Just find a spring loaded shower bar and use it. Holds up by simple tension, and completely removable if you don't want it any more. We use one in our Springdale to divide the trailer in half to make a more private changing room. Was was suppose to be just a temporary sheet hanging over the bar, turned out to be a permanent fixture for 8 years. The bar worked GREAT for drying towels too.
Also use those bars above the bed for clip on lights and fans. But near the ceiling, they work great for curtains.
Here's a photo of one we use above our bed in our current trailer. We have 2 clip on fans, and also use it to hold wires up, off the bed.
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I found of photo of our previous camper. We used the rod above our head board also. The rod above the bed, is a stair way banister I cut to length. It worked great for hanging cloths on. Not when traveling, but great for hanging a few items when we need to dry them.
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More searching, here's a photo of our previous camper with the bar. It near the very top of the photo. This worked absolutely great for us.
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I also found this photo. This was our Dutchmen Sport, our first trailer. Notice I used one of those shower rods at the end of the bed (vertical). We clamped fans and lights to it also. And if you look real close, you'll see another one under the cabinet on the back wall above the bed.
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They make GREAT curtain rods! I suggest trying it before anchoring something to your ceiling (which is VERY thin).