Hello Brent,
I send you a reaction on your mail about a
week ago with some attachements. I don't think they came through so i will give
it another try, this time without the attachments.
About 30 years ago i made photo-copies of a view
hundred pages of Stachiv's book. Unfortunately i didn't copy the pages
concerning conical viewports so i can't help you on that. Busby's
book (page 261 and 262) gives you some info on sealing conical viewports. I
did copy the pages concerning machining acrylics including a drawing of a tool
tip. I scaned the pages. If you are interrested please contact
me directly so i can mail them to your address.
Greatings,
Thijs Struijs
----- Original Message -----
Sent: Tuesday, June 05, 2007 7:25
PM
Subject: RE: [PSUBS-MAILIST] K-250
Restoration in Sandpoint Officially Underway
Thanks Jon and Alec for the good data, and
Alec I'll take you up on getting some tech pics of your K-250 after I get this
hull blasted and start to work on replacing componets. Ya I know what you mean
about the silicone retarding sand from removing it. On one of the small
viewport cover rings, I thought I had scraped off all the silicone, but there
was some old silicone still on it and so I had to stop in the middle of
blasting and scrap it off. I have all three of the cover rings sandblasted and
ready for a good quality epoxy primer. I didn't see much if any primer on them
when I was sandblasting, so I'm not sure what they used if any thing. If they
did use a primer, it was really thin grey primer that was not of good quality.
The large ring had rust on the inside and the small rings had some light rust
pitting on the back sides and around the bolt heads. I was a little surprised
to see that the drilled and tapped holes in the view port seating flanges were
only drilled about a 3/16" deep. I would of gone 3/8" to
1/2".
On some areas of the floor of the pressure hull they put some
sort of black rubber or tar coating for traction and protection of the
paint.
I got the inside of the sub cleaned out and
dry. I then removed all the electrical, some SCUBA tank attachment gear, as
well as some miscellaneous other loose items in preparation for sand
blasting . It looks allot better.
"BTW the coning
tower viewports are not standard on a K-250. The tricky bit in
fabrication will be matching the conical angle to the
seats"
I should be able to match the small view
ports and to double check that they are seating properly, I can applying
a thin coating of some tinted transfer fluid, that transfers some of the fluid
to any surface it touches so I can see what material needs to be removed if
any. This is how my gunsmith friend inlets barrels into the wooden
stocks in reproductions of old flint lock rifles.
I might have Greg Cottrel check the large
viewport, but since these view ports are likely much older then ten years and
very possibly over 30 years old, I'm not going to bet my life, or anyone else
for that matter on them. However they make great office props. What is 2 inch
acrylic going for these days? What is the best type of cutting tip for turning
the viewports on a lathe? Do you finish the turned surface by hand sanding it
while spinning with some fine grit sandpaper or does the proper cutting
tip give a smooth finish. It looks like the later to me. I'm planning on
aqua jet cutting the view ports. Then turning the small ones.
The large one may not need to be lathe turned at all with how
clean the aqua jet cutter makes it's cut.
Concerning the crush depth of these small
viewports, just from looking at them, I suspected they had allot higher depth
rating then many of the other components of this K-250. Also as you say it's
hard to know what an old viewport can support. So lets say I have
new acrylic conning tower viewports of the size stated, what is the
crush depth of just the acrylic portion of the viewport assembly, assuming
that the steel seating flange is much stronger then the acrylic lens and will
fail far later then the lens? I know how you guys love sub math. I'll see if I
have time today to do a stress analysis in Solidworks Cosmos and relay the
results and pics.
Here is the Frappr link to the pics of what I got done
yesterday.
Regards,
Brent
Hartwig
From: "Smyth, Alec" <Alec.Smyth@compuware.com> Reply-To:
personal_submersibles@psubs.org To:
<personal_submersibles@psubs.org> Subject: RE:
[PSUBS-MAILIST] K-250 Restoration in Sandpoint Officially
Underway Date: Mon, 4 Jun 2007 16:40:16 -0400
Very cool, it's great to have another K boat in the
process of being resurrected.
To clean those viewports without detriment to the
acrilic use mineral spirits. Silicone sealant is a bear to get off. It's
even tough to remove from the hull by sandblasting, because the
grains of sand tend to bounce off without removing the silicone where they
would cut right through paint in a second.
I agree with Jon, given the viewports have a finite
shelf life the proper course of action is to replace them. If I were you I'd
send the old ones to Greg Cottrell for evaluation and/or to serve as models
for replacements. BTW the coning tower viewports are not standard on a
K-250. The tricky bit in fabrication will be matching the conical angle
to the seats -- the match has to be very precise and is specced in PVHO and
Stachiw's book.
Good luck with the project, I'm looking forward to
another operational K-250. Since I have a K-250 myself, let me know if you
need anything like detailed photos of components to use as a reference in
the restoration.
rgds,
Alec
Hi
Brent,
I'll have to check the K250 drawings again, but I don't believe the
current plans call for tapered viewports. A tapered design would be
more safe, but not a requirement for the 250 foot depth limitation of the
K250 hull. Regarding the viewport integrity, I recommend you get a
copy of the ASME PVHO viewport standards and/or Jerry Stachiw's "Handbook of
Acrylics" for guidance on whether the viewports are still viable. US
Federal regulations for commercial submersibles requires replacement after
10,000 diving cycles or 10 years, which ever comes first. The crush
depth of your viewports is an unknown. You have to consider their age
and condition, and without actually setting up a test environment to
simulate the maximum depth plus a safety factor you may never know at what
depth they will fail. A brand new flat viewport rated for 350 feet of
water depth has dimensions of 1.25 x 8 inches, and requires a one inch width
seat (6 inch exposed diameter inside the sub). There are too many
variables associated with your existing viewports I think, to accurately
calculate a safe water depth for them and they should be
replaced.
Also, assuming the viewports fit within the requirements of less than
10,000 dive cycles and less than 10 years old, any buffing or other
machining of the lens to restore them will introduce new stresses and
require an annealing process to relieve those stresses. Again, let the
ASME and Stachiw references be your guide here.
Jon
I got two words for ya: Hot and
Humid. I got a chance to start working on the K-250 yesterday. I
carefully removed all three view ports. Drained most of the water and did
some clean-up. I scraped and poked all around the inside of the hull, and
so far I have not found anything but surface rust. We'll know more when
the sandblasting is done. I'll be sandblasting the three view port flanges
this morning and see how much of the interior piping and hardware we can
removed today, to get ready for sandblasting.
When I removed the large 2 inch
thick acrylic view port, about 6 inches of water came gushing out. On
that view port and the small port conning tower view port they used some
crappy white silicone that didn't hold very well and looked bad to boot.
The starboard conning tower view port was seated in clear silicone and had
the metal seating surface painted. The port side seating surface was bare
steel and lightly rusted. The taped screw holes on the conning tower view
ports, didn't have any grease on the threads and so there was some light
rust on the threads.
Here is the Frappr link to the
pics I took yesterday.
The large front view port after I cleaned it up,
looks really good with no crazing, yellowing, or scratches. It looks like
we can just polish it and anneal it. That view port is in a mostly shaded
protected position, so it didn't get much sun.
The conning tower view ports have some light
crazing on just the interior surface. I'm not sure why but it would be
interesting to know why? Perhaps the sunlight was focusing on the inside
of these view ports from the dome and that combined with the heat did the
damage. There are some very light scratches that should be able to be
buffed out and no yellowing. Are the type of conning tower view ports we
have on this K-250, with the beveled seating standard on K-250's and if so
what is there crush depth? They are 1.20" thick by 6-9/16" on
the exterior diameter and 5-3/8" for the interior diameter with
a 1/8" flat round surface next the the exterior face. Is there a good
solvent for cleaning silicone off of acrylic that won't damage the acrylic
or do I just have to buff it off?
More data to come about the identity of this K-250.
But for now I have sandblasting to get to.
Regards,
Brent Hartwig
"Everyone has a purpose in life. Perhaps yours is watching television."
- David
Letterman
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