Goblin 420 Sport

Goblin 420 Sport

The Italian brand SAB revolutionized the market for 3D helicopters with his first Goblin 700 some years ago. To complete the family SAB now launched a new size developed from the Goblin 380 design which was released in the beginning of 2015. The Goblin 420 Sport retains the famous design and aesthetics of the brand but other then its bigger brothers SAB opted to give it the same great look as the Black Thunder and Nitro range. Todays trend is the different mid size models with powerful motors that enable maximum performance for the pilots. With all the marketing done by SAB we are for sure that soon many many pilots will have a Goblin 420 among their fleet of helicopters.

SAB marked a real trend in tail boom fuselages with their design that caused many other brands, almost everybody to copy this as an option on their models. By now, Align, Gaui, Thunder Tiger, etc have speed fuselages for their range of products. But its true that just a few other brands then SAB achieved such a nice and attractive design as with a Goblin. Many pilots who were desirous for the launch of this model and it was remarkable how everybody counted the days until the release on for example Facebook, for many it took too long! We are sure that this little helicopter will have a big place in the market as the smaller sizes are the most sold helicopters at the moment. The new 420 size is a size that will be liked by many pilots because it is a small helicopter but not as small as a 250 or even a 450 size and its to carry were ever you want. It can fly in very tight spaces and the cost of crashes is much lower then with bigger models. For those who have not decided to have a Goblin yet either due to the sized available or the higher cost, now they will be able have this amazing helicopter.

THE BOX
The kit is available in a special designed yellow and carbon fiber color scheme like the Black Thunder! The design is very attractive and has a great visibility in flight considering how small this helicopter is. With so many new helicopter sizes is crazy to really understand how big it is. The Goblin 420 uses 420mm blades and has a main rotor diameter of 936mm. With the Goblin helicopter range we know that it corresponds to the measurement of blade to use on the model, so we know that this small Goblin uses 420mm blades.

The box has obviously a much smaller size then its bigger brothers but with the usual design of the SAB boxes. Inside the box everything comes very well organized in boxes and bags. When you first open a Goblin 420 box is curios to see the few pieces that make up this helicopter. As stated by SAB it has a very simple mechanics. The color printed manual is very well explain and makes the build very easy, it good. Also included in the manual we can find a sheet with all optional upgrades available for this model, such as magnetic canopy supports and much more. SAB also include a sheet with tips and tricks for a proper assembly of the Goblin 420.

MAIN FRAME
The frame of the Goblin 420 is made up by two carbon fiber side plates following the same design as the Goblin 380. To hold the frame together we build in the bottom of the frame the plastic battery support and in the upper part the the usual aluminum main structure and motor support. The frame is closed with 2.5mm button head cap screws. First we mount the battery support and the tail servo support before we close the frame with the second side. SAB managed to reduce weight and simplify everything to the maximum. One detail which is completely different from the Goblin 380 is the landing gear, the Goblin 420 Sport comes with a carbon fiber landing gear which in my opinion gives the model a much better look then the normal version. This new landing gear design gives the Goblin 420 an extra aggressive and modern look.

The aluminum main structure plate is manufactured in one piece. The main shaft with a diameter of 8mm needs to mounted together with the bearing block, the main shaft has a special design and any play can be removed by adding some shims when mounting the bearing block. The bearing block is mounted with three head cap screws directly to the main structure plate. Around the bearing block three plastic servo supports are mounted to mount the cyclic servos, optional available en aluminium (H0521-S). A simple and easy system with three mounting holes depending on which servos you want to mount. For example the MKS 95HV as used in this review needs two screws on each side were for example the Align DS450 servos only need one screw in the middle to mount the servo. The servos have a direct connection to the 120º swash plate. In the rear of the main structure we need to mount the carbon fiber rotation guide with 2 screws. To complete the assembly of main structure we now need to install the two pulleys, main pulley and aluminium tail pulley. The Goblin 420 uses a main pulley with 120T. It houses a one way bearing assembly and two normal bearings to provide smooth operation.

The motor support is mounted in the front of the frame to the main structure. It is refrigerated and use 4 screws to fit it to the frame. Ones we mount the motor to the motor mount we can install the whole assembly onto the helicopter. It is easy to install the best with the motor assembly pushed back towards the helicopter as far as it can go. First put the belt on the motor pulley and then put the belt around the big pulley, rotate the motor several times by hand until it sits at the correct position. Ones this is done we pull on the motor slightly to tighten the belt, ones the belt is very tight we tighten the M4 nut first and then the rest of the frame bolts. The kit includes a 20T motor pinion.

The carbon fiber canopy has a very streamlined and aesthetically attractive design. It gives the Goblin 420 the same image as the Goblin Black Thunder but in minature. Its held in place by two lock screws mounted in the rear of the frame. The system used is threaded which I personally don’t like and can be lost easily in flight. Too bad that the kit didn’t come directly with the optional magnetics canopy supports. The option part number is H0562-S, its really worth while.

ROTOR HEAD
The main rotor head comes fully in silver colored aluminum and retains the same design as its bigger brothers. Also Goblin has gone back to the traditional Flybarless rotor head system and no DFC style rotor head is used anymore. The new rotor heads of Goblin are called the HPS (High Precision System). The feathering shaft has a diameter of 5mm. The main blade grip arms are removable by just one screw. SAB engraved their logo on the blade grips and center hub. The radius arms are fitted directly to the center hub. The manual explains all steps very well and always indicates us exactly were to apply grease, oil and threadlock. The linkage rods of the blade grips connect directly to the swashplate same as the servos. A direct and precise control is obtained with this direct linkage system. The Goblin 420 kit includes a set of 420mm carbon fiber Thunderbolt blades.

COLA
As expected the little boy of the Goblin family retains the same aesthetic and design of the tail boom as the rest of the Goblin range. A carbon fiber boom in matching colors with the canopy. Painted on the tail boom we can read SAB Heli Division. The transmission system is by belt as all other Goblins with a the carbon fiber tail control rod that needs to be assembled by glueing the linkage rods into the ends of the carbon fiber tube, we have noticed that with the size stated in the manual it’s a little to short so we recommend adding an extra 5mm to it. Ones the epoxy is hardend we can screw the ball links at both ends. The tail boom is attached to the frame with a nylon screw. The kit includes a special tool to tighten this screw. The tail has a very simple mecahnical design and is formed by two sides. One side we have the vertical carbon fiber fin itself and on the other side a special designed aluminum tail side plate. On both sides we can find a flanged bearing. The whole tail system assembly is closed with four screws and is adjustable to allow us to tension the tail belt. The tail rotor has the same design as the main rotor. Each blade tail blade grip has two radial and one thrust bearing mounted. The Goblin 420 includes 70mm carbon fiber blades.

SPECIFICATIONS
Main rotor diameter: 936mm
Main blade lenght: 420mm
Tail rotor diameter: 196mm
Tail blade lenght: 70mm
Main shaft diameter: 8mm
Tail shaft diameter: 5mm
Spindle diameter: 5mm
Motor size: maximum 41mm diameter, maximum height 41mm
Battery compartment: 44x44x130mm
Weight: 1200 g (excluding batteries)

SETUP AND ELECTRONICS
In our case we mounted the MKS 95HV cyclic servos. The servos are mounted horizontal to the plastic servo supports on the main structure and linked directly the swash plate.

The tail servo is located in the lower rear part of the frame on the tail servo support and allows us to use a mid size servo. We have chosen to use the MKS HV9780 as tail servo. The flybarless controller is the Beastx Microbeast with the Spektrum satellite adapter to avoid more cabling to the receiver.
Special thanks to Kontronik to provide for this review the motor and speed controller. A good combination for the Goblin 420 is the Kontronik Koby 90LV together with the Kontronik Micro Pyro 380-9 Brushless motor.

The manual recommends a motor with a 22mm long motor shaft to avoid collation of the shaft with the battery pack. The Kontronik motor is specially designed to us in the Goblin 420 so the motor shaft has the perfect length and also the flat part on the motor shaft is exactly 6mm to fit the set screw of the motor pulley. We recommend you to use servo braid on the wires of your electronics to avoid wear by friction. The edges on the carbon fibre parts are very sharp.
Since this was the first Goblin 420 I have ever build I was unsure about the settings and setup so I took my basic setup from the Goblin 380 as a starting point. We tested various settings and this is how we liked it the most: We changed menu B into transmitter mode. The dual rates are set to 100%, exponentials on Ail, Ele, Rud to +10% on Spektrum, in case of Futaba it should be -10% and approximate 48% in idle up 2, 52% in idle up 1 and 56% in normal flight mode on the tail. To achieve the desired roll rate we needed to increase the endpoints (ATV) from 100% to 110% on elevator and Aileron and reduce the tail speed back to 90%. We used a Kontronik Koby 90 ESC and we set the ESC to Mode 4. I set 3 head speeds on the different idle up switch with the correct ratio as previous explained with a 22T pinion and a 930KV motor, 5:1. With this setup we can reach a maximum head speed with governor of approx. 3500RPM, this was the range I wanted to fly this helicopter.

The throttle curve is set the following way, we used the straight linear throttle with the Kontronik mode 4 governor. The motor has 900KV and we used a 6S setup with Optipower 2700mah 50C Ultra and the 22T pinion.

THROTTLE CURVE

Low 25% 50% 75% High
Normal 65% 65% 65% 65% 65%
Idle up 1 75% 75% 75% 75% 75%
Idle up 2 85% 85% 85% 85% 85%


Flight mode Aprox. RPMS
Normal 3000rpm
Idle Up 1 3300rpm
Idle Up 2 3500rpm


Pitch curve have been set in all flying modes to -12.5 at low stick, 0 at mid stick and +12.5 at high stick.

TEST FLIGHT

With some charged Optipower 2700mAh 6S packs it was time to do some test flights of this little monster Goblin. My expectations were very high for this new helicopter. To mount the canopy you need to have some patience… but with the magnetic canopy supports its really easy.

The spooling up sound of this helicopter is really nice, ones I lifted it up in hover I could notice the stability of the Goblin 420 dispite its smaller size. The visibility and look of the Goblin 420 in flight is very similar to the Goblin Black Thunder. Allthough we were flying this small size model I had the feeling that I was flying a larger helicopter. Time to do some fast forward speed flights and the model traced a perfect streight line without any strange tendecies. The feeling that this model gave me was very good. Thanks to the exterior design of the canopy and tail it has great visibility in all positions. With the Kontronik powerhouse motor and a 90A Kontronik Speed controller the Goblin 420 performed all demanding manouvers without even noticing head speed loss. It is true and I have noticed that in all the Goblin I flown until now that the Goblins have a very characteristic style of flight! Hard to explain but the feeling is different then with my usual helicopter even when they are setup in the same way. After activating idle up 2 with the maximum allowed headspeed of 3500RPM using a 22T motor pinion and castle governor the sound of this little machine became even more powerful and its in flight behavior even more agile and faster. The tail worked really well and held perfectly in all the performed manouvers.

I am not a real fan of small helicopters since I am used to fly the bigger sized models. But the truth is that the Goblin 420 has surprised me positively. It’s a really fun model to fly.

OPINION

There is no doubt that the Goblin 420 is a helicopter with design, quality and excellent performance in flight. Its size makes it ideal to fly were ever you want and makes it easy to transport. The Goblin 420 is a small helicopter capable of flying as the greatest. The final price ready to fly of this model is not very economical specially when you want to use high end products, but most of us pilots have have some servos, receiver, flybarless, etc … laying around to install on the Goblin 420. Using a single battery is a great advantage and the smaller 6S packs are quite affordable. It has simple mechanics, and easy assembly. This model almost does not require maintenance, just the correct lubrication and some regular check ups. In flight this helicopter can be very docile or a real devil! The dream to own a Goblin of many pilots has come true thanks to the Goblin 420. We are sure that this is going to be SAB super sale model for the upcoming year and a great companion for many pilots at the flying field.