To make flotation bags, all you need is some HH-66, which is an industrial strength vinyl cement/welding compound, a few yards of clear, 20 mil vinyl, some clear vinyl tubing, and some valves from NRS

Measure the kayak at the bow, around the point that you want the bag to end. Record the result. Go back to the point where the bag will begin, somewhere in front of the kayak's footwell. Measure around the kayak again and record the result. Now measure the distance between these two points and that's the length of the bag.

Mark the distance on your clear vinyl, which, in our example, is 32 inches.

With that as the center line, take the circumference measurement from the bow, and divide it in half, which, in our example, is 32 inches divided by 2, which is 16 inches. Mark a line that long at one end of the center line, 90 degrees to the center line.

Do the same with the other circumference measurement, marking it at the other end of the line. In this case, that measurement is 47 inches, divided by 2, equals 23.5 inches.

Draw lines between the two half-circumference lines, connecting them to each other. Cut this piece out, then lay it down on the vinyl again and trace and cut another half.

Apply HH-66, to one side of each piece and stick these together. Then do the same with the other side and the small end of the bag. At the wide end, glue it together, but leave one or two inches unglued.

After the HH-66 cures, cut a length of clear vinyl tubing, long enough to reach from the end of the bag to the cockpit, so that you can insert the empty bag, then inflate it. Coat approximately one inch of the tubing with HH-66, as well as the inch or two of the float bag that you left unglued. Insert the tube into the opening in the float bag and clamp it on either side to make an airtight glue joint.

When the glue cures, insert an NRS valve into the other end of the tubing and inflate.