Thread: Wing Tubes and Plug-in Wing Fastening

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  1. Wing Tubes and Plug-in Wing Fastening 
    Join Date
    Los Angeles
    I have read several forum threads over the past decade or so on the topic of plug-in wings but the one issue that I've never seen addressed is fastening the wings so that they do not come off in flight. I know about wing tubes, servos, wires, push-rods and connectors but, I have never heard anything conclusive regarding the fastening of the wings themselves or seen any photos or diagrams of the methods in any book or on any website.

    What bolts work best? Nylon or steel? What are the bolts fastened to? What reinforcements to the wings do I need to consider?

    Is this system of wing tubes and bolts the only method of fastening the plug-in wings to the fuselage? I remember Byron Originals used to have a system of metal tabs and slots.

    I'm seriously considering this option on my next project (a scale twin-engine plane) and my plan so far is to fix the center section of the wing along with the two engine nacelles to the fuselage and have the two outer wing sections (the part of the wing from the nacelle to the wing tip) plug-in to the nacelle. Are there any considerations that I have to make when fastening the wings to the nacelles? Should I extend the wing tubes through the nacelles and the part of the wing that will be permanently mounted to the fuselage and on through the fuselage to strengthen the wing because I'm dividing the wing into three parts?

    There are several methods of keeping wings on when using wing tubes.

    Sig's Somethin' Extra uses J hooks and rubber bands inside the fuselage. The hooks are screwed into the wing root rib (ply reinforced) and the rubber band connects the two wings.

    Its common to use nylon bolts to pull the wings snug against the fuselage. Again the screws go into the wing root. Some caution is required to ensure the bolts are tight or they can vibrate out in flight.

    Another common method is dowel plugs in the ends of the wing tubes and screws inserted through the wing into the tube end. This one can require a bit of fiddling to find the screw holes, so most people leave one screw in permanently. As the wings are put on the fuselage and aligned the other hole lines up every time.

    For small sailplanes we sometimes just tape the wing panels together.

    And you can use separate straps to connect the wing panels.

    What will work best varies with accessibility and the structural requirements of the model. I have seen twins with the tube/joiner going clear through the wing center section and I have seen them with the tube just catching 2 ribs each side of the joint line. Weight of the aircraft and expected flight loads will determine what is necessary. If you plan to just do lazy laps around the field you need far less structure than if you intend to attempt snap rolls at high speed.

    Note that a large twin engine plane can still be very wide after removing the panels outboard of the engine nacelles.

    Join Date
    Los Angeles
    Thank you fhhuber for your response to this thread. Your answer has taken me further on this project than I could have if I were to try coming up with the answer by myself. Many thanks!

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