[PSUBS-MAILIST] viewport questions

Tue Oct 28 23:18:12 EDT 2014

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 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

_______________________________________________
Personal_Submersibles  mailing list
_Personal_Submersibles at psubs.org_ (mailto:Personal_Submersibles at psubs.org) 
http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles

_______________________________________________
Personal_Submersibles  mailing list
_Personal_Submersibles at psubs.org_ (mailto:Personal_Submersibles at psubs.org) 
http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles

_______________________________________________
Personal_Submersibles  mailing list
_Personal_Submersibles at psubs.org_ (mailto: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/20141028/688134d8/attachment.html>