Hi there - I brought just that topic up a few
months ago about polycarbonate vs. acrylic. Phil Nuytten was kind enough
to give his two cents. I'm paraphrasing here.
First: Acrylic has been researched to the nth
degree and is very predictable because of that research. The numbers
are out there.
Second: It is more brittle, however, and in an
ambient wet or dry sub my choice would be the polycarbonate simply because of
collision, either with a falling anchor or a bump into a reef.
Third: Poly under pressure will creep
apparently. That makes it unpredictable. Which way is it going to flow,
etc. Bad news.
Forth: Poly is really really really
expensive.
Fifth: Poly is stronger but scratches easier and is
harder to get the scratches out (I think I've got this one right)
Sixth: They may have different UV light properties
that exclude using one or the other depending on your mission
statemtent.
Seventh: Failure with acrylic is often
catastrophic, meaning it's sudden. I would imagine incipient creep with
poly would give some indication of failure, especially with strain gauges
attached.
Some pros, some cons. Hope this
helps.
Rick L
Vancouver
----- Original Message -----From: skrewgun007@aim.comSent: Wednesday, October 04, 2006 9:39 PMSubject: Re: [PSUBS-MAILIST]sinking....The picture of the pump and valves are a little fuzzy and she never got a good shot of it surfacing or on bottom. I do plan on rebuilding the model and make some changes. It was extremely difficult to to get a good seal on the lines with it being so small a space to work with. The next model should be about 6' long and easier to use valves and fittings as well as build the ballast tanks as the full size model will be to look for any problems unforeseen at this point such as battery weight placement, conning tower, drop weight and instability in the trim tanks. I am trying to cover my ass Frank. The larger model will also be able to use air tank and fitting so that the hose will not interfere with the sub in testing neutral buoyancy stability test..
I would like if anyone can open a new topic on acrylic vs polycarbonate view ports. I have read in the past that poly has not been tested for this application yet and wondering if anyone knows of or has done any testing themselves yet. The polycarbonate seems like a better material being less apt to crack and chip being more flexible and I understand talking about sticking to what you know I am just interested if anyone has checked on it. Once again I apologize for the picture quality.
Tank cap removed from main and trim tanks. Bottom tank is trim tank. Top is main ballast
Bottom view showing tank drains.Side view showing lines into press hull![]()
Below is the pump and valves. walmart was shy one valve so I had to improvise on blow and vent.Surfaced from bottom on trim tanks only.
Not a perfect success due to rear left trim tank air leak into main tank but a minor problem to be fixed before I return home for another attempt. I have not taken this project lightly on the end of safety and have spent up to 60 hours a week for over two months on researching all the info I can find on the matter. Drawn countless drawings and revisions. thank you for you help and wish me luck on the larger model on its success.
P.S. Can anyone tell me what a porpoise effect is concerning trim tanks and should there be a space between the front and rear trim tank chamber walls?