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

["Daniel Lance" <lanceind@earthlink.net>]

Jon,
Thanks for the references. Pressure vessels used for external pressure are
completely different animals from the ones used for internal pressure. The
spreadsheet calculator on Psubs deals with elliptical heads pretty well.
Thats why I was surprised to see Franks preference for putting the ribs in
the heads. What was the diameter and wall thickness ?  ( 60" or 74"and 
3/8" wall thickness ) I think a 500ft depth rating is optimistic . When we
refit Greg's sub his depth rating was increased by reinforcing the
cylinder. The law's of physics have no mercy.
Dan Lance


> [Original Message]
> From: Jon Wallace <jonw@psubs.org>
> To: <personal_submersibles@psubs.org>
> Date: 11/1/2009 6:18:23 PM
> Subject: Re: [PSUBS-MAILIST] elliptical heads/ Git Kraken
>
>
> 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.p
df
>
> 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_0624Image005
4.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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