I'm not too worried about the OP. If he gets this up to flight speed, the wings will snap off at an altitude of 0 feet. The danger is that he make improvements that give a 1.3g ultimate failure strength.
Not defending the OP, but seriously, who would use PVC for a spar?
When I was a kid at the tender age of 9, inspired by an article I read in Boys Life, I made a rogallo wing hang glider, using bedsheets and PVC. Worked great running down the small hill, feeling it lift up big time, until I put my sub-100 pound weight into the structure. I heard and felt a big snap, then took a little tumble down that hill....after falling about 10 feet!
My first aircraft design...
My first 0.1 ...
My first unofficial solo...
...ending up scraped up and a little bruised & bloody in a pile of broken PVC and bedsheets. Pride slightly bruised, but devoted more than ever to become an aeronautical engineer and test pilot.
@Allen , do not attempt to use PVC on anything structural. You can use a PVC structural foam in a composite sandwich application, but PVC is a no-go for structural!