Shawn
could you share more information About the application of
carbon fiber, ie reinforcement, thickness, how it compairs to GRP. and
more about 8 by 45 boat idea. and what is a "nominal thickness".
Thank you
Andy
From: "Shawn H." <gambit7@bellsouth.net>
Date: 2005/11/09 Wed AM 01:33:31 CST
To: <personal_submersibles@psubs.org>
Subject: Re: [PSUBS-MAILIST] Composite Huls - self annealing?
Hehe... glad someone likes the idea, may have actually stumbled onto
something here. I have a dialog started with a CF-expert and I'm waiting
a response from him now on specific material definitions. I'll also do a
neat diagram to better explain what I'm thinking. The design is
everything here, I dont have the money to build much of anything to begin
with. The idea in itself is to accomodate LARGE pressure vessels, as most
autoclaves cant handle anything really big, hence you usually have to
build it in sections (which lowers strength and is a pain).
If you're building something SMALL, like a psub; then you simply get a
large cardboard cylinder and coat the outside with CF... send that to the
local autoclave and your'e set. Or like you said, use a propane tank
strengthened externally. They're usually small enough to get into the
cooker.
CF blows away steel in this application... in every way. There's a chance
here for a nearly "unlimited" depth rating; assuming you have enough money
for the CF... obviously, the smaller the cheaper.
I calculated a NON-pre-pregnated CF hull (wet application) for a sub 8x45
feet and it came out to over $100,000 in CF at nominal thickness. Once I
get the numbers from the expert it'll be easier to narrow down a figure.
Granted, pre-pregnated CF is much more expensive - heck, I cant even find
a price for the stuff. But, in the long run, it's cheaper then
fabricating a 1+" 537 steel hull.
In answer to your question, the cylinder is only capped at one end, the
other end will have the viewport obviously. Once all the CF is laid you
seal it up and then pressurize and heat it. You could also simply add the
endcaps later, but like I said... one-piece is the goal. Pre-preg CF has
a working time of like 30 days, so that's not an issue.
more later...
Shawn
----- Original Message -----
From: Akins
To: personal_submersibles@psubs.org
Sent: Wednesday, November 09, 2005 1:52 AM
Subject: Re: [PSUBS-MAILIST] Composite Huls - self annealing?
Hi Shawn.
What a marvelous idea you have. Use the existing autoclave and make it
the hulls outer layer while cooking under pressure laid down cf to
reinforce and increase the autoclave's
thickness from the inside. Sounds great except for one thing. As
mentioned with propane tanks here in the past and recently as well, these
pressure vessels are made to hold pressure
from the inside not the outside. Remember it is hard to blow up the beer
can but easy to crush it. However, it would be interesting to compute what
the autoclave's external crush pressure would be
and then compute what that increased crush depth would be if reinforced
with cf like you suggest. The addition of the cf on the inside of the hull
might overcome any shortcomings of the original autoclave's
unreinforced hull and make it so it would withstand greater pressures
afterall. Very interesting! If I was you and going to do this, before I
spent any money I would find out everything about the tensile strength
and makeup of the autoclave's metalic hull, its thickness and how much
pressure it could hold from the inside without blowing up. Then I would
have someone compute those figures into what its external pressure holding
force would be. Then compute the tensile strength of the autoclave's hull
reinforced with cf. You never know, you just may have something here. But
I would do it all on paper and computing first before spending
a dime. Just one question though. How do you propose worker access to lay
down the cf from inside the autoclave and then pressurize it?
Bill
----- Original Message -----
From: Shawn H.
To: personal_submersibles@psubs.org
Sent: Tuesday, November 08, 2005 12:16 PM
Subject: Re: [PSUBS-MAILIST] Composite Huls - self annealing?
I just came up with another interesting idea. We all know the basis
behind the autoclave right? An autoclave is basically a huge PRESSURE
VESSEL with a heating element inside. So, why re-invent the wheel?
Simply reverse the thinking:
Prefab D.O.T. pressure vessels usually have the stringers on the
outside, this is good. They also come with endcaps. Simply have one made
that can handle internal pressures with temps 250F+. (most chemical
storage tanks meet this I presume).
Next, we install a compressor at one endcap. Then, a power supply with
a heating element on the other, that runs the length of the cylinder. Or
better yet, if you can, install them both on the same side.
The CF is then laid on the INSIDE of the tube, closed up, and pressure
cooked. The autoclave itself is the outside shell of the sub.
Once you've laid as much CF as you want, you remove the compressor and
the heating element and voila - strongest personal sub. in the world. You
could also have the heat source on the OUTSIDE, but this doesnt guarantee
uniform temp. dispersal.
This technique makes simple sense to me, because the high internal
pressures are pushing the CF to the shell while curing, as well as
eliminating the voids WITHIN the CF and between it and the shell.
Only other thing I could think of is maybe using the shell to lay some
kind of thermoplastic, probably on the outside. The shell could be heated
to accomodate it and then cooled to solidify it. Thermoplastics are
actually going to put autoclaves out of business eventually, so they say.
Shawn
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