RE: [PSUBS-MAILIST] MBT Vents

Brian,

On my boat I tig welded a "Thread-O-Let" to both sides of the hull. These are heavy duty pipe fitting that a beveled for welding and have NPT pipe thread. I used this for all my hydraulic and electrical penetrations. In addition, for electrical penetrators, I used a SS pipe plug and drill and tapped the straight thread. These plugs also are machined smooth for the o-ring to seat against.

While I have not had any trouble to date, if I had to do it over again, I would go the route of machining a removable SS disk and receptacle with an O-ring face seal like what is used in the Deepworker. The SS reciprocal is welded into the hull like a viewport seat. I would then try and cluster thru hulls into these disk. This gives you so much flexibility. Off the shelf electrical penetrators with their o-ring seal will land against the SS disk. If you have unused penetrations, you install a plug with the same o-ring seal. Swagelok makes a line a fittings that will seal with an o-ring using straight thread. A an example, for a 1/4 tubing, their model SS-400-6ST ( SAE/MS straight thread, 9/16-18) could be used for air or O2 penetrations or a larger version of this for hydraulic penetrations.

It seems like a lot more work but it is worth to prevent leaks, particularly for high pressure air or O2 and to easily modify hull penetrations if latter on you want to add more lights, or an articulated arm, or underwater communications ...;.

An interesting thread some time would be "What worked and what I would do differently on my second boat, lessons learned"!

Cliff