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----- Original Message -----
Sent: Tuesday, June 02, 2009 8:15
PM
Subject: RE: [PSUBS-MAILIST] Hot Dip
Galvanizing a Steel Sub Hull
Greetings Dan,
It's good
to hear from you. Your correct that the galvanizing would coat O-ring grooves
and threads on thru hulls and what not, but for the most part I don't have any
in the new configuration of my hull. I still have those pesty blind
threaded holes in the two conical fustrum viewport seating rings on my conning
tower that hold the retaining ring on, that I would like to change. But the
current plan with those is to install screws in them before the
galvanizing is done. Then remove those after and clean up the surface and then
reinstall them before the final epoxy painting is done. Then install them with
moly grease in hopes that I won't have rust running out of them later. This is
why I want to figure out a different way to attach the viewport retaining
rings on those viewports that look good and don't have threads in the main
hull.
The bulk of my thru hulls are all going to go thru the
large plate thru hulls I'm welding into the hull. Two in the front head,
one in the rear head, two on top, and two on the bottom for over pressure
plate valves/wet exit sub drain, drop weight levers, and the two rotating thru
hulls for the two braking flap rudders.
So that leaves the two new SS
thru hulls for the side pods. Those will not have any O-ring grooves in them,
since those will be installed into the shaft portion some what like Alec's
electrical thru hulls, unless I find a better rotary seal before then. So on
those I will need to protect the smooth inner surface of those pod thru hulls
with a solid plug, unless I go for a mini plate thru hull configuration for
those pod thru hulls.
I've seen so many rust night mares that I'm
willing to go the extra mile now, so I don't have all the headaches
later. I might very well use this sub a lot in salt water in a more then
a weekend warrior capacity. Who knows, maybe I'll follow Scott Cassell around
the inside of the gulf of Mexico. He only has one small thruster, so I should
be able to keep up with my four.
I'm not really into the galvanized
look, so I plan to Rhino coat my trailer after it's galvanized. I found some
older Volkswagen bug fenders that I plan to modify to be used as my sub
trailer fenders, and then of course paint them yellow. ;}
The support
rings will have a number of small venting holes drilled into them and since
I'm more then doubling the strength of the support rings with a new set of
A516 GR70 webs and flanges attached to the existing rolled A36 angle iron, the
vent holes shouldn't be a strength issue.
I hope to be totally done
with welding before galvanizing, but if you remove galvanizing far enough
around a weld zone they say it's not bad to weld. Just don't breath any of the
fumes if you do get a lot of heat to the zinc. Then you need to recoat
the metal with a good coating like, cold zinc, hot zinc spray, or a high zinc
epoxy primer.
Regards,
Szybowski
From: Jumachine@comcast.net
To: personal_submersibles@psubs.org
Subject:
Re: [PSUBS-MAILIST] Hot Dip Galvanizing a Steel Sub Hull
Date: Tue, 2 Jun
2009 08:04:14 -0400
Brent,
How are you going to protect your through hulls?
Won't the molten galvanize coat the inside of things like O-ring grooves and
threads also? You'll never get the molten galvanize out of all the holes
and in places like behind frames to not have solidified puddles.
And, any welding you want to do later is a royal pain in the back
side.
Hot dipping a sub sounds like more work then it's
worth. If your a weekend diver like most P-subbers are a K-250 won't see
enough time in the water to justify all the bother. I can see dipping a
trailer if you want that look.
Just my thoughts,
Dan H.
-----
Original Message -----
Sent:
Monday, June 01, 2009 11:59 PM
Subject:
[PSUBS-MAILIST] Hot Dip Galvanizing a Steel Sub Hull
Hey Frank,
I was
wondering if some one was going to bite. Some time back I was
corresponding with Karl Stanley, and he mentioned that if he ever built
another sub he wanted to have it hot dig galvanized. That got me to
doing some checking. Karl's sub Idabel has a base coat of high zinc
epoxy primer, (green primer of death) and it has been operating in saltwater
for years. That basic type of primer is what many consider to be one of the
best steel primers for marine applications, and if Karl isn't completely
happy with it, he might just have a good reason.
I had data on the
last 4 ft OD hyperbaric chamber that my relative built and powder coated for
about $500. But unless your going to Rhino coat the whole hull inside and
out in hopes you don't chip the coating and the coating is a consistent thin
enough thickness to flex and not crack with the pressures you plan to dive
the sub. I don't find it to be the best option.
Hot spray zinc can
be good, but you need to spray it with in four hours of sandblasting from
the data I found, you will not be able to get it inside of small tubing and
blind spots such as the back sides of the flanges on my K-250's support
rings. Not to mention it cost about four times as much as hot dip
galvanizing on average. But for large weldment's that you are not able or
willing to take to a large enough galvanizing plant, hot spray zinc might be
your next best thing.
http://www.galvanizeit.org/images/uploads/publicationPDFs/hdg_vs_met_sheet.pdf
Some types of hot dip
galvanizing will give you a nice smooth finish if the surface finish is
smooth to start with, like you can see on many Simpson Strongtie brackets
for holding joist up and the like. So other then some areas that will have
some zinc drips on them that you will need to sand off you can have a good
base to apply your epoxy paints to and then be able to seal your acrylic
viewports, hatches, and what not against those surfaces.
You will
not want to leave the galvanizing exposed in fresh or saltwater long term,
with out a good top coating and sacrificial anodes, or it will not last long
term. I just got back from a boat trip on Lake Roosevelt in Washington
state, and saw a larger dock that was held up in this fresh
water lake by foam that was covered in galvanized sheet metal boxes. All the
galvanized sheet metal that was below the water line was almost completely
rusted away, and the dock didn't look like it was all that old.
One
of my local galvanizing plants in Spokane, Washington told me that the
common hot dip galvanizing finish that you see that looks like a sort of
crystalen structure with all sorts of pieces of a puzzle, has lead in the
mix, and it's called a spangle finish, and they didn't want to have hot lead
in there facility for health reasons.
That plant has a 7 ft deep
tank, that is 5 ft wide and 16 ft long. They quoted me $350 for
dipping my 15 ft sub trail, of which they would have to dip on edge and one
side at a time. They called it progressive dipping. All tubing and
areas that would have air pockets if dipped at a particular angle, need to
have small venting holes drilled into them. This will be a bit tricky
for me since I'm adding a flange to the other side of my support rings,
making them into T's like on the K-350's and the addition of horizontal
weldments between them. I don't know if they can tilt the hull when it
is in the molten zinc for some configurations to make sure all the air
pockets are vented. The original small threaded steel nipple thru hulls on
the heads of my sub will all be removed and the two large ring plate thru
hulls in each head will replace them, and those will drain much
better.
I've heard that some galvanizing plants weigh your weldment
before and after it is galvanized, and charge you by the weight of zinc that
was added to it. So don't bolt on any zinc anode molds and think your going
to get away with it. ;}
My K-250 will have to be progressive dipped
with it's bow up and then down so it can drain properly and fit into the
tank that is here local to me. Unless I have it done in Portland in one of
the larger plants there, or I make the from MBT front attachment means
removable, of which I might do for other reasons as well.
They
first acid dip the steel weldment to remove any oils, mill scale, and light
rust, and what not. Then it's dipped in a flux bath, then on to the
galvanizing tank. From the quote I got for my trailer, I suspect it
will cost $350 to $500 to have my sub and other large sub weldments hot
dipped galvanized.
Also of note, the SS tabs that will be welded onto
the hull for bolting on things to the hull should have now problem with
being hot dip galvanized, even though it's not needed on the SS. It might be
best to later remove the galvanizing on the attachment hole and other
unpainted areas of those tabs for corrosion issues.
The more
aggressive the surface profile of the steel the better the zinc bond. So
blasting with copper slag will work better for me then blasting with silica
sand. For those of you with new weldments, the guys I spoke to at two
different galvanizing plants said, you don't have to worry about removing
mill scale and light rust since that is removed with the acid wash.
This would save a lot of time, but for the best results I would media blast
it first.
When I considered the cost of coating my subs bare hull
with a good quality high zinc primer at $75 a gallon, and I knew I was
planning on getting the subs interior wet at depth for wet exit training, I
figured I'd like to go for hot dip galvanizing the whole hull once I was
done all the welding mods.
Regards,
Szybowski
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