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Re: [PSUBS-MAILIST] Response from Hunley archaeologist.
Hi Ian,
I always believed Hunley was 1 ATM.
Close the hatch and the cabin is at 1 ATM. Open a
seacock to the ballast tanks and water flows in.
Remember that the inlet for the flood valves are near
the bottom of the Hunley so there is a pressure
differential between cabin pressure and water
pressure. Water will come in.
How much the increased the cabin pressure gets from
air displaced by the ballast water I have no idea. I
will check Regan's book to see if there are any
dimensions.
Regards,
Ray
--- irox <irox@ix.netcom.com> wrote:
>
> I still don't see any reason that the Hunley is
> ambient. If it was ambient it couldn't
> dive without pressure compensation, this does not
> appear to the the case.
>
> Unless some piece of information is missing, the
> Hunley is 1ATM. The crew where
> always subjected to surface pressure (give or take
> the very small amount of
> pressure increase from the ballast tanks venting
> into the cabin). Once submerged,
> it doesn't matter what depth the Hunley is at, the
> crew will be under the same
> pressure, if it was ambient, the pressure the crew
> would be experiencing would
> be the same as the external water pressure.
>
> If somebody can supply my the internal volume of the
> Hunley and the volume of
> water used to dive, I will calculate the internal
> pressure after diving.
>
> Ian.
>
> -----Original Message-----
> From: Akins <lakins1@tampabay.rr.com>
> Sent: Jun 9, 2005 3:00 PM
> To: personal_submersibles@psubs.org
> Subject: [PSUBS-MAILIST] Response from Hunley
> archaeologist.
>
> Hi forum.
>
> I had contacted the Hunley organization and they
> told me they would have one of their archaeologists
> get back with me.
>
> He did today. From what he says, it seems the Hunley
> was technically ambient but not always slightly
> positively buoyant like the Holland was.
>
> It seems the Hunley's weight acted as a giant hand
> trying to push her under and just a small amount of
> water let into her ballast tanks would submerge her.
>
> Here is what he had to say about the Hunley. Bill
> Akins.
>
>
> Dear Sir,
>
> Thanks for your interest in the H.L. Hunley
> submarine ....and your questions. Hopefully I can
> answer them.
>
> "My information is that the Hunley had open top
> (bathtub style) ballast tanks that were open to the
> hull interior. My information is that the Hunley did
> not carry compressed air tanks."
>
> Yes, the submarine had no compressed air and the
> ballast tanks were open to the central crew
> compartment. However, I should clarify that the
> ballast tanks were in the interior of the submarine,
> separated from the crew compartment only by a thin
> bulkhead.
>
> "This would make the Hunley like an upside down
> glass trying to submerge without losing any air. The
> only way the Hunley could submerge in my mind, would
> be for the Hunley to use her forward motion and dive
> planes to force her underwater, is this correct?
> Then once underwater the superior water pressure
> would force water into the opened valve of the open
> top ballast tanks and compress the atmosphere
> in the Hunley."
>
> Well, not exactly. I think you are looking at this
> the wrong way. The Hunley would have been
> positively buoyant when the ballast tanks were
> empty, although just barely. We have a good
> indication that she was very easy to swamp -
> probably as a result of low freeboard and the fact
> that she was quite heavy. While she did in fact
> carry all of her air with her, it is the water in
> the ballast tanks that acts as the ballast for the
> submarine and determines her buoyancy. Air
> compresses, water does not. By opening the valves
> and allowing water into the ballast tanks, the sub
> would become heavy enough to overcome the buoyancy
> of the air "bubble" and sink. The air from the
> ballast tanks would be simply compressed slightly.
> In order to surface, the crew would pump out the
> water by means of two hand pumps, decreasing the
> weight and allowing her to rise. With minimal air
> pressure, water could always be let into the ballast
> tanks or pumped out as needed, but the key factor
> was alw!
> ays the WEIGHT of the submarine. In modern
> submarines, I believe compressed air is used to
> force the water out of the ballast tanks, but the
> air is only functioning like the pumps on the
> Hunley. It is still the water or lack thereof in
> the ballast tanks that determines whether the sub
> sinks or rises.
>
> "Also, has anyone done an analysis of how stable or
> unstable the Hunley would be if she dropped her keel
> weight to return to the surface, and were there any
> indications of that trying to be done inside the
> Hunley artifact?"
>
> No and no. I don't think they ever actually removed
> the keel weights while under water. I believe it
> was designed to be an emergency assent option only.
> We found no indication that they attempted to
> release the keel blocks on her final mission.
>
> I hope this helps answer some of the questions you
> had.
>
> Sincerely,
>
> Michael P. Scafuri
> *********************
> Michael P. Scafuri
> Archaeologist
> H.L. Hunley Project
> Warren Lasch Conservation Center
> P.O. Box 21600
> Charleston, SC 29413
>
>
>
>
>
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