A trick to let the windows glide better in the channel
In many cases, it seems, this does not necessarily solve the more common problem of the windows sticking. Solutions almost always suggest some form of lubricant for the channel which often doesn't work well. So, I tried another method that does seem to work: lubricate the window, not the channel!
How to do this? A company called McMaster-Carr (mcmaster.com) provides ultra-low friction tape for use in machinery, to keep rubbing parts from wearing. I purchased a piece of ultra low friction tape with Teflon (pn: 6305A23 fifteen feet long and two inches wide. The tape is 0.005 in thick with silicone adhesive on the back (peel and stick).
For each window, I cut a piece 19-3/4 long (2 inches wide) and pressed it on the window edge from top to bottom, including over the top and bottom aluminum pieces. I then folded it over the window edge and applied it the same way on the other side.
This reduced the resistance of the window in the channel very much indeed; so much so, the windows slid down and up with the press of a single finger. How to correct this so one could set the window in the travel arc where one wanted and have it stay put? The solution is to use 1 inch furniture circular "surface savers ($1.90 per 24)" which are used to reduce friction of the bottoms of chair legs on the floor.
These items have peel-stick adhesive on one side, but semi-thick fiber on the other. Peel the paper off and stick one on the metal pieces at the top and bottom of the window that slide in the channel, four to a window.
(This will work if the fabric channels below the window are clear and in good shape. If not, using four sliders may create too much tension as the window tries to slide through the channel. It is probably better to start with placing only two sliders in the corners of the window's top)
This holds the window in place wherever one stops it on the travel arc allowing it to slide freely and easily in the channel while not allowing the edge of the window to rub along the inside welt. It seems to work well and the tape, made for use in machinery, promises to last well.
This idea is not mine alone, but was stimulated by an idea provided by my grandson who is a master machinist (am I really already that old?). He told me that when dealing with problems of friction between moving parts, always lubricate the moving part, not the part it moves against! And so it seems to apply to Ercoupe windows.
Rick