Hi Jon,
point taken re material specs.
I had your same reservations re vision out of a
tube.
I guess in Brian's case it's not his primary
viewing port & it will be interesting to
here his experience if he has extended viewing
through it.
I spent a bit of time at a local
aquarium trying to get a handle on viewing through acrylic.
They had a number of large tanks
of differing thickness & shapes.One an acrylic tunnel
100 meters long. I was looking through at various
angles to see the distortion.
I came out feeling slightly nauseous. I was
thinking it was because my vision was
being screwed around a lot by the varying
distortions. My fear is that you might get that
looking up & down through a cylinder. If you
rotated your head from side to side the distortion
shouldn't vary.
Point taken Jens, I've made that comment before re
subject headings, will be more attentive in future.
Regards Alan
----- Original Message -----
Sent: Sunday, July 11, 2010 6:24 PM
Subject: Re: [PSUBS-MAILIST] pressure
gauge
Standard warning here...check the specifications of the
acrylic used. If they do not meet or exceed ASME standards then the
material is not acceptable. I've observed on more than a couple
occasions that fabricators who supply acrylic for terrestrial use often use
material that does not meet ASME standards (not necessary for furniture and
decorative items, etc) and don't even know what the strength specifications of
the material is.
I have considered an acrylic conning tower, however
Stachiw says that the cylinder provides the worst optical characteristics of
any viewport configuration. It acts as an asymmetric lens distorting the
shape of images perceived by the passenger. As the radius of the
cylinder increases, the distortion is less but that also depends upon the
thickness. Stachiw wasn't too specific and I wish he had provided more
info about this issue. I've hesitated designing around an acrylic
conning tower because I don't want to spend the money on such an expensive
item only to find out the visibility sucks. I suspect the visual
distortion is more noticeable when looking upward or downward since you are
peering at an oblique angle to the material and through more of it.
Viewing perpendicular to curvature should have the same viewing qualities as a
dome. Once Bryan gets situated with his vessel I hope he can describe
any visual deficiencies, if they exist.
Jon
On 7/10/2010
11:47 PM, Alan James wrote:
Hi Jon & Brian,
There are some pretty big cast tubes that are
done as a standard line
that I've seen advertised by Chinese
manufacturers. Might be an inexpensive way of doing
the conning tower in the future
I came across this supplier that
advertises 500mm diameter & up to 40mm thick
However the advert is a bit
confusing.
4" is a huge thickness. I could imagine forming
it would be fun- days in the oven. They'd have to cut the
angles of the mating surfaces first wouldn't
they, then clamp & glue it round a form wich they could remove
some how.
Brian you might be able to control your boat
from up in the conning tower. Pay a student to interface a
remote play station controller with your motor
controls. There is heaps on the net showing how it's done &
ready made circuit boards to help with
this.
Alan