Seagull Models 20cc Piper L-4 Grasshopper ARF

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The War-Time Cub

“All we had to do,” Bill Jr. (Piper) is quoted as saying, “was paint the Cub olive drab to produce a military airplane…”  And so they did! Well, they added a large plexiglass greenhouse window system to the rear to improve visibility. Otherwise, it has been stated that the Piper L-4 is identical to the J-3, right down to the last nut and bolt! The L-4 was mainly an observation aircraft, utilized in finding enemy targets, but one pilot decided that wasn’t enough. He added rocket launching tubes to the wing struts, and went out looking for enemy ground targets of his own – now I’m not going to say this guy was crazy, but he certainly had to have a death wish floating around in a Cub while tanks and soldiers shot at him!

Seagull has recently introduced a new 20cc ARF to the market – a Piper L-4 Grasshopper, sporting a 90 inch wingspan. This brings the model in right around 1/5 scale (21.27% scale to be exact), and it’s definitely large enough to be classified as a giant scale warbird! There’s lots to love about this war-time Cub, so let’s dig into the box!

First Look

The L-4 arrived in a brown cardboard box with a few labels on it. The labels included some nice photos of the Grasshopper, along with specifications and requirements to complete the model. Inside, I found all the parts wrapped in paper, or bagged and stapled to prevent shifting during transport. My model was shipped directly from the factory in Vietnam, and had just another cardboard box to protect the valuable contents. My airframe arrived without any damage, and it even got held up in Japan customs for an extra week waiting for X-rays! A stiff layer of cardboard separates the wings and horizontal stabilizer from the underlying parts.

She’s a good looking model, straight out of the box – nearly all the parts were accounted for, I’ll explain that in a bit…

There’s a lot of cool things going on in this 20cc Airframe – I really liked the metal, articulating landing gear, the eight piece detailed engine assembly, and the matte finish on the Oracover covering!

Seagull has gone the extra mile, and painted the fiberglass control horns – that should really help keep them hidden in flight. The elevator and rudder servos are mounted inverted in the bottom of the fuselage, and concealed with a cover, which keeps them out of the cockpit area. I really like that Seagull has also included inflatable tires and two-piece wheel hubs – this L-4 has a lot of cool features!

The cockpit has a nice mount for the included pilot, and Seagull did a great job on the printed instrument panel decal – it looks like the real panel! The greenhouse window framing looks nice, and should add to the overall look of the L-4.

A painted pilot bust is included, but he will need a little painting to look just right in the cockpit. A painted fiberglass cowl  is included, and completes the color scheme of the L-4. The fin is also part of the fuselage, and the horizontal stabilizer is inserted through a slot – this makes for a tight and strong joint! The tail is also braced with tail wires, giving the stabilizers even more rigidity.

A large aluminum tube is used to join the wings to the fuselage, and a bolt secures the wing to a tab in the fuse.

I really liked the aluminum, airfoiled wing struts. They look just like the struts on a full scale airplane! a pair of pins and clevises attach the struts to the fuselage, which means assembly and disassembly are a breeze!

Specifications

Model Name:   Seagull Models L-4 Grasshopper

Where to Purchase in US:   www.vqwarbirds.com – Seagull L-4 Grasshopper

Price:   $399.95 (at time of review publishing)

Wingspan:   90.0 in   (2286 mm)

Wing Area:   1182 sq in   (76.3 sq dm)

Length:   56.8 in   (1442 mm)

Weight:   13.2 lbs   (6.0 kg)

Engine/Electric Motor Size:   20cc Gas, 1.20ci glow, 1.20 equivalent electric motor

Radio Requirement:   Four Channel Transmitter (Minimum) and Receiver

Servo Requirement:   Five Standard Servos (Minimum 70 oz-in torque)

Wiring Required:   Two 18″ Servo Wire Extensions, Two 12″ Servo Wire Extensions,

One 6″ Servo Wire Extension

Batteries Required:   Two (Receiver and Ignition for gas engine)

Items Used for Completion

Controlling the L-4 from the ground, I will be using my trusted Graupner mz-32 transmitter. With 32 channels, it’s definitely a lot more radio than I’ll ever need, but it’s got a great operating system, a touch screen, and it announces my different flying rates and even plays music! A Graupner GR-16 receiver will be in the L-4 controlling the Hitec HS-5485HB digital standard servos.

Inside the cowl will be a BRAND NEW Stinger Series 20cc Rear Exhaust Gas engine from RCGF. The Stinger Series is a new line of engines, based on the older series, but with newer molds and better performance. A Falcon 16×8 Beechwood Civilian painted propeller, available from justmodelprops.com and Bob’s hobby Center at Steve’s Hangar, will be mounted to the Engine, and will look fantastic! I used a pair of  Turnigy Nano-Tech 6.6 Volt 2000 mAh LiFePO4 batteries for the receiver and ignition. These batteries should give me plenty of power to fly as many flight as I want while at the field, and they’re small and light weight!

A model just isn’t complete without some DuBro Hardware…  I used several items from DuBro, including a Fill It Fueling System, 1/4″ Protective Foam Rubber, Socket Head Servo Screws, and some Tygon Large Fuel Tubing.

To replace the missing pushrods and hardware, I used DuBro 2-56 pushrods, #212 threaded couplers, and 2-56 swivel ball links. Two 48″ pushrods were used for the elevator and rudder, and a pair of 12″ pushrods were used for the ailerons.

To assemble the Seagull Models L-4 Grasshopper, I will be using several adhesives. I trust ZAP brand adhesives for all my needs. For the L-4, I will be using 30-minute epoxy, 5-minute epoxy, Z-42 Blue Thread Locker, Formula 560 Canopy Glue, Zap Thick CA, ZAP Medium CA+, and ZAP Thin CA. See the links provided for all of these products!

Pros

* High quality balsa and balsa plywood, these make for sturdy, light weight construction

* Superb flying characteristics and a great-looking scale outline

* Plug-in wings make for easy assembly and disassembly, as well as easy transport to and from the flying field

* Realistic trim scheme with Oracover film covering with matte finish

* Includes durable articulating landing gear with inflatable tires

* Detailed Cockpit with Light Weight Painted Pilot figure adds sporty, scale detail

* Painted fiberglass cowl

* All necessary hardware included for either glow or electric power system

Cons

* My model was missing the pushrod package – I used DuBro hardware to complete the L-4, but Seagull would have sent the required parts at their expense.

* Painted pilot could have been painted in military colors instead of white – I simply repainted the pilot figure

Manual

The included manual is printed in black and white, and does a good job of guiding the modeler through the assembly process. There’s a great mix of written instruction and illustrations!

You can download and view the instruction manual here:   L-4 Grasshopper Manual.

Assembly

Wings

Assembly began with installing and gluing the hinges. To install them correctly, two T-Pins were inserted through the center of each hinge. This allowed only half of the hinge to be inserted into the aileron. With all four in the aileron, the hinges were slid into the pre-cut slots in the wing.

I used ZAP Thin CA to glue the hinges into the wing and aileron. When the CA had cured, I moved the ailerons up and down a few times to allow them to flex easily.

After drilling the servo mounting holes, I turned a servo screw into each of the four holes. I then removed the screws and applied a drop of ZAP Thin CA to each hole to harden the wood and prevent the screws from backing out.

When the CA had cured, The servo was permanently mounted to the hatch. I added an 18″ servo wire extension and secured it with a piece of heat shrink. The servo extensions also have a small latch to secure the connection, but I feel much more confident that they will not come apart this way. The pre-installed pull string was tied to the end of the servo extension, and the extension was pulled through the wing.

The screw holes for the servo hatches are ‘pre-drilled’ during the laser cutting process at the factory. I felt that the holes were too large for the included 3x10mm screws, so I opted to upgrade to #4 x 3/8″ screws. I bought a pack of 100 screws a while ago from boltdepot.com. It’s a great place to buy some of the smaller fasteners we use in large quantities. After running a screw into each of the four holes, I removed them and applied a drop of ZAP Thin CA to each hole. When the CA had cured, I permanently mounted the servo hatch to the wing.

The aileron control horn was epoxied into its pre-cut slot with ZAP 5-minute Z-Poxy. Before putting it in place, I ‘roughed up’ the unpainted portion of the control horn with a piece of 80 grit sandpaper for better adhesion between the inner aileron surface, the control horn, and the epoxy. The pushrod was made from a DuBro 2-56 swivel ball link and a 12″ 2-56 threaded pushrod. a simple Z-Bend connected the pushrod to the control horn.

Elevator and Rudder Servos

The servo mounting screw holes were also ‘pre-drilled’ during the laser cutting process. I emailed the factory, and told them the holes were too large, and they diminished the size of the hole from 1.7 mm to 1.2 mm so that a standard 1/16″ servo screw will be large enough to secure the servos. I was still able to thread the holes and apply Thin CA, so I believe my servos will be safe. The servos were mounted using a slightly larger screw for safety’s sake.

Main Wheels and Landing Gear

The two-piece wheel hubs are assembled with brass bushings and a wheel collar to capture the axle inside. Seagull has even pre-ground the flat spots in the axles!  Four machine screws and nuts hold the wheel hubs together – I added a drop of ZAP Z-42 blue thread locker to each machine screw to keep everything tight. an inner wheel cover is slipped over the axle, and protects the nuts from coming into contact with the landing gear.

After gathering all of the main landing parts, I started by installing the four gear brackets and two wing strut mounts. All eight of the machine screws received a drop of ZAP Z-42 blue thread locker prior to tightening them into the pre-installed blind nuts in the fuselage.

The landing gear legs and cabane vee assembly were installed next, followed by the shock strut assemblies. All of the nuts have the nylon insert, so thread locker wasn’t needed here. I like that Seagull has included fabric covers for the shock struts to add to the realism of the landing gear!

The last of the machine screws and nylon locking nuts were used to secure the gear legs to the shock strut assemblies, and a set screw secured the axle into the landing gear leg. With that, the L-4 main gear was complete!

Fuel Tank

The fuel tank stopper is pre-assembled from the factory, so all I had to do was add the correct length Tygon fuel tubing, insert the stopper into the tank, and tighten the stopper screw. The brass fuel clunk is included with the ARF. The chrome clunk is part of the DuBro Fill It Fueling System I will be installing later.

The included hook n loop strap was used to secure the tank, along with a couple pieces of DuBro 1/4″ protective foam rubber. Three sections of Tygon fuel tubing were slid onto the brass tubes and secured with short sections of mechanic’s wire. I used a safety wiring pliers to twist the wire – I picked it up at Harbor Freight for a few bucks, and it was definitely worth purchasing! The single hook n loop strap will work well for securing the tank. The throttle servo was also installed after determining which side of the carburetor the throttle arm was on – in this case, the Stinger Series 20cc Rear Exhaust engine from RCGF had the throttle arm on the left side, so the left servo mount was used.

Engine Installation

I determined that the custom engine mount included with the 20cc Stinger Series RE was a little short, so I dug through my scrap box and found a pair of wood spacers from another project. Note to every modeler everywhere- Keep your scraps! You just never know when you’ll need something! New holes were drilled in the spacers, and they were installed with the engine mounts. I left the engine mount bolts loose at this time, just to make installing the engine easier.

The engine was temporarily installed, so I could locate the correct spot to drill a hole for the throttle cable. In this case, I had to drill through the base of the engine mount – There’s a lot of material in these mounts, so I’m confident that the mount will be structurally OK.

The muffler was installed on the engine using the supplied gasket and bolts – I added a drop of ZAP Z-42 Blue thread locker prior to tightening the exhaust bolts.

The throttle pushrod was attached to the throttle arm, and then fed through the hole in the engine mount, and finally through the quick connector.

Once the engine had been permanently mounted, the Tygon fuel line was cut to length, and connected to the inlet on the carburetor. I wrapped the Ignition module in DuBro 1/4″ protective foam rubber, and installed it next to the fuel tank.

The fuel tank vent line and the filling line were run to opposite sides of the engine, and secured. I also installed the spark plug and connected the spark plug wire.

Cowl

With the muffler installed, the cowl doesn’t quite slip over the engine. I was, however, able to rub the muffler outlets on the inside of cowl enough to mark the initial location to cut for clearance. I also cut some small slots in the face of the cowl, as too much of the engine’s cylinder head would have no airflow if left without modification. The crankshaft hole was also slightly too small, so it was made larger as well. A small notch was cut into the top of the crankshaft hole to provide clearance for the magnetic ignition pickup on top of the engine’s crankcase.

Here’s where I get to have a little fun with the L-4. The cowl includes a set of dummy engine cylinders and cooling shrouds. After doing some research on the shrouds, I decided to cut them to a proper shape. Don’t get me wrong, the fact that Seagull included these extras instead of molding the cylinders into the cowl is great – I just want to make it look even better! I also painted the flat black cylinders a lighter grey color (acrylic paint and a brush) to look more realistic. There were holes in the shrouds for the cylinder studs, but I had to enlarge them to 1/4″. I used some flat black acrylic paint to touch up the shrouds.

 

A light coat of chocolate brown over the gold colored exhaust pipes gave them a better appearance, and I touched up the cut edges of the cowl slots with yellow paint. I tried a new metallic acrylic paint on the valve covers, and it turned out pretty decent. The brush strokes evened out a bit as well!

The cylinders were assembled to the shrouds – There’s no pre-drilled holes for the cylinder studs in the cowl, so I did a little research. I then marked and drilled the holes. The assembly looks pretty neat on the cowl!

 

Four nylon T-nuts are included with the ARF, and were used to secure the cylinder assemblies to the cowl. They were simply threaded onto the studs, and a drop of ZAP Thick CA was used to secure them. I located and drilled a hole in the cowl for the exhaust, then used mechanics wire to attach the exhaust to the cowl.

With the cowl taped in place, I marked and drilled the cowl mounting holes. The cowl was then removed and I turned a screw into each of the four holes.

A drop of ZAP Thin CA was applied to each of the holes after removing the screws, and allowed to cure. The cowl was then slid back in place, and attached with the four screws. This cowl looks really cool!

A Falcon painted civilian beechwood propeller was installed to complete the nose of the L-4. I really love these props – they look so realistic!

Tail Installation

I slid the horizontal stabilizer through the slot in the fuselage, centered it, and then drew locator lines on the top and bottom sides. These lines will be used to cut and remove the covering, as well as realign the stab when it is glued to the fuselage.

The covering was cut and removed from just inside the previously drawn lines, making careful not to cut the balsa – only the covering material.

Believe it or not, the stabilizer slot was so tight, that I used ZAP Medium CA+ to glue the tail in place. The CA wicked into the wood joint nicely, and bonded the surfaces very well! Though the instructions say to install the tail joiner before the stabilizer, I found that it can be installed after the stab is in place. You’ll want to check your individual model to see if you can do this prior to gluing the stabilizer in place!

The elevator halves and rudder hinges were glued in place using the same technique as I used on the ailerons. There’s one extra step on the elevator halves – I roughed up the joiner wire, mixed up some 30-minute Z-Poxy, applied the epoxy to the pre-drilled holes in the elevator halves, and slid the joiner wire into the holes.

THe elevator and rudder control horns had to be modified to fit in their respective locations – the unpainted tabs were too long, which didn’t allow the painted portion to sit tightly against the control surface. I cut them to the proper depth, rounded the edges, and drilled a couple of holes in them to allow for better adhesion to the control surface. The horns were then epoxied in place using ZAP 5-minute Z-Poxy.

As I mentioned earlier, the pushrods were missing from my ARF. Of course, Seagull would have sent them to me, but in the interest of getting the airplane completed, I went with a pair of DuBro 48″ 2-56 threaded pushrods. I measured the over-all length of each pushrod, cut them to length, then soldered the threaded coupler to the cut end of the pushrod. The swivel ball links were added to each end, and the pushrods were connected to the servo arms and control horns. This is a great setup, ensuring there is no slop in the control system. As a side note, I liked this so much, that I reworked the ailerons so they had the same setup.

 

After marking the tiller arm holes on the bottom edge of the rudder, I drilled the holes. A screw was turned into each hole then removed, and a drop of ZAP Thin CA hardened the holes.

When the CA had cured, the tiller arm was secured to the bottom of the rudder. I then installed the tailwheel bracket and lower tail wire mounting lug. A pair of springs connected the rudder tiller arm to the steerable tailwheel.

I loosely installed the other six tailwire mounting lugs, assembled the tailwires, and then snugged all the lug bolts and wires. This made the tail very sturdy, and it looked great as well!

Windows and Doors

The left side windows were glued in place using Formula 560 Canopy glue from Pacer products. This is the only glue I use for canopies and windows! Since this glue takes approximately 24 hours to cure, I called it a night after taping the windows in place. The next night, I glued the rest of the side windows in place – you could say that I didn’t get a whole lot done that night, but it’s OK to have a slow night at the bench now and then…

There are pre-drilled holes in the upper and lower door halves, so lining up the doors with the hinges was a matter of poking holes in the covering with a T-Pin. The hinges were screwed to the door halves and the fuselage, and lined up perfectly. The upper half has a lip that keeps it shut when the lower half is closed, and the lower half stays closed using a pair of magnets. Seagull even added a pull-out handle to make opening the doors easy!

Painting the Pilot

Remember when I said the ARF included a pilot figure painted white. Well, here ‘he’ is. Sure, he would work, but after researching photos of the full-scale plane Seagull used for a model, I just had to paint the pilot to match. All of the paints are acrylic, and I painted ‘him’ in one night using a heat gun to dry between coats! My pilot is far from perfect, but I think he turned out pretty nice!

Greenhouse ‘Glass’

Man, I love having a few sand bags around! Under all those bags is the ‘greenhouse’ window. It fit pretty well, but I used the bags (and some blue painter’s tape) to hold the window in place while the Formula 560 canopy glue cured. For anyone interested, the bags are just sandwich bags filled with playground sand – they work GREAT!

LED Light Install

There was a pre-cut hole in the top of the cabin for the included LED light. Before gluing it in place, I tried to make it light up – it wouldn’t, until I reversed the red and black wires – red is negative, and black was positive on this particular setup. I recommend trying yours before you install it – it’s much easier to solder an end to the wiring when it’s not in the plane!

Wing Strut Assembly and Wing Installation

Strut installation started with the outer strut mounts. A pair of machine screws secured the mounts to the wing – I added a drop of ZAP Z-42 blue thread locker to each screw before tightening. The aluminum jury strut mounts are threaded into blind nuts in the wing, and secured with Z-42 blue thread locker. Note- the holes in the jury strut mounts should be parallel to the wing.

I installed the locking nuts and Lift strut ends onto both ends of both lift struts, and attached them to the outer strut mounts. The jury struts were attached to their mounts using pins and clips. They are meant to be removable for transport and storage. All of the struts are airfoiled, so be careful which strut is installed where.

In the first photo, you can see the pin and clip securing the jury struts to the wing. The jury strut spacer tube and jury strut clamps are attached to the jury strut with a machine screw and locking nut, adding functionality and scale realism to the L-4. This plane just keeps getting cooler, the more I work on it!

I slid the aluminum wing joiner tube into the fuselage, and slid the wing panels onto the joiner tube. The wing struts are connected to the fuselage/landing gear mount using two more pins and clips. There’s enough clips for each of the pins (two per right and left side), but a single clip slides very nicely into both pins and locks in nicely! a machine screw and washer attach the wing to the fuselage at the top with a fiberglass tab in the wing.

I attached the simulated antenna to the cabin by turning it into the blind nut in the cabin. It is pretty strong, but also removable if needed for transportation. The red LED looks great with the lights turned down!

Power Switches

In a scale plane like the L-4, I would normally try to hide the power switches inside the cabin area, but the recommended locations sort of blend into the lettering on each side of the plane. I was OK with their positions! The switches are easy to install through the bottom opening where the elevator and rudder servos are located. There are a few slots in the cabin floor, which are great for routing the switch wiring. This floor space is the recommended position for mounting the receiver and ignition batteries.

Receiver and Belly Hatch Installation

With the wings removed, I connected all the servo wires to the Graupner GR-16 receiver, and strapped the receiver in place with a small piece of DuBro 1/4″ protective foam rubber and a Velcro strap. The dual antennas were installed using some scrap pushrod guide tubes I had glued into the fuselage at a 90° angle to one another. At this point, I also connected a pair of 12″ Servo wire extensions to the aileron channels – I separated each wing half to its own channel for easy setup and programming. With the servo extensions run up into the cabin, I put the belly cover in place and drilled the retainer screw holes in the fuselage.

The four screws were turned into the belly hatch mount and removed, followed by applying a drop of ZAP Thin CA. When the CA had cured, the belly hatch was permanently mounted.

Final Touches

The pilot figure was mounted to ‘his’ platform using a small batch of 5-minute Z-Poxy and three small screws. Before setting the pilot in place, the three screw holes were drilled in ‘his’ base.

After thinking about it for a bit, I realized I needed to add a choke actuator rod to the carburetor. This rod is attached to the choke arm with a steel clevis, and is bent to come out through the top right slot I cut in the front of the cowl . Yes, it IS that simple!

The Turnigy 6.6 Volt (2S) 2100 mAh LiFePO4 batteries were strapped in at the recommended location using two Velcro straps and a little more DuBro 1/4″ protective foam rubber. I also added a safety clip to each of the battery connections to keep them from coming loose in flight.

A small piece of grey tape was placed at the center of gravity, which was located at 100 mm from the leading edge of the wing at the fuselage. The plane balanced absolutely PERFECT as it was assembled!

With the CG checked, I set the control throws per the manual, and charged the batteries – the L-4 was ready to see some daylight and get the new engine running. But first… Some more photos!

Photo Shoot

Summary

Well I hope you enjoyed reading about the new Seagull Models L-4 Grasshopper as much as I enjoyed assembling and writing about it. It’s a great semi-scale model that’s big enough for giant scale fly ins, but small enough to easily transport to and from the field. The assembly was pretty straight forward and easy, but I added a few little steps to make it look even better. The assemble plane looks great, and I cannot wait to get it in the air – which I will do just as soon as I possibly can! Stay tuned for the flight review, which will be coming along (hopefully) very soon! I already have a great love for this plane, and I can imagine that it will only get better when I get a chance to fly it! As always – From my shop to yours Happy Landings! -GB

Contact Information

Seagull Models –    seagullmodels.com

VQ Warbirds –   vqwarbirds.com

Stinger Engines –    rcgfusa.com

Graupner –   graupnerusa.com

Hitec Servos –   hitecrcd.com

Falcon Propellers –   justmodelprops.com

Bob’s Hobby Center at Steve’s Hangar –   shopbobshobbycenter.com

Zap Adhesives –   franktiano.com/zap-adhesive

Du-Bro Products –   dubro.com

Turnigy Batteries –   hobbyking.com

Geoff Barber email –   gbarber726@gmail.com

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