Failure to seal all solid surfaces to include ribs and any and all sheeting will cause the wrinkle sydrome and make your airplane look just like a prune everytime you are in the sun for a few hours and or whether conditions (humidity) changes.

Yes the rib or sheeting will show thats its job or part of it.

It has been more than once I have seen some fellows new ship (and not just new flyers either but older ones who should have known better too) Suddenly and catastrofically peel entire sheets of covering from a wing in flight. This is among other things one of the causes of this.

The ones I enjoy are when the wing blows up like a balloon changing the airfoil on one side only.

If you do not beleve me go ahead and finish your wing (you can always compete the sealing later. and twist comparing the same airplane of you buddy which is properly sealed. This factor is even more important with trainers and oldtimers (airplanes that is) Than with our newer aerobatic types and airplane with a much more robust wing.

Ok so you will know what will happen with an airplane that has inadaquate torsional stiffness you can actually experiance an aileron reversal. Now that will get your interest. This is something that a few very large glass full scale gliders have demonstrated and it makes for a rather strange handling glider.

This lack of torsional stiffness with your trainer that has not been properly sealed can cause you to suffer the same problem if you get into flight.

John