July 2009

I bought 4 more sheets of foam board and 6 more yards of canvas today. It’s making me nervous that there is only 4 weeks left and I’m building something so complicated that has never been built before. Plus the scooter needs work and so does the wagon!!!

Here is the first production zipper with canvas sewn onto each half of the zipper. This is a #10 coiled zipper. We could not get a long #10 toothed zipper fast enough. This coiled zipper is cheaper to make but looks to be strong enough for our uses. At first I ran just one row of stitches to see how strong the seams would be. They had some flex to them in tension. I added an extra row of stitches to each side of the zipper and it really didn’t make the joint any stronger. In fact it makes it a bit harder to unzip the joint due to the canvas being right up against the zipper pull. Zippers sewn into a K-Hing will only have one row of stitches on each side. I folded a 1/2 inch of the canvas under the bottom to make sure the canvas does not come unraveled with use. This also made for a nice looking seam.

Here is the zipper after it was installed and then unzipped to clean up any excess glue that might get into the zipper teeth. The glue set up fast today since it was warm in the garage. I’ll do it at night the next time. The foam weather stripping was added to see if it would compress ok and fill in the joint completely so it would be as heat and dust proof as possible. This weather stripping will probably go between each of the 6 roof sections for best insulation from heat, light and dust. The ends of each canvas joint will need to have the excess material trimmed away after the glue sets.

This is the completed roof and wall assembly with the zipper glued on. Normally the zipper won’t be glued on, but since this assembly was a prototype this is how I decided to make it a useful part of the Yurt so there is no wasted materials. It also showed me how to do a zipper repair in the future if needed. I could simply cut off the old zipper at the threads, and glue this zipper and canvas assembly over the joint. Maybe not as strong as a zipper sewn into a K-Hinge, but should hold up. We’ll find out, that’s for sure!

Here is a mock up using wood of a K-Hinge with a zipper sewn in. This is the closed position. This allows the hinged joint to be folded over on itself when unzipped or to stiffen the hinged joint when zipped together. Leaning on this prototype with many pounds of force showed that it held together well. Surely the foam board would have broken with so much stress applied to it. Since the glue and canvas are in shear during the stress test, then only the thread and zipper’s cloth are the only weak spots. You can see the one corner of canvas where I peeled it up to see how well the glue held up. The glue bond is much stronger than the bond that the aluminum foil has to the paper on the foam board.

This is the open or folded position. Leaving a couple of inches of zipper hanging off of the end, makes it easy to start the zipper when assembling the Yurt.

There is the end view of the K-Hinge and the zipper. I’ll try and sew the gap between boards a little tighter when I build the foam board versions.

We stood the assembled wall and roof panel up against the garage wall. The tip of the roof panel was set to 8 feet high. This duplicates the roof angle of a fully assembled Yurt. So now, we are looking at how to adjoin the next wall/roof assembly to the one we just made. I worked out an idea yesterday. Today I have to find the materials and make up a test section. The idea is to sew on half of a heavy duty zipper to one roof panel and the other half of the zipper to the other roof panel. The zipper will have to be sewn to the canvas before it’s glued to the foam board. A few inches of zipper will have to be free hanging in order to be able to start the zipper each time. Each seam where a zipper will go it about 54 inches long. So a 60 inch long zipper should work fine. The sewn zipper should have enough tensile strength as the tape it is replacing.

There are two zipper joints that have to be tested. One is with a K-Hinge installed as occurs between the upper and lower roof panels. The second zipper joint will occur between two unattached roof panels. This second joint will have half of a zipper attached to each of the canvas end caps that are glued along the edges of the roof panels.

I’ll find a couple pieces of wood and attach them together with a K-Hinge with a zipper sewn in as well. This way I can stress the joint to see how the zipper will fail.

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