Hi
The way i read it, the nylon string is just to hold everything temporarily in place as work progresses (i could be wrong)
I agree with you that relying on the poly covering to hold the frame together is a strange idea :)
I would drill holes in the connectors and install stainless tek screws or something similar.

I think you got screwed. The whold rig looks MICKEY MOUSE to me. For the amount of the serious sized one you could have a HFGH.

1eyedJack and the Dawg

my hoop style gh has perlins-one going down the middle and one on each side...but, to give it a little more strength...we used 2 4x4s in concrete in the middle....just space them apart between the length of the gh....dig a hole and stick in a 4x4.... make sure it is right up against the top of the gh ceiling-we attached it to the frame with some plumbers tape and a few screws and then concreted it into the ground...that should work....
Lawanna

Thanks for the suggestions so far.

Sounds like the HFGH has it's own set of issues. For a beginner like me, this hoop style seemed to be a much simpler solution.

Speaking of hoop style greenhouses...I've seen a number of plans for PVC pipe greenhouses. I've also read posts by people who have them. I wonder...can Schedule 40 PVC be used or is Schedule 80 required? I can't find much Schedule 80 PVC here, but have found plenty of Sched 40.

I'd love to build a greenhouse this Spring, as soon as the snow is gone....

zengeos

As I look out my window and see the deep snow piled out in the yard, I am glad that I built my hoophouse (Gothic arch style) out of a galvanized kit (from Ledgewood Farm in Moultonborough, N.H)rather than PVC. I built one out of PVC a few years back, and even though it was fun and cheap, it only took one wet heavy snow to snap the bows and create a real mess. I probably could have avoided that if I had installed a center support of some type to hold up the ridge purlin, but who wants to worry each time the forecast calls for snow and who wants to step around a bunch of posts in the greenhouse? Not me. I learned my lesson and went with iron, rather than plastic, and with all the snow we've had in Maine this year, I KNOW I made the right decision. Sure, there are plans out there where you can insert rebar into the PVC pipe, and that does make it stronger, but those designs aren't particulary attractive and don't provide enough headroom, IMHO. Good luck with your plans, but it seems like you'll have plenty of time to ponder them, as the snow doesn't seem to be disappearing as quickly as it should for Mid March!!

Yep that's exactly what just happened to mine pvc went right through my visqueen thank god i hadn't moved any of my plants yet !

Speaking of hoop style greenhouses...I've seen a number of plans for PVC pipe greenhouses. I've also read posts by people who have them. I wonder...can Schedule 40 PVC be used or is Schedule 80 required? I can't find much Schedule 80 PVC here, but have found plenty of Sched 40.
I'd love to build a greenhouse this Spring, as soon as the snow is gone....

You will be better off using cattle panals instead of Schedule 40 or 80 pvc.
It looks like your in Maine and I am sure you get loads of snow. This link is what I did last year first it started off trying to build with pvc but I ended up using the cattle panals. I didn't have an exaust system in the hoop house and I ended up cooking most of my plants that I was overwintering(it was cloudy and dreary 50 degree day at my jobsite but 20 miles away at home the sun was out and raised my temps above 120. Needles to say this fall I built a 10 x12 harbor freight greenhouse that is doing great for my needs.

good luck and hope this helps

Here is a link that might be useful: my pvc hoophouse

Nielsent, I looked at your diagram, read your message twice and I have questions. Is the metal frame something like concrete reinforcing bar (re-bar)? Is it surrounded by plastic? Is the frame small enought to fit inside PVC pipe, either 1/2 or 3/4 inch? I have seen hoop houses made from re-bar and the re-bar is covered with PVC pipe. The top is held together by a dual system of PVC union which is glued together and then a screw is added to reinforce the joint. Let me know by regular email, not by replying here, if I understand correctly. I may have other suggestions but I need to better understand the situation.