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Re: [PSUBS-MAILIST] Hatch pressure
Hi Alan, the flood vale is much to big for this use.
But to put the flood vale on a position over the waterline
and get it inside with a hose down to the bilge is anyway wise..
vbr Carsten
"Alan James" <alanjames@xtra.co.nz> schrieb:
> Thanks Hugh,
> I'm now thinking of putting my emergency flood valve up high in the sub so I can use it to
> equalize pressure as well.
> I bought a $45- video camera that doesn't go, with the idea of using its 33x optical zoom lense.
> The thought of bird watching did come into mind. You wouldn't make any money as a
> Paparazzi in NZ though. Our only actor of note is Gollum.
> Alan
>
> ----- Original Message -----
> From: Hugh Fulton
> To: personal_submersibles@psubs.org
> Sent: Thursday, February 18, 2010 1:42 PM
> Subject: RE: [PSUBS-MAILIST] Hatch pressure
>
>
> Alan, PVHO says you should allow for 8psi internal pressure. Relief valves have a cracking pressure so you will get at least 2 psi from that for cheap ones. More expensive - better characteristics. If you are going to have air for BIBS buoyancy etc you have to allow for leakage or failure. Hugh
>
>
>
>
>
> From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of Alan James
> Sent: Thursday, 18 February 2010 10:57 a.m.
> To: personal_submersibles@psubs.org
> Subject: Re: [PSUBS-MAILIST] Hatch pressure
>
>
>
> Thanks Carsten & Alec, thats great information.
>
> I'll add a pressure equalizing valve. If I had a manually operated valve it may
>
> cause problems If I forgot to open it.
>
> I'm not building a K250, the dome on order is being blown 550mm O/D & from 35mm
>
> thick acrylic. I've asked them to trim the flange to 15mm wide & 15mm thick & will have
>
> a retaining ring holding it down.
>
> I was concerned that maybe I'd gone a bit thin to support the upward lifting force of the
>
> dome but it calculates out to about 1 pound for every inch of flange just at below the surface.
>
> Thats providing as Carsten said, the barametric pressure isn't higher than outside the sub.
>
> Alan
>
>
>
> ----- Original Message -----
>
> From: Smyth, Alec
>
> To: personal_submersibles@psubs.org
>
> Sent: Thursday, February 18, 2010 9:24 AM
>
> Subject: RE: [PSUBS-MAILIST] Hatch pressure
>
>
>
> Hi Alan,
>
>
>
> If it's a K-250 you're building, here's your other data point. I just weighed the hatch, and it's 23.5 kg. So it would be 6.5 kg buoyant.
>
>
>
> Alec
>
>
>
>
>
>
>
>
> ----------------------------------------------------------------------------
>
> From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of Alan James
> Sent: Wednesday, February 17, 2010 2:47 PM
> To: personal_submersibles@psubs.org
> Subject: Re: [PSUBS-MAILIST] Hatch pressure
>
> Hi thanks people,
>
> I was having trouble understanding this. I just put plastic wrap loosly
>
> over the top of a glass & submerged it. Some of the wrap bulged up
>
> but you could push parts down below the level of the top of the glass.
>
> ( This proves you right )
>
> I am going with a dome hatch, but haven't designed the locking mechanism yet.
>
> The dome will be close to 30kg of boyancy before its mounted.
>
> Alan
>
>
>
> ----- Original Message -----
>
> From: Smyth, Alec
>
> To: personal_submersibles@psubs.org
>
> Sent: Thursday, February 18, 2010 6:51 AM
>
> Subject: RE: [PSUBS-MAILIST] Hatch pressure
>
>
>
> First weigh the hatch in air. Then calculate the displacement of the hatch, which is the weight of the water that would fill an equivalent volume. Subtract the displacement from the weight. If you get a negative number, the hatch will tend to "float" as you describe. I doubt very much that would be the case for any conventional elliptical steel hatch. In the case of an acrylic dome hatch like the K-250, I'd recommend doing the math because I'm less sure of the outcome -- those might be slightly buoyant.
>
>
>
> Alec
>
>
>
>
> The contents of this e-mail are intended for the named addressee only. It contains information that may be confidential. Unless you are the named addressee or an authorized designee, you may not copy or use it, or disclose it to anyone else. If you received it in error please notify us immediately and then destroy it.
>
> From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of Alan James
> Sent: Wednesday, February 17, 2010 11:50 AM
> To: personal_submersibles@psubs.org
> Subject: [PSUBS-MAILIST] Hatch pressure
>
> Hi all,
>
> I've brought up this subject before, but are tackling it from a differant angle.
>
> How much pressure is exerted upward on a hatch at the moment where the submarine
>
> just submerges below the water? This is the point of most force before external water
>
> pressure helps close it.
>
> If you took your submarine, filled it with water & hung it upside down, would this be the
>
> same amount of force, or close to it.
>
> In wich case if you have a design like Franks flying saucer that angles up to the hatch,
>
> you'd have a lot more force acting upward on the hatch than a K250 where the lifting force
>
> would be spread more evenly along the hull.
>
> Am I thinking right?
>
> Alan
>
>
>
>
>
>
>
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