RCU Forums - View Single Post - Anybody ever witnessed an aluminum wing joiner tube fail?
Old 04-25-2018, 12:19 PM
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j.duncker
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I see the light! If I understand correctly you are working on converting a one piece wing into a two piece wing with a single joiner of somesort. Now this is not as simple as it might seem.

In a one piece wing the plywood joiner is glued in place which means the load is transferred from the wing to the joiner along the length of the joiner. If you allow the joiner to float in the wing without gluing it in place the join between the wing halves will be significantly weaker and you will have a major stress point at the end of the joiner.

Also it is common practice to apply a piece of fiberglass tape to the wing join at the center. This makes the wing skin a one piece monocoque through the center. The joiner just keeps the skins apart. [ mostly ]. This is the more important factor in making the wing to wing join strong.

To convert the construction to a two piece wing you will need two joiners one can be short and small just to locate the wings. The major joiner will need to be significantly longer and stronger than the kit joiner. You will need to modify the construction of the wing to create a box for the joiner to slide into. Generally this would form part of the main spar. Balsa ribs might have lite ply doublers and care needs to be taken to extend the mainspar reinforcement beyond the end of the joiner. If your ply joiner is near the full depth of the wing then you must reinforce the box where it joins the root rib which needs to be plywood or ply reinforced. I used to wrap epoxy glass string around the box there.