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Wednesday, June 20, 2012

RC Discount Codes


DISCOUNT CODES
The purpose of this blog post and reader comments is to gather and share known RC retailer online discount codes.  It will remain direct-linked in the "Z8RC Reference" box in this column, below.

RCG1109  = 10% off order, no limit

MANR6731 = 20% off order, expires 7/1/2012, not combinable
RCGROUPS = 15% off order, no limit, not combinable
Summerflying = Free shipping on orders over $100, no limit, not combinable


no code required = Free shipping on orders >$100, expires June 23, combinable
 

Non-club members save
 $100.00 - $149.99$10.00010FT
 $150.00 - $174.99$15.00010FV
 $175.00 - $199.99$20.00010FW
 $200.00 - $229.99$25.00010FX
 $230.00 or more$30.00010FY
 

Club Members save
$100.00 - $124.99
$15.00
$125.00 - $149.99
$20.00
$150.00 - $199.99
$25.00
$200.00 - $224.99
$30.00
$225.00 - $249.99
$35.00
$250.00 - $299.99
$40.00
$300.00 or more
$50.00
 

Gold Preferred Plus Members save
        $400.00-449.99
$60.00
        $450.00-499.99
$65.00
        $500.00-599.99
$75.00
        $600.00-699.99
$90.00
        $700.00-799.99
$105.00
        $800.00-899.99
$120.00
        $900.00-999.99
$135.00
        $1000.00-1199.99
$150.00
        $1200.00-1499.99
$180.00
        $1500.00-1999.99
$225.00
        $2000.00-2499.99
$300.00
        $2500.00 or more
$375.00


NITRO5 = 5% off $50 minimum order, no limit

Starmax P-51D Big Beautiful Doll Rimfire 60 Upgrade


Starmax's gorgeous P-51D is a pretty slow as shipped.  The plane gets a significant speed boost from a 5-cell upgrade alone, but the 4S-advertised motor sometimes balks on static runs to include takeoff.  In the air it seems to run fine and the big 4-blade sounds great. But is it fast enough to evoke thoughts of a V12 Merlin?  Maybe not.

At Z8RC, we don't cope well with sluggish warbirds, especially P-51Ds.  Call it a mental disorder.  It actually hurts to watch a vicious warbird airframe quietly paddling along like a broken wild animal that has lost its will to fight.

Starmax's nicely scale P-51D airframe screams for more speed.   It would one cruel act of torture to force the big Mustang to play nice, like some 1980's Chrysler K-car pretending that what people really crave is slow motion efficiency and resource squandering sensibility.   As if watering down products to a state of uselessness magically makes them more desirable.  It all makes me want to puke.

In an attempt to give the Mustang a proper personality, I learned a two things.  First, it's pretty hard to make a 63" chunk of foam hurdle through space.  Second, it's pretty hard to make a 63" chunk of foam hurdle through space.  Enter the well built Rimfire .60, 50-55-650 Kv electric motor.  It shares guts with the lower kV Rimfire .80 50-55-500 Kv .  The Kv gearing could be addressed alternatively with prop pitch, so the two are close cousins.  Aside from being a milled metal monster, the Rimfire motor is surprisingly efficient, not like the failed Power 46 experiment which guzzled electrons to little effect.

I think the .60 upgrade was a success.  This flight used a 14x8 Master Airscrew K-series prop and is running on 6S:

The Rimfire .60 was easy to install.  After unscrewing and removing the stock motor and mount, I sandwiched a standard 1" diameter PVC pipe coupler (50 cents) behind the Rimfire's beefy X mount bracket and the firewall.  Then I drove four long deck screws through the holes in the X bracket, past the PVC spacer and into the firewall, secured with a dab of Gorilla Glue on the point of each screw.  Done.

Monday, June 18, 2012

Banana Hobby F-22 Raptor (41" Wingspan) - Build and Flight Review





Update 6/18/12:  Already, a flap/slat servo has stripped and both elevon servos have started to behave very erratically as a result of normal use.

Plan on replacing the two elevon servos (minimum) with metal gear servos.    I'm not sure if I pinned the internal elevon servo wires when I initially glued the wings on, but when I decided to change them out the internal wiring was so tight I had to cut them off at the base of the servos, then carefully solder extensions onto the existing internal wiring.  Not the easiest way to swap out servos.

I recommend pulling out the elevon servos as soon as you open the box to see if you can get them out far enough for easy replacement, right away.  If not, expect  a pretty delicate operation in the not too distant future.

Back to a B overall for high risk flight control components.

Update 6/5/12:  FPV using two 4000mAH 3-cells in series.  These batts are well matched and have been mated together since birth but have less grunt and only last about half as long as one of my 6S 4000s:



Update 5/19/12:  Another video.  With youtube viewer shortcuts:
Shortcuts
0:02 Flaps/Slats Extend
0:20 Max Power Takeoff
0:40 Glide #1
1:30 High Speed Pass #1
2:22 High Speed Pass #2
2:27 Max Aileron Roll
3:26 Glide #2
3:55 Min Radius Loop
4:30 Low Speed Maneuvering



Update 5/16/12:  This flight video will have to work until I take a better one:
Also, I'm upgrading the plane from a B to a B+ overall.  The build has held up a little better than I thought it would to date.  I have done extensive taping and foam crash proofing.  The F-22 is a terrific flier.

Original review follows:


INTRODUCTION
One thing is certain about the Banana Hobby (LX Models) F-22 Raptor, it looks the part.

SPECS
- Wingspan: 1046mm (41.2 in)
- Length: 1513mm (60 in)
- Flying Weight: 2100g (74 oz)

FEATURES
- Construction:  Dense Styrofoam (not EPO)
- Motor: Twin 2100kV Brushless 70mm EDF units (measures 67mm rotor diameter)
- Servos: 10X 9g high speed micro servos
- ESC: 2x 50A Brushless speed controller w/ 5A BEC
- Landing Gear : Threaded rotary shaft driven servoless retracts
- Nose gear Landing Light which also functions as a (nose) gear down indicator
- Painted pilot figure (white helmet, USAF Vietnam era)
- Electable canopy module with parachute
- Smoke system with two colored smoke canisters (fireworks)

INCLUDES
- Four foam JDAMs and associated MAUs
- Two drop tanks (which also house the smoke canisters) and associated MAUs
- Instruction Manual* 

REQUIRES
- Radio: 6 to 12 Channels**
- Battery: 22.2V 6S 3600mAh 25C Li-Polymer
- Battery Charger
* Not exactly. It includes a small picture book, none of which answer the questions one is likely to have.
** 12 Channels is an exaggeration. Included channels (8 in total) are: 1 aileron channel that links one aileron, one horizontal stabilizer, and one thrust-vectored nozzle to act as the right elevon (Channel 1), 1 elevator channel linking one horizontal stabilizer, one aileron and one thrust-vectored nozzle to work as the left elevon (Ch 2), throttle on an internal Y harness (Ch 3), rudder and nose wheel steering (Ch 4), servoless retracts (Ch 5), 2 x flap servos which also operate the leading edge slats (Ch 6), smoke ignition (Ch 7), pilot ejection (Ch 8).


ON THE GROUND

UNBOXING
The plane ships as a box full of major components, each requiring some assembly.  Those used to foam ARFs requiring very little build time are likely to be disappointed.  The F-22 needs quite a bit of glue (included, but no thanks, I'll use my own), four servos need to be installed, and all the pushrods and belcranks need to be decoded.

The wiring also needs to be decoded.  The servo leads are tucked into the main fuselage where the forward fuselage needs to be glued in place.  To LX's credit, each lead is tagged with a label.  Once you figure out how simple the scheme is--each side's elevator, aileron and nozzle are all Y connected together for a total of 2 channels--it is easy to hook up your choice of receiver.  The only mildly confusing part of the servo connections is the servo lead coming out of the forward fuse labeled "Direction," which I eventually figured out meant "I am from the nose-wheel steering servo, please connect me to the open Y connection on the rudder channel."
We learn quite a few things from the box.  First, LX stands for Lanxiang China.  One side of the box shows some or all of their other models for sale.   On the box ends, we learn the plane has "color smoke" and cockpit ejection.    And in fact, the model comes with a smoke detonation system and two pyrotechnics that slide into the back of the included drop tanks.  There is a servo pre-installed in the cockpit for the sole purpose of knocking the canopy off of it's magnetic latch--I guess the the included parachute does the rest.  Hilarious, only a Chinese designer could get excited about pilots ejecting from an F-22.
The other box end seems to show an F-22 in the process of being shot down.  But it is hard to say what LX was thinking given that the box also clearly states the model is "Ready to Fly."  I don't know, that might be a bit of an exaggeration.  Mine was built and ready to go in about a day.  Much of that time was spent figuring out the Rube Goldberg, but somehow fiendishly simple, elevon/thrust vectoring scheme.

APPEARANCE / FIT N FINISH
The plane mostly goes together ok, but the wings are a tight fit and need to be patiently wiggle together with quite a bit of force.  Dry fitting first means doing that twice, which is no fun.  Worse, one of my vertical stabs (err, I guess I mean 45 degrees off from vertical) wouldn't go in its slot without significant trimming of the foam base.

Once together, there is no denying that the LX F-22 is one gorgeous bird.  It actually looks better in person than the photos portray.  The only minor detractor from the final impression is the artificial glue seam between the forward fuselage and the main fuselage.  I taped and painted that.

Unfortunately, the surface finish is dense Styrofoam,so it is extremely easy to scratch, dent, or otherwise mar the beautifully painted surface.  That said, the F-22's paint is more forgiving than industry standard Z-foam, as tape application and careful removal is possible without removing the paint.  But make no mistake about it, this is no EPO bird.  It is delicate indeed.

BUILD QUALITY/SETUP
Build quality is my first big beef with the plane.  It isn't a lack of care, but poor materials that let the Raptor downThat wouldn't be as big a deal if it were not for the premium price tag.  For $379 pre-battery, I have a hard time accepting a Styrofoam jet. 

Perhaps worse, the parts of the plane that have been assembled are glued up around the electronics, so replacing a servo could be impossible without clipping the lead and grafting the new lead into the existing internal wiring.   The fans are accessible via a screw-on hatch, but getting to the ESCs requires foampen heart surgery.

The landing gear is pre-installed and extremely clever, but all plastic.  I've already knocked off the nose gear by a simple pavement to grass overrun landing.  The gear is lightly glued in place, probably on purpose to save the plastic struts in the event of an impact.  But I screwed up--during the re-glue I used some Gorilla Glue which expanded into the back of the base and almost ruined the gear.  I wound up cutting the glue out, but only after the lack of movement over-stressed the motor's plastic gear-locking arm, cracking it.  The only way to fix it was to glue the servo arm attach screw in place along with a glued metal washer for added strength.  It seems to be working fine now, but all plastic gear? Really?

You'll also notice a main gear door stuck open in the video.
Ok with that out of the way, now for the good stuff about the gear:  It is quite strong.  It has built in shocks.  And out of the box, the plane taxis better than any plane I've ever driven.  It makes you want to find a slalom course.


ISSUES 
  • Left rudder too tight to fit
  • Soft foam surfaces
  • One Bel crank broke in half while inserting push rods (resorted to pre-drilling the holes).  Fixed by using an inner-half hole on both connected bell cranks.
  • Lower level of completion than other foam ARFs
  • Right nozzle's control horn was fractured at the foam base by the QC technician; neither caught nor corrected.  Root cause: vectoring nozzle binding with surrounding structure, needed 1/16th inch of foam trimmed from one side.
IN THE AIR

BLUF
OMG!  This plane flies fantastic.  Don't get me wrong, this F-22 is anything but aerobatically pure, but the combination of stability, agility, and slow speed float is unmatched. 
START/TAXI/TAKEOFF
Uneventful.  The Raptor's chunky plastic landing gear taxies perfectly with an excellent turn radius.  Takeoff roll is a brief 25/50 feet using half/zero flaps, followed by a strong, near vertical climbout. 

FLIGHT CONTROLS
I visually aligned all control surfaces and the plane required no trim for straight and level cruise--an RC first for me.    The Raptor is amazingly stable and well balanced at the recommended CG.  Elevons are never quite pure, but the airplane rolled very quickly on high rates with minor to moderate pitch/roll coupling. 

Pitch authority with assistance from thrust vectoring, is even more impressive than a real Raptor's full public disclosure. Rudder authority is excellent even at slow speeds, and you often need for post stall maneuvering.

Yaw control is impressive but actually the weak link as it can't match the strong vectored pitch and roll control at zero airspeed.

BALANCE & AEROBATICS
From full blower to idle, the Raptor tracks perfectly in all three axises.  The plane's pure stability and balanced feel is surprising, as is its low speed/float capability.  The 45 degree cant on the (sort of) vertical stabilizers seems to add a strong dihedral-like effect on upright stability.

The same cant detracts from inverted flight, which isn't nearly as friendly as upright, hands-off cruising, but very few warbirds exhibit pure aerobatic symmetry. 
Rolls are very fast in the warbird/sport category, and above average even for an aerobat.

Differential thrust vectoring and the use of elevons render each roll a micro barrel roll. Loops track perfectly through the full 360 and radius ranges from huge to less than the length of the jet.  Spins can be perfectly flat to nearly aligned with the vertical due to thrust vectored pitch control.  I have yet to explore the full capability of +/- thrust vectoring.

The Raptor feels perfectly balanced as the power comes off--the nose stays put until airspeed dwindles to almost nothing. As the airplane runs out of airspeed entirely, the tail settles slightly before the nose and slowly develops an almost elevator-like, nose high sink rate. With a touch of power the airplane will hold altitude in a high alpha pseudo stall.

POWER
Thrust - unmeasured, but slightly above 1:1 static
Amps/Watts -
Speed -
Flight Time - 5-6 minutes on 4000mAh 6S

ADVANCED HANDLING CHARACTERISTICS
AHC is where the Raptor earns its money.  The combination of uncanny lift from the clamped slats and flaps, double-surface elevons, and vectored nozzles adds up to a lot of more ooohs and aaaahs per maneuver than most EDF jets manage in an entire flight.  

My flaps are set to a 3 second servo travel speed, for smooth transitions during extensions.  I experimented with mixing 25% slow flaps to pitch control, and it seems to work beautifully.  High speed G gets slapped on hard, then as the plane slows the flaps and slats dig in.  The plane maneuvers well down to almost  zero airspeed.

The plane can perform a tight back-flip at any starting airspeed, down to zero.  The slower the start, the tighter the "loop" and the Raptor can essentially loop in place with almost no altitude delta required.  Truly impressive, high quality fast-to-no speed maneuverability.

Top speed is slighter better than I expected, but not outrageous.  I left the bombs and tanks off to maintain stealth.  The pure volume of rushing air out the back add a jet-like "whoosh," underpinning the typical whine of the twin EDF motors.  The resulting sound is a lot meaner than most EDFs.  The units ran  smooth and seemed well balanced right from the manufacturer.

Floating into a landing is a little unnerving, only because the Raptor gets so slow without much tendency to seek its previous airspeed via a natural pitch change.  It stays slippery and maintains energy well even with slats and flaps half to full down.

Ultimately, the nose needs to rise to maintain glide path as more AOA is required for lift generation, and at that point a slightly nose high sink rate develops.  The sink can be managed with power with the nose held high.

The plane never tried to tip stall/roll on me while slow, but it will start a manageable, uncommanded turn in a full stall unless opposite rudder is stomped on.

The Raptor is a joy to land with the nose jacked up with a touch of power.  Landing no flap/slat might get the nose up even higher--more practice required.  The reluctance to bleed energy requires quite a bit of runway even with full slats and flaps.

Speaking of slats, the inclusion of leading edge slats is not something you see everyday on an RC model.  Execution is as simple as it is flawless, the slats work perfectly and slow speed lift generation is stunning.  I hope more airplanes use this pull-pull flap-slat concept in the future.


IN FLIGHT ISSUES
  • Occasional hiccups out of one (or both?) of the fans near full power.  I initially thought it might be the plastic fans breaking in since it first occured right after the maiden takeoff, but the issue continues beyond a normal break-in peroid.  Doesn't seem to burp on the ground.  Strange, but so far harmless.  
  • The bottom-mounted thrust vectoring control horns are directly exposed to well flared off, high Angle of Attack landings--need to be protected with homemade covers
  • Main gear door stuck open once.  Seems easy enough to adjust the string door pull.

GRADES
Appearance: A+ 
Stunning airplane!  Did the Raptor always look this good or is it growing on me? 

Flight Characteristics: A+ 
Uncanny stability mixed with bizarre thrust vector agility.  A high rate G monster coupled with amazing slow speed finesse.  Wonderful balance and float. 

Power System: A- 
Couldn't ask for much more push.  Top speed is very good.  Nice fan smoothness, power and sound.  6S is not especially cost effective.  Reliability could be suspect. 

Build Quality/Durability: D  
Here lies the catch.  Overstressed servos.  Very soft foam.    Inaccessible wiring.  Slop in  flight control connections.  Fragile foam gear doors and nozzles.  Plastic gear struts and delicate mechanisms.  Nice fan units, ESCs and motors. 

Value: C- 
Very expensive for the cheap airframe build quality.  Nice power train components.  Weak servos.  Flight quality is superb even for the high price point. 

Overall Grade: B  
If you think jets are built to fly, A+.  If you think they are built to last, C-.  I'm going to reluctantly recommend it because it is such a hoot to fly.

Saturday, June 16, 2012

Quick Take: electric flight Magazine


Z8RC Quick Take
Killing time at the airport, I was shocked to see an electric flight Magazine in a small newstand - they never carry RC mags in airports - so of course I bought it for the plane ride.

A paragraph into the cover article, How to do a "Cuban-8 with a Twist" I almost vomited on the poor soul sitting in front of me.  The technical quality of the "how to" was so abysmal, so completely wrong, and just plain humorous (in a bad way) that I had to blog this correction for fear that someone might actually listen to the ground-pounders who write for electric flight and become aerodynamically retarded forever.  You could do irreversible damage to your cortex if you read this ridiculous magazine article.  Run away!

A long time ago, when I was instructing in the T-38A now C, a foreign exchange IP was sitting at the desk next to me introducing a loop to his US stud.  He picked up a Talon on a stick, carefully leveled in the air, made direct eye contact with his SP and began, "To doa a loopa, you musta pool pool pool pool pool pool pool pool pool (making the wooden model climb up and over the top) pool pool pool pool pool pool pool pool pool pool pool pool pool pool pool pool pool .  Youa understanda?"

I caught the students eye and we almost laughed our way into the legal office to clear up an international incident. The quality of instruction in the ef magazine article isn't any better.  It might even be worse!

So, I don't claim to be an aerobatic expert.  No way, I only have a few thousand hours of pure aerobatic time in 1:1 scale which not nearly enough to master the craft or even breach beginner status, 20,000+ hours of upside-down time would make one a lot more solid.    And so I'm not about to start off this article with something as arrogant as "When I first started aerobatic competition..."  That's for dorks without a clue.  6 words into the article, the dude lost all credibility.

The first section is called, "First Things First"

Here, the guy talks about his Carbon Z Yak.  Seriously?  You "compete" with a mediocre-to-crap airplane like a CZ Yak?  Then he talks about setting up "Flight Modes" which, he explains, means combining muti-axis dual rates on one switch.  Huh?  Obviously from the BNF foamie plug, he's a Spektrum user.  Aside from never having used a passable radio, to the point of not even knowing what the term "Flight Conditions" means, what does this mini advertising binge have to do with C8 execution?  I guess CZ Yaks are piling up in the warehouse, again.

Next is In the Air

More wasted real estate talking about how to help limit the severity of tip stalls, which is not a typical problem but a big problem in the brick CZ Yak-54. 

Finally we get to the "Overview of the Reverse Cuban-8 with half rolls"

Ok, so what kind of C8 doesn't have "half rolls?" again?  Sheeze.  Let's humor the poor guy and agree there is such a thing as a well defined reverse C8 and move on.

The first thing he tells you to do is climb to 400 for a 50" model.  I hate fascists.  Who cares how high you start when any good aerobat can go over the top in more, or less, than 400 feet?  The only real difference driven by altitude changes is how far away your offset-aimpoints will be on the down-lines, but more on that later.

Next he says, when the airplane is 50 feet in front of you (huh?) push over to a 45 degree line and set 40% throttle (...what motor, battery and prop are we using again?  ...and what's my throttle curve?).  Then fly a "short line and perform a half roll with the airplane directly in front of you.  Fly another short line equal to the first.  Increase throttle and do a 3/4 outside loop then establish another 45 degree line and decrease throttle."

No instruction whatsoever.  He even breaks it down by repeating the above steps under their own subheadings, but only adds a few adjectives to the cut and paste, like "slowly" decrease the throttle and a "gentle" outside loop.  Sheeze, make the pain stop.

Let's start with correcting some of the wrong info...
  • The rolls of a C8 have to be reverse direction, not in the same direction as shown in the mag's fold-out diagram.  A C8 with two rolls in the same direction is thrown out.  
Now, in this "competition" flyer's defense, most RC judges are every bit as cluedo as he is, if not more so, so you can probably get away with same-direction C8's til you run out of room in your AMA-sponsored trophy case. The reason the rolls must be opposite direction is obviously to set a constant difficulty airplane agnostic skills test, especially with torque in play.

 If only it were so easy to "perform a half roll" (rolla rolla rolla rolla rolla rolla rolla...).

When you roll an aerobat, you cause more lift on wing and less on the other.  The increase in lift on the up-going wing (the one that is increasing in altitude; aircraft orientation doesn't matter) results in more drag too, so it gets tugged backward (adverse yaw).  That yaw must be anticipated and corrected with a rudder blend that keeps the aircraft's longitudinal axis aligned with your intended flight path from roll initiation to roll completion.

The difficulty is that when the aircraft passes the point where it transitions through 90 degrees of roll, and goes from erect to inverted flight, you'll need to swap the required rudder direction while adjusting the rudder-blend needed to guide the aircraft's flight path through Knife Edge.  In other words, countering adverse yaw takes pro-aileron rudder when erect, and opposite-aileron rudder when inverted, blended at a rate adjusted to keep the nose from dropping as you transition through the 90 degree bank points.

Because of this, you should unload the airplane prior to rolling to minimize the G and thus lift being created. Unloaded (closer to 0G on the airplane) rolls are much more axial.  

Add constant left (pilot perspective for clockwise rotating engine) torque and the required left rudder inputs generally go away or decrease, the center position requires some right rudder, and the required right-most rudder inputs are amplified.  You must roll in opposite directions on the two leaves of the 8 to make aileron/rudder coordination equally challenging for all aircraft configs and motor types.
  • The author says it's important to do the maneuver at a constant airspeed.  That way you "can count out" distances to make them equal.  
Huh?  We aren't inside the plane, you can see the distances from outside the plane and make them equal.  And this is not a constant speed maneuver.  In addition to the roll/yaw coordination challenge above, the aircraft must stay on an exact 45 degree down-line, even as it inevitably accelerates down hill.

What does 45 degrees look like?   If you are in the plane, put you a$$ on the horizon or check canopy attitude lines on the wire guides.  What does it feel like?  Maybe 0.7g; correspondingly light in the seat.   But the RC community needs neither technique, because we have the luxury of viewing the plane externally and eyeballing the angles to make them look just right, as judged.

Once established on the downhill 45, the plane will pick up speed.  It's ok to throttle back as long as you can still get over the top, but most full scale aerobats would struggle over the top from a standing start.  As the plane speeds up, the absolute best way to set the 45 line in stone is to pick a stationary aimpoint on the ground and drive your eyes straight to it, regardless of changes in aircraft attitude.

As the plane goes faster, the wings will want to lift and cause your aimpoint on the ground to walk toward the horizon, so you have to drive pitch (thus angle of attack) lower, whether erect or inverted as you progress toward the next loop entry point, to keep that aimpoint from drifting.  When transitioning through 90 degrees of roll, apply rudder as required to stick the ground aimpoint dead stationary.

So there is pitch coordination required on the 45 lines, too.

If you start the maneuver high, your two 45 degree down line aimpoints will be far outside the center reference of the looping portions of the C8, and harder to gauge.  As you bring it down lower, the two 45 line aimpoints will become geographically closer together.    They should be equidistant from show center.
  • He says the half rolls should be accomplished using the same roll rate.
No.  That's wrong.  The 45 degree down line rolls should start and stop and the same points in the sky for symmetry between leaves from God's point of view.  If there is wind, that requires varying your rolls rates.

...more soon...


Friday, June 15, 2012

Quick Take: Spektrum DX18


QUICK TAKE
 

The DX18 is the latest evolution of Spektrum's DSM2/X product line.   After researching the level of change delivered by the DX18 radio, it is Z8RC's assessment that while the radio offers more channels, the core transmitter technology does not represent a step forward with respect to link agility/quality,  transmitter and/or receiver operating software (Spektrum receivers are not software up-datable so any link improvement [such as DSMX] requires buying an all-new set of receivers), telemetry implementation, or receiver power-on being physically tied to voltage droop of the servo bus.  At this time, it appears to be a large step backward in price point, at rather alarming $800 per unit.

Because the untouched development areas represent all of the major headaches associated with the Spektrum DX8+ and higher radio line, Z8RC strongly recommends customers AVOID the DX18.

Saturday, June 9, 2012

FMS P-47D Thunderbolt - Flight Review


INTRODUCTION
It is sooo past time for a Jug.
SPECS
- Wingspan: 1400mm (55.1 inch)
- Length: 1250mm (49.2 inch)
- Flying Weight: 2100g (74 oz)
- Motor: Brushless 4250 500 kV
- Servos: 4 x 9g, 2 x 17g
- ESC: 65A
"Even I can break this off."
FEATURES
- Contruction: EPO Foam, carbon fiber main spar
- Landing Gear: Servoless Retractable
- Propeller: 3-blade or 4-blade
- Spinner: Chrome hub included
- Cut-in flap ready

INCLUDES
-4S Battery
-3-blade and 4-blade prop hub

REQUIRES
- Radio: 6-channel
- Battery Charger
- Choice of 5ch Receiver (6Ch for optional flaps)


ON THE GROUND


APPEARANCE / FIT N FINISH
This is my first FMS model.  Based on the good things I've been reading about FMS, I was excited to get one for a first hand review.
The wide angle lens emphasizes a slightly too short wingspan for scale.
Although generally similar, the fit 'n finish is not quite on par with Starmax and J-Power, both of which feature generally stronger foam, reinforcement anchors, nicer decals, and more durable paint.  FMS paint reminds me of Horizon Hobby foamies, easy to peel.  The servoless retracts are essentially the same, undersized units bundled with all cheap foamies.

BUILD QUALITY/SETUP
Build quality is also a notch or two below other main Chinese generic brands.  There is a little too much  play in the gear anchors, the arm and hinge hardware, the tail wheel steering mechanism, etc.
Some sloppy paint and decal work.
ISSUES
- Loose gear needed to be glued down.
- Paint peels easily
- Paint is spotty, especially around the invasion stripes
- No white color, white is left as unpainted foam.

IN THE AIR

BLUF
Light construction has an upside, wing-loading and the corresponding flight experience is closer to an  aerobat with limited throws than a scale warbird.   The FMS Thunderbolt is an sheep in wolve's clothing.

START/TAXI/TAKEOFF
Ground handling:  Darn near perfect.  a very well behaved tail dragger.
Run-up:  Quickly pops the light tail in the air.  You'll want some power early to energize the rudder since the tail wheel gets light, fast.
Torque:  Easy to manage.  Stock motor is tame.

GENERAL FLIGHT CHARACTERISTICS
Throws and control authority are nicely executed.  Out of the box, aileron is reasonably effective for a warbird, but the clearly weakest axis.  Pitch is just about right.  Rudder is a touch too sensitive.

The plane is light and flies well, but tracking straight needs a little more attention than I would expect from a twin-radial Industrial Age fighter carving fast, graceful lines up into the delirious burning blue. 

It would be easy to rate this plane's flight characteristics rather highly, but to do so would ignore the wrong flight character.    When I fly the FMS P-47, I get the impression that my gas mileage is way to good.  Putting the hammer down doesn't even elicit a growl, let alone produce pace suitable for the venerable Jug racing to pick off Me-109s before they can damage the lumbering fleet.

When I buy a warbird, I want the plane to fly like a warbird.  The FMS P-47D flies more like a light sport, low wing aileron trainer than a fire breathing demon hunting death itself.  Too much knuckle ball, not enough fast ball.


BALANCE & AEROBATICS
The CG with a 3300 mAh 4S in the standard center tray position is absolutely perfect.  Chopping power from a trimmed-up 65% throttle cruise produces no change in flight path at all.  Nice!

Aerobatics feel light and the plane is more tossable than it probably should be.  Throws are a bit limited when airspeed droops causing sluggish behavior, especially in roll.   Power is excellent in the same way a Ford Fiesta has plenty of power in 1st and 2nd gear; initial pull is strong but speed plateaus way too early for an aluminum bullet.

POWER SYSTEM
Thrust - Soon
Amps/Watts - Soon
Pitch Speed - Soon
Flight Time - Approx 8 minutes of mixed flying on a 3300 mAh 4S

ADVANCED HANDLING CHARACTERISTICS

Slow flight is forgiving and slippery, cutting in some flaps would probably be worth the improvement in throttle response and more viscous airspeed control.

IN FLIGHT ISSUES
Low T.


GRADES

Appearance: B+
Beautiful from 10 ft.  Wingspan a bit too stubby for scale.  Hurried paint.

Airframe: A-
Light wing loading, airy aerobatics.  Perfect inflight balance. 

Power System: B-
Smooth, quiet.  Long flights. Strong pull from low gearing.  Inadequate top speed.

Build Quality/Durability: C-
Decent motor/ESC.  Junky hardware.  Loose gear anchors.  Longevity is suspect.

Value: C
55" span for $180 is a great price for last year, but only average for mid-2012.

Overall Grade: C+
Lightly built, nimble flier.  An amiable econo car in NASCAR colors.

Monday, June 4, 2012

P-51D Big Beautiful Doll 1600mm EPO w/Electric Retracts, Flaps, Lights (PNF)


Update 6/20/12:  Rimfire .60 and video.


Update 6/4/12:  I really enjoy the scale 4-blade prop included with this warbird, and the sound is tremendous (for e-power).  On 5S, the speed is surprisingly good for the size of the prop and the blade count (video below).  But as I broke-in the motor (or maybe just plain "broke" it), it started to choke on 5S during static runs, and more problematically on takeoff.  It continued to run fine once unloaded in the air.

My Soft throttle solution might have fixed the stock motor problem entirely, as might ESC timing changes, but I didn't start experimenting in earnest until my replacement motor, a Power 46, was already installed and it too balked right off the bat wien using 5S.

With the Power 46 installed, I was forced to abandon the gorgeous Starmax 4-blade as the motor was too weak to turn it with it's 700 kV gearing.  The stock motor is 400 kV.  So reluctantly and given that the 46 was already installed, I decided to try a 4" aluminum spinner with a higher RPM 2-blade solution.

Unfortunately, the Power 46 turned out to be disappointing, even with 2-blades hauling the plane on 5S.  Using Soft Throttle, I was able to achieve pretty good RPM with a 13x6.5.  But in the air the Mustang didn't seem much faster than stock running on 5S, and I had to give up the scale prop and much better audio.  I was ready to get back to troubleshooting that big beautiful prop spinning on 5S with the stock motor.

Then I saw a new Rimfire .60 on an LHS shelf for 50% off it's $99.99 marking, so I jumped on it.  The Rimfire .61 (50mm-55mm 650kV) fills out the motor bay very nicely, and at 2200W it is more than twice as strong as the 900W Power 46 with almost identical motor weight.

I videoed my first test flight on 5S then on 4S using a 14x7 (the Rimfire .60 has no advertised 4S option, but it runs just fine on 4S).   On 5S the plane is reaching new top speeds with spectacular vertical capability.  Even on 4S, the Rimfire gives the Mustang zip the Power 46 lacked on 5S.
Today, I flew the P-51D on 6S with flawless performance from the stock ESC and big Rimfire motor.  The big Mustang is finally getting close to matching my sweet imagination.  I hope all it needs now is the  optimum prop.  More soon...



Update 5/9/12:  Added video of a 5S pass and final grades.
Update: Although they held up fine, to be safe I changed the main retracts for these "super expensive" $14/gear reatracts.  These 2 meter wingspan gear are more substantial and have no play in the down position so ground handling is improved.  They do not come with gear struts and the stock struts are thin gauge for the bore of the heavier duty mechanism.  I added an inner diameter = outer diameter brass tube to the top of each strut for a snug fit.  
Other than drilling 4 holes to match the smaller, stock gear's bolt pattern, mounting is plug n play after trimming 1/8" around the frame of plywood anchors.  Not difficult.  I did like the slower speed of the original gear, but the new ones are not too fast.  The tail gear retract remains stock but for my upgraded pull-pull wires, see discussion below.

This P-51D continues to perform extremely well and out of the 10-15 plane variety pack I typical bring to the fly it always gets the most, if not all, spectator requests to watch it fly.  
The stock prop is gorgeous and it generates monster thrust and adds realism through the sounds it makes in the air, but top speed plane would benefit from a steeper pitch 2-blade.   But I like the stock 4-blade so much I hope I don't have to replace it for a long time (wishful thinking?).
Another interesting thing is how you find yourself treat genuine value vs. an obvious rip off so differently.  I enjoyed putting $28 upgraded retracts into this plane $175 plane and am already looking for other upgrades.  I would throw away one a same-price Ultra Micro before replacing a $30 part, and take the discount on a new semi-disposable POS instead.


Original review follows:
-----
The Starmax Big Beautiful Doll P-51 is quite a sight.  For $175, I had to give it a try.  The plane is much larger than your typical foamie with a 63" wingspan; it's a mega chunk of EPO foam.
Same price as an E-Flite Ultra Micro, really?
The kit comes with the electronics installed for you, requiring assembly of the big chunks.  Overall, the plane goes together pretty quickly and gives a very high quality first impression.
Picture taken at 12:27.
Picture taken at 12:50.
On the Ground:
The two pictures above were taken 23 minutes apart, and I took my time dry fitting the parts.  The plane goes together easily and everything fits well.
The main wing remains removable for transpo.
I glued my wing halves together by smearing the plywood main spar and joining faces lightly with Gorilla Glue.  The completed wing attaches to the fuselage with a pressure fit above the radiator and two bolts at the CG.  The wing could be removed for transportation, but there are 8 connections and not a whole lot of extra wire length on some of them.  Probably best to buy some servo extensions so you can leave the wires connected in a long bundle if you need to break the plane down to transport it.
Big prop; big motor.  
45mm x 58mm 4-5S with 80A ESC
The motor is listed as a 4558 400 kV brushless.  The ESC is 70 Amps as evidenced by the shrink wrap printing, though some retailers list it as 80A.
16 x 6 x 4-blade.
The 16x6x4-blade prop is gorgeously detailed and very hefty.  Mine was pre-assembled and well balanced.  Each blade is replaceable, assuming you can find them or buy an extra prop or two with the plane.  Initial ground runs show tremendous thrust, but little speed.   Using a 5-cell looks to be within limits and provides theoretically unlimited vertical, but I suppose it should because it still tops out with only 40 mph pitch speed.
Prop
Battery
Amps
Watts
Thrust
T:W
16x6x44S-4000mAh-20C58.566790.40.92
16x6x4
5S-3300mAh-25C
68.2
1148
127.8
1.26
The prop could use a lot more bite to convert some of that static thrust to top end speed.  To be sure, a honkin' 16" 4-blade was an aggressive target for an electric plane at this price, so it isn't surprising that it had to be geared low.  We'll see what the plane looks like in the air before a prop or motor re-attack.
The powered LEDs are bright.
The wing tip LEDs are very bright but have spot lenses that focus thin beams straight outward instead of flood lenses.  Diffusing them might help during low light flying.
The retracts are nice and slow, and seem reasonable for the size of the plane, if not a little rickety.  The doors aren't quite flush, and might be designed that way to help hold the gear up or maybe to help them down, but more likely it is a slight miss.  Slicing an 1/8th inch off the three gear door support points is an obvious and simple fix.
The tail wheel retracts too.  Steering is made possible with a pull-pull cable system that attaches to the full size rudder servo with removable and adjustable ball links; the cables fold in the gear up position.  It is straight forward and works well but adds about 30 minutes of assembly time to figure out, install and adjust, as the scant manual doesn't even include a photo.
Full-size servos move the rudder and elevator.  The rudder servo steers the tail wheel separately via the two ball links shown in the photo.  This was slight shipping damage to the wing root corners.
Nice paint and cockpit details.  The canopy mold needs to be trimmed and attached to the magnetic cockpit hatch (sharp scissors did the job cleanly).
Overall, this plane has an awesome presence.  While I think it is priced about right with it's .46 size motor, 70A ESC, three retracts, flaps and lights for $175 from HK, it is shocking that some flimsy, relatively featureless micros cost about the same.
HK will throw in a DSM compatible receiver for a few extra dollars, but I went with a $70 Hitec Optima 9 ch for voltage telemetry and to make each control surface independent per side, mixable and adjustable.  2 x ail, 2 x flap, 1 x elev, 1 x rudder, 1 x gear, ESC = 8 channels before tunable gyros or bombs--which might be forthcoming.
My final flying weight without modification measured 101 oz with a 17.6 oz 4S 4000 mAh inside.  The listed flying weight is 2800 grams, or 95 oz--sounds like ball park number, I don't think so.
Overall, value is through the roof.
In the Air:
The first flight couldn't have gone better. Well, unless you count the landing roll as part of the flight.  The right main gear set screw wasn't very tight and twisted in it's retract anchor upon touchdown--immediately seeking the only three ton vehicle within one mile.
No damage, yay!  Tighten those set screws!
A slight mod I performed as a fix was to Dremel both main gear struts so that each of the two set screws has a flat spot on the metal to hold.  As shipped, the flat spot machined into the strut is only wide enough to catch one of the two screws--of course, the one that wasn't very tight.
The big Mustang was sensational in the air--poised and reasonably powerful on 4S.  Unbelievably quiet.  it flew beautifully, no doubt due to its size and sleek scale design.   As you'll see in the FPV, it required a lot of down elevator trim, creating a slight but visually noticeable downward elevator deflection once on the ground.  But the CG felt good, well balanced in the air with no elevator correction needed in idle on final.  Darn it, the elevator incidence angle was adjustable as shipped.  It is held in place with two long screws, I knew I shouldn't have glued the stab in place.
A second mistake was to anticipate and pre-mix 10% down elevator with flaps.  None was required so the nose pointed down slightly with flap extension due to my mix.  Nice!
What a gorgeous and rock solid platform in the air.  This slippery Stang is faster than I anticipated on 4S, based on the calculated prop pitch speed.  That draggy four banger prop disk must unload considerably once airborne.
First impressions:  What a bargain!  Laser tracking.  Faster roll rate than expected.  Faster passes than I expected.  Sensitive elevator needs to be detuned.   4-blade pull is very strong, and it sounds terrific and realistic from the ground.  Flaps were perfectly symmetrical and very helpful, a first in my RC experience.  Stage presence is unreal for the money.
Takeoff - 1:35  Feeding copious down elevator trim.  The Aurora 9's trim resolution is so fine, it probably took 25 clicks to level out
1:40 First full throttle pass followed by a second
2:32 Low alt loop - the plane's handling was definitely confidence inspiring
2:51 Looking for railroad cars to strafe, the plane looks fantastic rushing by
3:20 Max roll demo.  125% aileron travel.  One hole from maximum travel on both the servo arm and the aileron horns
4:50 Beginning of flap extension testing
6:06  Half flaps down
6:18  Full flaps down
6:22 Right main gear twists
Next flight: 5S.
My second flight couldn't have gone worse.  Winds were dead calm all morning and forecast variable at 2-3 mph all day.  As soon as the wheels lifted off, winds started to gust, then quickly jumped to 10G15 mph.  By the time I landed winds were 20G30 mph in a quartering crosswind.  This was strong and gusty wind for 1:1 scale flight.  As you can see, the 6.5 lb Mustang was battered in the wind, especially on final, but there isn't another plane in my stable that could have survived even half this whipping wind storm.
This flight was on a 5S 3300 mAh 30C battery, which I slid forward thinking this battery is 1.9 oz lighter than my last flight on a 4S 4000.  The new CG measured slightly farther forward than my first flight.  I didn't retrim, thinking the CG move was not substantial and I was probably trimmed a bit nose-up for the last landing.  Immediately upon take off, the plane had a strong desire to dive, but I'm glad I had a more forward CG for this flight.
Fortunately, I was still able to perform my standard durability test, where I set up for landing then a 25 mph crosswind gust grabs the plane like it's a one oz micro and hurls it directly into a 3" diameter tree branch--whack!!  On one of my many attempts to get the plane down in one piece, the plane cartwheels hard right yaw after banging into a 50' tree, almost stopping it midair.  The Mustang's uncanny slow speed control allows me to power right out of the tree with little further drama.  No serious damage, partly thanks to crash proofing my leading edges.  Holy *^&$%!!
Extent of the damage from a 50' tree strike
I've posted some horrible flights, but this one has to be the worst.  I'd prefer to delete it, but what else could show the amazingly forgiving flight characteristics, slow speed control, and wind resistance of this sensational P-51D Mustang.  It is gut wrenching that some terribly made, poor flying toy planes are selling at the same price or more.  What a sad reflection on the clueless state of the broader RC market.
Takeoff   Calm wind
0:36 Too much left over down trim for new CG
2:40 Decent 5S pass in buffeting wind
4:40 Hands off inverted, nice CG
6:20 Tree strike nearly stops the plane midair
Landing 20G30 mph wind.  Gawd! 
While the eventual touchdown in the video above wasn't that crazy, it revealed a weakness in the Starmax tail wheel's pull-pull system.  The supplied string is plenty strong, but it apparently stretched under load.  This introduced some play into tail wheel steering.  Note, the pullrod distance decreases by a couple of inches as the tail wheel retracts.  I decided to try copper strand wire as my fix.  It seems a lot more solid:
Wires taught = tail wheel down
After a two relatively minor fixes, one to the tail wheel pull/pull cables and a second to main retracts, the BBD flies and taxis as good as it looks.
The sound of the big motor through high speed passes on 5S is a treat for the senses, in additiona to being one of the best looking and flying P-51Ds on the market, it is also the best sounding electric Mustang that I've heard:
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