I made new drapes to replace the originals for the front lounge in our '77 31' about 8 years ago.
When we purchased our '76 Argosy MH this year, it desperately needed new drapes. The pieces of fabric hanging in the windows couldn't even be called curtains!
I based my drapes on what I remembered from the '77. It's been a few months since I finished them, so I got out my notes. (Yeah, I made notes THIS time.
In my notes the term "panel" refers to one pleat and the fabric reaching to the next pleat.
3.33" of curtain track per panel.
10" of curtain track = 3 panels.
5" of fabric = 1 sewn panel.
I allowed 1" of fabric for each pleat, sewn on the 1/2" mark. I marked the center of each pleat at 5", allowing 4" of fabric between each pleat. I attached each curtain clip midway between the pleats.
I lined my curtains with Rain No-Stain, so that they won't stain if we get a leak or leave windows open while away.
The photo shows the curtains that are pleated both top & bottom. You can leave the bottom pleats out if you don't have bottom track.