The top opening is crucial, even more crucial than the bottom. The good thing is that a sphere has the best cooling of any shape. As long as you're surface area has good emmisitivity <(white) although,it is the best way to keep heat in as well>. Black interior and white or reflective exterior (both fairly well covered with the canvas vinyl you're using, assuming it is indeed white).

Neglecting air flow and a bunch of gnarly integrals to even begin to describe it (actually there's still never been a thesis to describe the "cooling affect" that dome currents create), simply regarding heat and radiation the general equation is:
R=AeST^4 that is Radiation=Area*emmisitivy*Stefan's constant (~ the order of 10^-8watts/meter)*surface Tempurature to the fourth power.

Interpreting this pulls two constants out of the equation (Area and Stefan's constant) leaving only emmisitivy in question, and surface tempurature driving the real power of radiation. Hence choose reflective material. White painted internally would be rad if there was a black base to do a really sick multi-spectrum mandala, but that might take DiVinci on his back or at least some similar feat.

Now, out of theory and down to tactile reality..... the cover is by far the hardest part of a dome to fabricate. I worked with a 60 year old fabric guru in Sebastapol out of a barn for a week to connect 4 bolts of fabric into one open topped and vinyl windowed 32' dome cover, and the last few runs had me heaving heavy guage cotton (never again) over my back while she ran it all through the machine. There's a couple hundred human hours that go into most dome skins you'll see. I was lucky to draw on her cellular memory to just simply know a 20' piece was going to be 1" off without having to be measured. It was finally snug in the end as a good mix of experiences came together.

Just curious, but what's the geometry to your design Vaugh? Keep in mind that you want to mimic the frame, or at least the basis of an icosahedron when you design your seems. Also, depending on diameter, make your skin a healthy bit (inches) larger than your frame for a sure fit. There's no shame in 1/2" of sag if nobody will ever notice because they're too busy enjoying your dome. If you're material is already white, play with the idea of painting it black (you want internal human heat at night to be absorbed and external solar heat to be reflected). This is the best I can offer, but am always curious to learn if you care to share your journey. If you're in LA and want some expert advice on it, try asking for Andrew Bangsbergs input. I really am curious in your choice of geometry and design. Drop a line and lemmeno.

Oh yeah, you might not want to attempt putting the skin on by 6pm as you want to put it on as hot and saggy and sundrenched as possible to allow for linear expansion and make it easier to put on. Besides, it's always a million times more gratifying to get your base coat singed into you early in the week and have drinks in the shade on the afternoon of a dome build. Enjoy!

heat weld all the way!!!

sooooooo
much better

=)

We've got all our pieces together and the pvc cement holds really well. We built the dome and threw the cover on it and I think it's going to work great.

V