- Why are we so concerned about attaching fabric to wing ribs?
>This is a very important step. When fabric is used to cover a wing certain precautions must be taken to ensure the fabric does not "balloon-up" in flight. Lift on a wing will cause the fabric to attempt to raise up on the top surface and separate from the ribs or from the plywood on a wooden airplane. This ballooning affect could be disastrous. You certainly do not want the fabric to separate from the ribs and spoil the lift on a wing. If this occurs in flight an accident is almost certain to follow.
Should I only secure the fabric to the wings?
>You must secure the fabric to any surface that creates lift-wings, control surfaces, etc.
How do I do this?
>It depends upon the type of airplane. Several methods are available. They range from sewing it to the ribs using a rib lacing cord to using screws. Rib lacing, screws, rivets, and fabric clips are the most common methods used.
How do I know which one to use?
>If you have a production airplane you must use the method originally employed by the manufacturer. If you have an experimental airplane you may use any method you choose.
On a Cessna 170 it is obvious the construction of the rib is different than the Piper in that attaching the fabric to the rib via clips as the factory did, will not pull the rib apart. The rib is designed with this method of attachment in mind.
And in my eye, assuming the rib structure would allow it, stitching should work just fine. But that doesn't make it legal.