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Greg,
Do you know if there is anything unusual about the material used for the
canopies on Graham Hawkes vehicles such as Deep Flight Super Falcon (but
not Deep Flight Challenger)?
Thanks,
Jim
In a message dated 9/30/2010 8:05:12 A.M. Central Daylight Time,
greg@precisionplastics.com writes:
I
recently saw a post suggesting glass as a viewport material for
Psubs.
Although there are many reasons that glass was rejected early on for
manned
submersibles, one of those reasons is quite interesting. There is a
form of
failure that can occur in glass that has never been fully
understood.
Basically, a viewport can sometimes shatter after
pressurization when the
pressure is being released. It can sometimes occur
at a relatively shallow
depth. The failure appears to be from a build up of
tensile force. Somehow,
energy is stored in the material and released
suddenly when most of the
pressure has been removed. This can be seen to
happen occasionally in glass
buoyancy spheres. It can also happen to
acrylic but, if I remember
correctly, only during rapid decompression. In
glass, it can happen during
slow decompression and without warning. I think
that Jerry Stachiw briefly
mentioned this in his book but I don't remember
exactly which page.
George Kittredge once told me about some tests that he
was aware of using
glass spheres that went to great depth and then
shattered near the surface.
At any rate, Acrylic remains the most
thoroughly tested and best understood
material for PVHO applications.
Greg Cottrell
Project
Manager
greg@precisionplastics.com
http://www.precisionplastics.com
P
please consider the environment before printing this email
-----Original
Message-----
From:
owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org]
On Behalf Of Marc de Piolenc
Sent: Wednesday, September 29, 2010 11:19
PM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST]
Electric Propulsion
Underwater the main component of drag is viscous,
so drag is
proportional to the square of the speed, and power required is
proportional to the cube. So to triple your underwater speed from 10 to
30 knots requires twenty-seven (three cubed) times the power. This is
not a feasible undertaking unless you provide a completely separate
power plant with a very concentrated power source - maybe a Walter
hydrogen-peroxide turbine. Just sizing your electrical installation for
this power range is impractical.
Marc de Piolenc
Archivale
catalog: http://www.archivale.com/catalog
Polymath weblog:
http://www.archivale.com/weblog
Translation services:
http://www.proz.com/profile/639380
Ducted fans:
http://massflow.archivale.com/
On 9/30/2010 10:18 AM, Firebolt
wrote:
> Hello Again thanks everyone for the shaft seal info, I
appreciate it. I
> am down to only a few more things I need to know, the
electric motor.
> For me I will want to travel at a speed of 10 knots
under water
> _but_ I would like for there to be a possibility for me to
go faster,
> say, 25 to 30 knots. I know it depends on the dimensions of
the sub, it
> will most likely weigh 50 tons since it is 60 ft and 10 ft
inside
> diameter. this is not a cylinder shaped sub though
> if
you want a picture I will give it to you just tell me. I thought
> about
a 70 kw motor but I don't know if it will give me the speeds I
> want.
And if you can, I want to know what the best battery would be to
> power
the sub with lots of electronics and appliances (TV's, microwave,
>
water pumps etc.)
> I await your assistance.
>
John
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