[PSUBS-MAILIST] viewport questions

Thu Oct 30 08:39:52 EDT 2014

Thanks, Tim, if it works that well in your ambient, it should be fine for a 
 1ATM.  

And thanks again for bringing your SportSub to Bellingham.  I had seen  
numerous pictures of that model, but seeing it hands-on and hearing  your 
descriptions of the operational considerations was far more  enlightening.

Jim T. 

In a message dated 10/29/2014 8:50:22 P.M. Central Daylight Time,  
personal_submersibles at psubs.org writes:

Dish  soap works fabulously, Jim. 
My  first dive with my semi-dry sub was spent running mostly by compass and 
 constantly wiping the interior windows.  I wiped liquid dish soap on the  
inside surface of the windows for the second dive and had no fogging.   
Cheap and easy. 
Tim 

From:  Personal_Submersibles 
[mailto:personal_submersibles-bounces at psubs.org] On  Behalf Of via Personal_Submersibles
Sent: October-28-14 8:18  PM
To: personal_submersibles at psubs.org
Subject: Re:  [PSUBS-MAILIST] viewport questions

Hi  Alec,

I had  forgotten about using dish detergent.  If I recall correctly it  was 
used on the inside of the dome for anti-fog also.  Have to put that  on my 
checklist before I forget it again.  And it will make the sub smell  "lemony 
fresh."  Looking forward to seeing your  pics.

Thanks  much,

Jim  T.

In a  message dated 10/28/2014 9:09:53 P.M. Central Daylight Time, 
_personal_submersibles at psubs.org_ (mailto:personal_submersibles at psubs.org)   writes:

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_ (mailto: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_ (mailto: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_ (mailto: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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