Re: [PSUBS-MAILIST] elliptical heads/ Git Kraken

[Jon Wallace <jonw@psubs.org>]

Frank, Dan,

Here's a reference to a document I found (about the ONLY reference I 
have found) that talks about stiffening rings for elliptical heads.  
Unfortunately it deals with internal pressure (muffler for a tank gun) 
rather than external pressure, but hopefully there is something useful 
in it.

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA241063&Location=U2&doc=GetTRDoc.pdf

Also, you might want to talk to Greg Cottrel since he has a similar 
design (albeit hemi's instead of elliptical heads).

http://www.psubs.org/convention/2006/photos/GregCottrelSub/2006_0624Image0054.JPG

Jon



ShellyDalg@aol.com wrote:
> In a message dated 10/31/2009 2:10:53 P.M. Pacific Standard Time, 
> lanceind@earthlink.net writes:
>
>     To determine a safe dive depth I would have an engineer with
>     pressure vessel experience look at it for you.
>
> Good advice Dan.
>  On the stiffeners being where the 6 inch center ring is.....Sorry, 
> don't agree. I've cut big holes in the heads seriously reducing 
> the inherent "dome" strength. To stiffen the hull I'll be using 1/2 
> inch X 4 inch stiffener pieces cut to fit the inside curvature. They 
> will attach to the hatch ring which protrudes down into the sub 4 
> inches and carry down along the hull interior to the "grid" pattern of 
> floor stiffeners. Yes, a little like the ribs on a pumpkin.
> The floor "grid" serves a couple of purposes. Obviously to stiffen the 
> bottom, but also to make a solid base where all the vertical 
> stiffeners will meet. Also the "pockets" created by the floor grid 
> will hold the lead ballast bricks which will be poured into shapes to 
> match each pocket.
> The weakest place on the hull is of course around the windows. 
> Additional stiffeners will be installed there.
> I haven't finalized the stiffener design yet, but basically I'll be 
> getting some professional help with this to determine how close the 
> vertical stiffeners need to be, and what type of cross bracing it needs.
> I may find that adding some extra reinforcing is required around the 
> window and hatch holes. Much like the early  K boats, where a big 
> piece of steel equal to the amount cut out for the tower was added to 
> the tower/hull connection perimeter. That was a standard method used 
> by tank builders when a hole was cut in.
> Again, a serious professional FEA study will be required to obtain a 
> safe operating depth.
> Thanks for the advice. _All_ thoughts and critisism are welcome.
> Frank D.
>  




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