Here are my photos of the bunk in the CT-13 that I took apart. As mentioned by others, the bunk takes up a lot of room when it is folded for a couch back. There is much less seat depth than other trailers. We are now using regular cushions for the back and prefer that.
That being said...here are some photos to help those that want to rebuild the bunk.
Also - another Uhaul
camper member used my photos to come up with full size template, I have a pdf of this I can send to interested parties, who would need to get it printed on a large sheet of paper. He is working on the bunk himself and will post a pdf with any alterations once he has made a functioning bunk.
The bunk has a large piece of hinged wood that provides support. I believe the hinges in the wood are important to move the bunk from couch back to bunk and to help fold a little in the couch back position.
Bolts attach the hinge on the front wall to the piece of wood through the bottom fabric of the cushion. In the upright position the wood is below the foam and above the bottom layer of the cushion.
The notch cut out is for the kitchen side, so it can slip over the kitchen. The piece of wood is seen from above if it were in the bunk position. Note the metal pieces - they are nuts that bolts went through, the ones in the diamond formation were attached to the folding legs. The ones in a row were attached to the hinge.
Here is the front wall with bunk removed, hinge still in place.
The hinge here, note the curve.
Here is a close up of one of the special nuts - has a flat side with stabbing bits to hold into the wood (this one fell out - all others are seen still in the wood in first photos). The nut/bolt combos for the legs are slightly thinner than the ones used to hold to the hinge.
Both bolts are seen in this photo.
Hope this helps,