Hello!
I employ saddle tanks on my sub Explorer. I don't have a diagram readily available but here goes a rough description of the vent system:
Each tank is a cylinder with flat endcaps over which is a hemispherical fairing. The opening at the bottom of each tank is a 4" diam "chimney" that extends down about 5". There are fore and aft vents, each at the 12 o'clock position on the interior surface of the flat endcaps.
I fabricated simple spring-loaded valves that are basically silicone stoppers in a tube with a sealing seat. The valves are normally held closed by the springs. Actuating arms run from each valve to a central pivot point inside the tank, then another arm extends down through the chimney to a lever arm welded to a rotating through-hull.
Inside the cabin are levers port and starboard. Moving the levers causes the actuating arms to pull the valves open, etc. The fairings have holes to let the bubbles out. Never had airlocks, and the chimneys allow for some serious fore-aft pitch without spilling air.
Confused yet? Sorry for the wordy mess. Let me know if you need a sketch. I'll scan something and email to you.
Best,
Alan
--- On Thu, 2/3/11, James Frankland <jamesf@guernseysubmarine.com> wrote:
From: James Frankland <jamesf@guernseysubmarine.com>
Subject: [PSUBS-MAILIST] Saddle Tank
Vents
To: personal_submersibles@psubs.org
Date: Thursday, February 3, 2011, 12:17 PM
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Hi All,
I'm nearly done with my hatch locking mechanisms and will be starting on the main tank assembly very soon.
http://www.guernseysubmarine.com/Extended_files/Page6497.htm
I have made the sub as per the plans to take the standard K350 main tank assembly. I was intending to make part of the front tank contain "viewports" so as to not destroy the view from my new dome. Similar to Doug Privitts sub. But im really very tempted to change the design to use saddle tanks instead. This would be for 2 reasons, first it would not obstruct my front dome and second, the tanks could be completely enclosed (appart from the holes at the bottom) which would make the boat a lot more resistant to accidental flooding of the tanks. The waters around here can be a little bit choppy even on nice days, so i'd prefer the stability of completely enclosed tanks.
Anyway, the problem is that i have the vents and high pressure air in the "standard" places. OK, the HP air wouldnt be too difficult to route to a saddle tank but the vents are not as easy. i only have 1 vent per tank and im pretty sure i should have the ability to vent either front or back or the tanks. So if the subs longitudinal trim changed and it tipped forward or back. i'd still be able to complete the vent.
Option 1 is to put a vent pipe from the back of 1 tank, passing along the top to the front of the tank where it joins to a second vent hole and then combined, they go to my valve. I dont think this will work as im sure if it tipped the wrong way, i'd get an airlock even though there was a vent there.
Option 2 is to pipe both tanks front vents together to 1 valve and similarily both tanks rear vents together to the other valve. Even so, with the position of the rear vents relative to the valve, i still may get airlocks.
Sorry its a bit difficult to understand written down, i should have drawn a picture but im at work, just thinking about what to do...
Any suggestions? What have other people done for saddle tank vents?
Kind Regards
James
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