Bingo 20 (oz12449)
About this Plan
Bingo 20. Radio control sport model.
The original Bingo (oz6535) first appeared in RCM March 1990. This here is a reduced size version, at 49 in wingspan, for .20 engines.
Direct submission to Outerzone.
Update 07/09/2020: Added article, thanks to RFJ.
Quote: "Bingo 20! By Dr DB Mathews. Success breeds success. Proven popular in a variety of larger sizes, it now takes form in .20. Features interlocking light ply fuse construction.
So there are Big Bingos and .60 Bingos and Bingo 40s, so why on earth would anyone add yet another Bingo to the series? Simply because the things all seem to fly well, are so simple to build, look neat, and have earned the respect of thousands of builders and fliers all over the world. Besides, if anything works this well why not develop it in all sorts of sizes?
My interest in developing a .20 size Bingo was stimulated by observing George Sauer, a member of my flying group, fly a thin wing section Quickee 500 design using an OS .20 four cycle. This neat model flies very well and is remarkably aerobatic using what most would consider inadequate power. This led me to wonder just exactly why we tend to think 350 square inch wing area when designing models for .20 to .30 engine sizes?
My development of the Bingo 20 leads me to conclude that powerplants in this size range are vastly more powerful than commonly credited, and that many of the models designed just a few years ago for these engine sizes are now grossly overpowered. Surprising, isn't it?
To spare you the effort of thumbing back to the flight report to find out if this Bingo 20 is worth building, let's start right out with it now. These have to be the simplest tail draggers to take off ever. The Bingo series tend to come up on the mains as pow-er is added until they just sort of take off by themselves. This is likely attributable to the landing gear placement.
Aerobatics are clean, with absolutely no nasty traits. Snap rolls, upright or inverted, are just a matter of full everything with instant return to level after neutralizing the sticks. Spins, power on or off, inside or out-side, are just like the snaps. Axial rolls are a bit slower than some of the thick sectioned hot rod designs, but comparable with most Stik types.
This roll rate makes for beautiful Cuban Eights. Inside and outside loops are almost identical which contribute to neat horizontal eights. Vertical eights are possible with careful speed management, but one must also be careful to slow down on the downhill legs as the Bingo 20 is a very clean design and accelerates rapidly.
For something far out, try a 'Wichita tumble'. Start with a 1-1/2 inside snap roll then, at its apex, immediately jam in full down elevator. If the speed and timing are correct, the model will start tumbling horizontally. Sort of a horizontal Lomcevac, and lots of fun to watch.
Landing the Bingo 20 requires a bit more skill than the earlier 4-20. The latter has the landing gear located with the axles just behind the wing leading edge. For construction simplicity and to avoid placing the landing gear in the wing, I chose to move the axle line forward onto the fuselage, a technique commonly used on jumbo gas powered type sport models.
This requires that a slightly different landing approach technique be used. The model must be slowed down farther out in the pattern (it will fly remarkably slow without any tendency to snap, so don't worry) and setting it down on the wheels with less flare on touchdown. In other words make wheel landings!
The worst that will happen should you miss and end up in a three point attitude is an extra bounce or two. Lovely landings can be done if the speed is bled off farther out and minimum up elevator is used on touch-down.
I don't mean to imply the Bingo 20 is at all difficult to land, rather I am trying to gently tell you the usual 'bang the nose gear quickly' sloppy landings we all see won't work here. You will have to learn to actually land a model airplane.
The thing is flat dabbed gorgeous when it is wheel landed, rolls down the runway tail up, then slowly settles onto its tail wheel. A little practice will make the flier proud, as a matter of fact this whole project will make him proud!
So what we have here really, is a compact sized Bingo that builds and flies very much like its larger sisters. This seems to prove a simple to build, soundly designed model will fly well in darn near any size.
Now to the nuts and bolts: Though at first glance this design may look a bit flimsy, it actually is light and very strong. One must realize light ply and spruce are many times stronger than equivalent sizes of balsa. Under no circumstance should balsa be substituted for the hard woods in this design without grossly increasing their sizes! Hardware items are standard and should be available at any well-stocked hobby shop. Personal preferences can certainly be substituted. Many of the specialized items such as the landing gear and pants, are available directly from ACE R/C, Box 511, Higgins-Ville, MO 64037.
Read and study the text and drawings carefully to avoid any confusion. Cut out a kit of parts by transferring the shapes to the appropriate wood by placing carbon paper under the drawings and over the wood. Use of a good straight edge is mandatory. All holes and cut outs should be made at the time of the parts fabrication.
A simple jig saw (such as a Dremel, etc) is helpful in building this or any other scratch project, a good knife will work, however. Cut outs can be made easily by drilling 1/4-inch holes in the ply, threading the saw blade into the hole and re-attaching the blade. Tabs and slots can be cut using a sharp modeling knife.
This model is very easy to construct and keep in good alignment. Use a smooth flat building surface and follow sound principles of construction. A straight building job results in a straight flying model. The prototypes were constructed almost entirely with medium and thin cyanoacrylate adhesives.
Wing: Since the wing will be needed early in the fuselage construction sequences, I prefer to build it first.
Stack cut the ribs using a master plywood or metal template as a guide. Notice that two rib patterns are needed. Carefully cut out each spar notch, as the spars must fit snugly for medium CyA to work properly. For improved adhesion on the spruce parts, sand the surfaces to remove residual oils that tend to come to the surface after milling.
The wing panels are mirror images of one another and are built flat on the board from the front spar rearward. Obviously, the building surface must be perfectly flat as the wing will match any warps of the building board. Wing construction is from the bottom up. Pin the sheet trailing edge and center section sheet over the plans. Position the bottom spars and then the ribs. Use a small 90 degree triangle or a House of Balsa 'Upright' to keep the ribs square. Fit the hardwood trailing edge filler and adhere it to the bottom center section trailing edge sheet..."
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