Wing Webbing By James Goss     Adding wing webbing is one of the cheapest things you can do to insure that you have the strongest wing possible. It adds very little weight and cost to the overall project and only takes a few minutes to install. In case there is somebody reading this that does not know what wing webbing is, let me describe it for you. You create wing webbing by adding balsa between the upper and lower wing spars in each rib bay for the length of the wing. This applies to built up wings only and not to foam core wings. It is important to arrange the balsa wood grain in a vertical position to insure maximum strength. If you take a piece of 1/16 balsa and try to pull it apart with the grain running toward each hand, it is very difficult or impossible to do. If you try it with the grain running at a right angle to your hands it will almost fall apart. 1/16-inch balsa makes a very strong web for your wings. How much weight do you think a piece of 1/16 balsa, only 1-inch wide will support? I have just completed a series of tests doing just that, testing the strength of balsa, actually the tensile strength, by seeing how much weight it will pick up and hold. Here are the results: 1/16 balsa, 1-inch square, will lift and hold 12 pounds without separating, of course this will vary with different grades of balsa. If you place 1/16 balsa webbing in five rib bays, on both sides of the spar, you will have increased the separation strength by 120-pounds. This is more than any high G force maneuver can develop.  In larger planes we sometimes find 1/8-inch light ply for the webbing. Light ply has a much higher tensile strength, but it is not much stronger than balsa as far as longitudinal strength.      What you are doing by installing balsa webbing is tying the top and bottom spar together to make them into an I-beam or channel, just like a piece of channel iron. You know how strong steel I-beams are. Some modelers will place the balsa in the center of the two spars that makes it a true I-beam for maximum strength. This takes a lot more time so most modelers will simply glue the webs to the sides of the spars, either on the front or the rear side. If you really want to make a strong beam you can place the webs on both sides of the spars. The webbing has to be able to withstand both pushing and pulling forces that act on the wing. If it had to only handle pulling forces then material such as ca hinges would be ideal because of their strength and lightweight. While in flight the wings have a tendency to bend while in a stressful maneuver such as a snap roll, a high-speed dive, or some of the tumbling that we do. On one of my giant scale planes the covering actually split on its leading edge from the wing bending during a high speed tumble, now that's scary. We would probably be amazed if we actually knew how much our wings do bend while under stress, even on a small plane.      When you place the webs it is not necessary that they touch the ribs. This is because the ribs with their grain running cord wise of the wing would add nothing as far as tensile strength to the webbing. I always leave space between the webs and the ribs so I can have access to get more glue to the leading edge sheeting after the sheeting has been installed if it needs it. Have you ever seen the time that you wished you could still get some glue to the leading edge sheeting? You have some areas that are loose and maybe it puffs up here and there where it didn't make contact to the rib while you were gluing it. By having these access holes you can very easily drop some thin ca glue in that area and let it run down the front edge of the rib and sheeting. You can also take a pin and perforate the area in need with small holes and let thin ca run through them, place a piece of waxed paper over the area and hold down until it cures. This is where I usually glue my thumb to the sheeting.      Remember that you are trying to make the wing as strong as possible while keeping the weight to a minimum. A full set of 3/32 balsa webbing in a sixty size plane installed with ca glue will only add about one ounces of weight. I don't think this amount will keep anybodies plane from going vertical. I have never seen a wing panel break anywhere other than at the root joint of the wing, or within a few rib bays from the root, other than on large gliders that have polyhedral in their wings. The wing is like a leverage bar with the tip of the wing being the holding end of the bar and the root end being the prying end of the bar. The longer the wing the more prying force is felt at the root end of the wing. So the longer the wing the more your plane will need webbing at the root end.      I have seen a lot of planes fly without any webbing in their wings at all. Some that were designed to have it but the modeler forgot to install it or just decided not to use it. These planes did seem to perform ok without the webbing, even in some stressful maneuvers, but when they hit the ground in a minor mishap the wing did break into several pieces. So why take a chance with the wing breaking in flight or when it hits the ground during a hard landing. Beef the wing up with webbing and then if it breaks you will know that it wasn't your building skills, it was your flying skills that got it.