We've used a variety of materials for our winter cover frames. We see shredded blue tarp stuff blowing all over the place in January around here. It doesn't stand up to the UV degradation and wears through at any chafe points. This allows the wind in, which stretches the tarp and allows it to chafe more. It isn't worth buying because it needs to be replaced more than once a year. We tried pvc pipe and thought it was great until it got brittle and started cracking all over, after about two seasons. We've now gone to electrical conduit arches, bent as described above. We bent matching shorter sections for the feet and joined them to arched longer pieces with standard conduit joins. Then we tape 1x2 furring strips fore & aft to hold them all together (they bend easily to match the curves, and are available everywhere pretty cheaply) and to hold up the heavy canvas tarps. To hold the tarps down we run old jibsheets along the outside of the lifelines along the toerails, tighten them with the winches
, and then tuck the canvas around the line
; outboard, then up and in, where we tie it off to one of the conduits or furring stips. This will be our twelfth winter with the boat, and the third year with this setup. We think we've learned some things.