This response may be too late to be helpful to you this season, but I've just constructed a frame for my Cheoy Lee '53 out of 1" PVC. This is a new boat to us, and it was always stored indoors in the past, so therefore was never covered. I plan to make my own canvas winter cover in the future, but we decided to have it shrinkwrapped this first year, and we were told by the marina staff they'd give us a discount on the shrink wrapping if we made our own frame. I wanted a frame that would be beefy enough for when we have the canvas cover as well.
The 1" PVC seems hefty enough when the ribs are spaced closely enough together. We spaced ours about 5 feet apart. We incorproated two bow-to-stern lines of PVC pipes on each side - the lower of which was an inch or so above the upper lifeline, and used PVC 4-way and T connectors throughout. Instead of PVC glue, we used tap screws to hold the PVC pipes in the connectors so that they can easily be taken apart in the spring. (We wished we'd thought to use some kind of lubricant in the joints, as those pipes can really get jammed in those connectors!)
The PVC framing supplies were pricey (about $300 for our boat) but we figured we'd get many years use out of it. Got lots of great feedback from folks at the marina admiring our work. I have to say, it really did come out well!
On our previous boat - a 30' S-2 - we successfullly constructed a nice frame out of a PVC-like electrical conduit piping. The main advantage - other than the much cheaper cost - was not needing connectors between the pipes for much of it, as the pipes come with one flared end to accept the insert of the next pipe (much like vacuum cleaner hose extentions). Also the conduit pipes are flexible, and therefore can be bowed into arched ribs. We dirilled holes through a one 2" PVC pipe that we used as a ridge pole, and passed the conduit pipes through the holes - one hole for each rib - to keep them all in formation and for sturdiness. Then we used baling twine between each of the bowed ribs - about 4 passes from bow to stern on each side about 2.5' apart - to keep the tarps from sagging between the ribs with the weight of any collected snow. That worked well for us for several years. The ends of the ribs we attached to the toe rail by drilling a hole large enough to pass a nylon electircal wire tie through. We then attached the wire tie to the toe rail. (The S-2 had multiple holes all along the metal toe rail that made this easy to do.) The conduit piping would not have been beefy enough to support either a shrink wrap plastic or canvas cover over the much larger deck space of the Cheoy Lee, with it's 14.5 beam, however. That why we went instead with the PVC for choice of frame material for the new boat.
Hope this helps someone.
