TufFlight 4D-Lite

The TufFlight 4D-Lite is a very light indoor/outdoor aircraft that I hoped I would be able to fly in my backyard. Constructed of EPP foam and carbon fiber, it was designed specifically for practicing 3D flight without fear of doing major damage to the aircraft with each and every mistake. I have to admit I was a bit skeptical after my experience with the U-Can-Do plane. Okay, call it cautious optimism.

There is one major difference, though. TufFlight already specialized in developing gas planes that could withstand rough treatment during combat flying. And unlike some companies, TufFlight seems to look for ways to improve their existing offerings. This is version number 3 of this particular aircraft. That says a lot to me about the company. So what is 4D? It is 3D + Durability. If anyone can test that claim, it is me for sure.

Joe from TufFlight notified me when the plane would ship and also offered this advice: "Please bear with the assembly. It's different, but it shouldn't take much more than a day or two to finish. Let us know how you make out." Oh boy! I wasn't sure what to expect after that.

Specs
Wingspan:32"Motor:Himax 2808-1160 outrunner
Length:31"Battery:Thunder Power 3s730 LiPo
Weight:10.3ozProp:APC 10x3.8sf
Wing Area:286 sq in

Construction

I scanned the contents and manual before starting. There were 311 steps! Wow! Seems like an awful lot, but they documented every single step, even those that identified parts and tools required. I've never seen instructions that were so complete. The picture on the right shows the kit contents.

TufFlight offers 3 versions of the kit: The basic kit, a complete kit based on a geared GWS motor, and a complete deluxe brushless kit. The complete kits contain everything except the radio and batteries. They even include a spare prop and spare motor mounts. I opted for the brushless version as I have become a believer in brushless motors. But even with the less expensive versions, I have to say that they use quality parts throughout. And they also show how to modify the less expensive GWS motors to use a prop saver type of arrangement. A nice touch for those on a budget. They even included special sized drill bits.

The first 13 steps were the most tedious and time-consuming, at least for me. You had to trace the parts templates onto plastic sheets using a hobby knife, then drill and cut out each rib and control horn from these sheets. I was a nervous wreck trying to trace these with a hobby knife, then "snap" them from the plastic. I was so afraid of breaking the parts. It took some effort to free the parts, but I found the plastic to be extremely tough, and everything worked as the instructions said it would. I can see how unlikely it would be for any of these plastic parts to break. They are very light and flexible.

Fuselage Skeleton
The fuselage skeleton provides the primary support for the entire airframe. It consists of carbon fiber tubes with brass rudder and elevator sleeves held in place by kevlar thread. This is all quite straight forward. Just be sure to get the 8 degree offset in the front nose boom.

Tail Feathers
The rudder and elevator are full-flying surfaces that pivot using carbon rods slid through the brass tubes mounted in the fuse skeleton. The thin plastic ribs used to hold the carbon rods also help stiffen the foam surfaces. Like the plastic ribs and control horns, templates were used to trace and cut the tail feathers from a sheet of EPP foam.

I skipped on to some of the other steps at this point while I decided how I was going to paint the plane. I really liked the looks of TufFlight's planes with the flames. I eventually decided to try my luck at using my never-used airbrush. Completing some of the other steps enabled me to paint both the tail and wings at the same time. The manual contained flame templates for the tail surfaces. I drew the template for the main wing. I have to say that it didn't turn out too bad.

There is little chance of getting the alignment wrong as the tail surfaces mount into the pre-drilled holes in the skeleton. Control rods are bent to shape using full-size patterns, then attached using the supplied Dubro EZ-connectors and quick-links.

Plastic ribs and control horns cut from plastic sheets
Tail feathers and fuse skeleton
Completed tail mounted on the fuse skeleton

Wings
Wing assembly required the most number of steps, mostly because the wings hold all of the servos and electronics. The EPP foam wings had been CNC-cut and were hidden in their shucks. It took me some time to get the first wing freed, but that was because I wasn't sure how far I could actually bend the foam to peel away the shucks. And the wing looked like no other I had ever seen, with extra overlapping flaps on the bottom surface. Those flaps, as it turned out, were used to get a nice seam when sealing the wing after removing the cores that produced a hollow wing. You may notice in the pictures below that the ailerons are not separate items, but cut as part of the wing with a thin area that provides a built-in, full-length hinge.

Once I worked my way through the wing assembly I could see just how unique it was in terms of design, especially for strength without weight. Rather than having a wooden, plastic, or even carbon fiber support across the wing joint, it uses several pieces of kevlar thread that have been saturated with CA. Once this hardens, it is quite stiff. I am anxious to see how this holds up over time as compared to a 1mm carbon rod.

Top shuck removed from wing. Notice overlapping flaps where the pencil mark appears.
One of the cores removed from the wing
Bottom of assembled Wing with servos installed. Notice the built-in aileron hinge.

You can see the access hatch in the photo above. This is where the radio receiver goes. The antenna is completely hidden inside the wing. It is run up one of the inside passages and down the other. Makes for clean looking aircraft. I used a small GWS receiver. This type of plane will generally be flown close in so a long-range receiver is not necessary.

Fuselage
The original 4D-Lite used a profile type of fuselage. This version uses a more traditional 3-dimensional fuse. While more for appearance than anything, it does help hide the control rods and some of the electronics. The fuselage is comprised of five pieces of cell foam (depron).

You will notice red marks on the fuse skeleton in the completed airframe photo below. These are actually the pushrod guides.

Completed airframe with wings attached to the skeleton and rear control rods installed
Installing the faux fuselage
Installing the landing gear

Landing Gear
The landing gear certainly isn't meant to land in grass as the Dubro wheels are quite small. However I don't view that as a limitation. The axle is .039" wire. The supports are fiberglass. These are all tied together using kevlar thread. It is an odd looking arrangement but it is very light weight. I'm anxious to see how this holds up on rougher "landings".

It takes a bit of patience to get the gear assembled, especially tying on the kevlar. You need to tack it it so the knots will slide during alignment. Even with only a tiny drop, the CA often wicked through the kevlar and quickly became a permanent attachment. I found that some CA debonder loosened it enough to enable it slide on the supports. I am still aligning the gear in the photo above. There will not be any bows in the axle or support rods once it has been properly aligned.

The instructions point out that the Dubro wheel hubs have a tendancy to separate after a while, so you are shown how to fix that problem during the build. That is quite proactive on TufFlight's part.

Power System
The motor is attached using a unique breakaway stick mount made from 3/8" balsa that is attached to the front of the carbon fiber fuse skeleton. It is designed to break on a nose-first ground strike in order to protect the airframe and to keep from bending the motor shaft. TufFlight includes four of these in the kit, along with instructions to build more when needed. A prop-saver provides additional protection for the motor and prop. It doesn't appear overly strong and my inital fear is that it will pull off under heavy thrust. Guess we'll see.

Front Cowl
The front cowl is a new addition in this version. It is made from EPP foam, and provides a more finished look to the plane. It is removable for access to the motor and electronics. It is not necessary to remove the cowl to change the battery unless you mount the battery on the top of the wing. There are more pieces to this structure than you would think. Once assembled, the cowl is held in place using a rubber band that attaches internally.

Himax motor on breakaway mount. A zip-tie holds the stick on the boom.
Front cowl assembly
Battery installed - not much room for adjustment

Finishing Up
  • I added wingtip covers from scrap foam. I used a very light coating of goop rather than attaching them permanently with CA. This will enable me to remove them without damaging the wing should I ever need to replace the radio (the antenna is inside the wing).

  • I used a scrap piece of the .015 plastic sheet to create a skid on the bottom of the rudder. This will provide some protection for the foam when landing on rougher surfaces like a driveway.

  • The speed control hangs outside of the hatch to allow for cooling. I attached it to the landing gear legs with a small zip-tie to be sure it doesn't interfere with the aileron servo.

    Rear weights added to achieve balance
    Left side view
    Right side view

  • The final step was setting the CG of the plane using the battery position to achieve balance, but the battery wasn't going to be any help in this case. I would have had to slide it back into the fuselage since the plane was quite nose heavy. Most planes are tail heavy, especially when using a small motor or battery. This one really surprised me!

    I pushed the motor back on the stick as far as I could, and while that helped a bit, it still wasn't enough. I hated to add weight, but had little choice, so I attached .4oz of weight at the rear edge of the fuselage under the elevator. Man that's a lot of weight for a plane this size. Most of my builds are spot on, or slightly under the advertised weight. The only thing I can figure is that all of the electronic components, including servos, are forward of the CG. If the rear control servos were mounted in the rear, like many lightweight planes, this would have provided better weight distribution. It would also provide more room for battery adjustment. But, it would distract from the looks.

    There was no mention in the manual about lateral balance. But I guess that if you are into 3D, you'd know to check that anyways. I did have to add a sliver of weight to the left wing to compensate for the radio and speed control being on the right. No big deal.


Flying

The first time one of my family members saw the plane, all they said was "gee, that thing looks awful fragile." And it does look that way. But as they say, looks can be deceiving.

Our early April snow had finally melted and it was a bit gusty, but I couldn't wait any longer. I had to give this plane a try. I took it over to the field across from the house so I'd have some room to trim it out. A few clicks of the elevator is all it needed. I do think I will experiment a bit with the CG setting, though. It is a bit pitch sensative although some of that is likely related to the wind. Man does it fly nicely. I wasn't sure what to expect after I plopped it down in the field a few times. No real place to land and it is rough over there. Even though it fell on its side once, or plopped onto the gear, there was no damage. One gust caught it while I was close to the ground and pushed it down on its nose. It hit on the gear and flipped over, but no damage. None of these "landings" were hard enough to break the sacrificial motor mount. I was pretty pleased.

I decided the real test would be to see if I could "fly" it in my back yard. There isn't a lot of room back there, but there are a lot of trees. Wow! Even though this was the first time I had flown in better than 5-months, I could harrier the plane all over the yard. It really does turn in its own length. I harriered it down for landings, dropping it in the grass. Twice it nosed over, but other times it actually landed nicely, even though the wheels are quite small. I know I was grinning.

All I can say at this point is that the guys from TufFlight have made a believer out of me. This plane is everything they claim it to be. The rest is up to me. Let the fun begin!

Followup

These are some of the things I have encountered or learned after having had the plane for a while, now. Everyone will build it a bit different and it takes a few flights to get it tweaked to your liking. The plane is sensitive so make any adjustments in small steps.

I learned from Joe at TufFlight that the stick mount can be shortened quite a bit to help move the CG farther aft. You just have to trim away some of the cowl for prop clearance. This enabled me to remove the weight I had added to the tail. Any weight savings always helps. As far as the stick mount, just as they explain in the instructions, once the mount loosens up a bit, you can extend its life by simply retightening the zip-tie.

The roll rate seemed a bit slow to me. So I drilled a new hole in each aileron control horn and moved the rod a bit closer to the control surface. That provided more throw. But the thing that helped the most was making sure the aileron hinge area is very thin to enable the aileron to move freely without overloading the servo.

The only real problem I've had with the plane is where the pin that holds the bottom of the cowl is attached to the lower front part of the fuse. No damage ever occurred from flying. It was just carelessness on my part in twisting the cowl out of the way to change the battery. The side force eventually cracked the fragile depron, shown by the arrow in the picture below. I simply cut a small gusset from a piece of scrap EPP foam and inserted that to provide more support between the sides of the fuse. So far so good.

The arrow shows the crack in the depron.
Foam gusset inserted for support.

I'm still working on rollers and rolling circles. But aside from those, it does everything shown in the video on TufFlight's web site. Even if I don't become very proficient at 3D flying, having the ability to grab it at any time and fly in my back yard makes it worthwhile. I'm hoping to get a few videos so people can see how it flies with a true novice at the controls. I love this plane!

I can be reached at dharbula (at) mdvl.net.