Here is the tarp I did.
Waterproof from above if not below. Maybe a bathtub midge net combo is a project for the pipeline.
1.5m x 2.4m of 20d silpoly ripstop with three mid point tie outs along long sides and centre line as well as the corners and short mid points. Comes in at 180+-5g in a bag on my kitchen scales.
Each edge tie out has ~30cm dyneema attached with a slippy figure eight knot and then loops at the base, middle and end for varying tension. I have two lengths on mini carabiners which I clip to the pole lifted points for extra length, one of these is several meters long for attaching to trees and other complicated things.
Side and corner tie outs were a right angle of tarp fabric cut out and stitched in place before the hem then a zig zag stitch doubled back to secure the webbing loop.
Similarly the mid points were a square of tarp fabric with double zig zag. In the storm I slept under it without seam sealing and had three pronounced drip spots on my quilt. Down was damper and lost a bit of loft, but could not feel it through the other side. I have since put some McNett silicone glue on it and have not noticed any drips since but has not been out in rain like that since.
It was extremely slippy to sew with and the main effort was going around the perimeter. Took best part of an afternoon and cost £44 in materials including postage so would not be worthwhile had I not enjoyed the process.
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