[PSUBS-MAILIST] Stability & Buoyancy

[Alan]

Thanks Carsten,
I hadn't thought of the water in a sail.
Good picture.
Alan

Sent from my iPad

On 30/11/2013, at 11:51 PM, " " <MerlinSub at t-online.de> wrote:

> Hi Alan, 
> 
> additional the sub can dynamic unstable during surfacing.
>  
> There is a lot of water in the free flooding open sail.
> If you surface fast and with to small opening in the 
> bottom of the free flooding sail the extra weight can 
> move the CG so high that the sub tends to get heavy 
> side angles during surfacing until the water rush out. 
> 
> The picture 8382a shows the higher waterlevel during surfacing 
> in the sail and the MBT sadlle tanks still under water 
> but for this sub the extra weight was not critical.
> 
> But on a military one with there tons of 
> water in the sail during a fast emergency surfacing 
> it can be a problem. 
> 
> By the way Euronaut has no Kingston valve without any problem
> and a positve GB alltimes greater than 2". 
> On dive station or surfaced. 
> And great openings in the bottom of the sail. 
> 
> Boats without Kingston valve tends to lost some 
> bouancy during rough sea. The tanks and the seastage
> work like a air pump and some water enter the tanks.
> 
> On the otherside a boat with Kingston and a 
> compressed air blow out system can blow away the 
> tanks very fast if you forget to open the Kingstons 
> during blowing the tanks or have a air leak 
> in the in the pipe to the tanks.
> 
> vbr Carsten 
>   
> 
> "Alan James" <alanlindsayjames at yahoo.com> schrieb:
> Hi everyone,
> While reading through some background info for the G.L.
> certification document, I came across this link with a good
> explanation of stability & buoyancy
> http://maritime.org/doc/fleetsub/chap5.htm
> There is a phenomena described, where submarines can be 
> unstable to the point of turning over during the transition from
> surface to diving & vice versa.
> This has to do with the centre of buoyancy moving upward past
> the centre of gravity. As it approaches the centre of gravity the
> submarine is at it's most vulnerable point.
> This would be different for individual designs & a worry if
> you dropped your emergency drop weight.
> I had been told by a pilot that he never stuffed around while
> descending & liked to drop as quick as he could.
> I didn't have a full understanding of this & thought there may
> be others in the same boat.
> Regards Alan
> 
>  
> 
> -- 
> 
> Carsten Standfuß
> Dipl.Ing.Schiffbau @ Meerestechnik
> Heinrich Reck Str.12A
> 18211 Admannshagen
> 
> 0172 8464 420
> WWW.Euronaut.org
> Carsten at euronaut.org
> <IMG_8382a.jpg>
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