Nexa L-4 Grasshopper Assembly

[Rentaroo]

I looked around the forum and didn't see a thread for this plane, so since I recently received mine, I thought I would write up my first ever assembly log.

The L-4 Grasshopper is essentially a Piper J3 Cub, dressed up in warbird livery. The plane was used by military forces in every theater during WW2 for artillery fire direction, pilot training, courier service, and casualty evacuation. Some were even equipped with rockets and used for anti-tank missions.

This model from Nexa is a very good representation of the plane. It's constructed of balsa and light-ply, with a nicely molded fiberglass cowl and assorted plastic detail pieces. It's covered in an olive-green adhesive backed vinyl material with invasion stripes and a checkerboard pattern on the tail. As on the full scale plane, the inside of the model can be accessed by opening the starboard-side fuselage doors.

This is my fourth Nexa (VQ) model. I have previously assembled the .20 size P-39 Airacobra, .46 size Tiger Moth, and the Canadian edition Twin Otter. I have been very happy with each of the models, all were packaged carefully and contained quality components. I used electric power systems for each of those models and plan the same for this Grasshopper.

The electric components I have chosen to use are similar to those that I have used in other models of this size, with one exception. In the past, I have used the Suppo 4120 electric motor (.46 size) with 80 amp Hobbywing ESCs and 6S batteries. For the Grasshopper, I have decided to use a Suppo 3520 electric motor (.32 size) with 60 amp Hobbywing ESC and 4S battery. I believe this power combination will provide ample thrust for the plane to perform scale flying maneuvers.

Unboxing was good, everything was well packaged. As with other models from this manufacturer, the CA style hinges are already secured on the control surfaces. You still need to CA the elevators to the horizontal stabilizer and the rudder to the vertical stabilizer, but half the job is already done for you. The ailerons are fully installed, nothing to glue on them.

I looked through the manual and learned the first step of assembly is to install the fuel motor. Because I'm going electric, I flipped a few pages into the manual and found the electric motor installation instructions…and this is where the first problem was identified. The supplied electric motor mount does not match the one in the manual, which has a very specific notch that allows the modeler to align the motor mount properly to the firewall for the purpose of drilling holes (picture attached below).

I have never encountered an issue like this with any other Nexa (VQ) model, so I'm rather bummed. I'm certain I can obtain the proper alignment with some measurements and good thinking, but it's not something I should need to do according to the manual.

That is it for day #1…need to relax. I'll tackle the motor mount tomorrow and press forward with the rest of the assembly.

[Alpha]

Rentaroo Thanks for starting this thread, I look forward to reading about your progress and comparing this bird to the other three Nexa birds you own. We noticed that many customers bought several Nexa aircraft over the past month. Side by side comparisons are helpful for those of us reading in the wings!

[Rentaroo]

Alright, it's a new day, let the assembly begin! I decided yesterday to follow the manual, rather than skip around to different locations to tackle other areas of the assembly while waiting for adhesives to dry or for whatever other reason (like not having the correct bolts or wood dowels).

So I left off with the motor mount and having to determine a work around to make sure the alignment was correct and the cowl would line up properly. First I used the motor x-plate to drill holes for mounting the motor, nothing out of the ordinary with this step.



Then I used blue tape to secure the motor mount to the plane's firewall so I could mark the location for the holes (the manual covers this process very well, though remember, my motor mount is not the one in the manual). I'm not going to lie here…I thought about this for a long time and took some measurements, then ultimately guessed on the proper placement of the motor mount on the firewall. The firewall has an angle built into it for right thrust, which means if I just centered the motor mount, the opening in the cowl would not line up properly with the motor shaft.

The kit contains hardware to mount the motor's x-plate to the motor mount, but I decided to use a little bigger bolts with blind nuts, because I like them better.



Then I used the supplied bolts, washers, and nuts to install the motor mount with motor attached onto the firewall. Now is the time to install your ESC (if using electric power). The manual does not discuss options for this, so you're on your own. I was able to push the ESC through the slot on the bottom of the firewall, so it will rest inside the plane, under the battery / radio tray. Routing the wires was a little fidgety, but it worked out well.




Next I test fit the cowl to the plane…I got lucky, my guess to place the motor mount about 1.5 centimeters above and to the right of center allowed the motor shaft to line up beautifully with the cowl installed. There are many types of screws in the kit, the screws recommended to attach the cowl to the plane are 2.5mm x 8mm. In the kit, there are shiny silver screws and black screws that match this description. I used the silver screws at first, and then later realized the black screws would look much better, so I changed them out.



Next up was installing the tail feathers. No problems with this step, everything fit well and lined up square. The manual does a good job of covering these steps and recommends using CA to install the tail feathers (and nearly every other part on the plane). You could also use epoxy or wood glue. I chose to use the CA. I have noticed that as it cures, CA will produce a white blemish on this type of covering. You can use Windex or similar to wipe of the white residue. Do not use pure alcohol or anything with acetone, as those will wreak havoc with the covering's color. Also, CA kicker will cause the color of the covering to smear, so be careful if you use any.



The main landing gear is next. These are pretty stout aluminum gear legs. I opted to paint mine dark green before installing. The green I used is darker than the covering, but since most of the gear legs are covered with the skirts, it looks good. You will need to cut out the plastic skirts for the gear. The manual shows a picture of scissors for this step. I recommend using a sharp razor knife (X-Acto or similar). Take your time cutting these out. By using the razor knife, you can make a couple score cuts along the corners of the skirts and then simply peel off the excess plastic for a nice even finish. The skirts are designed so that one part fits inside the other, to make installation on the gear legs cleaner.



Drilling holes in the gear legs to mount the skirts was straightforward and using the supplied hardware to secure them in place was easy. Installing the wheels required enlarging the pre-drilled holes to fit the supplied bolts. No problems with that step. Next up was the tail wheel. Manual is very clear on how this works. I chose to use epoxy to secure the plastic guide loop instead of CA. I feel that epoxy is much stronger and more durable.

[Rentaroo]

Finally, the radio gear installation begins! Everything must be installed through the door / window in the fuselage...it's like building a ship in a bottle. The opening is generous, but if you have big hands, best of luck to you.

Holes are pre-drilled for the rudder and elevator servo mounting screws, and I found these matched pretty good for my chosen servos. Linkage stoppers for the servo horns are included. I use these on smaller planes with good success, but I decided to use my trusty z-bend pliers for this installation.The kit contains a metal "domino" that allows you to connect both elevator pushrods to the servo control horn. This is a nice piece of hardware that my other Nexa / VQ planes included. After the servos are installed, you can secure the rear seat using CA.



Onto the wings. The cutouts for the aileron servos are for 17-gram sized servos, but there are lines marked to enlarge the cutouts to fit standard size servos if you want. I'm using Hitec HS-82MG servos for ailerons. I had to file a very small amount of material for these servos to fit. Because the covering is already trimmed to allow for larger servos, using the smaller size will mean bare wood is visible. To help make this look better, I painted the bare wood white.

[Rentaroo]

Now that all the radio gear is installed and major components assembled, we can put the wings on the plane! But wait…the wood dowels for the wings are missing…bummer. Thankfully I have some wood dowel I can use to make suitable substitutes.

The manual tells you to install the aluminum wing spar tube and to CA it in place. This is a first for me, because none of the 40+ aircraft I have built / assembled have ever recommended gluing the wing spar into the fuselage. After making sure the wing spar is centered (I measure an equal amount protruding from both sides of the fuselage), I decide to use some epoxy for this step instead of CA, because the wing spar is aluminum and the tube in the fuselage is basically made from rolled paper. More on this later...

After attaching my wood dowels and the wing supports to the wings according to the manual, I test fit the wings. Hmmm…neither wing will slide onto the wing spar smoothly. That's not too unusual, so I make a tool to lightly sand the inside of the wing's spar tube by using a long hot-glue stick, some sandpaper, and some tape. It works well…but the wing's won't fit tight against the fuselage, there is about 3/8" gap on the left wing and 1/4" gap on the right wing!

So I think about this issue for a while and determine the aluminum wing spar must be a little bit too long. I remove the wing panels and then use my handy mini-size pipe cutter to shorten the wing spar, just a little. Slide wings back into place, and hooray…they fit great.



Looking at the manual I see the need to drill holes through the wings, into the wing spar to fully attach the wings to the fuselage. This is why you must glue the wing spar into the fuselage. The wings are held onto the wing spar with two 3 x 15 mm self-tapping screws. If you don't glue the wing spar into the fuselage (so it won't rotate) and then remove the wings and reinstall, you will probably never get the holes lined up to reinstall those screws.

Now that the wings are installed, I attach the support wires to the tail and glue on the plastic engine details. I used hot-melt glue to secure the engine detail to the cowl, it's easy and quick, plus it holds very well.






It's finished...almost…I still need to program the transmitter and check the CoG. The recommended rates seem rather low, so I used them for a "middle" setting and then went slightly lower for low rates and slightly higher for high rates. I usually do this for new planes as it gives me options when performing the maiden flight.

Because I used a smaller motor than I usually would for a plane this size, I did have to add weight to the nose. Please don't ask how much I added, because I have no idea. I just added some weight to the firewall and motor mount bolts until it balanced at the recommended CoG point as listed in the manual.

What are my overall thoughts? Well, I think it's a very nice plane and I hope it flys as well as it looks. Except for a few small issues with included components, everything went together very well. The issues I did encounter, I was able to solve without too much banging of my head on the work table, so I'm happy.

If you like Cubs, and want something with warbird heritage, check out this Nexa model.

Planning for maiden flight this weekend!

[Rentaroo]

Well...maiden flight and a couple more were good today. Flys very nice, quite happy with this plane :)

Short flight video.

Yeah, the landing was not my best work..

https://youtu.be/366Nl4Rwenw

[Rentaroo]

James from Motion RC asked me if I would like to fly my Grasshopper for the cameras, and of course I said yes!

[miatateer]

Rentaroo, earlier you said "my guess to place the motor mount about 1.5 centimeters above and to the right of center". Center of what? The hole thru the firewall? Was the lightly scored line in the firewall useless?

[Rentaroo]

Rentaroo, earlier you said "my guess to place the motor mount about 1.5 centimeters above and to the right of center". Center of what? The hole thru the firewall? Was the lightly scored line in the firewall useless?

Hello,

The firewall on my fuselage did not have lines marked.

I centered the hole in the electric motor mount over the hole on the firewall and then moved the motor mount about 1.5cm diagonal, above and to the right.

[miatateer]

Thanks Rentaroo. The model I got (2 weeks ago) does have score marks and I think they are very close to your numbers. I stuck the aluminum tube into the motor plate (yes, it fits!) and used that through the cowl to get a rough idea. Once the motor shows up I should be able to get a better look.

[Greyfoxvt]

Hello Rentaroo, I have reached out to this thread to continue my discussion with the Grasshopper. I have rebuilt since my mishap, and it is new and ready. I took out the 46 in place of the eFlite Power 32 Outrunner with a 12x8 prop. Looking forward to flying this critter now. I also just purchased the Nexa PA-18 Super Cub Burda 1620mm (63.7") Wingspan - ARF and will put the 46 in that plane instead. I will update the process, but I am ready to rock!

Rentaroo, what size prop did you finally decide on?

[miatateer]

Rentaroo and/or Greyfoxvt, where did you guys place your ESC? I've got mine tied to the front of the firewall, but the battery lead is short enough to make connecting to a battery a real trick through that door! I'm not overly fond of cutting/soldering to extend the ESC's battery lead.

[Rentaroo]

Hello Rentaroo, I have reached out to this thread to continue my discussion with the Grasshopper. I have rebuilt since my mishap, and it is new and ready. I took out the 46 in place of the eFlite Power 32 Outrunner with a 12x8 prop. Looking forward to flying this critter now. I also just purchased the Nexa PA-18 Super Cub Burda 1620mm (63.7") Wingspan - ARF and will put the 46 in that plane instead. I will update the process, but I am ready to rock!

Rentaroo, what size prop did you finally decide on?

Hello,

I'm using a Master Airscrew 12x6 wood prop.

[Rentaroo]

Rentaroo and/or Greyfoxvt, where did you guys place your ESC? I've got mine tied to the front of the firewall, but the battery lead is short enough to make connecting to a battery a real trick through that door! I'm not overly fond of cutting/soldering to extend the ESC's battery lead.

Hello,

I was able to slide my ESC into the slot on the bottom of the firewall. I did use my Dremel to make the slot a little larger. With this small modification, I was able to route the ESC's battery lead far enough into the cabin area to make connecting the battery a simple task. The ESC receives enough air flow in this location to remain cool.

[Greyfoxvt]

I actually velcro'ed mine to the left front of the cockpit side wall. Good air and nothing close. Since it is a Spektrum SMART ESC, I can watch the temperature and have set alarms to be safe on my radio.

[miatateer]

Thanks guys. I went with the slot in the bottom of the firewall, after some careful fun with the dremel. Now to get it in the air!

[Jakeppf]

Hello Rentaroo, I have reached out to this thread to continue my discussion with the Grasshopper. I have rebuilt since my mishap, and it is new and ready. I took out the 46 in place of the eFlite Power 32 Outrunner with a 12x8 prop. Looking forward to flying this critter now. I also just purchased the Nexa PA-18 Super Cub Burda 1620mm (63.7") Wingspan - ARF and will put the 46 in that plane instead. I will update the process, but I am ready to rock!

Rentaroo, what size prop did you finally decide on?

Can I ask why you took the power 46 out? I ask as Im just finishing one up and I put a power 46 in it, did it have anything to do with your mishap?

[MANFRED]

Here are some shots of my Seagull L4 from Legend Hobbies. 90" wingspan, 8s on the 26cc motor from Motion RC, flies fantastic!

[Greyfoxvt]

Can I ask why you took the power 46 out? I ask as Im just finishing one up and I put a power 46 in it, did it have anything to do with your mishap?

I had the eFlite Power 46 in and it was too much torque and it ground looped. With the 32 is appears to be a more gentle scale like flyer. Rentaroo's video shows what it fly's like with a 32.If you want to eat the sky, then the 46 is the more, but I wanted a more scale flyer.

[miatateer]

I got my built. This plane flies great! I found pictures of the still operating "Mistress". It doesn't have a blue cowl. So I changed mine to match the real plane.