Steve,
Jason Shaffer kindly posts a link to some photos of a cape/tarp design I use. The pics show how the reinforcements can be made to form pockets to hold the lines. Here are some observations from 5 months of experience with the cape/tarp concept on the AT this year:
1. A cape is, I think, better than a poncho if it is properly constructed. I put a water resistant zipper on one hem to close it in front. This works much better than snaps. Otherwise, it will leak down your front. I use double Velcro tabs to define the hood.
2. A cape (or a poncho) is adequate raingear for gentle trails. It is not so good on challenging trails where you might want to see your feet and feel free to move. That said, the cape forms a cone so it is more wind worthy than a poncho which forms a sort-of flat envelope and tends to blow around.
3. A tarp will make an adequate cape only if it is not too long. Mine is 9 feet long (9X5), and that is too much. I would be happier with 8.5 feet or less. Even when the cape is worn over a pack, the corners of a 9-foot cape dangle too low and tend to drag against trailside brush. I am about 6'2", so anyone shorter will surely need a shorter cape.
4. 9 feet is a little bit small for a tarp set up on the ground. It is OK for covering a hammock. An 8 foot tarp works for me on a hammock. I was trying to make a cape/tarp that would do everything – rain gear, hammock fly, and tarp. It worked OK for a hammock fly, but as I said, it was marginal as rain gear on the AT. I will continue to use it for gentle trails. The next one will be, I think, 8'4" long X 5 wide.
5. If you want to turn an existing tarp into a cape, there are a couple of things to consider. First, you need to manage the lines. Taking them off is probably the easiest solution. Second, you can experiment with whether you like the cape at all by forming the "hood" with tape or paper clamps.
