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Jay,
That looks right to me. So what I could perhaps do to match things up, so I can match that same loss of air from the high pressure stored air on board while at the surface or submerged, would be to have a flow meter and let out the same volume of air at the same pressure in the storage tanks. But since the pressure in the storage tanks usually will vary in a real world application from one point to the next, there would be a need for further calcs. Or would there be a better way to figure that. I need to know more about how the flow meters work. Do they figure the cubic feet at ambient pressure or cubic feet at the pressure of the tank if it doesn't have a regulator and the valve to let air into the MBT's is after the flow meter or the pressure released from the last regulator the air went thru?
I would just prefer to blow the MBT's near the surface, so I can see what is above me better before I surface. But if one wanted to, add air to them at depth, I guess the goal would be to not add to much air that would just bubble out on the accent. On are smaller subs it's perhaps not really an issue, unless you want to do a number of dives without refilling your high pressure air tanks. I see Karl likes to blow a lot of air into Idabel at great depths, and ride up fast in a sea of bubbles to thrill the passengers, and pops out on the surface. I would be afraid of hitting a boat or mermaid doing that.
Regards,
Szybowski
From: bottomgun@mindspring.com
To: personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST] MBT Venting Options
Date: Thu, 11 Dec 2008 19:57:24 -0500
Brent,
Depends on what depth you are at: 1 cf of ambient air at 132 fsw equals 5 cf at the surface while at 297 fsw that 1 cf of air ambient equals 10 cf on the surface.
R/Jay
Respectfully,
Jay K. Jeffries
Andros Is., Bahamas
As scarce as the truth is, the supply has always been in excess of the demand.
-Josh Billings
From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of Brent Hartwig
Sent: Thursday, December 11, 2008 5:32 PM
To: PSUBSorg
Subject: RE: [PSUBS-MAILIST] MBT Venting Options
Hello Jay,
From time to time I hear guys mention how large MBT's must use up a lot of air as Frank just mentioned. But I always thought it wouldn't be a big deal if they blow them near the surface as you mentioned. Since I've been thinking about large MBT's on my live aboard sub design, I have been thinking about it. Also if they just added a small amount of air at depth, just enough to get them moving towards the surface, that air would keep expanding, and accelerating the sub to the surface. So when they arrive at the surface the MBT's would be partly or completely filled and if to much air was added much of it would bubble out the bottom of the tanks. I would think it would use the same amount of compressed air per cubic foot of air that is in the tanks when they are at the surface. Of course there is the disadvantage of the the free surface affect in the MBT's if they are not divided up enough, and a accent you can't stop unless you vent.
Regards,
Szybowski
From: bottomgun@mindspring.com
To: personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST] MBT Venting Options
Date: Thu, 11 Dec 2008 07:37:05 -0500
As Vance has noted, mushroom valves provide a clean hull solution for venting the MBTs. Note that on larger subs a cover flange is bolted over the mushroom vent valve when on the surface for extended periods of time (i.e. at anchor or at the pier) to protect against air leaks past the valve or an inadvertent venting of the tank thus preventing an unintended sinking of the sub. While submerged, the vent valves are left open to vent off any air that might be leaking from the blow line thus preventing unwanted changes in buoyancy while submerged. When submariners speak of “riding the bubble”, they are referring to the air in the hard trim tank as the MBTs are left completely flooded while submerged. Due to free surface effect and the larger size of the MBTs, rapid adverse changes to trim can occur if an attempt made to use the MBTs for trim control. To conserve of HP air for blowing the tanks, the sub is driven to the surface and the MBTs blown while at or near the surface. The Kingston valves at the bottom of the MBTs may also be closed when on the surface for extended periods.
R/Jay
Respectfully,
Jay K. Jeffries
Andros Is., Bahamas
As scarce as the truth is, the supply has always been in excess of the demand.
-Josh Billings
From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of Brent Hartwig
Sent: Thursday, December 11, 2008 4:49 AM
To: PSUBSorg
Subject: [PSUBS-MAILIST] MBT Venting Options
Dan and Vance,
I like your idea much better then what I currently have Dan. Some time I hope to see Vance's supper secret mushroom vent design. ;)' You guys got me to thinking and I think I might have a even better option that has some elements of both your guys ideas. A remote valve would need to be externally mounted above the highest point on the tanks in order to vent all the air. A large valve would stick out like a sore thumb or odd hood ornament. Then I would have two rods going down at an angle with a small pair of U joints at each end, unless I use two pairs of bevel gears near the conning tower and a short vertical rod between them.
So what I was thinking was to have a piston type valve inside the top area of the MBT's with a 2 to 3 inch opening with a spring around the rod that protrudes vertically below the piston head that has one or more soft O-rings mounted on it. Then to that I'll attach a horizontal arm to the bottom of the vertical rod, which is operated at the other end by a horizontal rod that goes through the pressure hull heads. Then for the front MBT, the rod that is now inside the hull would have a small pair of bevel gears attached to it so you can go towards the port side of the hull. Once at the port side of the hull you have one more pair of bevel gears added so you can run a rod up to the pilot. This way you can have a low profile valve that when you turn the lever to open it, you have to hold it there for a few moments until the tanks have vented, then when you let go they spring shut. I saw a mini version of this piston valve on two inflatable pontoon fishing boats that I needed to let the air out of today.
Another option to operate this type of valve, is to not use the internal actuating assembly I just mentioned, and instead use a pair of Habonim pneumatic valves just inside the heads. One in front and one in the aft. I've found them more commonly on ebay of late at very reasonable prices, from $50 to $150 each. I prefer the Compact 4's but the Compact II's are nice as well.
http://shop.ebay.com/items/?_nkw=habonim&_sacat=0&_fromfsb=&_trksid=m270.l1313&_odkw=hamonim&_osacat=0
Regards,
Szybowski
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] K-250 #118 In Action
Date: Wed, 10 Dec 2008 09:31:22 -0500
From: vbra676539@aol.com
Brent and Dan,
I converted mine to George's reach rod assembly. It works very well, of course, but was a pain in the A to do initially. To tell the truth, I'm not sure I would do it again. You still end up with tubing running from the fairwater tanks. Dan's suggestion of a valve on each tank is better. And use a BIG valve, an inch at the minimum. Waiting for the MBTs to vent is torturous through little tubing. My new ones, pneumatic mushrooms for lack of a better term, will be two inch clear opening. That's about the size on most of the old Hyco boats, and those boys dive quick when the time comes. Having spent a lot of time waiting as the sub wallows around trying to vent, I can tell you with certainty that faster is better.
Vance
-----Original Message-----
From: Dan H. <Jumachine@comcast.net>
To: personal_submersibles@psubs.org
Sent: Wed, 10 Dec 2008 7:46 am
Subject: Re: [PSUBS-MAILIST] K-250 #118 In Action
If I were you I think I would consider filling all the little holes and using the big holes for a standard rotating through hull with linkage to valves mounted directly on top of the MBT's. Or maybe plug all the holes and relocate new through hulls for the same purpose. That way you can eliminate the need for plumbing to the valves and the through hull / valve combination. The over all design may not look as clean but you can solve your valve and corrosion problems and they would vent much better also. I know if I had mine to do it over again, I would have done it that way.
----- Original Message -----
Sent: Tuesday, December 09, 2008 2:46 PM
Subject: RE: [PSUBS-MAILIST] K-250 #118 In Action
Dan,
I don't see any thing like that. It does have a standard snorkel, and you can see if you look carefully the downward turned float part of the snorkel. I also thought it might be an extension of the snorkel but the picture shows the snorkel float as it was when I got it.
Here are the pictures of the conning tower parts being removed.
I really don't like the multi-hole mounting design used for these valves. Dan isn't yours a single hole configuration that you turned some parts for it? Also the exterior top area of the valves holds some water, so that area got some heavy rust pitting I'll have to weld in.
From: Jumachine@comcast.net
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] K-250 #118 In Action
Date: Tue, 9 Dec 2008 08:53:40 -0500
Not much of an idea Brent.
It doesn't happen to have part of a 1950 Chevy pickup rear view mirror still stuck to it, does it?
That's the only thing I can think of.
Do you have a snorkel on it? Most of the K-subs have one but it should be closer the conning tower, unless they added a piece of tubing.
----- Original Message -----
Sent: Tuesday, December 09, 2008 3:06 AM
Subject: [PSUBS-MAILIST] K-250 #118 In Action
I had a couple of pictures that came with my subs documentation thats some of you have not seen. I don't know what the little rod coming out in front of the dome is for.
http://cid-5085d10eb6afe47c.skydrive.live.com/browse.aspx/K-250%20%7C3118%20in%20Action
Regards,
Szybowski
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