Re: Protecting a boat rack from the elements
It may seem like an overkill or expensive but how about shrinkwrap instead of tarps. One thing that will happen in a city environment is you'll get a lot of grime and air pollution that may accelerate the breakdown of the tarps' weave. Unless the PVC is pretty hefty it will bend in heat and under snow loads.
Mobile shrinkwrappers are probably out and about now uncovering boats in boatyards/people's backyards and disposing of framing and used shrinkwrap material (it can't be reshrunk). Worth a call?
“So we beat on, boats against the current, borne back ceaselessly into the past.”