[PSUBS-MAILIST] viewport questions

Tue Oct 28 22:07:49 EDT 2014

Hi Jim,

No mesh and no flushing system, it just takes about two minutes to remove
the outer dome as its a few screws. This BTW has never been in the water,
so we'll see and learn when it does. Just off the top of my head, it's
probably about 8 inches of separation at the apex and tapers to an inch and
a half at the base.

I don't use Rain-X on the viewports, I use Joy detergent, which is a Dr.
Phil recommendation that does wonders.

Best,

Alec

On Tue, Oct 28, 2014 at 6:00 PM, via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

>  Hi Alec,
>
> What is the average distance between the two domes?  Do you have any type
> of mesh etc. over the 1/4" holes to keep debris out?  Do you have some type
> of flushing system for cleaning the surfaces between the two?  Since that's
> an ambient space I'm guessing it wouldn't take too long to remove the outer
> dome when you want to do a thorough cleaning.
>
> All:  Have you been using Rain-X on your view ports and domes?  A while
> back I saw some ads for another hydrophobic product that claims to be
> superior to Rain-X, but I don't recall the brand.
>
> Best regards,
> Jim T.
>
>  In a message dated 10/28/2014 4:30:30 P.M. Central Daylight Time,
> personal_submersibles at psubs.org writes:
>
> Hi Vance,
>
> Actually it starts at 2" thickness, and at the time was the thickest dome
> Greg had made. It was an iffy proposition, meaning he didn't know if it
> would turn into sub jewelry or just a deformed glob of expensive material.
> Luckily it came out virtually perfect.
>
> My hull is 31" OD, a little smaller than yours. The window is a 120 degree
> segment, just under 27" OD. So the trick is how to span the gap between the
> 27 inches and the 31 inches. In the original design, this bow window also
> acted as a hatch, a la Deep Flight. I made a massive Al ring 31" OD, which
> telescoped on linear bearings and four 1.25" bars, driven by rams. With
> ensuing redesign, the need for all that disappeared because I now have a
> coning tower, so I've dropped the bars and rams, and the seat is now
> mounted to the hull very simply with four big bolts. It will make a very
> handy big door into the sub for maintenance purposes, but is overkill and
> the window could be mounted by using part of your existing endcap and a
> permanently welded conventional seat.
>
> One big decision is the window seat geometry. I like conical because PVHO
> rates it for twice the life of square edge, but it requires fabrication
> capabilities that Greg didn't have for the window and I didn't have for the
> seat. So its a square edge for the simple reason that we could make it that
> way.
>
> I should mention the Al ring actually has two domes on it, one inside the
> other. The 27" dome is structural, and the outside dome is 31" and only
> half an inch thick. The outside one is just for fairing, to protect the
> structural dome from abrasion, and to mitigate collision damage. The space
> between the two domes is free flooding, and there are 1/4" holes around the
> edge of the outer dome to facilitate that. In a collision, the water would
> squish out through the little holes, so the thing is basically a shock
> absorber.
>
> As for calculations, I will paste the window calcs below. It is really
> just table lookups from PVHO tables, a simple cook book. The seat would
> have to be calculated with FEA. I didn't have FEA, so I did like the Greeks
> and Romans. You know why the Partenon is still standing? Try to do
> engineering calculations using Roman numbers! It was too complex, so they
> simply made everything massive. The seat is one integral piece of aluminum
> of ridiculous proportions, and it backs into a 516 gr 70 ring on the end of
> the hull that is an inch thick and two inches deep. I'm pretty confident
> that ring isn't going wobbly before something else does.
>
>
> Best,
>
> Alec
>
>
>
>
> ----------------- pasted ------------------
>  Viewport Depth Rating per PVHO-1a-1997
>
>
>
> The following calculations and specifications are for a sperical sector
> window with square edge, to include an optional O-ring seal.
>
>
>
>
>
>
>
> 1) Determine Conversion Factor (CF)
>
>
>
> Water temperature  = 75 °F (tropical conditions)
>
>
>
> From Table 2-2.4, CF = 7
>
>
>
>
>
>
>
> 2) Given actual fabricated dimensions
>
>
>
> tmin = 1.73”
>
>
>
> Di = 26.847”
>
>
>
> \t/Di = 0.064
>
>
>
> Entering table 2-2.10 with STCP, t/Di = 0.064
>
>
>
> Solving for Critical Pressure = 3,460 psi
>
>
>
> Since Short Term Critical Pressure (STCP) = CF x P = 3,460 psi
>
>
>
>
>
> Solving for P,        P = 3,460 / 7 = 494 psi
>
>
>
> \ Safe operating depth for window = 1,139 fsw
>
>
>
> On Tue, Oct 28, 2014 at 3:48 PM, via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
>> Alec,
>>
>> I hope this is still you.
>>
>> I've been talking to Greg about a major retro-fit on my K-350--a full
>> hull-diameter dome segment viewport in place of the forward elliptical
>> head. He mentioned having built yours (the 1000' version) while we were
>> talking about thickness and whether to try and use something out of Pete's
>> junk pile.
>>
>> While we were chewing the fat about this, he said that to the best of his
>> recollection, yours started at 1.5" thickness, and that he could build it
>> for me (maybe a 150 degree arc segment) for what I thought was a very
>> reasonable amount.
>>
>> My problem (okay, one of my problems) is that I don't really know how to
>> do the calculations for these things. That said, I'm wondering if a partial
>> copy of yours might not do the trick for my application (it would be tested
>> much shallower, 500 feet or thereabouts).
>>
>> I don't know how you feel about sharing that kind of thing, but I have a
>> picture in my head of an acrylic bow K-350 with some fairings and a
>> Minn-Kota driven Deepworker style propulsion system. I think it would make
>> a great little boat, and so if I can get the viewport and frame designed,
>> then it's going to be built.
>>
>> It's time to play if I'm going to. So, what do you think?
>>
>> Best Regards,
>> Vance Bradley
>>
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>>
>>
>
>
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