[PSUBS-MAILIST] Sub Launch at Harbor

Wed Aug 26 13:26:07 EDT 2020

 If you are ballasted correctly for submerged operations so that the boat stabilizes to a horizontal attitude when the MBT is completely flooded, then  reducing the orifice size on the forward MBT vent opening will reduce this pitching moment when submerging.  On my boat, I made up a series of pipe plugs that would screw into my forward and aft MBT vent openings.  I then did a series of MBT flood test to see which orifice sizes nulled out this pitching moment.  It worked great.  The other way to solve the  problem is what Alec did my installing Hugh Fulton's MBT vent valves which have a very large opening.  In this case the boat submerges so fast there is no time for this pitching moment to act on the boat.
Best

    On Wednesday, August 26, 2020, 12:13:35 PM CDT, Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  

 Cliff,   I think that would only delay the inevitable , I think I would still be at the same angle.
Brian

--- personal_submersibles at psubs.org wrote:

From: Cliff Redus via Personal_Submersibles <personal_submersibles at psubs.org>
To: Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org>
Subject: Re: [PSUBS-MAILIST] Sub Launch at Harbor
Date: Wed, 26 Aug 2020 16:44:48 +0000 (UTC)

 Congratulations on the successful surface maneuvering test and dive.  You might want to experiment with different orifice inserts in the forward MBT vent opening to see if you can reduce the pitching moment when flooding by reducing the flowrate of air out of this tank.  I use this technique on the R300 for the same purpose.
Cliff

    On Wednesday, August 26, 2020, 11:27:53 AM CDT, Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  

 Yeah, that's my super secret emergency dive procedure !
Brian

--- personal_submersibles at psubs.org wrote:

From: Alec Smyth via Personal_Submersibles <personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
Subject: Re: [PSUBS-MAILIST] Sub Launch at Harbor
Date: Wed, 26 Aug 2020 12:03:20 -0400

Hey, that wasn't a launch, it was a dive!! Congrats! When the bow went down like that, did it rest on the bottom? That was a pretty radical angle, and the speed of it makes me think you had a massive free surface displacement in the MBT. Normally that induces lateral instability, but due to the length of your boat in this case it would be longitudinal instability.
Thanks,Alec
On Wed, Aug 26, 2020 at 10:44 AM Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Hi All,                 Have a couple of videos from down at the harbor:

https://www.youtube.com/watch?v=iERfLiioGJA&t=628s

https://www.youtube.com/watch?v=OGiAqeocq4s

Cheers,
Brian

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