|
Dan,
Similar to what I'm doing at the
moment?:
Hull's nearly ready to be glassed (I'll update when
I can).
Michael
----- Original Message -----
Sent: Wednesday, January 31, 2007 1:46
PM
Subject: Re: [PSUBS-MAILIST] Fiberglass
Plug
Brent,
The plug can be mocked up in many ways. I'm
not familiar with 3D CAD but I imagine working it out on a computer and
then making wafers of the plug and cutting them out of something would be
about the easiest. If not CAD I know you can do the same with
technical descriptive drafting. (Old School) But that's time consuming
and you can't get a 3D feel on flat paper. Once you have wafers, of maybe
half inch thick something, you could fill in or grind off the excess to form
the smooth 3D shape. I kind of did that but didn't use anything so
technical. I waited until I had my hull built to design my fiberglass so I
could see it all in real life.
With my hull already built, I
cut two shapes out of one inch Styrofoam, one for the X axis and one for
the Y, taped them to the hull and walked around it reshaping until I
was satisfied. Once I had the approximate size worked out I checked the
volume my MBT would have and tweaked the shape some. Following this
approximate shape I cut a stack of one inch thick Styrofoam pieces and glued
them together with construction adhesive. My sheets of Styrofoam were
stacked flat on the horizontal against the finished hull. Form there it
was a matter of sanding off the sharp edges that were sticking out farther
then the surface I wanted and then filling in the rest.
Actually I sanded the Styrofoam a bit smaller
then what the finished plug would be so I was sure to cover it all with
plaster.
Once my Styrofoam was to shape, I applied plaster
of Paris to all the larger sunken cracks and crevices. Plaster of Paris
doesn't shrink when it cures and cured to it's full depth fast. That was
then sanded to shape or a bit below.
After that I started with spackling
compound. Spackling compound sands easier then plaster of Paris so it's
best if you remove any plaster that you think will be to high before applying
the spackling compound. Also spackling compound cures slower and
shrinks some. It's better to apply it thinner and more times then
to thick and have it not cure to depth. With the spackling compound,
it's a matter of applying even coats until the entire plug is coated with
it. Apply enough so you can sand it to
the finished shape.
Once you start block sending on it you'll find
dips. You can apply a bit more to them and resand. It's a
simple matter of applying spackling compound and sanding over and over until
your happy with it. It's done exactly like a body man would does body
work on a car, only the spackling sands much easier then body
putty. Keep feeling with your hands and eyeing it up until all your
curves are smooth with no roller coaster looking surfaces. If
you think your getting out of shape, make some cardboard templates of one
side and fit it to the opposite side to see if your
curves match. Remember, you can't see both sides at the same time
anyway so if it looks good to you as your studding it, it should look great to
the casual observer late on. Be sure you have no Styrofoam showing
through because the fiberglass resin will eat it away.
Once your happy with the plaster plug, give it
several coats of wax to fill the finer sanding scratches and then mold release
if you want to. If I remember correctly, I had a tough time applying the
mold release to the waxed surface. Even if your mold stuck on the plug
in some spots, you could just destroy the plug to get it all out.
You still have a second chance to repair small
defects by working on the inside of your mold but it's tough working on the
concave inside rather them on the convex outside of the plug, so
get it as close as you can. Also, for durability, all repairs to
your mold should be done with auto body filler.
When your satisfied with the mold, wax it
and apply mold release, then the jell coat and lay up the glass. Even on
the finished part it's not that difficult to repair spots with fiberglass
resin body putty. You'll be painting the entire sub anyway. By now
your body man skills should be pretty good!
I have a friend in the body shop business.
He never did fiberglass plug and mold stuff but he was a great help in
teaching me how to work on achieving the surface I wanted by feeling the
imperfections and work them out.
There you have the long story. I hope it
helps. The best teacher maybe trial and error. Take it slow
and be observant as you go.
I'll look around to see if I have any more
pictures.
Dan H.
----- Original Message -----
Sent: Sunday, January 28, 2007 5:13
PM
Subject: Re: [PSUBS-MAILIST] Fiberglass
Hull
Dan,
I've enjoyed seeing your custom fiberglass work on
Persistence. I've been looking into different ways of producing mold plugs
and was interested in how you made yours. I think I've seen most of the
pictures of your sub available on the internet. How ever there is only
one pic I've seen of one of the mold plugs you made up and I would love to
see any other pictures of you forming the plugs if they are to be had.
From what I know now if I were to try to make those plugs I would render
section drawings with outside measurements from my CAD work onto
transparency's and then use a overhead projector to enlarge them to the
proper size. Once they are projected onto a sheet of plywood or thick
MDF which is vertical up against a wall, I could trace the outline of the
drawing onto the plywood then cut it out. These plywood sections are
then attached to a strong back and then covered with inch wide by 1/4" thick
strips of pine or cedar with a bead and cove milled into the tangent edges
like used on a stripper canoe or kayak.
Then I can sand and bondo to my hearts content, then primer,
gel coat, mold release wax, and apply PVA mold release agent twice. Is
there an easier way to make plugs or is this basically what I need to
do? I've also seen plugs CNC machined out of high density foam, but
that can be cost prohibitive for larger applications.
With regards to composite pressure hulls made out of
fiberglass, kevlar, carbon fiber, etc., when using a high quality epoxy
resin or other resin they do have some compressive strength. Look at
the Bionic Dolphin which has a carbon fiber outer hull and a kevlar inner
hull with syntactic foam sandwiched in between. For the lay up he is
using vinylester resin which is not as strong as epoxy resin and he's not
going that deep with the craft for a number of reasons not really having to
do with the main composite hull collapsing. However Doc is
putting an extreme amount of hydrodynamic external stress on the hull when
jumping and crashing into the waters surface. Of course the syntactic foam
is taking a certain amount of this stress off the outer and inter hull.
http://stinet.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=AD0605963
Regards
Brent
" The difference between genius and
madness is a fine line called success."
From: " Dan. H."
<jumachine@comcast.net>
Reply-To: personal_submersibles@psubs.org
To: <personal_submersibles@psubs.org>
Subject: Re:
[PSUBS-MAILIST] Fiberglass Hull
Date: Sun, 28 Jan
2007 14:58:05 -0500
>But where is the real advantage of the
design? You still need to
>have a rather elaborate
framework of steel.
>
>If it's the outward appearance your
trying to customize, you can do
>that with fiberglass
fairings.
>
>Remember, a sub has to replace it's weight in
water so the weight
>savings with fiberglass will have to be offset
with lead or steel or
>something making your sub as heavy as an all
steel design.
>
>All I see is, your trading some of the smell
of welding for the
>smell of fiberglass resin. And also
trading a long proven material
>for one not quite as proven in the
sub world.
>
>Dan H.
>
>----- Original Message
----- From: "Mark Roberts - Harbortronics"
><Mark@Harbortronics.com>
>To:
<personal_submersibles@psubs.org>
>Sent: Saturday, January 27,
2007 9:59 PM
>Subject: Re: [PSUBS-MAILIST] Fiberglass
Hull
>
>
>>I was just thinking something long those
lines too, as I arrived
>>home tonite.... of course
the framework will have to be sized to
>>hold all of the
stresses, but it could be done. The construction
>>process could be simplified quite nicely, and retro-fits would
be
>>so much easier.
>>
>>----- Original
Message ----- From: "Charles Perkins"
>><chuck@memetech.com>
>>To:
<personal_submersibles@psubs.org>
>>Sent: Saturday, January
27, 2007 12:19 PM
>>Subject: Re: [PSUBS-MAILIST] Fiberglass
Hull
>>
>>
>>>
>>>On Jan 27,
2007, at 10:37 AM, Mark Roberts - Harbortronics
wrote:
>>>
>>>>One guy per the link points out
a very important thing with
>>>>regards to
fibers.... they can be very strong in tension, but
>>>>have effectively no compressive strength.
To my mind, that's a
>>>>show stopper right
there.
>>>>
>>>
>>>
>>>A
show changer, true... but not necessarily a show stopper. All
>>>one has to do is put the casing of the pressure
vessel under
>>>tension, rather than
compression.
>>>
>>>How?
>>>
>>>As
a thought experiment, imagine a soccer ball. Let's replace
the
>>>seams with steal beams, and the skin with
fiberglass... but allow
>>>the fiberglass to bow inwards. The
fiberglass under tension will
>>>transmit the compressive
force to the steel framework which can
>>>resist
it under compression and bending
forces.
>>>
>>>One could make a cylinder
similarly... take a hexagonal lattice,
>>>roll it
up,
etc.
>>>
>>>Chuck
>>>
>>>
>>>
>>>
>>>>
>>>>-----
Original Message -----
>>>>From: Brent
Hartwig
>>>>To:
personal_submersibles@psubs.org
>>>>Sent: Saturday, January
27, 2007 4:34 AM
>>>>Subject: RE: [PSUBS-MAILIST]
Fiberglass
Hull
>>>>
>>>>Doug,
>>>>
>>>>I'm
not qualified to answere your questions about
fiberglass
>>>>composite sub hulls under
external pressure, but here is
a
>>>>interesting thred about just that sort of
thing. Here is the link
>>>> and a small quote
from the discussion that has the most meat in
>>>>it.
>>>>
>>>>http://www.eng-tips.com/viewthread.cfm?qid=174497&page=1
>>>>
>>>>"Spend
some time looking through ASME III (Unfired
Pressure
>>>>Vessels) for vessels under
external pressure. And keep in
mind
>>>>that if you intend to operate at 100
ft (~45 psi) that you'll
>>>>want a hefty
margin against any kind of pressure boundary
>>>>buckling failure. Think in terms
of emergency recovery time
>>>>from a
depth overshoot if you experience horizontal control
>>>>plane malfunction while descending at some
speed and down angle
>>>>when nearly at
your maximum operating
depth.
>>>>
>>>>I may be able to find a more
specific ASME reference for you, but
>>>> for a
number of reasons I don't think I can provide any hints
>>>>as regards a design collapse depth, so
you're on your own
there.
>>>>
>>>>
>>>>Norm
>>>>arto
(Mechanical)
>>>>12 Jan 07 9:46
>>>>also
look under ASME PVHO (Human occupancy) & Sec. X
{fiber
>>>>reinforced plastic) pressure vessel
codes"
>>>>
>>>>end
quote
>>>>
>>>>In the past I saw a web site
for a deep diving live aboard
>>>>submarine
project called the Neptune. They were working on a
>>>>design for a carbon fiber pressure hull
that they claimed could
>>>>be used down to
6000 meters. The web site
>>>>waswww.neptunesubmarines.com
but it's a dead link now. I was put
>>>>onto
this site originally by a web site for the Perendev
>>>>magnetic motor. At one time I thought
it might be a great motor
>>>>for subs in
general but there is some serious greed problems
>>>>with the owner of the company.
Neptune Submarines were wanting
>>>>to put the
Perendev magnetic motor in there live aboard
>>>>submarine to replace a nuclear type power source.
Maybe someone
>>>>here knows what happened to
this Neptune Submarines group out of
>>>>Switzerland? Here is a pic of there submarine
design.
>>>>
>>>>http://img224.imageshack.us/img224/7608/24243158bk0.jpg
>>>>
>>>>Regards
>>>>
>>>>Brent
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>From:
djackson99@aol.com
>>>>Reply-To:
personal_submersibles@psubs.org
>>>>To:
personal_submersibles@psubs.org
>>>>Subject:
[PSUBS-MAILIST] Fiberglass Hull
>>>>Date: Fri, 26 Jan 2007
00:35:40 -0500
>>>>
>>>>I
know it's an old topic but I have mostly ignored the
previous
>>>> post regarding fiberglass because
I never thought I was going
>>>>to give it a
second thought. ...wrong
again.
>>>>
>>>>1) Did anyone ever come up
with a way to calculate even a
>>>>ball-park working depth
given all, or at lease some of the
>>>>variables for
fiberglass construction? If so can you point me in
>>>>that
direction?
>>>>
>>>>2) I know that the
externally loaded working psi for a non-
>>>>reinforced
cylinder is lower than it's internal working
psi.
>>>>That makes even more scene
to me when thinking about the
>>>>alignment
and tensile strength of glass or carbon fibers
>>>>compared to their compression strength.
However it seems that
>>>>there would be a
ratio that could be used to estimate the
>>>>reduction in loading ability. Would that
be true? For example
>>>>if pipe section is
rated for 1000psi, could it's external load
>>>>psi rating be stated as x% lower, say 20%
lower, based on the
>>>>type of
material?
>>>>
>>>>Thanks --Doug
J
>>>>
>>>>
>>>>
>>>>
>>>>Check
out the new AOL. Most comprehensive set of free safety and
>>>>security tools, free access to millions of
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>>>>from across the web, free AOL Mail
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>>>>
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