installing si-tech p-valve & cutting big hole

[hmoffatt]

Hi, I've just received my Si-Tech P-Valve which I want to install in my membrane drysuit. Two questions;

1. The required hole is enormous! Over 55mm (over 2 inches). Start with a punch, enlarge with knife/scissors? Some other technique? Fortunately the valve port covers it so it seems the dimensions are not too critical?

2. Appears that after I cut the hole, I just glue the valve port on the top of the suit, screw the two halves of the valve body together through the suit with the port in the middle, and I'm done....? Only the port is glued down?

The manual was not very good. http://www.sitech.se/files/documents/products/11000/urindumpsmanual a4 081006.pdf

thanks
Hamish

 

[dave4868]

Never done that job myself, but I do have Steven Lindblom's "Wetsuit and Drysuit Maintenance and Repair", one of several excellent books from Vance Harlow's Airspeed Press.

WETSUIT AND DRYSUIT MAINTENANCE AND REPAIR by Steven Lindblom

Airspeed Press Homepage - Books For Serious Divers

On pages 157 & 158, regarding "Installing a P-Valve", the author suggests making a clean-edged hole with a sharp punch (for smaller holes, though). As a less desirable method, he also referred to cutting the hole with a knife and then cauterizing any nicked edges with a soldering iron to reduce the chance or tears developing. Another alternative mentioned is to heat up a thin-walled metal tubing to cut and cauterize the hole at the same time, being very careful not to set fire to the fabric..... :shocked2:

I've cut 1-2" holes in a variety of fabric or rubber materials using a hole saw that was modified by removing all the teeth and grinding a sharp beveled edge, angled outward, so the cutting edge is the largest diameter. Either hand-turned or drill-turned, it makes a very clean hole when the material is backed with a smooth, semi-hard flat surface, like a polyethylene or hardwood cutting board.

You may do just as well by modifying a thin-walled tin fruit juice can or other tube-like metal object, and then hand-turning to cut the fabric, perhaps following up with a soldering iron to cauterize any nicks.

On a thin membrane suit, I would think that very sharp surgical scissors would work well, too. I use those to cut latex seals with no nicks.

As to your other question, yes, the outer port is glued and sealed with silicone (RTV) or Aquaseal.

I suggest that you apply the sealant to the underside (fabric side) of the outer port, then only lightly torque the two halves of the fitting together, perhaps half a turn from fully seated, then waiting a day for the sealant to fully cure before fully tightening that last half-turn. In so doing, you will have effectively created a slightly thicker gasket which will be compressed and therefore less likely to leak.

Dave C

 

[bronk]

Wow that is a big hole. I just installed a Halcyon valve in a my suit a couple of weeks ago (TLS350). I used a 3/4" sharpened copper pipe to start against a maple board in the leg. However witht he thick double material for the knee patches (area where the valve was installed), I could not get a complete hole. I then finished up with asharp xacto knife. This worked very well. Aquaseal sealed it up and no leaks.

 

[hmoffatt]

Thanks for the comments. I did the work today and it seems good (I've pumped the suit full of air and it's holding)..

My suit is actually a bilam where the outer layer just joins with the inner with some velcro loops at the wrists and neck. So I figured out that I needed to stick the valve port to the inner layer because it's the water-proof one. Then I made a hole in the outer layer just for the valve to stick through...

The other valves (inflator and exhaust) appear to be stitched through both layers. I might yet velcro or glue the layers together around the p-valve, will see how it goes.

I used the hot knife to cut the inner layer (very thin), and scissors on the outer layer. Glued with Selleys Urethane Bond (Australian brand, water-proof and suggested for wetsuit repair etc).

Hamish

 

[crpntr133]

If you had to cut a 2" hole for a p-valve I would hate to think of the condom cath that you would need. Walk proudly my friend, walk proudly.

 

[hmoffatt]

Argh, the glue didn't bond the valve port down much at all and I got very wet on the first test dive...

 

[Bob3]

You really need to do the proper surface prep to the valve port:

Be SURE to "degrease, sand/scuff and degrease again w/ a clean rag."

The port is made out of chloroprene, same stuff as neoprene wetsuit material so plain old wetsuit cement can be used.
Preferred degreaser is toluene / toluol but MEK or alcohol will also work.
Most other commonly used drysuit cement / glue will also work.
Not recommended for glue is the silicone bathtub caulk / RTV sealant, unless the prior valve was boogered on with it before because nothing much will want to stick to it.

Hopefully you can re-activate the glue with solvent - I'm not familiar with that glue though.
Just keep the silicone bathtub caulk away from it & it won't get messed up TOO badly.

 

[Cave Diver]

If you had to cut a 2" hole for a p-valve I would hate to think of the condom cath that you would need. Walk proudly my friend, walk proudly.

 

[dave4868]

You really need to do the proper surface prep to the valve port:

Hopefully you can re-activate the glue with solvent - I'm not familiar with that glue though.
Just keep the silicone bathtub caulk away from it & it won't get messed up TOO badly.

Bob, I'm curious about the quoted instructions, which I assume are from SI TECH.

Does this SI TECH pee valve screw together like other exhaust or inflator valves which just need a sealant under the outer flanges or is this one different?

The valves on my DUI drysuit were installed at the factory with something similar to silicone RTV to create a gasket-type seal around the hole. That kind of seal allows the valve to be removed and re-installed later, usually without further glueing or sealing, which is nice.

Can you explain why using RTV sealant would be a problem with this SI TECH pee valve? Do the two halves of the valves connect together less firmly?

TIA.

Dave C

 

[hmoffatt]

Bob, I'm curious about the quoted instructions, which I assume are from SI TECH.

Does this SI TECH pee valve screw together like other exhaust or inflator valves which just need a sealant under the outer flanges or is this one different?

No it seems to be just as you describe.. here are the instructions fyi:

http://www.sitech.se/files/documents/products/11000/urindumpsmanual a4 081006.pdf

I never throught of silicone sealant being an adhesive though..