I was going to email this to the foildesign group, but decided to add it to my web site:

I don't know if this will help, but this is my tried and TESTED bladder making steps.

I got some polythene flat tube, this is a long tube of plastic on a roll. I got this for free from our local plastic firm who were recycling it (i.e. giving it away to a good home :-)

here they are : carters polythene

What you really want is polyethene, but I couldn't get hold of it....

Once you have the flat tube all you need to do is seal the ends and insert a valve/plug system.

Welding plastic:

Use a domestic iron as the heat source. Use black Teflon baking sheets as the non stick surface. These can be bought in Tesco's and Summerfield etc. for about 3 quid.

Let the iron warm to the cotton setting.

Layer:

• Teflon bake sheet.
• flat tube
• Teflon bake sheet.
• Ironing board.

Then use the iron to weld the end closed. I tilt the iron and use the edge of the bottom plate to make my welds a little thinner.

This method works great. You don't need to be super accurate, and you can trim the weld to a better size (approx. 2cm width) with scissors.

Another option is to turn part of the flat tube back on its self (think turn ups on trousers) then weld along the four layers for a nice thick weld line.

OK. Weld ONE end shut!!

Valve/plug:

The plug is made from micro bore plumbing pieces and some washers.

Then insert your valve/plug:

Cut a small 1cm with hole in the center of the tube. This is for the plug.

Build the outside part of the plug.

Use liberal amounts of glue (wickes home brand glue) between the micro bore and the metal washer. Then while the glue is wet push the plug through the hole in the bladder from the inside.

Add the rubber washer and screw the bottom nut onto the plug. Tighten firmly.

Give the glue ten minutes to dry a bit before turning the bladder inside out so the plug is now positioned correctly.

Weld the open end.

This leaves you with one weld inside the bladder and one outside. Hey. I never said my method was perfect :-)

	Because the polythene I got hold of was old, it had a lot of little tears and holes in it. Even the smallest hole is enough to deflate the bladder very quickly. I checked and welded all of these holes closed. This made the bladder a bit wonkey in places.
	This bladder is approx. 5 foot tall. It holds its shape for about 3 hours before getting soft. I think even soft it would have enough air to hold the rib shape.
	The 'interesting' colour scheme in my bedroom. Slate grey and blood red. Hm. Time for a change :-)

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