Hinged parts will not stay in place.

I just got a Cobi F-16 for Christmas, and erected it this weekend. It's a good model, but the tailplane keeps flopping down, the hinges have no friction. I looked for pieces to put on the tailplane to counter this, but to no avail, all that was left were the landing gear pieces (I chose to build the model with the gear up). Is there a way around this?