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Hangar 9 Twin Otter ARF Review

A larger, scale aircraft from Hangar 9 that can serve as an excellent introduction to electric powered Twins!

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Introduction


Wingspan:82"
Wing Area:738 sq. in.
Weight:11.5 to 13.2 lbs.
Length:65"
Wing Loading:36 to 41 oz/sq. ft.
Servos:Spektrum A6000 digital (6), JR Sport MC35 analog (2)
Transmitter:JR X9503 2.4gHz DSM2
Receiver:Spektrum AR7000 seven channel
Batteries:E-flite 3200mAh 3S 11.1V 30C LiPo (2)
Motors:E-flite Power 25 BL brushless outrunner motor 870Kv (2)
ESCs:E-flite 60-Amp Pro with Switch-Mode BEC (2)
Manufacturer:Hangar 9
Available From:Your local hobby retailer or Horizon Hobby
Price:$489.00
Flight Duration:6-8 minutes


One of the first posted photos of the Hangar 9 Twin Otter, Joe Nall 2008

T’was a time when the only way enthusiasts could learn of upcoming releases from radio control airplane manufacturers was to flip through the latest copies of whatever RC magazines were available. But the Internet has now made it possible for folks like us to rub shoulders with the engineers and designers who create new airframes and actually have input on their designs in many cases. The Hangar 9 Twin Otter was first revealed at SEFF and Joe Nall in 2008 as a prototype aircraft under consideration for production as an ARF. Hangar 9 solicited and received feedback as to whether the Twin Otter, 82" in span, would be well received or not. The rumor mill churned away with news on the Twin Otter for many months, and then in February of 2010, it was officially announced as being on the way!!


Jumpers away, from one of the three full size USAF Twin Otters

According to the introduction in the Twin Otter assembly instructions, the aircraft modeled by Hangar 9 is one of three UV-18 Twin Otters flown by the US Air Force Academy's cadet parachuting program. Interestingly, these three aircraft are the only Otters in the USAF and are capable of carrying a pilot, copilot and up to 17 jumpers. The UV-18B is the military version of the DeHavilland DHC-6. The end result of the decision to manufacture the Twin Otter under the Hangar 9 branding instead of E-flite is that both electric and nitro power systems are accommodated right out of the box. Fixed landing gear, a high wing configuration equipped with flaps and a Clark Y airfoil combine to create an aircraft with excellent slow speed handling and stable flight characteristics, thus creating a perfect introduction to a twin powered aircraft for intermediate to advanced pilots.

Kit Contents


Pint glass and ball cap to show that this is one HUGE box!

Though the Hangar 9 Twin Otter comes in a box large enough for me to place my 6' 0" frame without crouching, the number of components filling the cavernous cardboard container is surprisingly few. The big Otter fuselage takes up the bulk of the space, with the balance filled by the built up wings and horizontal stabilizers/elevators, a fiberglass nose cone and twin fiberglass nacelles, main landing gear, a gorgeous nose gear strut and the required hardware to fit either electric motors or small nitro powered engines to the airframe. Immediately noticeable is the long, narrow chord wing halves, complete with flaps equipped with hidden linkages. Features like pre-hinged control surfaces speed the assembly along considerably. Yes, the Twin Otter is large but large does not equate to a long build at all.







In The Box:

  • Balsa and light ply fuselage
  • Balsa and light ply wing halves
  • Fiberglass nose cone
  • Balsa and light ply horizontal stabilizer halves, with elevators
  • Fiberglass engine nacelles with cowls (2)
  • Clear engine nacelle (1)
  • Rudder assembly
  • Landing gear assembly (2)
  • Suspension nose gear strut
  • Fiberglass landing gear fairings (2)
  • Wing struts (2)
  • 3/4 x 19 1/2 inch aluminum wing tube
  • 3/8 x 11 inch aluminum stabilizer tube
  • 2 1/4-inch white nylon spinners
  • Fuel tanks 200cc (Unused in this review)
  • Glow engine mounts (Unused in this review)
  • Pushrods
  • Control horns
  • Pull pull assembly for rudder
  • Servo and electric motor mounting hardware
  • Assembly instructions
  • One sheet of manufacturer’s logos decals







Required for Completion:

  • Twin glow power systems or electric power systems
  • Minimum 5 channel radio system
  • 3 servo Y cables
  • 7 nine inch servo extensions
  • 2 thirty six inch servo extensions
  • 6 standard servos (Spektrum A6000 digital recommended)
  • 2 micro servos, if using electric power systems (JR Sport MC35 recommended)
  • 2 propellers (APC Thin Electric 12x8 recommended)

Included for Review:

  • E-flite 60-Amp Pro Switch-Mode BEC Brushless ESC (2)**
  • E-flite Power 25 BL Outrunner Motor-870Kv (2)
  • E-flite 3200mAh 3S 11.1V 30C LiPo, 12AWG w/EC3 style connector (2)
  • Spektrum A6000 Digital Aircraft Servos (6)
  • JR Sport MC35 Micro Servos (2)
  • Spektrum AR7000 DSM2 7 Channel Receiver

** NOTE: The recommended ESCs for the Twin Otter are the smaller E-flite 40 amp Pro-Switch mode units; due to them being out of stock, the larger 60 amp units were supplied for this review.








Assembly


The included 48 page black and white photo-illustrated assembly instructions may seem a bit on the thick side but at least 7 of these pages do not even require a glance, as they detail the installation of a two stroke power system. This review will utilize a pair of clean and quiet electric power systems. Using electric power systems lowers the overall number of servos required to complete the build by two, as the twin servos require to operate the engine throttles are not needed. Several features of the manual I especially liked were the absolutely comprehensive list of the hardware included in the box, right down to the last 4/40 washer, and also the list of major components with their respective part numbers included for reordering purposes. The black and white exploded view photo of the major kit components lays to rest any fears that this large plane will take any longer to build than a comparable 40 or 60 size kit. I wholeheartedly recommend reading the entire manual over BEFORE commencing the build. I actually look forward to this! It helps one get a quick fly-over (no pun intended!) of the build to come and to visualize how it all will go together. The manual is so well written and illustrated that it convinced me that I could knock this build out in a long evening or two!




Twin Otter Assembly Manual

Wing


Assembling the pair of Otter wing halves involves the usual "preparing" of the servos (installation of rubber isolators and grommets) for installation onto the aileron and flap mounting plates. I find this task somewhat mundane but thanks to the help of my young daughter, we together knocked it out in record time. The recommended servos for the ailerons and flaps are the new Spektrum, affordably and attractively priced A6000 Digitals.



The flaps and ailerons both come from the Hangar 9 factory pre-hinged and the control horns pre-installed. More and more ARFs are arriving with these tasks already performed for the builder. I like the time savings offered by this arrangement, although I do spend a few minutes examining each and every hinge, giving them all a mini pull test to insure that they are all properly and securely installed. The flaps and ailerons on the Otter come with a plastic overlay attached to them which simulates the corrugations found on the real Otter's control surfaces. They look great! One caution worth mentioning in connection with them is that they do not play nice with a heat gun. Should you have to get rid of any wrinkles in the covering, be very careful when working any where near these corrugation surfaces or they will irreparably distort and contort.




The Spektrum A6000 Digital servos are dimensionally large enough that they push the hard wood servo mounting blocks out a little, so that they protrude off the edges of the ply servo mounting plates. I used a emery sanding board to eliminate this overhang. It is essential to use CA to harden the servo mounting holes and also the servo mounting plate holes, located in the wing halves.





Pull strings are included, to facilitate an easy pull of the aileron servo leads in to the root of each wing half. When making up the short aileron and flap push rods, I decided to go with a Z-bend on the servo horn end, rather than the illustrated 90 degree bend and plastic snap keeper. It was necessary to open the flap control horn holes up a little using a pin vise and drill bit, as the clevis pin would not initially push through the hole. Also, it is important to note that the two flap servos are not identical in the position that they get mounted in on the plywood servo mounting plate. There is a slight difference between the two that must be taken into consideration, in order for the flap push rods to properly align with the holes in the trailing edge of each wing half. I really like that Hangar 9 makes the flap push rods completely hidden inside the wings!


Fuselage


The Twin Otter fuselage is cavernous! A total of four doors and access panels are provided. The coolest one is the double door located aft and on the left side of the aircraft. It features a functional latching, spring loaded door handle that is used to open and close the two doors. Another hatch, mounted with four screws is located on the other side of the fuselage, a bit farther to the rear. A third hatch is located atop the fuselage, directly between the wings, and is also secured with four screws. The final opening is a small hatch located forward, just behind the fuselage former/firewall to which the nose gear attaches. The nose wheel steering servo gets mounted inside of this access panel. All four openings will be used to get ones hands and arms inside the fuselage when installing the pull-pull rudder cables and also when routing the various servo extensions to the receiver, which will be located in the center of the aircraft and is accessible through the large hatch on the top of the fuselage. I made sure not to forget to secure all servo extensions with heart shrink, or one could use a piece of dental floss.






The bulk of the required assembly of the fuselage involves mounting the fixed tricycle landing gear and wing struts. While I really like the cool factor of retracts, the almost maintenance-free factor of the fixed tricycle gear are perfect for easing one into the overall increased complexity that a twin aircraft involves. The landing gear is beefy and robust. The nose gear suspension strut is especially nice looking. Another nice touch on the part of Hangar 9 is that all three wheel/tire assemblies come pre-mounted to the gear assemblies, saving a little more time on the overall build.




The nose gear gets mounted to the ply forward former using four 8/32x1 inch cap head screws. Thread lock should be used on these fasteners but it can be applied after they have been threaded into the blind nuts via the forward fuselage access hatch, which permits access to the backside of the ply former. It is necessary to over drill the hole in the metal nose gear steering arm, in order for the metal nose steering push rod to slip into it. Drilling this hole too large could introduce slop into the nose steering assembly, so it is important to drill cautiously and check the fit of the push rod often.





The main gear assemblies each get mounted with a trio of 8/32x1 inch hex head screws. The wing struts also get anchored into the aft hole of each gear mount. The main gear fairings get secured into position using canopy glue. This process works best if tape is used to hold the fairings in the proper position, which then permits the running of a filet of canopy glue around their perimeter. It is important to be accurate when laying the canopy glue filets down around the gear fairings, as using too much glue makes for a messy and troublesome clean up. I decided to end one of my building sessions with this step, as the canopy glue is best left to dry overnight.


The fiberglass nose cone is mounted to the front of the Otter fuselage using a clever twist-lock technique. Three short screws are threaded into the perimeter of the front ply former so that their heads protrude the proper amount. The nose cone has three holes in its outer edge, which align to these three screws. The nose cone is then rotated a small amount to lock it into position, with a machine screw threaded into a blind nut mounted into a hardwood block locking it firmly into place.


Tail



The vertical stabilizer on the Twin Otter is part and parcel of the fuselage. The rudder is built up and is attached to the vertical stabilizer with a series of CA style hinges. A pair of control horns get mounted to the lower part of the rudder, in line with the exit points on the fuselage for the pull-pull rudder cables. The rudder servo, also a Spektrum A6000 Digital servo, is mounted in the middle of the fuselage with the radio receiver. The numerous access doors provided in the fuselage are invaluable when making up and installing the pull-pull rudder cables. Hangar 9 includes everything you need to make up the pull-pull rudder assembly, including a couple of spare ferrules. Bravo!




The Hangar 9 Otter uses a pair of horizontal stabilizer/elevator halves, which are joined together using a a carbon spar that passes through the vertical stabilizer. The elevators are pre-hinged, with the control horns pre-installed. The configuration chose by Hangar 9 results in a horizontal stabilizer that can be removed if necessary. A pair of JR MC35 micro servos get mounted internally in the stabilizer halves, in much the same manner as the aileron and flap servos are mounted in the wings. Long 24" servo extension leads are required to get the elevator servo connections forward to the mid-ship mounted receiver. Each elevator servo receives it's own channel on the Spektrum AR7000 receiver, necessitating a custom mix be programmed on the radio transmitter.




Power Systems Installation








Hangar 9 is noted for designing their airframes so that either nitro or electric power systems may be utilized. This is also true of the Otter. The motor mounts and fuel tanks are included in the box, as are the nylon stand offs for mounting electric motors. To ensure that either choice of motor is correctly positioned on the firewalls, Hangar 9 includes a plywood motor mounting template that contains holes for both the recommended Power 25 brushless outrunners or the included nitro motor mounts. It is easiest, and recommended, to first mount the motors before gluing the nacelles to the leading edges of the wings. The required and recommended E-flite electric power systems are a very economical and affordable choice, given the larger size of this scale plane.




Another notable feature, to be used only when powering the Twin Otter with internal combustion engines, is the clear plastic cowl that is provided to simplify making accurate cut outs for any protruding pieces of the engines. Mounting the E-flite Power 25s is straightforward. It is first necessary to first "set" the blind nuts into the firewalls before actually mounting the motors. The Otter kit includes cap screws of the proper length for mounting the motors. The screws included with the motors are not quite long enough. A hole must be drilled in the firewall in order to pass the three motor wires into the interior of the nacelle. Excess wire length must be neatly bundled and ty-wrapped to the stand offs to keep it positioned inside the cowls and away from the rotating outer cans of the brushless outrunners. The E-flite ESCs are attached to the inner walls of the fiberglass nacelles with hook and loop, while the 3200mAh 3S lipoly batteries use the same type of fastener to secure them to the plywood trays. A hook and loop strap goes around each lipo to make sure it remains in place in-flight. To prevent the lipos from accidental puncture due to the protruding motor mounting screws, a small scrap piece of balsa should be glued to the bottom of the firewall at the front of the battery tray. Access to the innards of each nacelle for battery change insertion and removal is easy and quick, thanks to removable hatches that are equipped with spring loaded latches. One of my hatches seemed a bit lacking in the strength of it's latch spring.






Once the power systems are completely mounted, it is time to attach the nacelles to the wings. I practiced sliding them into position several times in order to familiarize myself with the best method for quickly getting them oriented. It is best to do this before you are dealing with the added potential mess of oozing epoxy. 30 minute epoxy provides enough time to get the glue applied and the pieces in the correct orientation. I mixed up a second batch of epoxy after the initial batch had dried and brushed it all over the mating seams of the wing-to-nacelle joints. Once the nacelles are fixed firmly into place with the epoxy, canopy glue is used to seal the gap between the nacelles and wings.






The recommended 12X8 APC E props should be double checked for balance. Hangar 9 includes a set of basic white spinners in the box. It is necessary to ream the hole in the spinner back plate in order for the Power 25 collet to fit properly. I really wish Hangar 9 would properly size these holes at the factory so that they work with the recommended motors. If one is not careful opening this hole up, out of balance spinners will be the end result. APC makes their 12X8 E prop in a pusher configuration. thus, for the small effort of reversing the rotation of one motor, a pusher prop can be used on one motor. This results in a counter rotating prop configuration, which can lessen the possibly harmful effects of losing one motor in flight. In connection with this though, it is interesting to note that the designers and flight testers at Hangar 9 report that the Twin Otter is remarkably well behaved when flying on a single motor.

Radio Installation


The total number of servos required for completing the Otter includes standard sized units for most of the control surfaces, except for the twin elevator servos which are smaller micro sized units. I was excited to see that Hangar 9 sent a full compliment of the relatively new Spektrum A6000 full size digital servos for this review. I was anxious to see how these very attractively priced digital servos wold perform. Standard analog servos could also be used and would help lower the bottom line of the total radio equipment costs when outfitting the Otter.





Hangar 9 recommends at least a five channel radio system for the Twin Otter. While that may certainly work, more channels make for easier setup and programming. A Spektrum AR7000 seven channel receiver was included for this review. Personally, I would prefer a nine channel receiver for the added ease of programming it would offer by letting me plug each aileron, flap and elevator into it's own channel on the receiver. However, a seven channel receiver is entirely workable and the programming feature set of my JR X9503 transmitter helps get the Otter configured in no time. Whichever receiver you decide you use, there is an absolute abundance of room to mount it within the fuselage of the Otter. Uniquely, Hangar 9 provides only one set of recommended control throws in the instructions instead of the typical low and high rate recommendations.


Spektrum AR7000 Receiver Channel Mapping
Channel # Function
1 Throttles (Y Cable)
2 Ailerons (Y Cable)
3 Elevator 1
4 Rudder and Nose Steering (Y cable)
5 Elevator 2
6 Flap 1
7 Flap 2


Though a custom mix could be used to functionally couple the two elevator servos together, a better approach is to use the X9503's Dual Channel option. This programming option allows you to assign a second channel to ailerons, elevator, rudder or flaps. I mapped the second elevator servo to channel five (gear). An additional benefit to setting up dual channels in this manner is that the channel labels in other programming menus, such as the sub trim menu, are changed to properly reflect their programmed function.


Though I could have used the same Dual Channel feature on the flaps, I instead used a custom mix to set them up (OK, I confess! I did not realize that I could configure the flaps in the same manner as the elevators, using Dual Channels, until I sat down to write this part of the review). I have only owned my X9503 for a few months and I am still acclimating to it's generous and capable feature set and programming options. Suffice it to say it is very versatile and many functions can be accomplished in several different ways.


A little programming was also in order in connection with the flaps. I used Hangar 9's recommended flap throws, as listed in the assembly instructions. The X9503 is very intuitive and configuring the throws on the flaps is as easy as selecting either the in flight position (full up), take off (middle position) or landing position (full down) and then dialing in the amount of deflection desired. And of course I had to dial in the maximum amount of delay available in the flaps programming, in order for them to slowly deploy and retract. A transmitter without this delay feature results in flaps that "snap" into each position, potentially upsetting the airframe until it can readjust to the new shape of the airfoil. Hangar 9 also provides suggested amounts of down elevator that can be programmed and mixed in to prevent the aircraft from ballooning when the flaps are deployed.


Radio installation should not be considered complete until you have clearly labeled each and every servo lead and extension. This will make assembly at the field much easier and will prevent having to remove the top access panel several times to get the receiver connections right. I used a small piece of white electrical tape wrapped around each servo lead, writing a descriptive label on each with a fine point black Sharpie.

Completion

In order to hit the recommended center of gravity, which is 2.5 to 3.9 inches (64mm to 76mm) behind the leading edge of the wing, I had to add a little ballast to the nose of the aircraft. I ALWAYS hate to add so called dead weight to an electric powered aircraft and will usually opt for a larger battery, which at least provides a little additional flying time for it's added mass. Larger batteries are really not a viable solution to the CG variance on the Otter due to the batteries being located very near the center of gravity. I initially decided to add the needed ballast to the ply former that serves as the nose gear mount, thinking it was the obvious choice due to it's structural strength. However the long nose of the Otter beckoned and I revised my solution to instead place the needed weight as far forward as possible, in the tip of the fiberglass nose. Obviously this approach also brings the added benefit of cutting down on the actual amount of ballast required. I would be hesitant to add TOO much weight to the fiberglass nose cone, as the excess mass it adds, when subjected to any type of high G load, could result in the fiberglass fracturing. I decided to use sand due to it's desired mass being infinitely adjustable. A couple of smaller Zip-Lok bags stuffed one inside the other act as the holding container, with two strips of double sided tape adequately anchoring it all in place.




Uniquely, the Twin Otter assembly instructions only offer up one set of recommended throws instead of the more typical low and high rate throws. I used the suggested throws as my low rates and then set up some high rate throws to utilize a little more mechanical throw on all control surfaces.

Recommended Control Throws
Ailerons 3/8" (10mm) 3/16" (5mm)
Elevator 1/2" (13mm) 3/16" (5mm)
Rudder 2" (51mm) 3/16" (5mm)
Flaps Half=1/2" (13mm) Full=1.5" (38mm)
Flap-to-Down-Elevator Mix Half=5/32" (4mm) Full=3/8" (10mm)

Note:Dual rates left to discretion of user

My completed Hangar 9 Twin Otter tipped the hangar scales at a weight of 11 pounds 6 ounces All Up Weight, which is just a smidge under the range of weight specified in the assembly manual (11.5 to 13.2 pounds). Another piece of data that we modelers like to consider is the wing loading of an airframe. The Twin Otter's wing loading number works out to be around 34-36 ounces per square foot. That number may sound a bit on the high side to many of us but it reminded me of an article I had recently read, written by Scott Stoops, and dealing with something called wing cube loading. It is the opinion of many modelers that wing loading, which is based on the square footage of a wing, can be a bit inaccurate in defining how an airframe will perform and that a more accurate barometer for measuring and defining performance may be wing cube loading. This seems to be especially true when it comes to larger aircraft such as the Twin Otter.


Francis Reynolds and Wing Cube Loading - 1989

A little on line research turned up a paper from whom many view as the original author of this alternate formula and concept, Mr. Francis Reynolds. According to Francis Reynolds, Scott Stoops and others, wing cube loading is a much better way to determine how a wing will perform than the commonly used wing loading. Francis notes that the WCL for gliders will average around 4, R/C Trainers around 6, Sport Aerobatic ships about 9, Pattern jobs about 11, R/C Racers around 12, Scale Models from 10 to 15, and Full-scale Airplanes 15 to 20. The Twin Otter ends up with a wing cube loading of around 14-16, which coincidentally lands it squarely in the realm of what the wing cube load formula defines as a scale plane!


A cool little application to quickly calculate wing cube loading is WCube.zip

Flying

When it comes time to take the Otter out of the hangar for a little flying, most of us will have to set aside a little extra time for tear down, load up and then reassembly again at the flying field. The front part of my single car garage does double duty as my hangar. The Twin Otter is so big that I had to do some summer cleaning to make room for it! With the wings removed however, it becomes quite manageable storage-wise. I like to perform a initial radio range check and some basic ground testing out in the street in front of my house. I usually secure the airframe just inside the garage and then take a stroll into the neighborhood, walking down the street a block or two for a range check. When it is time to do a little taxiing, I usually carry the plane down my slightly inclined driveway. The transition from driveway into the street is a cut curb of about an inch in height.


Several firsts occurred with this large Hangar 9 ARF! It is the first plane that I have owned that when fully assembled just barely fits through the opening of my overhead garage door. It is also the first that I was able to taxi both down the drive and out into the street and then also back up the drive, with the twin electric power systems having the necessary power to pull the Otter up and over the short curb that is at the foot of the driveway and up the incline and back into the garage. Also, the landing gear are large enough that they could easily negotiate the bumps that have stopped my other planes cold. This is one large ARF! Suffice it to say that you will most probably need a SUV, pickup truck, van or station wagon to transport the Otter to and from the field. My primary plane hauler is currently a Toyota FJ Cruiser and the Otter fits into it with no real issues. We have successfully packed the Otter, a 90mm EDF, a ParkZone Habu and a couple of profile foamies into the FJ at one time. Blankets and towels are required, as stacking is necessary! And remember, always allow for a little extra time for assembling the Twin Otter when you arrive at the field. (You DID mark the servo leads, right!?)


I force myself to NOT be in a hurry when it comes to assembling the Otter. It goes together quite easily, with the two wing halves each being retained by means of a large nylon screw with a wing-type head for tool-less tightening. The only slightly tricky part involves the landing struts. They must carefully be threaded into an oversize opening in the rear of the engine nacelles as the wings are mounted onto the round carbon spar. An assistant can be invaluable for this step, but it can be done solo. A single cap screw retains each strut inside the nacelle but the holes are recessed and a little difficult to see. I use a small piece of Blenderm tape to hold the hex head fastener to my Allen wrench, feeding it down through the hole in the nacelle and into the necessary hole. Removal is a little easier, with a pair of hemostats being invaluable to reach down into the nacelles to retrieve the two screws once they are loosened.

Taking Off and Landing

I was not quite sure what to expect when it came time for the first takeoff of the Twin Otter. Several things weighed a bit heavy on my mind in connection with the Otter. And they all had to do with math.

One piece of data that we electric radio control modelers like to throw around is the number of "watts per pound" of a given aircraft. Almost all of the airplanes that I have flown for which I have calculated this number have had over 100 watts per pound available, with some of my EDFs even having upwards of 300 watts per pound! Common opinion however is that scale planes and war birds can and should fly handily on less than 100 watts per pound. Yours truly has yet to fly any airplane with a number south of 100 watts per pound, much less one that spans 82", weighs over 13 pounds and with the recommended power systems is reported to have around 65-70 watts per pound?! Another number that had one of my eyebrows raised a bit was the calculated wing loading of the Otter. At around 35-40 ounces per square foot, the Otter is approaching what may be considered a heavier wing loading (See discussion about cubic wing loading above). Just how would this big Otter fly!?


I decided to skip the flaps for the maiden flight. Though I favor a scale take off for a scale plane, I tend to push the throttles to the stops and just get her up and aloft ASAP for a maiden flight and trimming. I was just a bit surprised when the Otter almost jumped into the air after what I would define as a pretty short roll out. With only low rate throw recommendations provided by Hangar 9 in the assembly manual, I flew the initial flights on the high rates that I had arbitrarily configured. Very little trim was required. Once aloft and at speed, I was able to pull the throttle back to slightly above half and still cruise around the sky with no sign of a stall.



My initial landings were mostly good, although I had one or two that were not so great. Notably, the landing gear on the Otter is substantial and robust and capable of absorbing the energy of any less than perfect landings. This not to say that landing the Otter is in any way difficult. With a head wind of a couple miles of hour to land it into, the Otter will really slow down to a very scale looking speed.




The real fun begins though when you start using the flaps for take offs and landings. The use of flaps wonderfully reconfigures the wing and transforms the Otter into a plane so fun that I found myself shooting endless touch and gos. The sight of the Otter, it's inboard flaps hanging down at a steep angle as it slowly turns base and then final, is SO awesome! Throttle management is of course important when landing with full flaps and the sound of the twin Power 25s modulating to control the rate of descent is addictive. It is possible to hold the Otter off when in ground effect by feeding in very small amounts of up elevator. This, coupled with ever so slight decreases in the throttle setting as you float along the runway center line a few inches off the ground, will result in the prettiest and softest landings you will ever see!




Very scale takeoffs are possible by setting the flaps to the full down position and then slowly rolling into the throttles. The Twin Otter will gracefully leave the ground on its own, with no need for me to feed in any up elevator to initiate the rotation. I did have to decrease the amount of down elevator that was trimmed in in the flaps set up menu. My initial settings were causing the nose of the Otter to pitch down at full flaps.

Aerobatics/Special Flight Performance

The Twin Otter will make a believer out of you! Can an airplane really fly on only 60-70 watts per pound?! YES! And fly it does! The twin Power 25s have ample power to pull the Otter out of any compromising situation you may accidentally get it into, although do not expect to go vertical with them. Steep climb outs are however possible and they look pretty cool to boot. Although I really did not feel the need to explore the aerobatic side of a plane whose full size counterpart is not known for it's aerobatic capabilities, the Otter is capable of basic aerobatic maneuvers. I know because I watched a pilot whose thumbs are better trained than mine put his Twin Otter equipped with the recommended nitro engines through it's paces. Inverted flight, consecutive slow rolls of a sort, loops and a crazy Lomcevak type tumble that had me covering my eyes are all possible should you wish to try them.


As for me, I instead enjoy trying to fly the Otter in as scale a manner as possible. It really excels at this in my opinion. All in all, it flies and feels like a very light plane, with the long and narrow wing generating an amazing amount of lift! The recommended 3S 3200mAh lipo batteries provide plenty of run time, and with judicious throttle modulation, flights of 7-9 minutes are possible. I accidentally flew two flights on the same set of batteries, thinking I had swapped to my second set. My total flight time on that one set of batteries was nearly ten minutes! And I still put less than 2800mAh back into them when recharging them.

Is This For a Beginner?

The Hangar 9 Twin Otter is not a difficult plane to fly. It is very well behaved and really does not have a mean bone in its entire airframe. I would be very comfortable taking mine up to altitude and giving a relative newbie a little stick time via a trainer cord or buddy box. With the throttles pulled back and the rates set to low, a beginner could easily be coached through flying some basic oval patterns. The Otter is very docile on take off and landing and can make a pilot look like he really knows his stuff! Probably the only caution in order when flying the Otter is that you can get too slow and the wing will eventually stop flying. The ensuing stall is not severe or unrecoverable but it could catch a beginner off guard. Landing with the flaps, while not difficult, can be a little challenging in that any excess airspeed carried to touch down can result in a bounce that can usually only be stopped with a delicate touch on the throttles. Is the Otter a good first twin? I would say emphatically yes! The fixed gear eliminate any need to tinker with retracts and they are sturdy to boot. The required power systems are not at the high end of expensive at all, although having to buy a pair of them does take a little coin. All in all, there is very little technical tinkering required with this Twin Otter when powered with electric power systems, making it a great choice for one who wants to transition into twins.

Flight Video/Photo Gallery












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Conclusion

The Hangar 9 Twin Otter comes with a huge WOW factor! It is a large aircraft and every time that I have taken mine out to a flying field, folks have excitedly gathered around it with questions aplenty. It's large size and bright color scheme make it visually appealing and easy to keep ones eye on. Though the Twin Otter ARF may be a little pricey in the eyes of some modelers, when built with "clean" electric power systems it will be an airplane that you can assuredly fly for a long time! With no oily exhaust residue attacking the airframe, about the only thing that can lead to damage is a case of dumb thumbs. It is an airplane that you will WANT to fly for a long time. I get a real kick out of going around and around the pattern, shooting touch and go after touch and go. The flaps really slow the big Otter down, so much so that in my opinion it could almost be mistaken for the real deal as it slides down the glide slope.


Grins

  • A large, scale, twin model that flies nicely on a pair of modestly priced electric power systems
  • Suspension nose strut included
  • Pre-hinging of most control surfaces; almost all control horns pre-attached; landing gear fully assembled
  • Snappy color scheme, with good color matching on covering and fiberglass parts
  • Sturdy landing gear
  • Flying with the flaps is just too fun

Grumbles

  • Included spinners require modification to work properly with Power 25 collets, which can result in out of balance spinners when using the tools available to the average modeler
  • Difficult to insert strut fastener cap screws into the engine nacelles


A special thanks to Hangar 9 for providing the kit for review, as well as to Don and Terry for always being willing to lend a hand!
Last edited by Bajora; Jul 21, 2010 at 09:12 AM..

Discussion

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Old Jul 22, 2010, 08:59 AM
I tell her RC is cheap !
carguy1994ca's Avatar
Quebec, Canada
Joined Sep 2006
13,337 Posts
Jon, this your best review yet ! The pictures are awsome ! You really do justice to the plane. I followed the thread on RCG since the beginning about the possible coming of this bird and bought it as soon as it was available. I don't regret it. It flies nicely, is very stable and looks amazing with its nose down while on full flap approach. Just like the real thing. It is costly to fully equip such a plane, but it is well worth it. I love this plane.

For the spinners, I used a prop reamer to enlarge the hole in the back plate (not all the way through). And I use a short lenght of fuel tubing to hold the strut screw on my hex driver. Some guys on the forum lenghtened the screws with some brass tubing so they could easily remove them without pliers. I also bought a small folding aluminum table to assemble the otter at an easy working height at the field. It gives me room to go around the plane to attach the wings and all the wires without bending and stretching.

Carguy
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Last edited by carguy1994ca; Jul 22, 2010 at 09:05 AM.
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Old Jul 22, 2010, 10:07 AM
Wandering IT geek
ronin4740's Avatar
United States, NV, Reno
Joined Aug 2005
3,965 Posts
Another great review Jon! The Otter's too big for my plane hauler but if that changes and I get interested in another twin your article has done it's job in convincing me that the Hanagar 9 Twin Otter would be an excellent choice.
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Old Jul 22, 2010, 10:30 AM
Fly Every Day
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United States, FL, Sebastian
Joined Apr 2001
801 Posts
What a comprehensive and thorough review. I love it. You did an excellent job. I love my Twin Otter. It is one of the most thrilling airplanes I have veer had.
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Old Jul 22, 2010, 11:42 AM
AMA #916425
Stiknrudder's Avatar
Shenandoah Valley, VA
Joined Sep 2008
361 Posts
Nice review Jon.
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Old Jul 22, 2010, 09:33 PM
lawndart aerobatic ace!
gr8taz nitro's Avatar
Joplin, Misery
Joined Mar 2007
407 Posts
Nice review. The one I put together for a friend we did a couple of things differently than the instructions showed. One of the things we did was instead of epoxying the nacelles in, on each side of the nacelle I drilled them and bolted them in place with 6 screws for removal if needed at a later date, i.e. if something happens not looking at having to replace everything from a damaged wing. We also modified the top hatch and made it magnetic instead of using the 4 screws for access to the wing bolts. The spinner issue we fixed by switching to dubro spinners instead of using the ones supplied.

If you've got the mixing open you should try setting up the motors separately and mix them to the rudder for ground handling. I mixed the motors to the rudder and on the ground she'll turn around in a 2 foot circle.

It's amazing how well this plane flies on the recommended setup, and it looks killer on final with the flaps down and a nose high approach.
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Old Jul 22, 2010, 10:37 PM
I tell her RC is cheap !
carguy1994ca's Avatar
Quebec, Canada
Joined Sep 2006
13,337 Posts
They should make esc with reverse so we could park them like the real ones
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Old Jul 22, 2010, 10:39 PM
KK6MQJ
Bajora's Avatar
Joined Sep 2004
13,790 Posts
Quote:
It's amazing how well this plane flies on the recommended setup, and it looks killer on final with the flaps down and a nose high approach.
Yes, I agree wholeheartedly. Landings with flaps are tons of fun.
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Old Jul 23, 2010, 12:25 AM
KK6MQJ
Bajora's Avatar
Joined Sep 2004
13,790 Posts
BTW, wow and thanks to whomever gave this review thread a 5.0 rating.

BUT, I have to say that the current version of the site software seems to have a bug.

Only one vote can usually be registered and then the vote gets locked. Soooo, the thread ratings are really not indicative of how the the general populace truly feels about a thread but only track the first vote! I have asked the admins to drop the thread rating from these review threads, at the very least. Very few folks even know how/where to register a vote anyway.
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Old Jul 23, 2010, 12:45 AM
Lipo abuser ... smoke on!
gp125racer's Avatar
Joined Feb 2005
1,920 Posts
I had the chance to fly Jon's Otter and I must say it's an awesome plane! No bad habits what-so-ever, and super easy to land, even with no flaps ....... the only thing missing is a squad of jumpers headed out the back

Don
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Old Jul 23, 2010, 01:11 AM
KK6MQJ
Bajora's Avatar
Joined Sep 2004
13,790 Posts
Dons first flight on the Otter saw him greasing the landings from the get go. We had a particularly memorable evening, in the final hours before sunset, where we burned a couple of sets of batteries through it, taking turns at the sticks. The evening fog and overcast that customarily comes in was on the horizon, making for some spectacular lighting and color contrast!

Fun stuff for sure!
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Old Jul 23, 2010, 08:53 AM
AMA #916425
Stiknrudder's Avatar
Shenandoah Valley, VA
Joined Sep 2008
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Quote:
Originally Posted by carguy1994ca View Post
They should make esc with reverse so we could park them like the real ones
use a car ESC. they usually have reverse.

Rick
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Old Jul 23, 2010, 09:39 AM
I tell her RC is cheap !
carguy1994ca's Avatar
Quebec, Canada
Joined Sep 2006
13,337 Posts
Quote:
It's amazing how well this plane flies on the recommended setup, and it looks killer on final with the flaps down and a nose high approach.
Nose high approach ? The real one approaches nose down and flares just before touch down. Mine does the same with full flaps. I find if you pull the elevator on descend, it makes the plane less stable:

Twin Otter short landing & takeoff (2 min 20 sec)
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Old Jul 23, 2010, 09:51 AM
lawndart aerobatic ace!
gr8taz nitro's Avatar
Joplin, Misery
Joined Mar 2007
407 Posts
Quote:
Originally Posted by carguy1994ca View Post
Nose high approach ? The real one approaches nose down and flares just before touch down. Mine does the same with full flaps. I find if you pull the elevator on descend, it makes the plane less stable:
I use a nose high approach to keep my rate of descent in line, then use the throttle to control it. I have yet to see a problem with the plane losing stability in any attitude. Even a full stall is a non event on this plane, wings stay flat and the plane just mushes down, little power and your out. Maybe I fly the edf's too much cause a nose down approach just doesn't seem right.
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Old Jul 23, 2010, 11:59 AM
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United States, CA, Cameron Park
Joined May 2007
1,259 Posts
Coming in with a nose high attitude is asking for trouble as you are sitting on the backend of the power curve where a stall will be always lurking around the corner with the only way to salvage such situation is pushing the nose down to get your speed back on track. If you are lucky you did not drop a wing and crashed.

Coming in with the nose pointing down the only thing you have to worry about is your airspeed which is easier to contain than a stall. Cut back the throttle over the numbers and start your flare (nose high attitude) a feet above the runway and you will be at least assured that if you crash you will do it on the runway and on the airplanes wheels.

It's the same as with real airplanes....
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