There are a few different versions of the Avistar, and to be honest, I'm not sure which is which. But one of them uses a plywood joiner to join the wing together. If you have this one, be really sure to get a good epoxy joint. Make sure there is no gap and that the epoxy covers all of the center rib faces and the joiner. We had a wing fail here due to a poorly done epoxy joint. Note that this isn't what I'd consider a problem with the design at all, just something easy to mess up if you aren't paying attention.