I’ve recommended polycro tarps several times.
Here is one in action.
It had shock cord at the corners (connected with a sheetbend knot) and a ridge line.
In this case I set up a copper Spur 2p tent up under it in the rain—set up dry and was dry in the morning.
The tarp weighs less than the extra weight a wet tent has.
I would usually set it up a little higher so that there is a little airflow between the tent and the tarp. The pitch of the tarp in the picture was not optimal.
The way the available trees and such were it was hard to reach up high enough to get the space given the rise I got from the tent platform and how tired I was that night.
The picture was taken the following morning. That is my food dry sack brought back to the tent and my backpack sticking out.
You can also make this into an ultra light tent by using just a bug net with the tarp and using the tarp like you would use the outer layer of a tent/rain fly. Ounces for pounds.
For a ten dollar window film kit (I get the heavy duty ones) it is a great item to have available.
For more, including links on how to make one and other uses for polycro:
- https://www.trailjournals.com/journal/entry/596227
- https://backpackinglight.com/forums/topic/how-to-make-a-polycryo-a-frame-tarp/
- https://adrr.com/d20/2021/08/08/tarps-on-the-trail/
And someone else doing the same thing (photograph used with permission):
That is a larger 20’x10’ sheet of polycro but the same principle.
Postscript:
This is the sort of heavy duty window film you can buy at Home Depot or Amazon to make your rainfly with.
You can fold over the edge seam over a small plastic washer instead of making a grommet or using a sheet bend knot.