www.mcmaster.com

Search for "heavy weight vinyl" and you'll go to the page of polyester reinforced vinyl fabrics.

vinyl glue will hold this material, or you can heat seal it.

Look at the opening of drybags from Sealine. They are simply folded over and secured with a strap. Such an arrangement would be fine for homebuilt drybags, too. For $20 you can get a good sized drybag just to play with it. You can make something like these.

Or, you can dig out the sewing machine and make your bags from canvas or heavy nylon which you then waterproof like the skin of a skin on frame kayak. You cna use lighter weight fabrics than you would use to skin a boat, as they will not be subjected to as much scratching and abuse. 10 ounce duck from the fabric store is fine. Heavy polyester from aircraft spruce or other sources is another option.

REI and Campmor (www.campmor.com) sell a liquid urethane material for sealing tent seams and recoating the waterproof tent floors. it comes in an 8 ounce size at a reasonable price. More than enough there for several floatbags or dry bags.

Your local fabric store may sell clear vinyl in the upholstery fabrics area. If not, try www.joann.com. Get the heaviest gauge vinyl offered. This is suitable for small to medium sized drybags. The stuff is cheap, so why not make 6 or 8 small bags instead of one or two big ones? Redundancy like this has an additional advantage. Even if one or two fail you still have several left to keep you afloat and reduce the amount of water you have to bail out.

Valves: Sevylor (www.sevylor.com) has replacement valves of several sizes. you cna get their catalog from this website, or they'll send you to Shipstore for online buying of their products.

http://www.shipstore.com/SS/HTML/SEV/SEVTVL.html

Is the page with the valves and plugs on it. Several other part numbers with other sized valves.

You can always make a tube from a strip of vinyl glued to the bag. Use it to inflate the drybag, and then fold over the end and secure it with a heavy clip.

Hope this helps.

PGJ