|Mar 03, 2013, 02:40 AM|
Xieda 9938 Scale MicroHeli Review
Xieda 9938 Review
Along about the first week of the New Year, I began an Odyssey in the RC game which is still playing out; Alizee, my contact at TMart, asked if I could do a review of this helicopter:
Of course I said yes; I've flown a few of their 9958s and have had a lot of fun with them.
A week later, I received confirmation it was on its way from Beijing; it finally arrived 6 days after that on Jan 22nd.
As with previous shipments, it arrived in a durable mailing envelope with Retail packaging inside; the carton was free of labels and the envelope protected it from scuffs during shipping. Ready for gifting.
Inside the Box
Included with the 9938 helicopter are a spare set of main blades & tail rotor, single 500mAH 3.7V LiPo battery and USB Universal Charger which takes about an hour to charge this battery. Tucked under the styrofoam is a printed manual in the now-familiar Chinglish dialect.
The heli also comes with the usual Game Controller-style transmitter we've all seen included with RTF toy aircraft; this one has an LCD display which shows Throttle, Cyclic Input, Trims and Battery/TX Power levels. Red & Green LEDs indicate Flight mode VS Bind mode; the TX has High & Low Rate Modes selectable by pressing down on the left stick.
What is really hard to express with just photographs is the quality and detail molded into this scale body; upon removing it from the packing, one can see a beautiful gloss finish, with lines representing all major body panels as well as doors. Based on the iconic Hughes 500C, this Civilian-Model body sports a paint scheme traditional to the '70s vintage of the design; my model came in medium blue metallic with black & silver trim and the Tee-Tail stabilizer. A charcoal grey version is also available. The metallic finish is gorgeous, it just glows; extra fine flakes in the paint enhance the "scale" feel of the model.
The body is stuffed with the Xieda 9928 helicopter's upsized motor and drivetrain. This heli is larger and heavier than the 9958; it weighs 73.4 grams compared to its smaller cousin's 31.4 grams, so it needs the power.
Here you can see it compared side-by-side with my venerable 9958; it is really hard to show in photos just how much more substantial the 9938 is in real life.
Actually, I think the tail view shows the best comparison; the 9938 is just plain beefy.
So the following day after charging the battery, I head out to my flying club meet to test my new baby.
I'm maybe 90 seconds into its maiden and it's flying a little tail-heavy; it doesn't want to move forward so I'm trying to trim it out and BAM!!! One of my fellow members wails into it full-speed with his 600mm biplane, knocking it out of the air and killing it instantly.
The impact was hard enough to tear the brushless motor and both wings from his airplane; a couple weeks later he rebuilt & brought it back, but it still won't fly straight.
I contacted Alizee to see if they had any parts available, as I was unable to locate any on the internet & it looked like I needed at least a new mainboard. "No, this heli is too new... we don't have any parts in stock yet. I'll send you another one."
And just like that, my review of the brand new blue beast was postponed until a replacement could arrive from Beijing.
While I waited, I did my best to patch it up; here you can see the damage to the blades...
and to the front "windshield" and cockpit area.
Right behind that damage is the mainboard; as I suspected, it suffered a large crack right in one of the main power supply areas.
I repaired it successfully...
But when I put it back together, I found the main rotor hub had been cracked out as well, so I tried this quick & dirty fix with coat thread & CA adhesive. I was able to fly it at the next week's meet; it lasted about 3 minutes before my patched head grenaded, costing me my only spare set of mainblades.
A couple weeks later, a NEW, COMPLETE 9938 RTF Kit arrives. Not just the Heli, which would have been excellent, but the full kit, complete with TX, battery, etc. This is great; Alizee is THE BOMB.
But... here is where Murphy's Law and the fact (Yes, it IS a fact) that it has taken a personal interest in my life comes into play. I have a gift for attracting little projects which due to my bad luck, turn into big time-consuming ones. This review has become one of those.
My preliminary inspection of the new heli revealed excessive endplay in the mainshaft; this only required disassembling the heli down to the chassis and flipping the Mainshaft locking collar over the right way so it seated properly against the top bearing. No problem. While I'm in there, I take a moment to tack down the tail motor wires with a spot of hot glue so they can't get in the linkages.
WHILE I'M WORKING on that, the battery door and holder are loose & getting wiggled about; as I'm buttoning up the body, I discover that the negative wire has broken due to misapplied glue reinforcement.
Disassemble, resolder, apply hot glue & route wires to clear maingear again. No major problem; I've had to resolder battery wires on every MicroHeli I ever owned. Just the timing of all this was annoying, as I picked it up from the Post Office the afternoon of my flying club meet.
Now, it's all together; I pack it all up with 2 charged batteries and head out to my meet to test fly it and... IT FLIES FABULOUSLY right out of the box! No adjusting the linkages, trims all set at zero. It takes off, ascends and hovers about 5 feet in front of me with hands off the cyclic; I give a little rudder as I'm lifting off, so it piros once but that's all. Impressed, I move it out into the middle of the gym. A few piros, a few throttle-pumps. It ascends well, but not as snappy as its smaller cousin. I expected this. Tail lock is good; just a little wiggle. Lateral movement is smooth; but the usual "right-hand tilt" is very pronounced. It doesn't drift laterally in either direction, however. Nice. First I try some circles; increasing speed I find I can bank up to maybe 45 degrees before it loses stability and the tail blows out. This is stable and repeatable. My V911s and 9938 will go deeper; maybe 60 degrees but they weigh about 60% less. This is to be expected as well.
I find that in hard acceleration and right rudder, it has a tendency to ascend sharply from a combination of gyroscopic reaction and angular lift; it has a cored motor, so that effect is greater. It also tends to smooth out the power though; headspeed never drops, even when you spill and piro hard enough to stall the blades all you get is a moment of blade clatter, then they flatten out and start to build lift again.
The big difference is acceleration. It doesn't accelerate as quickly in any direction as its smaller cousins; it CAN go fast; but it takes it a while, and once it is moving, it can be a bit hard to change directions. It has almost 2 1/2 helicopter's worth of weight to move though, compared to them. This, coupled with the rigid plastic required to make all that gorgeous detail in the fuselage, really makes this more of a "Scale Flyer" than an "Aerobatic Flyer". It flies beautifully, with very "scale" reactions to input; you can imagine yourself at the stick of a real M500, taking a sightseeing flight. My flights last approx 8 minutes; almost twice as long as my V911 & 9958 provide.
This means that you can get yourself into trouble; it will go fast, but if you don't plan far enough ahead, you just plow into obstacles and walls you could zip around with the smaller helis. And when you hit... it doesn't just bounce off. It breaks.
These are more complicated airframes; the Tupperware plastic that the canopies on the V911 and 9938 are made of is heavy, and just not rigid enough to make a detailed fuselage like this.
So far, I haven't broken anything on the new 9938 badly enough to ground her; but that gorgeous paint has some scuffs now, and the windshield has several cracks. Skids and main blades have held up well; as have the tailrotor and T-Tail stabilizer. It's a nice heli to fly when you just want to relax; you CAN go fast with it and it will even fight a few MPH of wind, but in my opinion, it's best to just "take it for a walk" and imagine yourself flying the real thing.
Below is my flight video from a couple weeks ago; I've had a lot of work which delayed completion of this portion of my review. Thanks to Brook, who piloted the heli for the video, and extra thanks to Alizee at TMart for giving me this opportunity, and for being patient, and as always, asking only for an honest review.
The Xieda 9938 is a gorgeous scale heli with mild handling characteristics which make it an excellent next step after coaxials. It is especially suited to "Scale Flight"; offering lifelike response and feel. Get extra batteries; a single 8 minute session passes much too quickly!
Beautifully detailed, lifelike fuselage with gorgeous metallic paint
Larger & more stable than smaller microhelis
More "Scale Flight" flying characteristics
Great, well-mannered intermediary step between coaxials and CP helis
Approx 8 minute flight time
Rigid plastic breaks more easily than smaller aerobatic models
Maintenance requires disassembly of fuselage
Need to offer extra batteries as an option; a single 8-minute session just isn't enough
Big enough to get you into trouble if you're not careful
A bit large for flying in the house; garage should be fine.
Product Page at TMart, who graciously provided review model:
In the next couple days, I'll add my usual Tech Teardown of this heli; I have a LOT of interesting, detailed photos; there's a lot of interesting tech in this heli.
It's late, I'm vapor.
As I've mentioned before, this heli is built on the Xieda 9928 chassis; which itself is based on the 9958, only everything is scaled up about 25%.
The head geometry is the same between the 9958 and the 9928; it uses an underslung flybar with the "floating eyelet" pivot arrangement and 120° equilateral spacing on the aileron, elevator and anti-rotation pin.
The 9938 alters this geometry by moving to a longer, overhead flybar with heavier weights; this is necessary to tame the collective action since they had to move to a narrower 140° spacing on the aileron & elevator arms so it would fit inside the scale shell.
They've also upgraded to an actual swashplate with a ball socket; along with eliminating the "floating eyelet" pivot arrangement on the flybar, these changes improve the precision of this head greatly.
I've always felt that the 9958 was at best a temperamental heli (actually, I've referred to every 9958 I own as batBLEEP! crazy at one time or another); with careful adjustment you can make them flyable, but I've never had one with the good manners out of the box that my V911s have all had until I got this 9938. It is, in my opinion, the best flying bird I've ever gotten from this manufacturer. I think this redesigned head is the reason, and personally, I think they should let the technology trickle down to the other members of the family.
Xieda, I hope you're reading this.
It's hard to see from just a photo; but this head is built on what appears, from all the measurements I can make, to be the same mainshaft as the 9958 uses. The flybar assembly actually attaches to the blade pivot head assembly, and all the other geometry remains the same.
The updated design is, in fact, very familiar; as you can see in this closeup of the head from my V911 review. Aside from changing the shape of the intermediate links, they're the same basic design.
Because the working bits are all inside the shell, gaining access to perform service is a bit more hassle than with the sport models. You have to split the shell apart to get to anything; this means that getting in the habit of performing basic maintenance regularly is a must.
First, you have to remove this screw and take off the shroud around the linkages. You'll also need to do this to gain access to adjust the linkages.
Next, remove this retaining collar. It goes around both halves of the shell, so it's pretty easy to break. Be careful.
Once the collar is removed, you can move onto the tail.
The Tee-stabilizer doesn't necessarily HAVE to be removed to split the shell; but it is only held on by a quarter-turn lock, so I prefer not to have it in my way. Now that's removed, we can begin actually disassembling the shell.
Place the heli so the right side faces up and remove these 8 screws. Remove the tailrotor by gripping firmly at the center, not the ends of the blades, and pull straight up off the shaft. Then gently separate the tail housing from around the tail motor. The rest of the shell will come loose easily; it doesn't have any "snap-together" type closures. Note that the two screws labeled FRAME have counterparts on the opposite side of the shell; they must be removed as well to release the chassis completely from the shell.
This is what the guts look like out of the shell; you can still see the tail bracket for the 9928.
No, you're not imagining that. This little guy actually uses a ducted fan to pull air around the battery & motor to keep things cool inside that shell. Clever.
Here you can see inside the fan housing with the main gear removed; it's got a pretty aggressive compression ratio. You can actually feel the exhaust when the heli is running.
The tail motor is an 0820SR coreless with 1mm shaft; it spins a 45mm rotor with a wicked aggressive pitch. Yes, that's right, this thing uses the same motor for the tail that most microhelis use for a main motor.
Tailrotor is modeled after the mCPX Pro V2 upgrade rotor; only expanded to 45mm diameter. I see this combination as a potential solution for Genius & Mini CP flyers having trouble keeping the tail locked-in after a brushless conversion.
This model uses a cored-type DC motor; these produce more torque than the coreless type, and are more resistant to heat damage. The larger working area suggests possible brushless conversion, if you're so inclined.
The 9938 uses 2 linear-action servos; they have no active components, so conversion to conventional servos should be a snap, as should adapting them to other uses. They are very light at only 2.24 grams.
Overall, this heli is going to appeal to casual fliers rather than aerobatic fliers; it looks good, it has good manners and it's inexpensive. Hackers like me will see it as a wealth of potential parts for other models:
Head/flybar assembly: $8/ $10 with swash
I believe that using these parts on the 9958 could drastically improve its flight characteristics; enough so that I fully intend to try them as soon as I can order parts. Look for a related tech article on that project soon. I'm even toying with the idea of using the larger blades as well, just to see what the 9958 does. I don't actually own a 9928, so trying these parts on that model would best be left to some other adventurous soul.
While it is a 140° spacing swash, I'm fairly confident it can be adapted to work with the 9958/9928 as well; having an actual ball pivot rather than the "floating eyelet" should drastically improve precision on these helis too.
The main motor on this appears to be the same as the Walkera Mini CP/Mini FP/Master CP and a couple other models use, only at half the cost. I think for the price I can be bothered to change a gear and resolder a PC board.
Tailrotor: $2/2 rotors
The 45mm Pro-style tailrotor on this heli, combined with the 0820SR motor, could prove to be a much simpler solution to tail-hold problems experienced by many fliers of microhelis across the spectrum of brands. All the major brands have exhibited issues with maintaining tail-hold after brushless upgrades; the forums are full of people trying to keep the joy of brushless main motor and civilized flight characteristics at the same time.
This heli uses an inexpensive 550mAh battery of undetermined C rating (High enough to keep a 70gram heli in the air for 8min, though). HOWEVER, it also uses the very common JST-PH power connector found on all kinds of Park Flyers airplanes and mini/micro helis. I see it being a good inexpensive upgrade for people seeking to increase runtime on all sorts of small, 1S aircraft.
The linear servos used in this model are very light; this, added to the fact they have no integrated electronics, makes them a very good candidate for modding either onto "all-in-one" type micro receivers, or to connect to the control board of a cheap 9gr servo (or any old broken servo one might have lying around), to get linear actuation where you need it cheaply and with little weight.
These parts are readily available at HeliPal.com and HeliDirect.com here in the States; I'm sure there have to be a few China resellers also stocking them.
Well, that about wraps it up; hope you found this review useful, or at least amusing.
They make 'em. Somebody's gotta fly 'em.
|Mar 03, 2013, 09:59 PM|
Great review! I've also got a 9938 and it's fun to fly. You should try the 9968 if you haven't already. It's got its battery mounted more forward in the fuselage so I find FFF to be slightly faster with the 9968. They're both great helis though.
|Mar 07, 2013, 08:05 PM|
Joined Aug 2012
maybe i want to buy one for myself
|Mar 30, 2013, 10:40 PM|
[ UPDATED REVIEW: Tech Teardown Added! ]
Thanks for the positive response! Hope you like the Tech teardown as well!
The 9968 has a lot more weight to contend with than even the 9938; I think it's almost 20 grams heavier. But it does have the same overhead flybar, so I expect similar good manners as the 9938.
I always had a soft spot in my heart for the Huey; their wake was "The Angel's Wings" in so many stories told by members of my mother's extended family who came home from the war broken inside.
Vaya con Huevos!
|May 03, 2013, 09:32 PM|
Or else get a DoubleHorse 9116 transmitter in mode 1 and figure out how to set the servo directions on that.
Or else upgrade and get a Turnigy 9x in mode 1...but that's obviously more expensive...
|May 24, 2013, 08:38 AM|
I received the 9938.... I only tried it 10s coz need to work ...
Humm ... actually, he is absoluptly not trimmed correctly (backwarding and right shifting) ... Will have to perform mechanical trimming, don't want to play to much with electronic trimming. I guess will have to mount/unmount many time the canopy to perform this fine tuning ...
EDIT : Thank to your very good review especially the dissambly part . To fix my linkage, need to unscrew one to tune ... Perfect
|May 24, 2013, 01:25 PM|
Here are my first photos during unboxing of the 9938. Got the grey version and some spare.
After removing the part hidding the linkage, I performed the mechanical trimming. Now the bird is much more stable in stationary fly and have a faster forwarding. The motor seems to become very hot and plastics look very fragile. Anyway this bird is cute ...
Last photos show the Xieda 9958, Xieda 9938 (of course), Hubsan H102D FPV and the WLtoys V912
|May 25, 2013, 12:31 AM|
Wow dude... what you spent in spares, you should have just gotten a second heli!
Seriously... parts you wanna stock up on are:
The smoked windshield part of the canopy; it gets cracked something awful, main blades, tail rotor, flybar, main head (part the blades pivot on) & extra batteries. Get 2 or 3 at a time.
I've never broken skids, shell, servos or links (Knock on wood). Motor and gears and shaft are pretty well-protected by the shell; wear and heat will be their main enemies.
A few notes:
Don't fly 2 batteries back to back; allow at least 10 min between flights. The main motor will be sizzling hot after 2 back to back.
Get used to the T-Bar popping off all the time, or hot glue it on.
Inspect the area where the wires are soldered to the back of the battery connector; if they aren't well-reinforced with silicone, add silicone sealant or scrape what's there off and hot-glue them. They'll break off after about 10 open-close cycles on the door if not properly reinforced.
|May 25, 2013, 01:07 AM|
Thank you for your advices . I already noticed during trimming that the motor becomes very very hot ... so of course I will wait a bit between twio LiPo. I took mainly some fusalage and rotor head part ... and a landing skids (it's a reflex I have since the S033G where I already broke 3 ...). Missing a tail motor ... You had problem with ?. I don't know if I will use it a lot , but time to time and mainly outside (when wind here will stop a bit ... ). Whatever thank for your review and advices
|May 25, 2013, 03:11 PM|
It seems that Xieda 9958 and 9938 are using two different radio protocols .... I can't bind the 9938 radio on the 9958 .... What's a pity....
|May 25, 2013, 09:39 PM|
As I mentioned in the 9958 thread, I found I had to be very fast with the transmitter. Once the heli LED starts to flash, you only have a few seconds to bind it to the radio. hold down the left stick until it clicks and power on the transmitter. If it doesn't bind, turn TX and heli off and try again.
|May 26, 2013, 01:46 AM|
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