James,
I think the acrylic forward main ballast tank is an idea worth
trying. It is something I have thought of doing to my K-350. As far
as durability goes I do not think acrylic would be too much worse
then fiberglass. I encountered a situation while recovering my 350
one day where the seas picked up pretty good. The load line on the
crane was just slack enough for my sub to come up under the stern of
the boat. The boat being heavily built out of steel did not even
flinch the fiberglass MBT shattered like an egg shell. Luckily no
one was in the sub.This is a good reason to have a way of securely
dogging the hatch from the outside. The MBTs I have were built by
George Kittredge so I assumed they were made as well as they could
have been.
The most expensive part of making an acrylic MBT is the "form" you
will need. If it was me I would form the MBT in one piece. Use the
K-350 drawing that gives you the best top looking down view of the
forward MBT, scale up the dimensions and cut the outline on a piece
of 6mm steel plate. For a one off maybe you could get away with
using a thick piece of plywood. You will probably have to start with
10mm acrylic because of the thinning that takes place at the apex of
the finished object. When you are done you will have a thick outer
perimeter where it really counts.
Greg Cottrell is the expert in this field maybe he will get involved
in this discussion. I hope I have not given you any bad advice as
far as the fabrication aspects.
Dan Lance
On 3/15/2011 5:57 AM, James Frankland wrote:
Hi Dan\Glen.
i think saddle tanks would have been the best way to do
things. Similar to Nemo sub. But ive already made the through
hulls for the standard tanks and i dont want to start cutting
into my hull again, im done with all that now so im just going
with what i have.
Im investigating if its going to be financially viable to
have a clear forward tank made. I cant do it myself so i'll
have to get a company in the UK to do it. I'm thinking It could
be made in sections and glued together to make it easier to
fabricate. Stachiw's book shows an acrylic sphere that was made
in sections, glued together and tested to destruction. It did
not fail at the glued joints.
The one thing im concerned about is that the entire tank may
be too brittle and crack if crashed. At least glass fibre has a
bit of give in it.
Anyway, im waiting for some companies to get back to me with
some prices. Will probably be too expensive.
Regards
James
On 15 March 2011 06:18, Glen Brown <gbrown091@gmail.com>
wrote:
James
Acrylic saddle tanks could
be a way .One could purchase acrylic tubing this way
one could monitor the contents ,have more stability and
better view ,even if its slightly distorted.
Glen
----- Original Message
-----
Sent: Tuesday,
March 15, 2011 12:44 AM
Subject: Re:
[PSUBS-MAILIST] Main Tanks Question
James,
A clear forward MBT
sounds real interesting. Most of the time you'll
be looking down but to have a totally unobstructed
forward view would be nice. You should be able to
vacuum form something from sheet material. It
would take a big oven and a pretty elaborate
pattern to form into. It would probably just
about disappear in the water. Look into Lexan
also. I've formed it in small molds before and it
works well. It's tougher and shouldn't be as
prone to cracking.
Forming big parts
from plexi or Lexan probably isn't easy but
neither is making molds and laying up all that
fiberglass. Maybe Greg Cottrell can advise you.
Dan H.
----- Original
Message -----
Sent: Monday,
March 14, 2011 7:35 AM
Subject: Re:
[PSUBS-MAILIST] Main Tanks Question
Hi Dan\all,
I dont actually know what im going to do with
the main tanks yet, so i think i'll make them
first and then fabricate the mounting arrangement
afterwards.
>I discussed my MBT alterations with Kittredge
before I built them. He cautioned me to be
careful enclosing to much of the bottom so I
wouldn't find myself in a situation where the sub
was nose or tail >up like a buoy, with no way
to vent the air from the upper MBT and no way to
hold air in the lower MBT.
Yes, i'd heard of that somewhere before, maybe
from you. Makes sense. I'll do the same as you
with the vent holes.
What about this for an idea?
As you probably know, ive modified the front
viewport to be a large dome. I've been thinking
of how i can make the main tanks as near to the
originals as possible but without losing
visibility through my port. How about getting the
orward main tank fabricated completely from say
about 1/2 inch clear acrylic and having a
completely clear front main tank. Protect the
tank with some crash bars.
Otherwise glass fibre tanks with maybe some
acrylic ports on similar to Doug Privit's sub
Delta.
Any thoughts on that anyone? Completely clear
main tank made out of acrylic. Sounds
expensive.....
James
About 4400
pounds.
-----
Original Message -----
Sent:
Friday, March 11, 2011 11:07 PM
Subject:
Re: [PSUBS-MAILIST] Main Tanks
Question
Off the subject, but how much do
those K boats wiegh on land?
Brian
On Fri, Mar 11,
2011 at 9:22 AM, Land N Sea <landnsea1@hawaiiantel.net>
wrote:
Hi
James,
I am
building a K-350 and have
always admired Dan H.
beautiful job he did on his
MBT,s. I was planning on
glassing in the bottoms of
mine as well with a 6" opening
in the centers or one in the
front and one in the rear of
each one to prevent the
"burping action" when towed by
a boat.
I see
what you were saying about
where the MBT,s interface with
the pressure hull as well as
the problem with the strap
that holds them in place.
I have
done some glass work in the
past but wasn't looking
forward to this step in the
future as I don't think I have
the talent to make the finish
look as nice as Dan's but what
the heck.
I would
love to see any/all pictures
of your MBT,s and any advice
on how you formed them, got a
fair front curve on them
etcetera.
Thanks
Rick
Patton
Sent: Friday,
March 11, 2011 5:51 AM
Subject: RE:
[PSUBS-MAILIST] Main Tanks
Question
James,
I have
the standard tanks,
but based on using
them this is one area
where I would suggest
you consider a
significant departure
from the plans, and
not just to make them
look better.
Specifically, I would
close the bottoms and
provide downward
stovepipes. But you
will find that hard to
do with the standard
method of attaching
the tanks with a strap
around the hull (I
actually glassed in
the bottoms in an
attempt, but ended up
undoing it). I would
suggest giving the
tanks three sides and
a bottom, as opposed
to using the pressure
hull as one of the
sides, and bolting
them from underneath
over supports that
will need to be a
little different than
the standard
ones. Just something
to think about.
Thanks,
Alec
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Hi All.
Im finally at the
stage where i am
starting on my main
tanks. Ive decided just
to stick with the
ordinary ones shown on
the plans, but i'd like
to jazz them up a bit
like Dan H has done as i
think they look a lot
better.
Question is: For
those of you who have
"modified" K350 main
tanks, did you make the
framework as per the
plans and adjust the
tanks to fit, or make
the tanks first, and
modify the framework to
fit the new shape. I
suspect the latter. I
was hoping to be able to
get the metalwork
complete and then get
the sub painted. If i
have to make the tanks
first, it will mean more
time unpainted. Anyway,
any thoughts suggestions
always welcome.
Many thanks
James
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