[Ayrstest] Some stuff3--longer

[Dave Culp]

Delivered-To: daveculp@oberon.dnai.com
Date: Tue, 15 Aug 2000 20:10:55 +0200
From: Brian Southwood <briansou@iafrica.com>
Subject: Re: Lifeboats/life saving boats
To: ayrs@kfs.org
X-Priority: 3
Status:  U

I have had a few thoughts over the years on the subject. Some of my conclusions
to date are as follows:
1    The most dangerous part of the operation is recovery of the lifeboat by
the mother ship. My solution is to wait until the conditions are better.
This means the rescue boat must be able to either wait for better conditions on
site, or be able to go somewhere else under its own power.
2    Self righting ability is highly desirable, but not at the expense of good
stability and comfort in bad conditions.
3    It must be possible for a very small working crew to load a large number
of hypothermic, half drowned, oil soaked and injured survivors on board, and
keep them alive until they can be transferred to better facilities. First aid,
cleaning and warming facilities are essential.
4    To allow the crew to load the survivors the rescue vessel must be able to
get to them without injuring them, then stay there until they have been
recovered. This means the rescue vessel must drift at the same speed as the
victims in the water. This is a feature I have never even seen mentioned by
anyone else, but to me it is the obvious flaw in most rescue systems, where the
boat usually drifts far faster than the victim, making the rescue much more
difficult and dangerous.
5    The vessel must have a loading area which moves as little as possible
relative to the victim, with a working surface which requires minimum lifting
to get a disabled person on board. this implies low freeboard at the loading
bay, and soft surfaces. the working surface could even be below the water
level, open to the sea, if this part of the vessel is not moving much relative
to the victim, it will not be moving much relative to the sea surface (a human
body floating in the sea follows the surface very closely except in heavily
breaking waves.)
6 The rescue vessel must be able to get from one victim to the next rapidly and
safely. this requires good manoeuvring ability and fair speed. The ability to
spot the victims from long range is of secondary importance if the mother ship
and possibly helicopters can help with this function.
This requirement is apparently in conflict with the requirement to drift at the
speed of a human body. Some sort of quick braking system is implied.
7    The propulsion system must not injure victims. A waterjet system may do
the job, but relatively low jet velocities would probably be best
8    It must not be possible for victims in the water to get caught under the
rescue vessel, so a multihull is probably not the answer, unless the bridgedeck
clearance is so high that it is safe to pass though between the hulls, This
would give high windage in conventional multihulls which could cause drift
problems.
9    It would be useful if the boat had a totally self contained air supply, at
least for a few minutes in case of passing through clouds of smoke, toxic fumes
etc. This would not be difficult, maybe a bit expensive.

The style of boat that comes to mind would be rather like a flying saucer. In
this case a floating saucer. flat bottomed and low profiled for minimum
windage. Most of the interior does not need much headroom, survivors can be
accommodated in couches, which is best in rough conditions, especially when
cold and sea sick. A powerful ballast pump system to adjust buoyancy may be
useful. A sea-brake would be needed. The idea that has just occurred to me is
to have a sort of crossed plates with an endplate under the centre of the boat
that can be deployed vertically like a daggerboard for drag rather than lift.
Hydraulics could be used to operate it. A circular deck around the perimeter
below the water level by about 500mm to 750mm with an inflatable bulwark
outboard could provide the working platform that goes all the way round the
boat. This would be a slatted platform allowing the sea to drain back to its
usual level immediately after a wave comes over the bulwark.A continuous track
for safety harness for the crew would run around the hull at waist level
(possibly two tracks to allow crossing without disconnection). Several airlock
type entrances (at least three) around the perimeter would allow access from
the most sheltered area.  The coxswain could work from a rotating seat with
controls attached in the centre under a plastic dome, so he gets an all round
view of the action.
Self righting by inflatable bag may be suitable.Thrust vectoring would be
desirable to enable the boat to move in any direction. The controls might be by
joystick and work relative to the coxswains orientation in the control seat
Three jet units with full thrust vectoring on the underside of the hull would
give amazing manoeuvrability A single point lift in the centre would facilitate
launching and recovery. a cable should be provided which can be lowered through
the centre of the underside of the hull so that when the boat is lifted, it can
be lowered to the recovery crew to allow them to control the boat while
lowering it onto its chocks. It could be dropped into the water from a moderate
height for launching, so the crew must have acceleration couches for launching.
These could be mounted on shock absorbers if necessary. During recovery the
survivors should be strapped down on similar couches to avoid injury in what
could be a bumpy ride.
The deck crew would be kitted out in diving suits (wet or dry depending on
circumstances) to keep them warm and protect against injury. They might also
wear small SCUBA breathing apparatus for emergencies.
A spray system might be fitted for cooling in case of nearby fire and
decontamination in case of pollution by oil, chemicals etc. This could include
foam generator and detergent.

This would be a rather expensive boat unfortunately, but it might do the job. I
haven't given much thought to size, but it feels like it would be better to
have several medium size than one large. I would guess it should carry at least
twenty survivors in couches, but should have the buoyancy to cram in as many as
can fit in.

Well, that's enough thinking on the fly for one night. Over to the rest for
comments, criticism, additions etc.