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RE: [PSUBS-MAILIST] Pressure hull framing options.
Carsten,
Great photo and explanation. Is it possible to see some more photos of the
inside and details of your hatch mechanisms and other build details. Have
seen your video of the inside but that was finished. That is hardly p-sub
but a proper underwater ship. Very impressive. Also what do you use for
navigation. It has always intrigued me how submariners allow for tides,
currents, uncharted obstacles, Fishing nets in murky waters,etc. regards,
Hugh
Hi Brent,
I use H-Frames bended in both directions and also longitudinal H-Frames.
http://www.euronaut.org/content/upload/notes/H-frames.jpg
http://www.euronaut.org/content/upload/notes/IMG_2289.JPG
http://www.euronaut.org/content/upload/notes/Pic00003.jpg
http://www.euronaut.org/content/upload/notes/Pic00046.jpg
This Frame : (called: double T) v = weld
============hull===
v-----v
I
I
-----
is nearly perfect because it is self supporting and need only a small all
around weld to the hull.
And the longitudinal tensile strength goes soft into the frame..
And this Frame :
=================hull===
vI Iv
I-----I
I I
is nearly perfect to integrate an internal endcap-
=================hull===
vI Iv
I-----I
vI Iv
========I
I
I
I
I
Endcap
No worry about double plating and corrosion.
Only a small amout of oxygen inside the gap - eaten
by a very little amount of FeO2 - than corrosion stops.
VBR Carsten
"Brent Hartwig" <brenthartwig@hotmail.com> schrieb:
>
> Hello Ian,
>
> I'll order that book. Thank you for the heads up on it.
>
>
http://books.google.com/books?hl=en&id=8fKg6wHPpecC&dq=External+Pressure+Tec
hnology&printsec=frontcover&source=web&ots=rNugPdjA3s&sig=40O1miUIxpn6E51tO6
kavvPunBk&sa=X&oi=book_result&resnum=1&ct=result
> You make some good points. The void area on the High H design requires
good welds to seal, and if you want/need to insulate your sub you would need
to fill it with urethane foam or the like, through drilled holes, and then
cap them. Carsten thought it would be ok to have sealed in areas in the
interior of the sub like my void and high rolled H beams outer surface, if
you weld them properly. The idea for the high H stiffeners primarily came
from a skilled metal fabricator relative of mine. A big part of the
reasoning for that design was that one of the primary failure modes of I and
H beams, is there loose edges bending in a wavy ribbon effect. So if you
have an existing trailer built with I beams, and weld on metal plates the
the vertical sides, making the I beam into a rectangle. You will have a much
stronger frame. This is why you see Ford bragging about there fully boxed
frames on there trucks. Instead of the channel type they used to use.
>
> The Euronaut's stiffener configuration is easier to install then the high
H design, but you can't get the H beams in A516 as far as I know. Perhaps
there are some other steel alloys available for H beams. In any case I think
mild steel H beams will work great for a lot of applications. You can also
space them closer if need be. This means more weight, but in a lot of cases
you will need a lot of weight any ways. It's only the change in metacentric
height with extra metal up high that gives me pause in doing that. In the
same basic size and thickness of material of both the rolled H beams and the
high H design. I would suspect that the high H configuration would be
stronger and lighter. especially if you used A516 for the material in the
high H stiffeners.
>
> I've seen one of Carsten's Euronaut drawings, that showed 8 horizontal H
beam weldments spaced out around the hull, between the stiffeners. For some
reason he chose not to install them. Perhaps it was cost and the extra
weight up high. In any case your stiffener rings will be much stronger with
those in place to stop the ribboning effect of the loose edges of the inside
rolled ring. For my live aboard sub design, I had decided to change from the
high H stiffeners to the rolled H beams like in the Euronaut, but with the
horizontal weldments add and made out of T stock. This way It was far
cheaper to not have to cut rings out of large sheets of A516, a lot less
welding, easier to insulate and inspect, and easier to install and inspect
the wiring and piping.
>
> I plan to do FEA analysis of a number of different configurations to get a
better picture of what is going on in regards to failure modes and strength
versus weight. For a angle iron stiffener configuration like in my K-250 I
plan to install A-36 T stock horizontal weldments to restrict the angle iron
stiffeners from ribboning. I could also use angle iron for the horizontal
weldments, but I need the extra rib to lock in the infusion molded syntactic
foam I plan to install.
>
> Regards,Brent Hartwig> Date: Tue, 22 Jul 2008 17:26:49 -0400> From:
irox@ix.netcom.com> To: personal_submersibles@psubs.org> Subject: Re:
[PSUBS-MAILIST] Pressure hull framing options.> > > Hi Brent,> > I'm not
going to discuss propane tanks, this is already done (many times!),> any
thing I say is already in the archives (normal for many different people).>
> However, I will discuss framing issues with you. If you want to do
advanced> designs like this, I would highly recommend getting a copy of:>
Pressure Vessels: External Pressure Technology> by Prof Carl T. F. Ross > >
This will help you start to understand some of the math (reason) behind>
different framing designs. It's a great book - although kind of bleeding>
edge. Once you see what's going on for a simple framing solution, you'll>
get an idea of how complex your is and figuring out the potential failure>
modes is going to be tricky.> > Note, with most H beam, it is the side of
the H the contacts the pressure hull,> like with an I beam it's the top or
bottom of the I attached to the hull.> First understand the general reason
for stiffener like this. It's really> making that part of the hull a small
diameter (small diameter means more> pressure resistance), one side of the I
attaches to the hull (lots of contact> area), the long part extends into the
hull attaches the hull to the inner> ring - the inner can take more pressure
than the hull, hence re-enforcing> that part of the hull.> > With your
design, it looks like you have no plate attached to the hull,> so the legs
of the H are weld straight to the hull metal. They extend> out, then before
the end is a inner ring welded between the legs (the cross> bridge of the
H). Before using this design over other you really need> to understand how
that design is going to buckle and fail. Once you> understand how it can
fail, you can do some simulation with different> designs, spacing, metals
thickness, etc.. Then time to start building> some models on different
scales and destroying them to verify your calculations> and research, you
might have to revisit your calculations and simulations> to make some
adjustments, then repeat destroying some models.> > Eventually your new
design will be ready to use in a manned submersible,> and providing the
original research/design/work was done correctly, then> it will not fail
you.> > Also, how you inspect the section between the legs of your H, for>
rust, leaks and the likes?> > I have a feeling you can loose one of the legs
from the H and just have> an L bean with the same strength instead, saving
you metal, time and money.> > Cheers,> Ian.> > -----Original Message----->
>From: Brent Hartwig <brenthartwig@hotmail.com>> >Sent: Jul 22, 2008 3:12
PM> >To: personal_submersibles@psubs.org> >Subject: [PSUBS-MAILIST] Propane
Tank Hull Options> >> >> >Hi Jon,> > > >"Regarding your second point about
materials. Whether it is true or> >not, people have suggested that the time,
effort, and cost required tomodify a propane tank for sub-use, is ultimately
more expensive thanjust ordering the parts and starting from scratch.
Perhaps that isnot strictly true from the perspective of
cash-out-of-your-pocket ifthe propane tanks have cost you nothing. However,
it does seem to bethe general consensus. Therefore, the issue does not
appear to bewhether a modified propane tank is better/worse than a
similarraw design from a performance perspective, but rather that the
propanemodification is definately worse from a time/labor perspective,
andcertainly from the chemical "smell" inherent in propane tanks."> > > >You
make some good points Jon. Some of us have the extra time, and are willing
to do the extra labor when funds are limited and we still want a reasonably
safe submarine.> > > >"I'm sure you realize that once you cut the end off to
install theribbing, the quality of the robot welds are immaterial since
theweak link is now the the weld you made to reattach the end."> > > >Very
true, but now you only have one head to attach, meaning you have one less
circumference weld to worry about applying correctly. Also I have what I
call a high H support ring design that if the three different basic
components of each ring are cut into three sections and then the butt joints
staggered, I think you could install them readily without cutting off one of
the heads. The high H support ring design allows you to apply all the weld
beads in relatively easy to see and work on areas, when compared to a T type
stiffener being installed in a hull that has the heads already welded on.
Here are some pictures of the concept I worked up some years ago. The model
is I believe over kill in stiffener size and thickness, but you can see the
idea in any case.> > > >
http://www.frappr.com/?a=viewphoto&id=4001713&pid=10216832> > > >You can
also use the angle iron configuration like on the K-250 and add horizontal
pieces of angle iron between the rings for extra strength in keeping the
ring from ribboning when bending, as well as seriously strengthen the hull
from collapsing in an accordion fashion between the stiffener rings. Not to
mention a lot of extra collision protection. But as many of you know you
can't get angle stock in A516 Gr 70, (or so I'm been told) so that's why
someone might want to use a the high H design.> > > >Another option might be
to install a mini version of the Euronaut's stiffeners, If you can find
small I or H beams.> >> >Regards,Brent Hartwig> >> >From: jonw@psubs.orgTo:
personal_submersibles@psubs.orgSubject: RE: [PSUBS-MAILIST] Yunk Yard Wars
Submarine BuildingDate: Tue, 22 Jul 2008 01:14:49 -0400> >> >> >> >Brent,> >
> >> Can a reasonably safe ambient or wet, oil drum submarine be designed>
and built? I believe there are lots of options. The Chinese oil drum>
submarine builder will likely put his sub in shallow water for testing> and
see he needs a lot more keel weight before he even gets into it.> He can add
more weight to the wheel assemblies and/or a keel of some> sort below the
hull. The RV Needlefish had the same basic metacenter> problem, and Bill
found that out without ever diving it.> > > >Bill owned a very large and
successful marina, and had almost unlimited > >resources available to him.
Bill tested his sub by lowering it from acrane into a relatively shallow
area of water used for boat launchingat the marina, so that if there were a
problem he would not be in dangerof entrapment and drowning. His sub was
connected to the crane at> >all times.> > > >> How many people have died in
1 ATM and/or ambient propane tank sub?> > > >I don't know, but I do know the
facts surrounding a couple of engineering > >students who built what they
considered a safe sub, but in which one of > >them died. The other
fortunately survived the ordeal, but suffered severetrauma. I interviewed
both the mother of the deceased, and thesurvivor last year. Interestingly,
the day prior to the accident theyhad performed an exact similar dive in the
sub without incident, andther e fore assumed that the sub was safe for
shallow-depth diving. > >Funny how you can't determine the safety of a sub
by the number > >of dives you perform in it. You can read about it
athttp://www.psubs.org/accidents/seaker100.html> > > > > > > >> I have
literature in my K-250 paperwork that has the George> Kittredge saying that
you can build your whole K-250 sub out> of A-36 mild steel and be just fine.
He did say how ever that> A516 Gr 70 is a great upgrade. Here is the quote.>
> > >What did he say about using 55-gallon drums?> > > > > > > >> Designing
a $2,000 US 1 ATM sub that anyone in the world could find> the same
materials for the same price, is not likely. When one has> the need and/or
desire to construct a inexpensive sub, it's not> always about getting new
products cheaply, but usually about found> objects that are very cheap or
even free. To build those same> objects brand new would be in many cases
very expensive. I have two> used, but solid nice 500 gallon propane tanks
with half hemisphere> heads that I got for free from a neighbor. Should I
not use them for> a 1 ATM sub because they are not made of new A-516, they
have a> little bit of rust on them, and they smell funny?> > > >You talk
about cost as if safety is a constant that doesn't have tobe accounted. It's
not, and has to be built into the cost of the sub.You can't base your design
and fabrication on cost of materials aloneif you are serious about having
expectations of diving and returningto the surface safely, consistently. At
some point, you are going to > >have to assess the risk of failure
associated with the design andmaterials you have chosen.> > > >Regarding
your second point about materials. Whether it is true or> >not, people have
suggested that the time, effort, and cost required tomodify a propane tank
for sub-use, is ultimately more expensive thanjust ordering the parts and
starting from scratch. Perhaps that isnot strictly true from the perspective
of cash-out-of-your-pocket ifthe propane tanks have cost you nothing.
However, it does seem to bethe general consensus. Therefore, the issue does
not appear to bewhether a modified propane tank is better/worse than a
similarraw design from a performance perspective, but rather that the
propanemodification is definately worse from a time/labor perspective,
andcertainly from the chemical "smell" inherent in propane tanks.> > > > > >
> >> The heads are robot welded with three passes. Most of us can't weld>
even close to that good. Besides I would likely have to cut one end> off to
install the ribbing unless I cut the ribbing into three> sections.> > > >I'm
sure you realize that once you cut the end off to install theribbing, the
quality of the robot welds are immaterial since theweak link is now the the
weld you made to reattach the end.> > > > > > > >> One thing that this group
needs to be reminded of from time to time,> is that the synergy of
experiences and combined brain power of this> global group, is incredible,
if not impeded.> > > >If you are suggesting that people who have an interest
in safety arean impediment to this group, then I strongly disagree with
you.> > > >Jon> > > > > > > > >
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