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[PSUBS-MAILIST] Acrylic Towers in Sub Designs

Hello Paul,
 
I've been interested in using acrylic tube sections in pressure vessels for some time now. Several years back I designed a hyperbaric chamber with a relative for plants and/or animals, that had a vertical tube of acrylic for it's main central body, with metal top and bottom plates with grooves machined into them to receive the acrylic tube. Then the metal plates were pulled together by bolts mounted externally of the tube to seal the chamber. I've also seen this basic concept used in larger hyperbaric chambers used for humans in a horizontal position. For are design we wanted the tube section to be vertical for easier use as an hyperbaric aquarium for feeding and clean purposes on one model of the design.  We even got data from the acrylic manufacture on what the different size and thickness of tubes were rated for in regards to internal pressures. I don't have that data any more so I'll  have to get it again. We only planned to use the small chambers to 15 to 25 PSI internal pressure, so it wasn't going to be a big deal. 
 
What these tubes can handle in regards external pressure, I would guess you could input the material properties, size of tube, and thickness of tube into the Excel spread sheet hull stress calculator, and get a pretty good idea, if not be on the money. I'm not an acrylic expert as of yet, so I will yield to the experts in are group on this.
 
Then a couple of years ago I saw Paul Moorhouses designs using acrylic tube sections for the conning towers on the S101, S102, and S103 Lula, and loved it. They have less visual distortion then a dome and I figured they shouldn't be to hard to get, and should be less expensive then a dome as well. Paul used long bolts mounted internally to hold the flanges tight to the acrylic tube, instead of externally like on my small hyperbaric design. I hadn't seen another sub using an acrylic tube section until I saw the pics of the 2Dive sub. I don't know of any other subs that have one besides those listed above. The 2Dive sub has slightly conical tubes, which really surprised me, since I didn't know they were available without having them custom made. Perhaps they were custom made, I don't know, but allot of larger custom made acrylic components can get outrageously expensive, so I try to used non-custom acrylic components, when ever possible.
 
Does anyone here know where he got the conical tubes for the 2Dive sub, or were to acquire some? I did a search for larger acrylic tube sections a couple of months back and got bogged down with all sorts of web sites that basically said you need to make a custom order. Isn't there a company site that shows some basic sizes of large thick walled tubes, like used on the S101 I can look at and get a price quote?
 
I would really like to see some close up pics of the 2Dive subs hatches, as well as some drawings and specifications. The hatches look to be really light. Perhaps even turned out of aluminum. Also there looks to be no long bolts to keep the flange on top of the conical acrylic tube section, tight to the top of the tube section, of which transfers sealing pressure to the bottom of the tube to keep it sealed to the lower flange groove. So that must be done with a glued on acrylic strip attachment the the top and bottom of the tube or the like.  Much like used to attach the K-250 domes to the steel flange. I would be concerned with having more collision protection in my design.
 
 On Pauls S101, it looks like he's got a strong steel and FRP assembly behind and above the acrylic tube, that can give it a fair amount of collision protection. On the S101, I would add a couple of strong stainless steel curved tubes coming up from the front deck, up to the sides of the top of the conning tower, to further protect the acrylic tube section.
 
http://www.frappr.com/?a=viewphoto&id=2384531&pid=4158205
 
I've always been interested in how Paul designed the assembly behind the acrylic section on the conning tower under the FRP fairing, so that the top steel flange seated on the tube evenly when hydrostatic pressure increased. While still being solidly attachted to the steel assembly behind the tube of which would be solidly attachted to the subs main pressure hull to to give some collision protection to the acrylic tube. There is two bolts that I can see from inside the metal tube above the acrylic section that are mounted horizontally to what is likely the metal assembly inside the FRP fairing aft of the tubes. Perhaps all the weight and pressures from the steel tube and hatch assembly are bearing down on the acrylic tube without much if any help from the hidden assembly aft of the tube. I hope not.



Regards,
Brent Hartwig


Date: Tue, 14 Aug 2007 17:04:17 -0700
From: paulkreemer@gmail.com
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] German homebuilt

I was going to ask what people thought of those acrylic towers.  I liked the idea of good visibility too.


On 8/14/07, shellydalg@aol.com <shellydalg@aol.com> wrote:
I like the design. Looks like good visibility through the towers. Simple in design, and probably easy to maintain.
Seems like a buyer could add some fairing, and have a great craft. Frank D.