If you are building your own wing or one from a kit this next tip is one you should consider if you are building a one piece wing (when finished will not be removable) and a wing that is going to be under high stress. Most wings have a top and bottom main spar and this is where all the stress is located. To ensure that the wings don't fold up, you can cut a block of balsa that is as wide as the spars (probably ¼ inch) and will fit securely in between the top spar and the bottom spar. The center of the block should be in the center of the wing. This block should be about 12 inches long, if you have to slice through ribs to make it fit that is okay just no more than 2 ribs per side. Once it fits correctly and is snug epoxy it in place. Once the epoxy hardens find the center of the wing use epoxy and fiberglass ribbon between the first rib of the left panel and the first rib of the right panel. This will add extra strength to the spars and the block between them.
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If you build your own wings you should consider a wing jig. This cuts building time considerably and makes perfect wings by maintaining all the critical angles for you with ease.
This program allows you to design your own ribs and wings. Or modify a rib from a selection of hundreds to fit your wing design. This program takes a little time to get use to but is worth it. It just prints out the rib patterns then you cut them out and glue them to the wood and then cut those out and you are set. It a must if you want to design your own plane. Check it out!