[PSUBS-MAILIST] K-600 buoyancy mystery

Mon Aug 1 13:06:39 EDT 2022

Specifications

------------------------------
Group Size 27DC
Part Number SRM-27
Cold Cranking Amps 600
Cranking Amps 750
(RC) Min @ 25 Amp 160
Amp Hours 88
Length 12-3/4
Width 6-3/4
Height 9-1/2
Weight 50.3
Voltage 12
Wet/Dry W
Hi Jon sorry it took so long for a reply on the battery I just bought.  Was
waiting on the vender to send me the data sheet which they didn't provide
when I bought them and got tired of waiting so I found it online.
Hope this helps. I had planned on going with an AGM battery but when I got
ready to purchase them, the price after the Covid hit had put them out of
my budget.
Rick

On Sat, Jul 30, 2022 at 9:53 AM Jon Wallace via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> Hi Sean, thanks for doing a sanity test for me.  Yes, the diameter
> specification is I.D., and your calculator matches my calculation almost
> exactly which was 301.6 using a 2 inch skirt.  But I think Cliff is correct
> that a 36 inch elliptical head has a longer skirt (flange) and therefore
> provides even more buoyancy.  Regardless, my mistake was to deduct the
> weight of all the tank heads twice which caused my initial calculation of
> total buoyancy for the vessel to be much lower.
>
> Love your software and I see you have updated it to include tank heads.
> The one we have on the website is cylinders only.
>
> Jon
>
>
>
> On Saturday, July 30, 2022 at 09:03:55 AM EDT, Sean T. Stevenson via
> Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>
>
> Jon - If it helps, I ran weight and buoyancy calcs on one of the heads
> alone (per your description of 36" - I assumed ID because that is what head
> forming dies are based on, x 0.5625" wall thickness).  Straight flange
> length per ABS spec because my program didn't have a field to customize
> that.  Results in in-line image below.
>
> Sean
>
>
> [image: image.png]
> ------- Original Message -------
> On Thursday, July 28th, 2022 at 12:35 PM, Jon Wallace via
> Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>
> Thank you Cliff, you got me back on track.  I was deducting the weight of
> the tank heads from their displacement which is unnecessary since I know
> the overall weight of the vessel from the CAT scales.  As such, all I need
> is the displacement of all the parts and then subtract the total known
> weight.  Also, I have been using 2 inch skirt on the tank heads which I
> think is correct for the battery pods but not for the main hull.
> Recalculating the tank heads bring me to a total displacement of 4202 lbs
> which is definitely in the ball park that I would expect.
>
> Jon
>
>
>
> On Thursday, July 28, 2022 at 01:09:26 PM EDT, Cliff Redus via
> Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>
>
> I modeled a K350 awhile back.  It has a similar hull to K600.  I think
> your displacement for the Main tank heads is wrong.  These are
> semielliptical heads with a 4" skirt. Displacement should be 5.96 cu ft per
> head x 62.4 ft^3 = 371.9 lbs per head for total of 743.8 lbs not 133 lbs.
> This would bring your freshwater displacement numbers to 4,127lbs.
>
> I think your battery pod displacements are low as well.  For K350, they
> are 442.5 lbs.  Also make sure you are adding displacement for any part
> that displaces water.  I am not sure you have accounted for all parts.
>
>
> Below is the buoyancy table for the modified K350
> [image: Inline image]
>
> Buoyancy and Center of Buoyancy Database
>
>
>
> [image: Inline image]
> Modified K350 hull that these calculations were made from.  36" OD x 72"
> Seam to Seam.
> [image: Inline image]
>
>
>
>
>
> On Thursday, July 28, 2022 at 10:45:03 AM CDT, Jon Wallace via
> Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>
>
> I'm stuck on a buoyancy issue with the K-600.  The operating and service
> manuals state that the working weight of the vessel (dive ready) is 4500
> pounds less operator.  However, when I calculate the buoyancy of the vessel
> based upon it's physical dimensions I don't even come close to offsetting
> the projected weight as documented by Kittredge.  I know the stripped
> weight of the vessel is 3060 lbs, because I had it weighed at a CAT scale
> used by truckers which is suppose to be guaranteed accurate.
>
> My buoyancy calcs (inches) and results in pounds are:
> Main hull - 36 x 72 = 2712.96
> Main tank heads - 36 x .5625 = 66.5 each = 133
> Conning Tower - 24 x 18 = 301.44
> Battery Pod - 12 x 45 = 188.4 each = 376.8
> Battery Pod Tank Heads - 12 x .365 = -1.83 each = -7.32
>
> Total potential buoyancy comes out to 3516.88 lbs.  Deducting the 3060
> known weight of the steel leaves 456 lbs of buoyancy however there is
> easily more than 456 lbs of machinery, electrical, and plumbing components
> that will be added to the stripped hull.  For example, Kittredge used 8
> lead-acid batteries with a combined weight of approximately 320 lbs, 200
> lbs from three 1-ATM motor containers, 150 lbs drop weight, and then
> operator weight would produce a combined total of about 800 lbs additional
> weight not including electrical, plumbing, and instrument components.
>
> So from a weight perspective, 4000 to 4500 pounds sounds reasonable for a
> dive ready K-600.  But with only 3516 lbs of physical vessel buoyancy it
> would be 500 to 1000 pounds negatively buoyant which is obviously an
> impossible configuration.  Given that we know this submarine dived
> successfully, what am I doing wrong with my calculations?
>
> Jon
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>
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