|
Jay,
I noticed you used the word "testing" not the word
"Inspection." (Well.....sort of)
Testing and inspection are different things. I am
not against testing anything, I would absolutely test my hull past the
operational depth to insure that I'm not going to die in it. This would be
unmanned.(Naturally)
On the other hand, I will probably not x-ray
inspect every weld contained on the pressure hull.
So are you saying if
you build, going to build, have built a sub you
are going to have (or had) every pressure hull weld inspected by
x-ray? ( if you are planning to go below 500 ft. I know you are.....I
probably would too.)
I want everyone to understand, this is not an
argument, just a discussion.
I'm debating the necessity of some of the more
elaborate "inspection" methods.
The pressures involved are relative to what the
desired target operational depth. Therefore, if I'm trying to achieve a depth of
250 ft. I should build a sub capable of withstanding 500 ft. (this is for
safety margin, as we all know)
On the other hand......if I'm trying to obtain 1000
ft. I realistically need to build to a safety factor of 2000 ft. If you ask
me.....that is a huge difference. The physics do not equal out, anyway you
calculate them.
(It should be noted, I plan on a pressure hull
with structure inside, which to some may stray from typical design, I
don't know, but thought it may need to be known.)
I think someone can (and actually have) build
personal subs, MIG weld them, test them, and use them. This is not
what I consider a short cut. It's just a
different method of analogy. If I build a sub for an operational depth of 250
ft. and test it to 400 ft. Are you saying it will not be safe operating at 250
ft?
Yes.....sure I could lose a huge investment(sinking
at test time), by having it sit on the bottom of the ocean, but I can take that
risk. The cost of the other method would probably make the sub cost more
than twice as much anyhow.
I did not ever say that a true test of the pressure
hull isn't necessary(unmanned). I don't care if you x-ray every weld in the
whole sub, the true test is depth test. There are many more things that can
cause the submarine to fail. I see many more things that are likely to fail than
the welds.(If done properly)
Please also let me reiterate, I'm speaking for
myself, not for the whole community/new-guy/perspective
builder/etc. This is my viewpoint, not anyone else's, it should
be read and taken as such.
I don't want anyone on this group thinking I'm
debating this, to prevent others from doing what they feel necessary, to be safe
in their submersible. If you feel you need to stand on your head, cluck like a
chicken, swallow peanut butter on the first day of launch, please feel free to
do so. (the afore mentioned was to be funny, not to be an
ass.)
I'm just not convinced the need of x-ray
inspection.
James Long
Owner/Designer
Lil Brother LLC (Instrument Division)
----- Original Message -----
Sent: Wednesday, July 25, 2007 7:17
PM
Subject: RE: [PSUBS-MAILIST] Re: Mig
welding a sub
James,
Safety
Factor is a formal submarine term that is first and always a design issue
which in all references is never less than 1.5 times operational depth and
generally should be at least 2.0 for a personal submersible. The safety
factor makes allowances for not having a perfectly formed hull,
discontinuities in materials, transients in operations (especially for those
of you considering high speed ops), etc. It is first a design issue that
carries over into later dive operations.
As
far as the level of due diligence necessary for testing a submersible capable
of reaching 200 fsw as compared to one that dives to a depth of 1000 fsw, the
same level is required. A shallow water sub is designed with materials
suitable for that depth while a deeper diving sub uses stronger
materials. Both can have similar failure modes…either of the hulls and
fittings can rupture. The failures will be relative to depth. So
the same level of inspection is necessary for both hulls. I agree that
there is more effort required to build the deep diving sub compared to the
shallow sub and it is easier to recovery from a shallow water catastrophe.
R/Jay
Respectfully,
Jay
K. Jeffries
Andros
Is., Bahamas
A
skimmer afloat is but a submarine, so poorly built it will not
plunge.
|