cheapest, most practical materials
Home Depot has all of the protoyping materials you need, namely: various thickness of polyethylene sheeting and gorilla tape. A 100′ x 10′ roll of 4 mil poly runs for around $40. Gorilla tape runs for $8-$9 per roll. It’s a bit expensive, but it’s also one of the few tapes that will really stick to polyethylene. If you’re impatient (and/or not interested in black seams), you can forgo tape and heat seal instead with a normal house hold iron and a teflon pressing sheet (available at Joann Fabrics) or piece of aluminum foil (to keep the gunk off of your iron and to prevent burning up your polyethylene).
Outdoor Wilderness Fabrics Inc has, so far in my search, the best deals on ripstop, vinyl and “hook and loop” (aka, generic velcro). If you order 100 yards of ripstop, you’ll get an even bigger discount than what shows online. Their selection is fairly limited though.
Westmark Corporation has the best selection of nylon fabric in New England. They also have good prices and will send free samples to you, which I highly recommend (if you have time) before purchasing.
Fabric stores sell clear vinyl, which runs from $1.99 / yard to $4.99 / yard depending on the weight. Most fabric stores also sell colored 18 mil vinyl (weldable), waterproof coated spandex (the coating is often plastic-y and weldable), waterproof coated polyester (non-weldable). If you are in or around Cambridge, MA, check out the selection at SewLow or a few blocks away at SewFisticated. Click on the image below for photos of their selection:
Army-Navy stores often have ripstop nylon parachutes which may not be good for parachuting, but may be great for inflatables. Here in the Boston area, check out the Army Barracks (617-437-1657). I called them yesterday (Jan 20, 2010) and they said they had a few white and one green parachute for about $25.
websites & books
Here is an online syllabus for an Inflatable Making Class. There’s lots of good info in here. I have been through the entire reading list, and recommend all of the books.
Ant Farm’s Inflatocookbook is the seminal resource on making inflatables. This book is informative and also really fun to read. My father, however, announced as he was leafing through it, “This is meant for a drug-addled brain.” I owe a big thanks to the wonderful Brandon Roy for (a) finding this, (b) cleaning it up, (c) giving it to me.
Calculate the tiles you’d need to build a dome, using the dome calculator!