Part 2 - RNLI Thurrock

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Part 2

TEAM > Tender Safety


RECOVERY FROM A CAPSIZE OR SWAMPING

Unwanted and unwelcome events such as a capsize, or a swamping can in normal circumstances largely be avoid by practising good seamanship – see parts 1 and 3. Recovery from such events should be possible in a well-found dinghy fitted with adequate reserve bouyancy; and the crew should afterwards be able to row safely home.

Getting the dinghy upright

This begins before going afloat with crew and boat checks (see Part 3).

How to roll upright

To upright an inverted rowing dinghy a sufficiently large righting moment must be applied to overcome:-

 l The weight of the dinghy, W ( see figure 6b), which acts downwards so opposing any applied righting moment.

 l Surface tension forces, T ( see figure 6b), which effectively glue the dinghy to the water’s surface.

Applying a righting moment to a rowing dinghy is more difficult than when attempting to right a sailing dinghy, as there will be no dagger plate or centreboard upon which to lever it upright with. Instead the crew must apply the righting moment by using the keels ( see figure 6a), or a grab line (see figure 6b) taken over the hull.






Figure 6a The picture shows the dinghy in figure 1 of Part 1 under construction. The skeg is nice and deep providing a good up stand for the crew to grab hold of. As the crew pulls down on the skeg the hull will sink down in the stern quarter region releasing some of the surface tension forces so easing the job of righting the dinghy. On this dinghy the bilge keels have minimal upstand because it is intended for easy rowing (see Part 1).They would be difficult to hold onto when wet and the crew is cold and tired..






Figure 6b
The grab line can either be a temporary line tied to the middle thwart or a more permanent fixture. It is passed over the hull to the crew in the water. By pulling down hard enough on the grab line taken over the hull , the weight W of the dinghy and the surface tension forces T may be overcome. The dinghy should then roll upright . If the grab line is fitted permanently and taken round underneath the gunwale to the the transom it will provide the crew with a line to hang onto when in the water.

Tip: The grab line should be secured to the transom at gunwale height with an easily releasable clip. By inserting a small length of strong shock chord at the clip end of the the grab line the line may be kept tautly positioned underneath the gunwale.'

CAUTION: Grab lines must be firmly and very strongly attached to the thwart. Also beware of using heavy clips to secure the line to the transom as the line may need to be thrown to a crew member when in the water and it could injure them.

Rolling upright


Once the surface tension forces, and the weight of the dinghy pushing downwards, are overcome by the righting moment the dinghy should roll upright.

CAUTION: As the gunwale breaks free from the water a light and buoyant dinghy will roll very quickly upright– so beware!

TIP: Remember the surface tension forces can be broken by pushing down on the stern quarters of the dinghy on one side of the hull which reduces their effect by raising part of the gunwale on the other side of the hull out of the water.

How Much Water Onboard?

As the rowing dinghy rolls upright it will scoop up water. How much water will depend on how the dinghy floats when upside down; this will be influenced by its weight; the amount of buoyancy fitted, (bags,built in tanks etc), together with it's positioning within the dinghy’s interior.

CAUTION: Remember too much buoyancy may leave the dinghy floating so high that it starts blowing down wind faster than the crew can swim after it!

TIP: With adequate buoyancy and the minimum righting moment applied the amount of water taken on board can be minimised.


Getting back on board.

Climbing back on board a dinghy after a capsize or falling overboard is difficult and requires lots of effort. The more freeboard , the higher the climb, and the more tiring and difficult it can be. The amount of water in the dinghy also affects the crafts stability both transversely (see heeling in part 1) and fore and aft (see trim in part 1) and will determine how the dinghy is reboarded.

Figures 7 to 9 outline reboarding techniques:-

    
l in figures 7a and 7b a lone crew is reboarding over the gunwale in a heavy and a lightly built dinghy

    
l in figures 8a to 8c the lone crew is reboarding over the transom in a light built dinghy

    
l in figures 9a and 9b one crew, from the crew of two , is reboarding over the gunwale in a light built               dinghy.

    
l in figures 9c to 9e The remaining crew member is reboarding over the transom with the aid of a                    stirrup .






Reboarding over the gunwale -- heavy built dinghy





Figure 7a Scrambling back over the dinghy's gunwale is an easier task when the dinghy is well swamped because the weight of the dinghy plus the weight of the swamping water lowers the freeboard . It also increases the dinghy 's stability ( see part1).(This picture is reconstructed from the dinghy in part 1 which had capsized under sail: it lay upon its side and scooped up quite a lot of water as it rolled upright).


BUOYANCY ALERT:

ALL DINGHIES IRRESPECTIVE OF THEIR MATERIALS OF CONSTRUCTION MUST HAVE ADDITIONAL BUOYANCY EQUIPMENT/GEAR SECURELY FITTED ( sometimes referred to as floatation equipment/gear) AND IN WORKING CONDITION SO THEY FLOAT WITH SUFFICIENT FREEBOARD TO ALLOW THE CREW TO BAIL OUT AND ROW HOME AFTER A SWAMPING,OR CAPSIZE.

*
The WOODEN dinghy in figure 7a has buoyancy bags fitted securely under the seats ( see part1) : were these not fitted the dinghy would still float, because the water pressures pushing upwards on the hull would be sufficient to support the light wooden hull complete with the swamping water inside. The dinghy would not sink but its freeboard would probably be too low to allow the crew to board and bail out .

*
This would not be the case if the hull was built of heavier materials such as GRP or ALUMINIUM rather than wood. Without additional buoyancy equipment in the form of bags, tanks or slab foam the dinghy would sink; or at best lie with its gunwales a wash supported only by the buoyancy of its wooden seats and trim if fitted .

* Hulls built in composite construction with a light weight foam or wood core sandwiched between two layers of GRP or some other material may be able to develop sufficient buoyancy to float so the crew may be able to board and bail out.



TIP:
Whatever the type of construction, a dinghy should be periodically tested to ensure it floats and can be recovered if holed, swamped,or capsized.


Reboarding over the gunwale - lightly built dinghy





Figure 7b Scrambling back over the gunwale with the light dinghy is more difficult than with the heavy one of figure 7a, because in a lightly swamped condition the dinghy has more freeboard, and less stability. The dinghy is well heeled by the reboarding crew's weight. The risk of recapsizing the dinghy may be avoided by reboarding over the transom .

Reboarding over the transom - lightly built dinghy





Figure 8a The crew is on his own and is preparing to re-board over the stern by leaping up into the dinghy over the transom.





Figure 8b Leaping up on to the transom immerses the transom so lowering the freeboard thus making re-boarding that much easier.








Figure 8c Finally the crew reboards. Leaping back on board takes a lot of effort and so is quite exhausting. The dinghy's trim is well down by the stern which will affect its stability. The crew should aim to get his weight more central as soon as practicable.



Reboarding over the gunwale -- lightly built dinghy.





Figure 9a
One crew member steadies the dinghy on one side, while the second crew member prepares to reboard, by laying flat in the water alongside the hull. To board the crew then hooks one leg over the gunwale, and then pulls himself up and over the gunwale using legs and arms.The first crew,still in the water, may help the reboarding process by allowing the dinghy to heel slightly so as to reduce the freeboard on the side over which the crew is boarding.






Figure 9b Completing reboarding with the second crew still holding the gunwale to balance the boat as necessary. Second crew is shown reboarding over the transom in figures 9c to 9e.


Reboarding over the transom - lightly built dinghy





Figure 9c The second crew prepares to reboard using a stirrup formed by tying a long bowline ( see part 3) in the stern line .






Figure 9d The stirrup, by placing one foot into it, is used to climb up and over the transom . Although less exhausting than leaping over the stern it still requires the expenditure of quite a lot of energy.






Figure 9e As the crew climbing over the transom completes reboarding ,  the second crew must anticipate his actions and requirements assisting where he can. For example ,a reduction in the the transoms freeboard may help the crew climb more easily onboard; this may be achieved by moving slightly aft to sink the dinghy's stern quarters, and then as the crew comes over the transom moving back towards the bows so as to rebalance the dinghy's trim. It is vital during the reboarding process for the dinghy to be kept well balanced both fore and aft and transversely ( see part1) thus reducing the possibility of a recapsize.



Caution: Beware of getting tired. Climbing back onboard after a capsize always takes a lot of effort and will tire the crew. Also a light weight dinghy with little water on board may re- capsize in the boarding process. The danger is that the crew will start tiring and the situation may start to become more difficult and serious.

Bailing;-

After re-boarding, bailing will be by bucket and scoop bailer: possibly with only one crew member on board if the dinghy has insufficient flotation gear to support the others when it is well swamped. Those crew members left in the water should hang onto the grab lines if fitted or the bow and stern lines, until the  dinghy has been sufficiently bailed out so they can safely reboard. Many light dinghies when fitted with adequate flotation gear may right with little water on board, and in such cases all the crew may be able to   reboard before bailing out.

Bailing with a bucket





Figure 10
Bailing with a bucket is back breaking work! This dinghy fortunately had a dagger plate case which, together with its adequate flotation gear, allowed the water to drain out through the case. This helped the bailing process. Compare to the other pictures where a light capsized dinghy has been righted with little water on board and so requiring little bailing . (This picture follows on from 7c and was likewise reconstructed )

Recovery of gear:-

After righting and before reboarding the crew must collect essential items such as the oars and put back onboard.Once bailed out and before attempting to get under way again, make sure all the grab lines, rip-roaring stirrups, and any other lines are brought inboard – check also that the anchor and line (warp) is still in on board (always stow and secure well before going afloat).

Collect essential floating gear





Figure 11 The crew before reboarding are wisely recovering the oars and other essential gear before  climbing back onboard.

Caution: Beware of getting tired.  Climbing back onboard always  takes  a lot of effort and will  tire the crew. Also a light weight dinghy with little water on board may re- capsize in the boarding process. The danger then is that the crew will start getting very tired and the situation may  then start to become more difficult and serious.

Experience counts:-

Racing dinghy sailors are usually well practised in the art of recovering from capsize situations; if not familiar with capsizing a few practise sessions in a controlled environment are well worthwhile.

Caution: If tests are carried out when it is cold, wear a wet suit or dry suit, and beware of inhaling water as a result of the shock of cold water coming into contact with the body: keep your mouth closed. Make sure there is a competent person on hand to help if a well-planned exercise should start to go wrong.


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