intended.  With a pair of AS3X micros on deck waiting for good weather, I feel mildly inspired to insert a GWS single axis gyro to keep the mini Cessna's wings on perpetual attitude hold.  My hope is to create a versatile, compact, take-it-anywhere evening flier that, like the real 150, always flies a little better than I expect.  "Hope" is an important four letter word in the previous sentence.

With 196 square inches of Wing Area and an advertised RTF weight of  13.7 oz, there seems to be plenty of Chinese workmanship in the box to work with.  Kudos to Horizon Hobby for leaving the product alone and letting the builder make the design trades, as E-Flight has proven to be one of the worst RC design houses in the business when it comes to analyzing power systems.  They seem to use a De Beers sales model:  creatively package new products to peddle whatever has trouble selling on its own.  Or, said another way: double-down on your worst products to unload them at the customer's expense.   That was certainly the case with their Ascent 450 BL, which include the heaviest brick motor I've tested in a long time--in a motor glider.  Well, if you are going to try to rip someone off, you might as well go all out, I guess.  The bare bones nature of this Cessna seems like a safer bet.

With the airframe by Cessna, the build accomplished in a sweat shop in China, that leaves simple price mark-up in the deal for E-Flight.  And hey, that is just the kind of deal I can strike with an incompetent RC design house.

For the power system, I elected to go with a $24 Super Tigre 370 ($20 after typical discounts) instead of the recommended $40 E-Flight 250.  The reason can be found at the 5:00 minute point in the video clip below:
The ST 370 costs $24 and has a lot more power.  I know from powering my 14 oz 39" GWS Brushless DHC-2 Beaver that a 2S 370 had nowhere near enough power with an 8x4.  A 2S 250 powers my 8 oz 31" E-Flite Jenny without much slack, often coming up short.  So even though the Super Tigre 370 weighs a fraction of an ounce more, this is a no brainer.

Again, E-Flight is in La La Land recommending a 2S 250 driving a 7" prop for a 37" plane.  I guess they have 250 motor inventory they need to move.
The 370 fit perfectly with a few 1g, custom cut, thin brass tube spacers.  I selected a 10A Common Sense RC Swift ESC, which like the motor, is less than half the price of E-Flight ESCs which have the same specs, but without E-Flite ESC's lousy track record of burning up on me.  A $45 Hitec 6 Lite tops off the internals.  Commonly available store coupons brought the deal down another 20%.  But this plane is anything but cheap, after store discounts: $96 (airframe) + $19 (motor) + $11 (ESC) + $36 (Hitec 6L with built-in V telemetry) = around $162 before $36 in servos that I have stocked.  I used a metal gear servo for the rudder given its double-use to steer the nose gear.

Total cost came out to just under $200 as a Hitec Rx BNF with built-in V telemetry.  As an after thought, I added a GWS wing leveling gyro that I had laying around new in the box, which tacked on $27.

My thrust scale read a preliminary 12.6 oz of installed thrust operating at full bore while spinning a GWS 8x4 HD.  Once better aerodynamics are in place, namely the cowl and windscreen, that number should read closer to 14 oz.  Max Amps on the Wattsup were 5.49A from an 800 mAh 3S, suggesting 18 minutes flight time at 50% throttle or 9 minutes at 100%.   Nice.

I later switched to a 8.5x5 prop (clipped from a 9x5) for 18 oz of thrust at 8.5A, more on that below.
In the Air:

This Cessna is an excellent flier.  From the realistic/scale rotation on takeoff roll, to the stable puttering cruise, the 150 lives up to its venerable reputation.

So to save time gushing over the good things, I'll jump right to a few rough edges.

First, the airframe is expertly built and covered.  It is exceptionally light and quite sturdy.  But E-Flite managed to screw up the plane anyway by under-powering it substantially.  Even with my decision to jump straight to a 370 spinning an 8x4, the prop really wasn't big enough to overcome the 1000 kV RPM limit and generate plentiful thrust.  The Cessna had enough thrust for better than scale flight, and most people would probably consider the 370/8x4 combo sufficient, but for the way I like to fly and if there is any wind to fight, the 37" Aerobat needs a little more pull.

E-Flite's recommended 250/7x3 power system should not even be considered, as it would be way too weak for comfort.  I found that even an 8x4 prop spinning near the kV max limit wasn't quite strong enough.  It was reminiscent of, bad not as bad as the old Select Scale Super Cub's way to weak stock 8x4 prop.

I tried an ST 400 to see if the bigger motor generated more thrust, since the mount's form factor is the same.  It didn't, because the prop shaft to wheel bottom limits you to an 8.5" prop diameter, and with such a small paddle, a larger motor's kV limit dominates.  Since the 400 is 950 kV vice 1000 for the 370, the 370 actually pumps more air.

After a good amount of motor+prop+thrust scale+Wattsup experientation, I think the best prop and motor combo for the 150 is the lightweight and powerful Super Tigre 370, a GWS 9x5 clipped to 8.5".  The extra .5 inch and steeper pitch actually adds 50% more thrust, at 18.2 oz after installation losses.  The chosen motor/prop pulls 8.5A at max throttle, which seems very reasonable for my 10A (continuous) / 12A(burst) 0.3 oz Common Sense RC Swift ESC.  The final power system comes in at a little better than 1.1 early in the battery, with mostly-aerobatic flight times in the 10-12 minute range from an 800 mAh 3S.  Super!

Next, the wing is somewhat prone to tip stalls after crossing the ragged aerodynamic edge beyond critical AoA.  I think my particular setup bears a third or more of a the blame, but not all of it.  I decided to put an a GWS PG-03 Gyro on the ailerons, just to use it and do something interesting.  It worked tremendously well to stick the wings where you left them.  But I think the gyro works so well that it makes tip stalls seem a little more pronounced by fighting bank until there isn't anymore air left to support the plane.  Then whoosh, down comes a wing.

On the flip side, the presence of the gyro probably reduces wing drop, right up to the limit.

Another issue I caused, or, well, didn't preempt, is the vice of fully symmetrical ailerons.   Because of the gryo, I opted for a Y harness to connect the ailerons.  I knew it would hurt, but I decided the gyro route anyway, since it isn't like this plane is hard to fly.  The downside of the Y harness is aggravated stalls near the wings tips because neutral aileron doesn't offer any washout, and when wing drop is countered, the down-going aileron moves as far as the up going aileron, making the lifting-aileron-wing prone to stalling first and stalling hard.

I know, the Y harness isn't really an excuse, but I was too lazy to dwell on wingtip aero with this plane, just in case it stalled gently without wing tip magic.   It didn't.  So I'll go back and dial-in mechanical washout and differential.

The Aurora 9 has me spoiled, it is so easy and configurable to do this stuff via computer, and a bit of a pain to set it up manually.  Spoilerons can be hardwired, or set to a switch or roller.

To set up mechanical washout, two options come to mind.  One is to physically twist the wing tip incidence angle a few degrees lower than the root, then melt it there with a heat gun.  The Aerobat is beautifully covered, so this method would be no problem.  The other way is to increase the length of both aileron push-rods (assuming they are under-wing), which deflects both ailerons up a little.  As long as the ailerons are not full wing, this method works well and allows adjustments in knowable increments.    I'll use method 2.

To dial-in differential ailerons mechanically, I'll need to open the aileron servo compartments and adjust both servo arms to forward-of-center when the stick is neutral, then again, lengthen the push rods to compensate.  By adjusting the servo arm forward-of-center when the aileron stick is centered, when the aileron gets pushed up the servo arm's arc is more tangential, which generates more linear travel than when it pulls on the aileron.

Still, I want to emphasize that the 150 is a superb flier even without perfect dial-in.   The video below shows a typical flight with the final power system described above, but still with no mechanical wing tip /aileron wasout/differential adjustments.  The 8.5" prop has min clearance and strikes a few pebbles, but overall the tricycle gear protects it pretty well.  The wind was swirling at a turbulent 5-10 mph, and you can see the aileron gyro working hard on some of the closer passes (see minute 1:20, you can sort of see some large flags strongly billowing, below the plane and behind the tress, at the beginning of that pass)--what fun!

Since my HD camera is arbitrarily limited to 10 min clips thanks thanks to bad decisions made by Canon, I tacked on a landing from the next flight after the first flight video stopped filming at 10:00:
As you can see, aerobatics are very spirited.  Loops can be about as big as you want, but due to the high camber airfoil, you have to push around the top to avoid an egg.  Aileron rolls are a little strained due to the basic airframe design, but with blended controls on each axis the plane as no problem completing a roll with no altitude loss.

I really like the effect of the swept rudder, and I don't know why more floaters don't employ them.  By sweeping the vertical stabilizer including the rudder hinge, deflecting the rudder control surface also has some up-elevator and aileron effect.  As such, the Cessna is an excellent plane to steer with the rudder.

Inverted flight is surprisingly stable (gyro enhanced, for sure), but total down-elevator travel is too limited after subtracting the amount the plane requires to hold level flight, in order to confidently transition into an outside loop.  I need to take a better look at increasing elevator down travel.  The lazy exit also could have been due to a near-dead battery. 
Landing couldn't be much easier.  The plane slows down nicely even without pushing stall speed.  I popped a few wheelies on the taxi back to illustrate how easily prop wash rotates the airplane.

At 16-20 mins aloft with mixed aerobatics, flying time is probably too high using an 800 mAh of 3S pure vertical-capable power.  A 500-600 mAh 3S would be ideal and allow 8-12 mins of spirited flying.

I like giving grades like these, mostly due to layering my own design on top of the fine craftsmanship of the Chinese builders.

Appearance: A+
Classic lines.  Funky but cool two tone red/orange vintage paint scheme. 

Airframe: A-
Beautiful flier; glides well.  Nice aerobatics in pitch/yaw; roll is strained.

Power System: F (E-Flite)A+ (Z8RC)
Super Tigre 370.  Prop clearance limited to 8.5".  10-12 mins aerobatic power w/800 mAh 3S.

Build Quality/Durability: A+
Strong airframe--nothing else included.  Great details: sturdy pants, cowl, hatch.

Value:  C-
High China mark-up at $120, minus internals.  Needs other-brand electronics to score avg-minus.

Overall Grade: A+ (with Z8RC power system)
Great looking and great flying classic.  Braves wind very well with a gyro or two.

Monday, December 19, 2011

FlyZone Fokker Dr.1 Micro EP RTF - Flight Review

Update: Also see: Fixing the Flyzone Fokker Dr.1 Micro

Update:  After all that was discussed below, the little Fokker's motor shaft reduction gear completely stripped dead on the 8th flight.  I was really trying to give Flyzone the benefit of the doubt.  Now there is no doubt.  Overall grade updated to F for consistent power system failures with both the Albatros and now the Dr.1.  Video of the latest failure uploading now.

Winds in the following video are swirling 5-10 mph mostly on the nose.  You can see the plane torque hard right out of a left correction as the gearbox seizes:  Dissection of the dead gearbox confirmed the plastic motor pinion and main reduction gear had seized together.
Original review follows:
SPECS:    Top Wingspan: 14.1" (358mm)
          Length: 12" (305mm)
          Weight: 1.27oz (36g)
Drag and Drop the pic into the URL input window and
click to magnify to 100% if you can't read the 
box with the standard Blogger picture viewer.
Oh great, another radio!

The cockpit after a little black paint and gluing the 
machine guns. Flyzone should have done both.  Note the 
impression for the included, unpainted foam 
pilot figure, which I decided to omit (see first picture).
Very nice scale details!  The wheels turn independently 
which caused severe pull off to one side during 
taxi--a trivial fix is in my review.   There is only a 
tail skid which compounded the problem.
The wind mostly calmed down for an hour or two.   I thought I could squeeze in several reviews, but got stuck on this one.

First, this mini Triplane looks fantastic in the air, for a micro. The scale lines are impressive for such a tiny model. Even better, it flies a lot like a Dr.1. That's good because it adds interest and challenges the flier, but it is not great news for beginners. This plane is best suited to advanced novices or intermediate to advanced RC fliers, especially in anything but zero wind. Here is why:

Fokker Triplanes are notoriously finicky to balance, as the effect of CG movement is amplified by the tall wing stack.  Imagine that you and a friend are moving her dining room table.  You each take a side, and lift it up.  The placement of your hands matters.  If you spread your hands wide apart, the table is easier to balance.  Imagine that you try to lift the table with your hands only a few inches apart, suddenly the table's CG becomes much more important.  Now imagine stacking a few heavy boxes on the table, in a tall vertical stack at that CG point.

This is the Triplane dilemma.  The wing(s) chord gets thinner as the stack gets higher, to keep total wing area and total weight near the design goal.  It is like placing you hands closer together when you lift a table, and it is like stacking weight high on the table at the same time.  As you lift and move the table around, the situation is a lot more precarious then if you placed your hands wide apart to lift a table with nothing on it.  Now, add swirling wind.

One thing Flyzone did to help alleviate some of the Dr.1's handling challenges is sneak in a little dihedral, which helps alleviate most of the intentionally embedded roll instability inherent to the fighter's tall, squarish wing box.  Without the non-scale dihedral, a Dr.1 falls off to either side very easily, and needs to be constantly balanced with rudder and aileron (which are unfortunately not applicable to this 3 channel micro); with it, the micro baron happily putts along upright, but is not as stable in roll as some might be used to.
Some false dihedral makes the Flyzone Dr.1 a lot more beginner friendly.
Depending on your level of flying proficiency, the Triplane dilemma described above can either sound like fun or sound very painful.  I find it fun; others will not.

The fun arises because the big wing stack is the thing lifting the plane, not you.  So it feels quite effortless, because low wing loading (arising from a large total wing area) is a very good thing for nimble airplanes, as long you keep it all precariously balanced in the air.

The challenges are plentiful:
  • Finding the exact right battery position
  • Controlling pitch changes, as the wing stack tilts fore/aft
  • Controlling roll changes, as the wing stack tilts left/right
  • Landing on the narrow wheel stance without dragging a wing tip
The benefits are powerful:
  • Light, nimble handling
  • Tight turn radius
  • Very slow flight capability
  • High wing efficiency from high aspect ratio wings (a longer total wing span)
  • Short takeoffs and landings
  • Appreciation of the skilled pilots who flew these unique aircraft
 In a few words, I love it.

So what could possible be more fun than flying a Triplane around your own front yard?  Uhm, well, I have an idea... how about flying one that doesn't break down!

Within five flights of CG tuning, the main gearbox apparently failed.  It seemed like the motor shaft shifted and decoupled the motor pinion from the main reduction gear, causing initially intermittent, then a permanent loss of thrust, as the engine oddly surged faster.  The combination of motor surge and decreasing thrust in the air was strange, but familiar to me:  http://z8rc.blogspot.com/2011/08/flyzone-albatros-flight-review.html

Compounding the problem is British Sports car-like motor access.  The plane is buttoned up tight.  I started trouble shooting the still prop during high RPM with a brand new number 11 blade.  After an hour of painstaking cowl removal (if the cowl was tacked with tape instead of glued it would've been simple) it turned out, the Dr.1's eerily similar failure to the Albatros was a red herring.  The gearbox was fine.  In fact, examination of the gearbox indicated that Flyzone had improved it with a much longer motor pinion, presumably to eliminate the Albatros problem.  The thrust problem was actually a more simple, decoupled prop!  The motor shaft was spinning inside of a hollow prop hub. 

The shaft/prop connection is not threaded, it is splined.  This is a minor design flaw, because the prop hub is not solid plastic.  The metal shaft's splines can actually migrate into the hollow interior portion of the hub and lose their grip entirely.  The prop was a bit fussy to pull off while holding the shaft with small needle-nose pliers, but once removed, a dot of CA on the shaft before pushing the prop back in place was a relatively simple, 100% fix.  Uhg!

I won't blame Flyzone for spoofing me with the previously unreliable Albatros gearbox, or my wasted time and risk opening a gorgeous little tightly sealed airplane.  I should have avoided jumping to conclusions. But this less minor problem still resulted in total inflight power loss and (perfect) forced landing.

At least all went well in the maintenance hangar, and I got a few interesting pictures as a result!

Flyzone went through great pains to stuff the servos 
right up next to the main gear in the nose, all to 
make the plane way too nose heavy.
Aside from the obvious FAIL, the plane is really fun in the air.  It is extraordinarily nimble when properly balanced.  Slow flight capability is uncanny.  Loops are very challenging to keep axial due to the height of the wing stack.  And the plane needs to be trimmed well and flown as hands-off as much as possible, to keep it humming (more like screeching) along smoothly and on top of the correct CG.  No wind will help this plane more than most, I didn't have that luxury, but I am really looking forward to flying it on a no wind day.

Speaking of proper balance, Flyzone has the Dr.1 set up all wrong.  Manufacturers like to keep their planes nose heavy to be beginner friendly.  The thought is that nose heavy planes are flyable and tail heavy planes may not fly.  But with a Triplane, this is an even worse idea than usual for reasons stated above.  Flyzone really screwed the dog on the set-up.  Many-a-beginner will crash and crash again.

The nano Dr.1craves pavement with power off and the battery in the design position.  The wing stack tilts forward and so the balance does too, making the CG problem even worse (imagine the tall stack of boxes on your friend's dining room table, tilting forward as you lift, with your hands placed close together, yikes!).

By trial and error I discovered the proper battery position is with the leading edge of the battery at the leading edge of the bottom wing.  So you'll need to stick-on another piece of Velco.  Flying with the proper CG is critical with this plane.
The proper CG requires a battery position well behind the range 
possible in the plane's stock battery bay.  The plane exhibits 
alarming pitch tuck-under using the manufacturers' CG range.
This makes the battery a lot easier to attach and replace 
without breaking the delicate airframe or landing gear.
I do not recommend flying your Dr.1 with Flyzone's criminally nose heavy setup.  The plane tucks-under hard with any solid pitch down, exacerbating your stick forward input and bringing pavement up uncomfortably quickly.  Doing my CG test (see side bar) on your maiden flight will help determine if you should land and re-balance before continuing.

Interestingly, even when balanced properly the plane needs to glide more nose low than most, just to overcome all the drag it is carrying abound.  It is almost like the plane has its own drag chute.  Proving one again that lots of lift = lots of drag.  The lift/drag intensive design makes the Dr.1 naturally happier putting around than screaming into a formidable drag wall.

Another interesting but unrelated characteristic of the Triplane is how hard it is to orient from the ground.  Simply stated, there are wings everywhere.  You have to be really careful when trying to determe if the plane is banked left or right.  Take your time when flying the Dr.1 in anything but good lighting, no false moves.

Next up, a landing gear design flaw.  The large scale wheels turn independently on a shaft that also spins.  Bad idea.  Wheel axle friction differences made my plane pull uncontrollably to the right during initial takeoff.  Two tiny dots of CA on the outside wheel hubs fixed both wheels to the free axle (careful not to glue the inside hub or the axle itself might not turn), removing the possibility of any unwanted and inevitable differential braking on a notoriously finicky, narrow undercarriage. This will also stop the inevitable main wheel departure, see my Albatros review linked above.

Was this plane even tested by Flyzone?

As far as aerobatics, hmmm, well, not so much.  The tiny Dr.1 motor is both loud and slightly to moderately underpowered, even for a floater like the 3-wing.   Simple loops are strained.  Full bore climb-outs need to be measured.  Frantic audible feedback from the motor coupled with low power output lends a false sense of security.

Battery life is excellent; 10-12 minutes with the included 1S 130 mAh LiPo.

Overall, this plane might be the most fun and most frustrating micro I own.  Fun: because the airframe has so much raw capability for a slow, front yard flier, and it flies correctly once set up right.  Frustrating: because it was boofed as tuned by a typical, aerodynamically clueless toy manufacturer and it has systemic quality problems.

Appearance: A+
Gorgeous scale rendition.  Tall wing stack is surprisingly difficult to orient from the ground. 

Airframe: A-
Exceptional low speed capability.  Nimble as hell.  Must trim to fly smoothly.  Too nose heavy as shipped--easily fixable. 

Power System: C-
Underpowered.  Loud. Several reliability issues.

Build Quality/Durability: B+
Prop decoupled after five flights.  Real sub-micro servos.  Solid nose and frame.

Value:  B
Around $70 RTF after typical discounts.  Locked to a toy radio.

Overall Grade: A
Wonderfully scale lines!  Tricky flight characteristics when pushed.  Wrong CG.  

Sunday, December 18, 2011

Jiggy Gets a Heart Transplant

Update: Video added, below.

Jiggy makes a really easy brushless conversion.  I used a UMX Beast motherboard and motor.  The conversion is plug n play, plus a few dots of medium CA and very minor foam trimming.  Conversion time: about 20 minutes.

Believe it or not, the CG is at the 20-25% chord line with a 120 mAh 2S Velcro-mounted mid-wing.  This sort of emphasizes the tail heavy nature of Jiggy as sold.  The new weight is 1.7 oz without battery.  Thrust:Weight ratio is about 1.5:1 in RTF form, turning a GWS 5x3.

Flight test.  My tail wheel fell off before the test, I don't know where.
Nice performance at last, though nothing outrageous.  My 120 mAh battery crapped out so this is with a 180 mAh 2S, which is probably a little too heavy.

Parkzone Spitfire Mk IX Flight Review

Update: Please see my related blog articles:

http://z8rc.blogspot.com/2011/12/z8rc-clipped-wing-spitfire-mk-lfixe.html
http://z8rc.blogspot.com/2011/10/spitfire-vs-butcher-bird-parkflyer-head.html

Update: Latest Mk LFIXe video.  Shows the final variant with retracts, 4S, 4-blade prop and LFIXe mods.  Awesome performance!  A 5-10 knot headwind is slowing most of the high speed passes. It really does sound like an Indy car.  There is a nice pass is at 2:10.
Update:  Latest Mk LFIXe video.  Shows the improved roll rate and slow flight:


My full Flight Review of the PZ Spit Mk IX follows, including one amazing surprise!

On the Ground:
This plane goes together incredibly quickly.  The following photo was taken exactly 9 minutes after the in-the-box photo.  And I was in no hurry.
Top/Bottom paint scheme and colors are very similar to the Mossie. 

The Spit Mk IX has some nice details.  Once the plane is together, which doesn't take long, you can't help but stand back and admire Supermarine's lines.  It is one good looking plane, its a shame they went out of business (actually they were snapped up, but their design prowess was lost in the sale).

Parkzone's landing gear  exaggerate the odd foldaway orientation of the original design, and the model's poor  landing gear proved problematic during my flight tests.  I would up straightening the struts on a vice, to resemble the original plane, with good results (re-bent gear not shown).
The actual landing gear are straighter than Parkzone's pigeon-toed model.
The Parkzone gear not only look way off, they function very poorly.
The wing leading edge gets two long plastic canons, held in place using two small machine screws.  Coaxing the screws into the usual fussy Horizon Hobby misfit plastic foam inserts consumes about half the total assembly time.




In the Air:
Maiden video:

Not the best hat cam work, but not my worst either.
My HD video mode only records 10 min clips
so no landing recorded but the plane was very easy
to land - given plenty of runway for the fast/heavy
glide characteristics as configured by Parkzone.
The surprise I alluded to at the top of this article, and discuss in more detail in my Focke Wulf vs. Spitfire dogfight, is perfect 4S operation--right out of the box:

On 4S, the Spitfire is a lot of fun to fly and worthy of the Spitfire name.  On 3S, the plane can't quite reach speeds that inspire.

The Mk IX airframe is a good version of Spitfire, because it looks cool, but it reflects a time when designers were chasing ultimate efficiency via trendy, theoretically ideal elliptical wings.  Elliptical wings generally don't fly well, and tip stalls in the RC realm are a real problem as Reynolds numbers become too low as the chord fades to zero at the tips--all you really get at the ends is drag on a heavy moment arm.  The pure elliptical wings add interest, but in almost every case they were abandoned in favor of better wing tip designs, at least for high speed warbirds.

The nice thing about Parkzone's visually trendy but poor RC design choice is that the Mk LFIXe is a very easy conversion.  And because the LF is based on a Mk IX, it looks even cooler than the old rounded Spit and it flies a lot better at small scales.  I quickly converted mine and anyone who wants to improve their Spitfire's speed, roll rate, and low speed handling might do the same.  In fact, all warbirds with elliptical wing planforms fly better in RC form when updated to their more advanced clipped variants:

All that said, it you like the look of the full ellipse, it flies fine for the most part, and on 3S the Spit won't set any speed and agility records anyway.  Tip stalls can be tricky as shipped by Parkzone, so you have to carry more juice to land controllably with the round tips in place.  Removing the tips allows you to reduce landing speeds by another 20% or so before dropping a wing, battery weight constant.

The Spitfire Mk IX is a competent flier, but on 3S the plane is too lethargic to give a valid warbird experience.  No doubt, Parkzone would prefer to keep the airplane as beginner friendly as possible, but the plane losses substantial value when flown as shipped.  Aerobatics are lazy and slow flight gets squirrely near the rough bottom edges of the full elliptical wing flight envelop.  It's hard to believe the plane tests at exactly 1:1 installed T:W when running on 3S, as it feels a little lame in the air for a fire breathing monster.

To bring the Spit to life, a 2000-2200 mAh 4S battery is required.  Speed is magnificently improved with almost 1:5 T:W; the graceful high speed airframe is just begging for the grunt to move out.  The Z8RC Mk LFIVe mod adds even more speed and roll performance, plus rights most low speed wrongs although the wing loading is made theoretically worse.  

The Parkzone Spitfire is a fun pocket rocket, and an exciting ride in fully tricked out form like any good warbird should be.  The price is high for a foamie, especially considering tough competition the $140 twin engine J-Power/Hobby King P-38.

Given a stock choice, the J-P/HK P-38 is the easy pick with its impeccable flight manners, built-in flimsy retracts, and yes, even better lines in the air (wow, it is better looking than a Spitfire--now that is saying a lot!).  The 38's half-price tag makes it more appealing still.  But in its very easily hopped 4S Mk LFIXe incarnation, the Parkzone Spit is both more challenging and exciting to fly; in mostly in good ways.
The meaner looking tail sacrifices a bit of yaw 
stability in bumpy flight conditions, but is not 
a control issue.  4-blade prop coming soon.
Final grades:


Appearance: A+
Classic.

Airframe: A-
Very good behavior can be made even better with a number 11 blade.

Power System: 
A+
Needs Viagra as shipped, but is 4S ready out of the box.

Build Quality/Durability: B+
The plane can handle some abuse (flight tested).  Cheap clevis pins break.

Value:  C+
Bonus points for 4S ready.  Still awfully pricey for a foam warbird.

Overall:  B+ (3S), A (4S), A+ (Z8RC Mk LFIXe)
Since no additional expense is required, I've graded all three.

Saturday, December 17, 2011

Blade Scout CX RTF - Flight Review

Update:  Correction:  I found a 3 Ch BNF, though I personally wouldn't trust the Scout Tx at range:  http://www.amazon.com/Super-Cub-Transmitter-sold-separately/dp/B002SX7ELK/ref=sr_1_1?ie=UTF8&qid=1324357149&sr=8-1

What to call the new Blade Scout CX RTF?  How about a UMnX helicopter?  Whatever it is, it's small and a bit cheaper than other UM Helis.  The obvious question: What are the trade-offs embedded in the lower price?  Second question: Is it worth it?
The answer to the first question becomes apparent soon after the little copter breaks ground.  My initial reaction was, "Wow this flies as good as a Blade mCX."  And it does, as long as it is sitting still.  The problem is controlling movement.  As a 3 channel heli, there is no aileron, so the only way to steer is by pointing the nose with rudder rotation, then moving forward or aft.  While this sounds like a reasonable trade-off, it's not.

The main reason (all) 3 channel heli's don't fly acceptably is difficulty in the landing phase, or whenever you are tracing a precision flight path relative to obstacles.  Let's say you want to land on a coin.  Inevitably, as you approach the ground and the coin, your rotor wash will upset your flight path.  With a proper 4 channel heli, you can counter any side-to-side movement with opposite aileron, which in turn drives the heli towards 3 or 9 o'clock.

With the Scout, the heli simply drifts left/right with no way to stop it.  Sure you can rotate the Scout 90 degrees left using rudder, then drive to your 12 o'clock which used to be 9 o'clock, but then you drift again, and have to chase another side-to-side correction.  And while you are chasing the coin with your nose, what happened to the last required forward/aft correction?  It is transformed into a left/right problem.  Uhg.

Perhaps the worse thing about the Scout CX is that it is marketed to beginners.  But for a beginner, the hardest thing about flying an RC heli is tail-out orientation.  As long as you can keep the tail pointing at you, a helicopter is relatively easy to orient and thus control.  The Scout CX removes the possibility of setting up a beginner comfort zone, at least in the area you want to fly, because if you keep the tail pointing at you the helicopter cannot control side-to-side drift.

For more advanced fliers looking for something portable and fun, it all translates into too much frustration, as the copter is simply incapable of being flown precisely.   If the Scout sold for under $25, I might give it the nod, but as it sits on the shelf both beginners and advanced fliers alike would be much better off spending $30 more for a gen 1 mCX.  Those switching from airplanes who already have a radio, or others with a clear urge to learn and progress in helicopters could opt to spend only $10 more for an mCX BNF without the toy radio, and use their own or put a bit more money into a better radio.

Good things about the Scout:
  • 1S battery charger is finally built into the Tx, Hobbico-style
  • Can charge a second battery while flying
  • Decent indoor forward airspeed
  • Great hands-off hover stability
  • The small box
Bad things about the Scout:
  • 3 Ch = Frustrating lack of precision
  • 3 Ch = Harder for beginners to stay oriented
  • 3 Ch = More crashes from lack of aileron control
  • Rudder on the right stick = negative training 
  • Transmitter is limited to controlling 3 Ch BNFs 
  • There are no 3Ch BNFs
Strange things about life in general:
  • The name "CX" with no "m" for micro.  
  • The mCX's suddenly, abnormally large box.
Bottom line:
  • Answer to Q1 is "No ailerons."  Answer to Q2 is, "No."

Appearance: A
Looks like a baby predator.

Airframe/Design: D
Tremendous hover stability.  But what happens next?

Power System: B+
Super light.  Plenty of power as shipped.  No wind capability.

Build Quality/Durability: A  
Comparable to an mCX.  Expect more crashes from less control.

Value:  C-
See Q2, above.  Same unit price as a two-pack of FHS mCXs ($99).

Overall:  C-
Frustrating for beginners.  Disappointing for intermediate/advanced.

Blade CX3 on 3S

It works.

It flys better.

I remain disappointed with my CX3; it continues to degrade over time, without crashes to blame.

I think the gyro is a basket case.  If you leave it hanging loose (as shipped), it provides spurious inputs during helicopter movement, often resulting in oscillations. It you tighten it down, it vibrates the tail badly.  If you gain it down enough to eliminate vibrations and oscillations, the nose consistently drifts.

The setup is best left as sold, which presents a constant variety of annoying but limited vibrations, oscillations, and nose drift.  If you try to correct any one of them, another vice just becomes more dominant. 

Additionally, aileron and elevator controls are becoming increasingly coupled, seemingly without explanation.

I'm downgrading the CX3 to AVOID.

Thursday, December 15, 2011

Fixing the E-Flite Ascent 450 BL

Update:  Perfect setup! 45 minute aerobatic flight from an 800 mAh 3S.  Climbs out 45 degrees nose high with the 7" prop.

Update:  The Ascent has finally reached design Nirvana.  By substituting an original Ascent Park Glider 7x3 folding prop, which is a lighter and more streamlined drop-in replacement (after switching the shaft adapters) for the Ascent 450 BL's 11"  prop, and replacing E-Flite's absurdly heavy and mismatched 1.3 oz 22 Amp ESC with a 0.3 oz $13 Common Sense RC 10A brake-able unit, then moving the wing a total of 0.5" aft, the glider finally weighs-in at a respectable 13.6 oz pre-battery. I used thin foam weather stripping to seal the fuselage against the wing in its shifted position. 

Measured installed thrust from an 800 mAh 3S is a spirited 12.3 oz with a max load of 9.58 Amps. Perfect.

The only big challenge left is how to get it on the ground.

Original article follows:

The Ascent is another great Chinese build ruined by E-Flite's impressive design incompetence.  I gave the Ascent an A- based on it's airframe potential, alone.  Here are the fixes required to realize the strength of the model.  Avoid the E-Flight Ascent unless you are willing to put a little time and about $100 into fixing E-Flite's long list of internal gaffs.

Jumping right in: the power system is ridiculously heavy, giving the glider a WCL of a light powered plane.  The Ascent's only power-off advantage is derived from it's high aspect ratio wing and sleek fuse.  That's a lot, because like I said, E-Flight's exploited, abused, and underpaid China sweat shop did a wonderful job crafting the basic airframe.
From left to right: Radian 9" folding prop (slightly thinned 
hubs to fit Ascent spinner), added the white flange and black 
peg to match a notch made to the canopy (velcro secures
the aft end), E-Flite 370 motor (a lightweight drop-in replacement),
lightweight Rx and ESC (both pushed forward),800 mAh 
2 or 3 cell LiPo (not shown),moved wing backward 1/4th inch for CG.
Some of the fixes are obvious and easy, but a complete fix is a bit more involved though not technically difficult.  In the end, you can have a truly superb motor glider vs. a pretty poor performer as shipped.

Among the low hanging fruit is a lighter motor, discussed in my original Ascent article. E-flite's 450 is a bad choice, as it is a very heavy motor and it is way too strong, even with the motor's low thrust to weight ratio, for the artificially heavy Ascent it helps to create.  Leaving the 450 inside basically ends the possibility of having a good motor glider.

There are two ways to go with the motor.  I decided to put the E-Flite 370 inside.  Although it is a poor performer in absolute terms (producing a relatively low thrust to weight ratio), it fits into the fiberglass fuselage without modification making it an incredibly easy substitute and dumps a quick ounce out of the nose.  The other way is an even lighter and significantly stronger (in terms of T:W) Super Tigre 370 motor, which requires a few new drilled holes, a similarly easy shaft reversal, and trimming the width of the included aluminum tri-point mount.  The weight difference is only 0.2 oz, so it is important to mount the motor without additional structure to realize a gain over E-Flite's 370.

Substituting a more appropriate Parkzone Radian 9" folding prop for the 11" stock prop saves another 0.3 ounce in addition to extracting more flight time out of a lighter battery driving a lighter motor that's lifting the lighter plane.  Additionally, the smaller prop can fold in the amount of air flow generated by this relatively small scale glider, unlike the 11 incher which hangs an open blade while gliding. 

The lighter battery saves another 2 to 2.5 ounces (3S vs 2S; both fly fine) for a total of about 15% wieght savings before any real mod to the airframe. The glider's overall thrust to weight ratio is only slightly reduced, to a more flyable and actually still too high 1:1+.   The more important effect is the power-off flight time improvement, which accounts for an increasingly large fraction of the total flight time as weight is thrown over board.

All of the above can be accomplished within the stock setup, but you have to shove all the electronics as far forward as possible to keep the CG viable.  You may notice a little less yaw and pitch stability due to a marginal CG when using a properly sized battery, which is roughly an 800 mAh 2 or 3 cell.

To fix the airplane to maximum capability requires lightening the interior components even more, then doing a quick wing mod to keep the CG in check.  

The ESC shipped from E-flight is as inept as the 450 motor choice, incredibly heavy for its low end 22A capacity.  E-Flight's brick ESC has to go.  Even E-Flite's usual low quality ESCs are generally very light weight, as the lack of a decent heatsink is what makes them unreliable in constant power airplanes.  For some reason, E-Flite decided to incorporate a very large, very heavy, very low capacity ESC in this motor glider--unbelievable design incompetence given they usually put their ultra-cheap, ultra crappy ESCs in much more demanding airplane power systems.  I can't count how many flimsy, glossy black E-Flight ESCs I've burned out--why didn't they include one when it finally made sense to go light?  Crazy.

With the 370 driving a 9" foldaway, the battery drain max's out at only 12.6 Amps.  So a 12-15Amp ESC will be more than enough depending on your throttle technique.  You could get away with a 10 Amp with short bursts or by limiting max thrust to 10A by computer--even on a 10A diet there will still be enough power to go near vertical.  The key to your ESC choice is to get one with a proper brake, otherwise the prop will windmill and energy will bleed much more rapidly in a power-off glide.

Any light weight Rx will do.  I used a 0.3 oz Hitec Optima 6 without its plastic case.

Once the cabin is adequately lightened and a 2S 800 mAh is installed, there is really no way to get the CG in a pleasant place (although the glider will fly controllably) without a small wing adjustment.  I moved the wing 0.25 inches back by drilling the twin bolt holes 0.25" forward of their stock position.  The wooden dowels that secure the leading edge of the wing root are plenty long to pull out slightly; they still work fine.

Astute Ascenteer's will also notice I substituted a small white aluminum flange over a black plastic peg for the front canopy screw, caught by a notch in the canopy plastic, and added velcro in place of the rear screw.

In the misc category, I had to balance the plane laterally with the addition of a dime taped under a wingtip, and then bend one wing under a heat gun to un-warp a semi-permanent aileron input as the wing was shipped from E-flite.
Notched (front) and Velcro'd (aft) canopy for convenient removal
covers the new 1/4 inch wing/fuselage gap required to set the proper CG.
Result: near perfection in the air.  This is another "night and day" Z8RC fix that took less than a few hours that completely transformed the stock flight characteristics from poor to exceptional.

The final flying weight (with battery) was reduced from 19.6 oz as shipped from E-Flight to 15.4 oz, a 21% reduction.  Thrust to weight ratio remains higher than 1:1, raising the possibility of going smaller scale power system.   Flight times are dramatically improved over E-Flites stock setup which delivered up to 30 minutes of careful soaring.  Extended flight times of up to 45 minutes are achievable on an 800 mAh 3S battery after these Z8RC mods.  With good soaring skills, 60 minutes is within reach.

Parkzone Spitfire Mk IX - $10 Landing Gear Retract Tutorial

Wind has prevented flying, so it is a good time to upgrade.  

The Z8RC Mk LFIXe Spitfire (now with a big honkin' 4-blade APC 11x6x4 clipped to 9.5x6x4) hauls a$$ on one LiPo cell for each prop blade.  But I thought... you know... this thing could go even faster with retracts.  So it had to be done.  
 
Rather than fork out a mind numbing $85 for the E-Flight retracts plus $4 for the pre-bent struts, I decided to go with the same servoless retracts I recently installed in my P-38.  Total cost is $24, and 20% of that was the Parkzone pre-bent retract struts.

I bought the recommended E-Flight 10-15 size retracts a long time ago for my PZ T-28 Trojan, they are well made, but they don't lock down as solidly as these extremely stout  $10 (32g) retracts from no name China. For $1 more you can even get a metal version, which I didn't notice until after I bought mine.  They ship with no struts (except the steerable nose gear, which is n/a to this tutorial):
I wasn't sure if I should buy the pre-bent Spitfire gear sold specifically for retracts or modify the existing gear, but for $3.99 it seemed worth the money.  As it turns out, the extra strut length, above the spring, of the pre-bent retract gear was required so I'm glad I did.
This set of retactable gear is a close fit, but it is not perfect, mostly because it is a little beefier and stronger than the E-Flight 10-15 retracts. The screw pattern is the same.  Weight is 2 grams heavier per gear unit.  The finished product is perfect in gear fit and function, even better than the E-Flite retracts I've seen installed in Sptifires.

No adjustment or bending of the retract or the landing gear itself is required.  Once installed, both the wheel and the piano wire strut completely disappear into the wing from the airstream, gear doors would be an option.  Vertical strut alignment in the gear down and locked position is better than the stock gear.

Even while making the modifications to the gear well, below, total installation took less than an hour to figure it out as I went along. If you follow this tutorial, it won't take that long.

The plane is pre-wired for retractable gear. Pull the connector out and stash any extra wire in the back of the stock under-wing air scoops.

Step 1:  Remove the original gear and find the pre-wired connector.
Step 2:  Remove the bottom plate to make room for the slightly bigger retract.  I keep an old soldering iron on hand to cut plastic and melt away foam.  A Dremel with a router bit could work too.
Step 3:  Shape the gear well.
Step 4:  There are two 1.5mm hex nut set screws on both sides of the strut where they insert into the gear housing, each set screw is inside a brass fitting.  Tighten them lightly against the strut at first, so you can still slide it in/out to center the wheel in the well and turn it to the angle required during a test fit.  Then remove the gear and tighten the set screws down

Step 5:  Cut the cover plate that comes with the pre-bent gear (or leave it off ).  Even as shipped, this cover plate leaves some black showing on the far side of the two rear  mounting screws.

x2 and done!!
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