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Unfortunately, there is no one particular methodology for protecting your vessel against the possibility of a lightening strike, however, there are a series of steps that can be taken to mitigate that risk.
Firstly, the use of common sense and sailor’s intuition (ie – don’t cast off in the middle of a lightening storm) should always be considered the foremost method of avoiding the hazards of lightening. Of course, if you are already underway when a front rolls in, this option is not always available.
A lightening protection system can help to reduce the damage to your boat if it is hit by lightening, as well as the possibility of injury, as an effective system will allow the lightening strike to follow a path to the ‘ground’ without using the entire vessel as a conductor. The key elements of such a system include a lightening protective mast, a conductor and a ground plate.
The ground plate should be placed on the hull closest to the base of the mast. If your mast is deck stepped, then the logic can still be followed, by running a straight wire down to the hull and ground plate. Similarly, if your mast is made of wood, and therefore not conductive, a large copper wire (conductor) should be run from the top of the mast as with the deck-stepped mast.
Consider the devastation normally caused by any fire, then imagine what would happen if that fire took place on a boat. Normally with a prevailing wind and no nearby fire station. prevention is therefore the best course of action and fitting an adequate gas alarm system. Many sailors indeed avoid gas aboard for this very reason. This doesn't need to be the case however provide the gas appliances are fitted and checked by an approved CORGI engineer and the right gas alarm is selected.
Why is the risk of gas explosion higher on boats?
All boats contain a bilge which is where gas will tend to buildup (LPG is heavier than air) if a leak exists. Unfortunately this makes detection difficult unless one of the sensors is located in the bilge. Similarly if a gas locker is fitted it should be external and well vented.
The average gas alarm will detect contraction of gas at 25% of the Lower Explosive Limit (LEL). Thus giving time to stop the leak and prevent disaster. A human can detect gas concentration at around 5% LEL. LPG is given its bad smell particularly for this reason so that leaks can be detected by humans.
There are 2 types of alarm systems those that merely alert you to the prescence of gas and those that can actively shut down the gas source through a solenoid valve. Pilot Gas alarms offer such a system. This is especially suitable for boats in remote locations where the owner can be at peace of mind no gas leak is occuring on his boat.
How do the sensors work?
The sensor is made from a sintered metal oxide that is heated on detecting gas passing over it increases in electrical conductivity. Separately another part of the sensor is enclosed and not exposed to the gas. This is used as a control and the differential between the two is used to trigger the alarm.
What else will set the alarm off?
The sensors will also detect other flammable hydrocarbons such as paint thinners and other solvents, petrol, diesel and Alcohol. Similarly a fault in the system will cause the alarm to go off. Different lights will advise whether it is a real danger or not.
When a Gas Alarm sounds
You should prepare an emergency plan incase the alarm goes off. Generally this would involve avoide using and electrical devices and open all doors and hatch and ventilate the area.
Fitting a Gas Alarm
Most units are 12V however some 24V versions are also available.
Position the control box in an easily accessible area and also in view so that warning lights can be seen.
There are both single or multi sensor alarms available. Fit one also in areas in the boat that gas is likely to collect e.g install a sensor head in the space under the gas locker or in a space where gas pipe joints are not easy to inspect, in which case a multi sensor system would suit. Similarly install a sensor close to the bilge and follow the installation instructions carefully. Check the sensor regularly for dust buildup as this can prevent the sensor working.
Consider also the ALDE Bubble leak sensor which performs a test everytime the gas is turned on.
The trip ashore after a voyage is often the most eagerly anticipated part of any trip. Often made at night the trip should be carefully planned to prevent mishap.
Firstly, when in an inflatable it is important to note that all your safety luxuries are left behind and so to better prepare yourself take the following with you when travelling any reasonable distance in a tender:
• Waterproof bag to carry any valuables;
• A bailing bucket or similar device; and
• Spare oars / paddle if under motor.
• Handheld VHF radio switched on to CH16;
• Handheld flares;
• Waterproof flashlight with a good beam length to enable you to find your boat on your return;
• A small anchor with line attached – be careful not to put too large an anchor in the dinghy;
Secondly, be wary of motoring around bays at night as large powerboats have been known to not see the inflatable until too late hence the need to a carry powerful torch.
When using a harness in conjunction with a tether, it is essential to check that both the harness and the tether are designed to the same standard, and specifically to the same breaking strain level. The breaking strain is defined by the original standard, but also by the age of the harness or tether : the ageing and general condition of the webbing impacts negatively its level of performance. The latest generation of tethers have load indication device which show if the integretity of the tether has been compromised and needs replacing. Whilst expensive they provide piece of mind that your harness system is going to work when asked to do so. The load generated by a person being dragged by a moving boat is significant due to the large surface area.
The tether: its essential features
Number of lines
A double tether has 2 lines and 3 hooks. It enables you to remain clipped as you move about the boat and to secure you to a position in the cockpit in rough seas. A single tether has one line and 2 hooks or 1 hook and a loop and is the most popular tether with sailors.
Number of hooks
Tethers either have 1 (attached to the harness via a webbing loop), 2 or 3 hooks
Hooks are either self-locking such as the Gibb type (easiest to engage and disengage) or the screw bezel type (less expensive but equally as strong).
For most fore and aft along the boat using jacklines the self-locking is the best choice as it enables the wearer to quickly unclip and reclip him/herself to the line.
Length of lines
The standard length is 2 m. In the case of a double tether, the 2nd line is reduced to 1 m so that you can clip yourself on a shorter length. The very principle of a harness is to prevent a man falling overboard and being dragged ; one must therefore be clipped on a short length, as often as possible. Tethers on children harnesses are shorter.
Tethers are either elasticated or webbing. The elasticated tether stretches out when needed and contracts when not under tension, which contributes to a greater freedom of movement and improved safety, as it stays out of your way on the deck. The elastic tether is the obvious choice for yachtsmen who wear their harness regularly. It does however not have the same visible guarantee of strength as ordinary webbed type and so consider a load indicator version such as the Plastimo ISAF tether.
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