You can build TufFlight Kits
artwork appears courtesy of R/C Modeler Magazine
How do you build a lightweight airplane without balsa wood?
Well, almost no balsa. We still use wood for the ailerons and sub TE. When folks open one of our kits for the first time, they're often shocked to see plastic pieces, and a large hunk of squishy white foam (not to be confused with the usual "styrofoam" with which we've grown accustomed in foam core wing construction). We are proud to say we believe no one has ever built a plane designed to flex on impact using these materials before -- especially a gas powered one. Our basic design is very innovative, and we've had to re-think some traditional kit building processes, as most of the knowledge we've learned for putting together wood kits DOES NOT apply to TufFlight kits. "It's a culture shock!" as Dave Sanders of Dave's Aircraft Works says, and a whole new technology must be learned.
If all you know is wood or styrofoam based airplanes, you're still in good hands. Our customers will tell you once they learn the few easy steps that are required, our kits go together fast. And the best part is, they are designed to stay together! Our flying wings are so durable, they will help you log more flying hours and still outlive any other high performance plane you've ever built before!
If there is no fuselage, where is the radio installed?
The servos and all radio components are installed in cavities within the foam wing. They are perfectly "shock mounted", due to the excellent energy absorption properties of the EPP foam (never before used in R/C glo power modeling!)
All components are mounted within the foam wing. Parts are simply placed on the wing surface where they best fit to balance the plane, and then the wing is marked where cavities will be cut with a hobby knife.
Here is shown all radio components installed within the wing. Servos are mounted flushly with wing surface so only servo splines protrude through covering which is applied later.
Servos are glued securely in place.
The receiver is safely mounted in a foam lined cavity on left, with a piece of thin packing tape to hold in place for covering.
Servo wires are routed where needed in shallow slits cut in foam wing surface.
An aileron extension makes a simple and lightweight switch/charging receptacle
What kind of glue is used?
For airframe assembly, 2 specific glues are used:
For gluing servos in place, these glues may be used:
- Hot Melt Glue
- Elmers "Ultimate" polyurethane glue (formerly called "Pro Bond")
All these are found at home improvement stores, such as Home Depot or K Mart.
Goop is used for structural bracing around the engine mounting area. Goop comes in several varieties, including household, marine, plumber's and automotive-- all work well for our kits. If you can't find "Goop" by name, Shoo Goo, PFM, Zap-A-Dap-A-Goo are acceptible substitutes.
For gluing servos in place, our favorite choice is polyurethane glue. It foams and expands to fill voids in the foam and gives a strong lightweight joint. It cures in only 3 hours. If you're really in a hurry to get airborne, hot melt glue is a quicker alternative to Poly U or Goop.
3M77 comes in an aerosol can, and is lightweight. We use it for many steps during construction, including adhering the covering to the foam. There is no acceptible substitute! It holds quickly, and can be used as either an instant glue, or contact cement. Once you try it in your shop, you'll wish you'd discovered it sooner!
We find 3M77 easy and quick to use. It bonds these materials well with proper application. It's perfect for joining many structural parts, and necessary for prepping the wing for covering.
A large box on the floor makes a convenient "spray booth"
3M77 overspray is minimal, settles rapidly, and cleans easily with odorless mineral spirits.
Masking tape holds all components together while Goop dries.
Once you get to this stage, all structural gluing is finished. This is usually completed during the first evening's work.
Here we're using Goop to create fillets for the central fin joint to the wing
Goop is somewhat like silicone, but cures a bit harder, and the resulting bond is VERY tenacious. It holds parts with a tough, semi-flexible joint -- just what is needed for a plane to survive impact.
How do "Elevons" work? What if I don't want to use them?
Most of our designs employ elevon control - if available. Elevons both move up when you give "up elevator" and both move down for "down elevator" transmitter control. The right elevon moves up, and left elevon down during "right roll" and opposite for "left roll." With elevons, only two servos are used, but as you can see, each servo has to perform differently, depending on how much "elevator" and "aileron" control is given simultaneously.
Elevons are efficient and lightweight. They perform very well on our planes, however some sort of mixing is required to achieve this function. A transmitter mix is preferred, but several on-board electronic mixers are available. We offer an adjustable compact electronic mixer to compliment our kits -- see our Accessories page.
If you don't have a mixing transmitter (computer radio), and don't wish to acquire an on-board mixer, you can still get very good performance using separate split ailerons with separate elevator control. Our instructions show how to build the non-elevon setup using supplied kit parts. All you'll need is an additional aileron servo, and "Y" harness connector wire to hook up the 2 aileron servos in "parallel" from your receiver.
Elevons are mounted to the wing using the covering for a hinge. The result is strong, gap-free and perfectly suited to the semi-flexible design of the wing.
Our instructions show how to easily make these hinges during the wing covering phases. Here we see the elevons flipped up during the bottom covering reinforcement strip placement.
A similar method is used for separate elevator control hinging-- also shown in kit instructions. A small clearance is cut in the fin (installed later) to allow elevator travel, and 2 aileron servos are used for separate aileron control with a "Y" harness. A separate elevator and elevator servo are mounted at the wing central area for this option.
How are these planes finished/covered?
There is one skill you've learned in making wood airplanes that will come in handy here -- covering! Fortunately, you only have a wing to cover, and then you're finished.
On our sport planes we use Hangar 9 or Goldberg Ultracote, as it's the strongest and most resilient covering available for a plane that's designed to be semi-flexible. Other coverings give substandard results.
For our combat planes we've devised the new "Icarex Method" which gives the toughest and lightest skin strength possible for.
3M77 spray adhesive must be applied before covering, as Ultracote won't stick well without it. However, once it's applied, you'll get a torsionally stiff wing that will flex on impact, and "heal" amazingly after horrendous crashes. Also, you'll easily be able to perform many field repairs with ordinary clear packing tape. You can apply more covering and iron any dents or wrinkles to make it "pretty again" once you get home.
You'll be happy to discover that very little sanding is required! A few passes with 40 grit paper (yes 40 grit!) is all that is needed to blend the edges together before covering.
Ultracote is easy to apply, as it's easily positioned and shrunk. It won't scratch like many other coverings, and it's among the most "beginner proof."
Ultracote gives a strong, yet semi-flexible wing -- perfect for a plane to survive impact!
Here we see the covering edges being sealed before final fin installation.
Note how neat everything looks, with only servo splines protruding through covering. The tank is installed last by just pressing it in place.
Note battery charging wire and aileron extension receptacle mounted flushly at wing surface. This makes a simple and goof proof switch.
The CG is critical, so how is proper balance achieved?
The plane is easily balanced using the mass of the engine. Our instructions show the balance point of the plane "before covering" to allow you to get all your radio components installed so the engine will be "in the ballpark" on the engine mounts after covering and fin installation.
The CG is easily adjustable, as the engine mount blocks can be re-drilled after flying, to move the engine forward or backward. This is superior to adding weight (weight is the enemy!)
A simple balance jig can be made from a board, some pencils and erasers.
A rubber band holds the engine while you slide it into position for marking the lug mount holes.
If these planes are so durable, how is the engine protected?
We like to use large plastic spinners to protect the engine crankshaft and carburetor for collisions. A plastic spinner is cheaper than your engine.
One of the greatest crash-proof attributes of our designs is they feature a "break away" engine mount. Even if you nose in at high speed, all you will usually break is the propeller, and the nylon bolts which hold the engine mount in place.
The propeller and sacrificial nylon bolts take the energy of impact, leaving your engine and plane to survive! It is not uncommon for flyers to be airborne in less than 15 minutes from a "serious" crash. Just replace the bolts, the prop, and perhaps a spinner.
Engine mount bolts pass through wing bottom and are held in place by nuts in the round recesses.
Note the fuel tubing which connects the throttle push rod to the servo. This "slip fit" is snug enough for control, but it will slip off on impact to save your throttle servo gears in crashes.
The average builder will take about a week to learn our techniques and finish a TufFlight kit. Our repeat customers can build a plane in 3 evenings. That's not much work for a plane with a design that makes it nearly unbreakable!
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