By Vario Team Pilot Lee Cheesman
Introduction
Around 15 years ago, I built one of my first Vario scale helicopters. It was a 1/6th size EC135 with a benzine engine. I have always admired this helicopter; what Vario made possible back then was magic for me. The EC135 in the ADAC scheme has always been a favourite of mine. When I found out that Vario were releasing a ¼ scale version – I knew I had to have one; it had to be an ADAC scheme – it was going to be a special project that would provide many hours of enjoyment and challenges. I wanted to re-live that earlier build on a grand scale! Vario helicopters provide a fantastic canvas to achieve whatever suits you. You can go as far as you want to with scale detail or build a great looking model to get in the air quickly! Whatever appeals to you – the kits give you the basis to start and finish a project with whatever goals you have in mind.
The Real Thing
I based my model on the ADAC EC135 P3 based in Straubing, Germany. The distinctive absence of vertical fins on the horizontal stabiliser, small bumper on the underside of the tail and large air filters gives a hint to the more modern version. Through the transition from the Eurocopter group to Airbus, we see many varieties with different branding and modifications. The newer H135 features a raised front cowling in front of the air intakes. I really wanted to build an EC135 with a hoist…but it had to be in the ADAC scheme. With the help of some friends, we found Christoph 15 with a Goodrich hoist mounted so I started digging around for more photos. I was satisfied there was enough material for me to work from and set off on the build.
The Mechanics
The usual high quality from Vario is evident in the mechanics for the EC135. Very robust, well laid out and slightly more complex than most. I opted for the Jet-cat SPT5-H version which is heavier than its electric equivalent but has plenty of power. As always, great attention to detail is needed to ensure all parts are installed correctly following the diagrams closely. It is critical to make sure frames are square and that gear meshing is perfect. I pay particular attention to the diagrams to ensure all bearing holders are installed in the correct orientation as are the main shaft collars. Assembling all components to one side frame leaving the allen screws a touch loose will help when it comes to combining both side frames to form a solid mechanical assembly.
Excellent quality Gears 
Laying Out Mechanics Parts 
Very Robust Mechanics
The gears and mechanical components supplied by Vario are excellent quality that have been accurately machined. Installing gear hubs is straight forward. Pay attention to the mounting direction and do not overtighten screws. Firm pressure all around, tightening as you would car wheel nuts/bolts avoids the possibility of axial play or wobble.
Parts ready for assembly 
Side frames 
First Servos Mounted 
Double Thick Auto Gear 
Gear Support Bearings 
Main Mast Installed 
Tail Drive with Auto-rotation Hub 
All Gears and support blocks loosely in place ready for second frame and alignment
The first side frame starts out with the three frame supports, four bearing holders and the main shaft assembly. Note that Vario have thought ahead here and used two drive gears atop of each other allowing for the added torque required for this large model. The main gears sit either side of the autorotation bearing with longer m3x25mm screws. As they are drilled identically, the teeth align nicely. At this point I mount the servos in their correct orientation. I always triple check the main shaft collars or clamp ring orientations. Failure to do this can result in the clamp screw being on the opposite side to the access holes provided in the frame.
Moving on through the mechanics build, further bearing supports are installed along with the intermediate shaft and its two Delrin bevel gears. Significant strength is provided here through the support of the metal bevel gears. The forward gear is free running providing balanced support and the other inputs power via a lay shaft from the second of the drive gears. The familiar small bearing guides of which there are four, are installed with only light pressure on the delrin gears. These assist to keep the gears firmly meshed and perpendicular to the intermediate shaft. All shafts throughout the build are milled with flats in the correct places for the gear hub set screws. The remaining drive gear is installed above the lay shaft gear which also outputs through the tail freewheel assembly. The turbine bracket attaches to two small adjustable metal supports which allow for the turbine pinion to be meshed properly. I opted to install the turbine at this point for better accessibility to adjust before the second side frame was installed. All frame support screws were loosened, and the frames aligned 90 degrees to a flat surface and then screws tightened with medium thread lock. This step is critical for any build to ensure gears mesh together consistently and all shafts run true.
Turbine Installation
The power plant for the EC135 turbine version is a two stage Jet-Cat SPT-5H. Two stage turbines are more efficient than single stage turbines and have two shafts. The secondary shaft is not connected to the primary shaft – thrust provided from the primary shaft impeller drives the secondary shaft which translates power through a planetary gearbox to the pinion.
The turbine is held in place by two supports. The rear support is an aluminium frame that surrounds the planetary gear box, held in place with M6 screws. This is attached to the adjustable metal blocks (described earlier) sandwiched within the two frames. The forward body of the turbine is supported by a two-part cylindrical cage that also has adjustment. Using both forward and reward adjustment allows the turbine to be levelled so the pinion gear is meshed correctly to the tail drive gear/main input gear.
The SPT-5H gearbox is lubricated via a length of Teflon tubing. The tube is fed from a T-piece or Y-connector from the main fuel supply, into a metered valve. A T-piece after the valve connects to a bleed valve on the turbine body before continuing to the gearbox. It is important to keep the tubing straight to ensure the small needle is not bent that protrudes from the metering valve.
Now the turbine is installed to the mechanics, the complete assembly can be set aside safely while I focus on the fuselage and woodwork.
SPT5 installed with bracket 
Gears meshed correctly 
Turbine Mounting blocks visible 
Test fitting mechanics and turbine into fuselage 
This is a very big model!
Fuselage Prep and woodwork install
This is a very large helicopter! The shape of the EC135 leads to a very bulky front cabin area. At 2.47m long, the model is imposing due to the design. The GRP fuselage is in twelve parts – the body, upper front and upper rear cowling, tail, horizontal stabiliser, two vertical stabiliser fins and four doors. As I would be basing my model on the P3 version I would be modifying the horizontal stabiliser with no requirement for the two vertical stabiliser fins. As usual, I gave all grp pieces a wash with washing up liquid and warm water – just to be sure any realise agent or resin that may interfere with adhesion is removed. The quality of the GRP is excellent and the double skinned doors fit very well.
With the fuselage washed and ready, I cut out the window and door ports first, to gain better access to install the wood frames. Depending on the helicopter and structure, sometimes it is better to leave this step if possible, to maintain the fuselage shape. My usual method to cut window and door ports is to border the permitter in 5mm tape. I then use a dremmel with a cutting wheel to cut close to the tape, then Permagrit tools followed by Wet and Dry to give a smooth finish.
With the cabin now open, I can easilygain access to install the wood frame structure. The plywood parts are supplied in two laser cut sheets. The plywood is of good quality and thicker than some other builds due to the size of the helicopter. With the parts pressed out and edges lightly sanded I can dry assemble and set them out inside the fuselage. All parts interconnect throughout the entire structure. Small quadrant formers support the sub floor side struts and an aft bulkhead integrates a sturdy base for the 2.5L fuel tank. Once the parts were dry fitted and I was sure that everything was aligned correctly; I marked out where the parts contacted the fuselage. I removed the parts and keyed these areas with 180 grit sandpaper and de-greased to ensure proper adhesion.
I usually leave the glazing until the end to prevent scratches, but will mention it here anyway. My method for glazing has always been the same. I rough cut a panel out of the mould and position it over the frame with tape. I then use 5mm vinyl tape ontop of the glazing, following the frame appeture underneath. I cut around the tape to leave the perfect shape. I use wet and dry to smooth the edges.
Floor support formers 
Woodwork ready for Hysol 
All floor supports in place 
View from rear 
Front view, looking impressive! 
Mechanics in place
I had already taken to mounting and aligning the mechanics at this point, drilling the four holes for the undercarriage, and using a level. Throughout the build, I found it useful to keep the undercarriage mounted with four temporary bolts. This allows more access underneath the fuselage and a stable model to work on.
Slots in the sub floor supports can be used for the door sliding mechanism if required. With all parts ready and the GRP resin keyed, installation can begin starting with the floor formers and sub floor supports. My method I have always found successful; is to use cyano to spot tack pieces in place and then run a bead of Hysol epoxy around the interconnecting surfaces. Hysol is my go-to epoxy and I have always found it to be effective. It is especially convenient when used with a gun and mixing nozzle. To the rear at the base of the bulkhead is a rectangular recess which allows clearance for the long mechanics sub frame assembly.
Overall, I am impressed with the design and layout of the wood structure. The fit is snug around most of the fuselage with only a few minor areas which needed a bit more support from the Hysol.
Undercarriage
The EC135 makes use of a sub frame to raise the mechanics in the fuselage. The sub frame is again formed of two halves with four frame mounts. This forms a solid structure and attaches directly to both horizontal skid cross members. The mechanics sit within the subframe secured with spacers, screws and M3 nuts and washers.
At this point I have powder coated the undercarriage satin black. The mechanics were installed onto the sub frame and secured at the upper wood formers in the bulkhead notches. It was then just a case of aligning with the fuselage and the undercarriage and the floor marked and drilled to accept the M5 bolts. I was careful to drill these holes accurately as this is key to ensuring the skids align along the length of the fuselage and that the mechanics sit even. Smaller steps in the process were also involved including temporarily mounting the torque tube in its clamp mount to allow for better alignment.
Tail Assembly & Alignment
Having already installed the mechanics temporarily and removed a section of grp at the end of the tail cone, I can install the torque tube to the rear of the mechanics to achieve accurate alignment. Unlike most other models, the larger 135 features an open gearbox. This makes servicing access much easier. The gearbox as pictured to the left is very easy to assemble and features four bearings. The bevel gears are larger in diameter and of a lower module than standard Vario bevel gears when looking at the diameter/teeth. This should result in a stronger more efficient gear for this higher torque purpose. The gearbox is usually secured with three grub screws – but instead, M3 allen bolts are used to secure the back plate of the gearbox to the torque tube adapter. It is therefore crucial when it comes to epoxying the torque tube adapter into the torque tube that it is very well aligned, and the tail shaft is oriented correctly.
The circular template takes a lot of the fuss away here – but take extra care as it cannot be adjusted (rotated) like on grub screw set ups if an adjustment is needed.
The rear of the fuselage features a GRP reinforced cone shape. The tail has a matching recess allowing both parts to be epoxied together to form a strong bond.
It is also possible to make the tail removable with a few modifications, but I opted to fix the tail permanently as transport was not a limiting factor. Vario supply a plywood circular template for fenestron models and there is no exception here. The idea being that the gearbox can be mounted on the plywood circle and pushed into the fenestron tunnel. A hole can then be made centrally to ensure the torque tube exits the fenestron tunnel in line with the gear box. This is the trickest part of the tail assembly and an area where accurate measurements need to be made to avoid misalignments resulting in the tail blades contacting the fenestron tunnel.
The manual shows that bearing supports need to be installed inside the torque tube. I left this step until after all cutting of the torque tube was complete to avoid metal filings inside the tube. Once I had a rough idea of the length that the torque tube needed to be, I used an adjustable pipe cutter to make the cut. Take care to remove the burr on the inside of the tube when cutting. With the torque tube cut to length, I can now dry fit in place ensuring the tail pushes right up to the fuselage with no gaps whilst the torque tube is in place over the black tube adaptor secured to the gearbox mounted on the plywood circle. It is important to make sure the tail boom is level when measuring and flush against the rear of the fuselage body. Small deviances in angle alter the length of tube required so be careful!
With the torque tube cut to length, and the hole cut through the fenestron tunnel, I can now remove the tail and epoxy one of the plywood supports in place which supports the tube. The support needs to be mounted inside the forward end of the tail. These formers serve to add reinforcement to the tail structure preventing the tail from moving adding additional rigidity to the air frame. Using masking tape, I simply pulled the larger former in place and epoxied with Hysol for a strong bond. This gives clearance for the inner cone on the rear of the fuselage body. Before fitting the circular former at the tail end, preparations need to be made to the horizontal stabiliser.
The torque tube passes through the upper part of the horizontal stabiliser. Once the two aerofoil shapes have been cut either side of the tail boom, the horizontal stabiliser can be slotted through. Trial fitting is required, and I found using a large convex permagrit tool gave a perfect recess for the torque tube.
The control rod for the tail passes on the underside of the horizontal stabiliser; this also needs some clearance made to the underside of the stabiliser. The instruction manual calls for the torque tube to be epoxied in three places. At the forward wood support, the horizontal stabiliser and the circular former behind the fenestron tunnel. To get to the rear wood former, an access hatch needs to be cut into the underside of the tail. The manual does point to two locations to remove to allow for access, although I found I only needed to cut the rear one for a good result. The EC135 features a hatch on the front underside of the tail, right about where I needed to gain access. So, with the scale hatch to hand I made the opening as large as I could get away with. Through this opening I could see the hole that I had made for the torque tube.
Before I epoxy the torque tube in place permanently, I installed the tail control rod support – taking note of a slight offset to align with the input ball on the bell crank. I opted to use a slightly oversized length of brass for the carbon control rod to slide through. This isn’t required, but it does reduce friction. The control rod itself can be installed later after test fitting.
Finally, I arrive at the point where the torque tube, horizontal stabilizer and tail can be combined and epoxied to form the tail structure. (I took other steps and modifications to match the P3 version prior to epoxying which are covered later). I measured from where the tail boom contacts the main body to the front of the horizontal stabiliser. I translated this measurement to the torque tube still attached to the mechanics. From my marked point I then measured the width of the horizontal stabiliser and marked that on the torque tube too. The underside of this area would be where epoxy would be applied to bond to the upper recess I had cut out of the horizontal stabiliser earlier. I roughened this area with 180 grit paper and applied a good amount of hysol. I slid the tail back over the torque tube, still secured to the mechanics, feeding through over the horizontal stabiliser. I had also applied Hysol to the recess made at the top of the Horizontal stabiliser and inside the two stabiliser aerofoil cut outs. I placed the circular wood support over the torque tube just before it exits into the fenestron tunnel by using the access hole cut in the underside of the tail. Applying plenty of Hysol to the rear of the support I then pushed the torque tube through and over the tail drive black adapter, also coated with plenty of hysol. Using a wood stick I was able to push the circular support in place and apply more Hysol, all through the access hole I had cut earlier. All that was left to do was wipe away excess epoxy and align the tail fin vertically and horizontally with tape and supports. I opted to use a laser to align as best as possible. This is important as the forward section of the torque tube has two small slots that fit over two lugs inside the mechanics torque tube clamp. Now, just to wait 24hrs for the epoxy to harden. Once hardened, I could remove the template.
Tail Gearbox and Fenestron Assembly
The gearbox is an open design with larger gears than the standard vario tail gearboxes. Assembly is straight forward. The fenestron hub itself required a great deal of care so ensure the small bearings are seated and fixed in place properly. I made a small nylon plug to push eash of the blade holder bearings into place. This worked well and prevented any damage to the bearings.
Assembled Gearbox 
Inserting Bearings 
Assembled Fenestron
Electronics Layout
This helicopter with all of its detail was anticipated to be over 25kg. It is possible to keep the electric version under this weight, but it isn’t possible with the turbine version. I take great pride in electronics layout and wiring. This model needed power and receiver redundancy for the Large Model Association scheme. I wanted the mechanics to be easy to access and remove to service. I built a small wood structure to support ABS sub floor electronics. The stabilisation is achieved with a Futaba CGY760. Powerbox batteries are used for receiver power, turbine power and a dedicated battery for the Unlight system. All batteries have a Powerbox batt guard in place so that all batteries can be discharged slowly to a safe storage state.
Full power redundancy 
Powerbox Batt Guards 
Batteries mounted
Scale Detail
To cover off all steps to complete the model to a high scale standard would take a very long time. I would like to think that the hundreds of hours of effort paid off. Some of the steps I took to bring the model to as near to the full size helicopter possible:
- Horizontal stabilizer modification to P3 Version
- 3d Printed cowling filter intakes
- Fenestron bumper
- Sheet metal exhuaust guards
- Small machined parts for overflow outlets
- aluminium machined pitot tubes
- 3d printed winch and fittings
- Full leather effect seating
- 9 screen OLed working cockpit with instruments
- Realistic retracting landing light
- 3d Printed and covered pilot and crew seats
- Full scale rivets using Vario Rivet glue
- Complete Unilight system
- Seating rails
- Recessed tail collar like on full size
- 3d printed Cyclic, pedal and collective controlls
- Scale pilots with name badges and correct ADAC suits
- Rear clam shell door window
- 3d printed Door lock
- + many other scale 3d printed parts
Painting
The higher the detail level of a model, the harder it becomes to paint. Small recesses, hatches, handles and rivets all make for a challenging painting surface. All lettering was painted using paint masks and flatted back. Small paint decals were used for small lettering. It was a challenging paint job as the yellow Ral 1021 needs to be built up to get the correct colour. Panel lines were achieved by lightly scoring the gel coat only to prevent weakening of the grp.
Helicopter in Primer 
Vario Rivets 
Fenestron Cap 
Carbon Head Cap 
Fenestron Tunnel Painted 
Tail drying after blue paint 
Marking out for orange section 
Notar writing, tricky masking! 
Black paint added to doors 
The ‘D’ of ADAC 
The famous stars circle 
Lettering and clear coat added 
Nearly there 
Airbus lettering, Germany flag 
Dobrý den, Mr. Lee Chesman. Velice krásný vrtulník. Já jsem měl postavený vrtulník Lama SA 315B od Hugo Markes. Bohužel jsem za letu v r. 2014 ohnul hlavní hřídel. Už není.
Přeji Vám moc a moc vzletů a hlavně přistání.
Hello mr Lee Chesman. A very beautiful helicopter. I had built a Lama SA 315B helicopter from Hugo Markes. Unfortunately, I bent the main shaft during a flight in 2014. Is no longer.
I wish you lots of take-offs and especially landings.
S pozdravem
Stanislav Brož
Hyacintová 3222/10
106 00 Praha 10