Re: [PSUBS-MAILIST] what is the diference k250- k600

[MerlinSub@t-online.de (Carsten Standfuß)]

Ian Roxborough schrieb:
> 
> On Sun, 12 May 2002 23:48:50 -0400
> Dan h <machine@epix.net> wrote:
> > A K-350 and a K-600 are almost alike except for the hull thickness.  A
> > K-350 has a .250 inch thick hull with .375 inch thick end caps.  I
> > believe the K-600 has a .375 inch thick hull and .5 inch end caps.
> > Other than that they are the same.
> 
> I find it interesting that the end caps are thicker than
> the hull.   I had thought that the end cap dome shape would
> provide better resistance to pressure than the cylinder body
> and hence be constructed of material the same thinkness or
> even thinner.  Maybe this is to compensate for the ribs in
> the hull.
> 
> Maybe there is another reason for the differences.

Hi Ian, the normal industrial endcaps are designed for tanks. 
Thats means for pressure inside.  (= Pressure =)
(So thats is another problem with this dammed propan-tanks..)

If you press them from outside they react like in the stress analysis 
picture shown at http://www.psubs.org/psub_pic/cssx4.html 
(one of the last 3 pictures). 

For example the force to one endcap at test deep (320 meter)
of CSSX is : 2,5 x 2,5 x 3,1415/4  = Area 4,9 m2 with 
1t per 1m dive deep = 4,9 x 1 x 320 = 1568 metric tons.. 

A Endcap on a 600 feet (183 m) small sub say diameter 0,7 m (2,3 feet)
has : 0,7 x 0,7 x 3,1415/4 x 183 = 70 metric tons pressure
on it.  

Means the stern endcap of CSSX want to go forward with a pressure 
of 1568 tons - and the forward endcap want to meet the stern endcap with 
the same force. I am just between them :-) . Also the connection between 
the endcaps and the cylinder has to be checked carefully - one reason 
that the standard endcaps comes with a short cylinder part - is to get
the 
connecting welding out of this  area.. all this force turns from the big 
curve of the encdcap to the hard curve - and than to the cylinder. 
The point between the big curve and the hard curve is the weak point. 

Halfball endcaps are much better - unfortunatly not so easy available 
and more expensive. 

Another good solution is to have a smaller diameter endcap, than a conus
part, than the cylinder, than the forward conus part, than the dome or 
forward endcap. 

One way is to go just with stronger tickness in the endcaps - the other 
way will be just to turn the endcaps - so the curved side is shown 
to the inside of the cylinder.  pressure )=( pressure
The diverchamber bulkhead endcap on the drawing CSSX goes this way
- and has no stiffteners. For the same reason the diver exit hatch 
is curved to the inside of the pressure hull. 

On CSSX we build stiffteners inside the standard endcaps - but this is 
not according to the most classification rules (the endcap have to
breath..
- means to move under pressure free some milimeters) and for this reason 
need a special FE-analysis to go this way - because you generate some 
very local stress. On CSSX a very local stress point will be the main 
propeller shaft which prevent the stern endcap from breathing. 

On CSSX the Endcaps of the mainhull gives the limit for the dive deep. 
This boat get some inch shorter under full load pressure..  

Carsten

> 
> Anybody have any insight into this?
> 
> Thanks,
>   Ian.