On this momentous day in 1986, the Space Shuttle Challenger broke apart 73 seconds after launch, leading to the deaths of all seven crew members. A faulty o-ring, known about beforehand, caused a breach, allowing pressurized burning gas to reach the outside, which caused the overall structure to fail. On this day in 2016, I'm choosing the o-rings which will seal our endcaps against the water outside.
While there are many materials for specific o-ring purposes, two materials stand out as multipurpose and extremely common-- BUNA-N nitrile and silicon. BUNA-N is very cheap and very available. However, it has less resistance to water abrasion and petroleum products than silicon. Given that we're operating in the water surrounding NYC, it's safe to say we're going with the silicon.
We'll place two o-rings on the flange adapter, which will seal against the inside of the hull. A third o-ring rests in the groove on the face of the flange adaptor, sealing against the endcap when it's screwed down.
This is all I know about o-rings. I write this post with the hope that some o-ring expert, sleuthing the internet for o-ring related blog posts, will happen upon this one and tell me that my logic and decisions regarding o-rings are flawed and that disaster is imminent. Please, if you're out there, take me to o-ring school. Let this not serve as a "last words" before Rowboat1 careens to the bottom of the Diamond Reef.