Finishes for the vac bed;
 
Close the bag:
To seal things up I went super simple. Simple close
Simple close 
Used:
- Rubber      cord 
- Plastic      track (found in wiring section of the hardware store)  
 
This works by simply pressing the envelope into the channel of the track with the rubber cord.
 
I have in mind a side opening bag with a magnetic seal but this is far to complex for a first attempt at a vac bed.
 
One way valve:
 All   valve parts The purpose of the one way valve is so that one can turn off the vacuum pump (this case a shop-vac) and have the vacuum inside the bed remain. A crude valve is a flap of rubber that sits on top of an airway allowing air to pass in only one direction. This works because in the flow direction air can easily pass beneath the flap. In the stop direction air will push the flap closed blocking the airway.
All   valve parts The purpose of the one way valve is so that one can turn off the vacuum pump (this case a shop-vac) and have the vacuum inside the bed remain. A crude valve is a flap of rubber that sits on top of an airway allowing air to pass in only one direction. This works because in the flow direction air can easily pass beneath the flap. In the stop direction air will push the flap closed blocking the airway.
 
This ended up having two solutions. First was a double flap valve that I made myself. Second and far more effective was to use the exhaust valve from the mask (see below for mask)
 
Plan A: Plan A valve
Plan A valve
- cut      two circular pieces of acrylic to fit inside a pipe coupling. 
- drill      a centre hole to mount the flap
- drill a      number of larger holes for air flow.
- Cut a      circular piece of rubber and put a hole in the centre
- Mount the      rubber flap on the acrylic (I used a Chicago      screw) 
- Be sure      the screw is tight enough to hold the flap in place but not squeezing the      rubber. If squeezed the rubber will pull away from the acrylic and not      seal. 
- Use a      drop of thread locker or super glue to prevent the screw from coming apart 
- Mount your      new valve inside a pipe coupling and seal it (bit of silicone calk woks      great here) 
 
Problems encountered with Plan A:
- Thick rubber      does not close to seal. (fixed by switching to thin latex)
- Acrylic      does not dry seal well (fixed by using some calk) 
- Screw head      and flap lost to vacume (fixed by letting thread locker cure or use      superglue) (yes I did think ahead on this one just was not patient enough)
- Flap pulls      away from acrylic (fixed by making sure lose fit; do not stretch rubber      flap)
 
Plan B: Plan B valve
Plan B valve
- Use exhaust      assembly from the mask
- This happened      to fit perfectly in the end of the 2’’ pvc pipe
- Stick this      in the end of your tee and add a small bit of pipe to hold it there and      done. 
- Can mod      this by adding rubber O ring to improve seal or make a unit with a      coupling and some pipe bits calk and glue for good seal. 
 
Breathing rig.
See post: http://arcnet01.com/the-lab/2010/8/4/vac-bed-breathing-rig.html