Dome/flat port deconstruction

Hi all - I previously came across this post on a DIY dome port, and having a backlog of "stuff I wanted to try" (eg, a custom port) I was curious to better understand how current ports are designed, and hopefully, without having to actually take mine apart hah.   

Does anyone have pictures (or hand drawings) from deconstructed dome/flat ports?  Having a closer look at my Subal flat port, it does look to be (see my mspaint drawing):

- flat edged glass inserted from "outside"                           (Saga lists it as "BK -7 8mm" thick for one of their macro ports, how thick are dome ports usually? guessing this can be calculated for depths)
- some form of o-ring                                                              (is this a standard "round" o ring?) 
- a inner diameter smaller than the water facing side       (to make a lip/edge that the glass "sits" on) 

This appears to be the same idea for the Nauticam flat port that I have too, as best I can tell.  And also, what it looks like for my zen mini dome (for Subal). 

If the above is accurate, do you just "pop" these out via pushing from the inside out?  I get this is a "do at your own risk" type of thing, I just wanted to ask in case anyone already has some old ports pulled apart (or super cheap, junked ports for sale).  

View archived post in: DIY 4 inch Dome build

The Subal flat ports have a flat glass window about 8 mm thick; the glass has one right angle edge and one beveled edge on its front or outer surface, held in place and sealed by one O ring.  The inner surface of the port has a built-in rim for the inner edge of the glass to rest on, and a ~3 mm wide groove for the O-ring. The O ring is 2.6 mm thick, its inner diameter is the same as the glass outer diameter.

The Subal dome ports use the same O-ring arrangement.

Removal: The glass is removed by pressing it out with a blunt object.

Installation: 1. The O ring is first lightly lubed w silicone grease, as is the outer edge of the glass and the groove and inner surface of the port. 
2.The glass is installed with the beveled edge aimed to the front.
3.The O ring is laid between the port and the beveled glass, and pushed  into the O-ring groove at 12 and 6 o'clock with a narrow blunt object, for for a length of 15 mm or so, then is pushed into the groove at 3 and 9 o'clock, followed by the remaining O ring. =

Thanks Eli - should of figured you would have some insight and experience here! 

Here's a SeaFrogs 8-inch dome - I got a nasty scratch on the front and didn't have access to polishing tools, so replaced it (SeaFrogs sells replacement domes for $80 + shipping).

The acrylic dome is clamped on using a plastic ring held by ten screws:

Here the ring has been removed.

The shade is retained by the same ring, so now it can be lifted out:

Underneath the glass is a simple o-ring in a shallow groove:

That's a very neat arrangement and very maintenance friendly!

Good documentation, Thanks. I see there are glass parts also available for service... were you tempted to try a glass replacement? Obviously the glass doesn't have the drill pattern so the pressure application would not be an exact match. I would love to see the glass package in a 'take-apart' set of images like yours.

14 hours ago, polyroly said:

Good documentation, Thanks. I see there are glass parts also available for service... were you tempted to try a glass replacement? Obviously the glass doesn't have the drill pattern so the pressure application would not be an exact match. I would love to see the glass package in a 'take-apart' set of images like yours.

If you're referring to my post with a SeaFrogs dome, they do not offer a glass dome in 8-inch size; only in 6-inch. I do not have personal experience with that particular model.