The VacSack as you call it (I like that better than Vacuum Bed, is 1 meter wide by 2 meter long although I wish I had made it a little longer. The sack is permanently sealed on both long sides and the bottom with duct tape. I made this air tight by sealing it once then folding this over and sealing it again.

You have to wriggle into the sack from the top opening. The sack it's self is about 18" longer than the tube frame. This excess is tucked inside first and then rolled up from inside, with a spare piece of tube cut to the inside width of the sack. I have attached a bitmap drawing which attempts to show what I mean.

I have not experienced any problems with the pressure build up as once it reaches its maximum it simply remains constant. And after all isn't the pressure part of the fun!!

Yes the noise could be a problem but I have a long hose which allows the vacuum to be in another room. However even when you cant hear the vacuum there is always some noise of air rushing. Ear plugs are good hear and add to the experience.

There are of course some warnings:-

The sack works well with either a breathing tube or a stretchy collar (I made this by tapeing a piece of latex over a large square hole. A round hole cut in the latex about half my collar size means that it makes an air tight seal once my head has been stuck through). If you go for the breathing tube then make sure it is of the ridged divers snorkel type. The mouth piece can be firmly gripped between the teeth and is then held in place by the sack meaning you can't use the tube as a way to let air in and thus escape. More importantly the soft rubber type of mouth piece may tend to crush as the sack contracts.

Domestic vacuum cleaner motors are designed to be cooled by the air flow from the hose. As when the sack is deflated there is no more air flow, then there is a real danger of the motor over heating if run for a long period. I really don't know how long this would be but I have had no problems with periods of 15 to 20 minuets. One possible solution I have considered would be to remove the motor from the vacuum cleaner. Discarding the cleaner the motor would be remounted in a new box with an additional cooling fan, perhaps the type used to cool computer and similar cabinets obtainable from the radio spares shop. This fan when arranged to blow across the motor should keep it cool.

Apart from my initial trial which I described before, I have carried out all my tests with a remote control. All this consists of is a relay to switch on and off the power. The relay is only 12 volts and is operated by a push button on a long length of cable so that I can safely take it inside the sack with me.

Lastly, I don't know how strong the latex sacks are, but a big let down of the plastic sack is that it can be fairly easily punctured by fingers. I solved this by fixing sleeves inside the sack. the sleeves are about 12" long, made of the same plastic and sized to be a lose fit. The arms can be easily slipped in and out normally but when the sack is deflated they contract just the same as the rest. Hand sized hard plastic pads fixed into the sleeves ensure that the hands are help firmly palms down and so totally incapable of damaging the sack.

Any way that's enough prattling for now. I also have some Vacuum Bed pictures. perhaps we could trade or something. I will have a look at how well they will zip up so that I can e-mail them to you.

Hoping that you can translate my garble well enough to make a functional VacSack.
Please keep me posted if you do.
Regards
Jack