Has anyone made their own inflatable flotation bags? (and what happened to Seattle Fabrics?)

I need to make some replacement inflatable sponsons for a couple of older Pakboat folding kayaks (a size the company no longer makes). The originals were made with a batch of defective fabric and the owners at the time Pakboat discovered the problem were unaware of the recall at the time and failed to have them replaced.

Picture float bags (as used in whitewater boats and non-bulkhead and skin on frame kayaks) but very long and skinny tubes, 13 feet long and only 7" wide. I’ve searched the Pnet archives and not found much information on making DIY inflatable bags, though I know many people have done this. Has anybody done this themselves and/or knows of sites with good advice on material and techniques? I know the book “Building the Greenland Kayak” has a section on it but I have lost track of my copy (I tend to lend books and not keep track.) I’ve bought a quart of H-66 vinyl adhesive and was considering 12 or 18 gauge solid vinyl. Would prefer TPU-coated fabric but quality is so variable with that stuff (which is what failed in the original sponsons.)

Side note on Seattle Fabrics – I have often bought materials for outdoor recreation projects from Seattle Fabrics previously excellent on-line catalog, everything from yards of Gore-tex and technical fleece, to sewing patterns for gaiters and anoraks, bungee and deck rigging cord, all kinds of metal and nylon plastic fasteners, neoprene, etc. But I just went searching for what they might have in the way of materials for my project and they have COMPLETELY revised their site so that it is virtually unusable. Searches are fruitless and they no longer have a tabbed menu to drill down to the product ranges that you want, like every other digital format catalog IN THE WORLD. I hope this is a beta version in progress because it is completely useless and I am going to have to find other sources. I would suggest that if you have ever bought materials from them that you check out the new catalog and send them your reaction to the change. I did, as politely as I could.

Did you say that you are coming Qajaq-TC this week? If so, there will be people there that do this. Two years ago there was a session making float bags for SOF quajaqs. Last year it was making neoprene mitts.

Yes, I’m registered for Qajaq-TC. It does sound like I can garner some advice there.
I was actually thinking of posting for advice on the qajaqusa.org forums (did a search on the topic there earlier today and didn’t find anything recent enough to have still active links to instructions.)
Meanwhile I ordered 4 sets of full Boston valve assemblies (including the “female” socket assemblies, which most vendors don’t sell) so they should be here by the time I get back from Frankfort. I found a source for heat sealable vinyl bonded to ripstop nylon at diypackraft.com (source of the valves) but it’s pretty pricey to get the 9 yards I would need to make four 13’ sponson sets, so I will wait on that until I can talk to some people who have made float bags, or even better, anyone who has made one of Tom Yost’s DIY inflatable kayaks, since that would be more relevant to the sponson construction.

A bit off topic, but DIY PackRafts looks to have some pretty cool patterns and kits for making your own pack rafts. Might be a project for this winter.