Saturday, September 23, 2006

PVC Greenhouse: Wrapping the greenhouse

So now you have the frame complete (except for the door which will come later). You are ready to wrap you greenhouse.

The supplies I used were:
- 1 - 20' x 25' - 4 mil plastic sheeting (note: this year I'm going for 5 mil)
- about 50 snapclamps (various sizes)

Snap clamps, pictured below, are these need litte device that are used to clamp tarp and plastic sheeting to pvc pipe.

So, before you unroll your huge plastic sheet makes sure you either have a non-windy day or a buddy. The thing will blow around and you'll never get that big thing onto you frame.

Open up your tarp. Take one edge and insert it under the greenhouse to the half point. Now take the tarp and roll it up one side of the green house, over the top and back down the other side.Tuck the edge under the greenhouse. Have the two edges meet in the middle under the greenhouse.

You now have the plastic sheeting forming a big tube around the greenhouse with plenty of slack on both ends. You can now attaching the plastic sheet to the rib poles using the correct sized snapclamps. You can place about 3 per rib. Start by the door, completing and entire pole on ight then left, and work your way back. Two important tips: First, if the tarp is too tight applying the snapclamps can tear the plastic. The tarp has to be loose enough that is can wrap around each rib then add the clamp. The second is that winter winds will put stress on you sheets where they meet the clamps. Consider adding a small patch of duct tape to the sheeting where it meets the clamp. (I have never done this but will for this winter)

Now, you have to wrap the end of the trap around the frame. This takes a bit of creativity but is like wrapping a giant birthday present where the tarp is wrapping paper. Standing outside the greenhouse, I took all the excess tarp from the right side and wrapped it around the rear until it met the the leftside. Now bring the left excess over to the right. make sure the trap is alway laying in such a way that rain will run off, and not into, the folds of your tarp. Secure the sheeting strategically with more snap clamps. Tuck the extra at the bottom under the greenhouse and also secure with snapclamps.

The method above gives you overlapping layers of plastic sheeting. Not as pretty as if you cut the sheet to fit perefctly but it lasted all winter and was quite air tight.

Take your time and you'll end up with something like this:

(Nice picture...right? truth is, that sheet is wrapped a bit to tight and did not leave enough slack around the snap clamps. I has plenty of tearing that year and learned to leave the sheeting a little more baggy)

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Saturday, September 02, 2006

PVC Greenhouse: The Ribs

Once the square support and the back wall are assembled, it become pretty obvious how to attach the ribs. After all, we've done the work of aligning the 45 degree connectors on the ridge pole and the T - connectors on the base.

Grab a ladder and start adding ribs between the ridge pole and the base. If you plan to take your greenhouse down in the summer (or ever!) do not glue the ribs. Friction fit only at top and bottom. When you are done it should look like this. (that long horizontal bend intentional at this point)

Since attaching the ribs is so easy this step is more about tips and tricks. First, without some kind of fastener the ribs would pop out at the first big wind of the season. To attach at the top and base I chose plastic wire ties. I drilled a small hole through the 45 degree fastener and the rib pole. Be sure there is enough overlap that the hole can go cleanly through both. Once you have the hole slip the wire tie through and secure. See image below.

Repeat top and bottom for all poles.

You should also attach the first and last pairs to the square supports be just wrapping them together with more ties (no drilling needed).

Remember that horizontal droop we saw? Well you should also attach the rib p[airs to the long horizontal bars...Again with wire ties(again no drilling).

Here's a pretty good shot of the completed frame. See the wire tie loose ends on the top right poles? Trim those extra bits off before we wrap in the the next step.

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