[PSUBS-MAILIST] viewport questions

Tue Oct 28 18:06:46 EDT 2014

Alan,
I saw that. He's something, isn't he?
Vance

-----Original Message-----
From: Alan via Personal_Submersibles <personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
Sent: Tue, Oct 28, 2014 5:39 pm
Subject: Re: [PSUBS-MAILIST] viewport questions

Vance,
in case you didn't see the post. Emile has his dome press / walk in
oven built. Can't remember the size he can go to, but it was quite large.
Alan

Sent from my iPad

On 29/10/2014, at 10:29 am, Alec Smyth via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

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 DepthRating per PVHO-1a-1997

The following calculations and specifications are for asperical sector window with square edge, to include an optional O-ring seal.

1)Determine Conversion Factor (CF) 

Watertemperature  = 75 °F (tropical conditions)

FromTable 2-2.4, CF = 7 

2)Given actual fabricated dimensions

tmin = 1.73”

Di = 26.847”

\t/Di = 0.064

Enteringtable 2-2.10 with STCP, t/Di = 0.064

Solvingfor Critical Pressure = 3,460 psi

SinceShort Term Critical Pressure (STCP) = CF x P = 3,460 psi

Solvingfor P,        P = 3,460 / 7 = 494 psi

\ Safe operating depth forwindow = 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

_______________________________________________
Personal_Submersibles mailing list
Personal_Submersibles at psubs.org
http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles

_______________________________________________
Personal_Submersibles mailing list
Personal_Submersibles at psubs.org
http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles

_______________________________________________
Personal_Submersibles mailing list
Personal_Submersibles at psubs.org
http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.whoweb.com/pipermail/personal_submersibles/attachments/20141028/f84a85c0/attachment.html>