If you can find 1" wide tape, simply deflect your control surface to be sealed
fully in one direction, then apply the tape to one surface and push using a balsa stick
or small tool into the gap forming a "V".
This will stick the tape into the gap so it won't bind. Then adhear the tape to the mating surface.
I use clear Econokote. Same procedure except using a small detail trim iron.
Flutter is another problem that sealing won't fix.
All you are doing is making a more efficient control surface which translates
into smoother control input/output tracking especially on gliders, less parasitic drag.
Less deflection=less drag=more time aloft

A quick question, do you seal the TOP or BOTTOM of the control surfaces?? I had been told you seal the top but not real sure now after reading all the posts. Thanks.

To install any kind of tape/covering to make a seal, first cut a strip about 1 inch wide and the length of your control surface. Fold it in half lengthwise so that you now have a 1/2-inch wide strip. Remove the clevis from the control horn and move the control surface fully so that the bottom of the hinge line is exposed. Insert the fold all the way into the gap, right up against the hinges. Seal in place.

If you want to experiment, you can use Scotch brand removable tape. It won't last long, but it will stay in place long enough for you to determine if you want to make a more-permanent installation.

To clarify, you seal the bottom.

In once case, I saw a modeler who used a very thin line of silicone seal right along the apex of the aileron, where the vee of the control surface met the wing. It was very thin and flexible. Did an excellent job.

You can seal top or bottom, it really doesn't matter. I you want to hide the material you used to seal the gap do the bottom of the wing. On my Aeroworks Ultimate the guy I got it from (I traded for another plane) sealed the hinge lines with matching ultracote, so he did both sides of all the surfaces. It looks sharp!

I agree with most. Seal them. I have found that they quiet the pane along with making the surfaces more efficient.

can someone plesae post a picture showing what a sealed hinge looks like.