Noddy Guide to Making Block and Tackle MOB system

[Daydream believer]

Whilst a 6:1 block gives a good mechanical advantage getting it extended & stopping it from tangling will be difficult.
It is not like a mainsheet or mast lift where the ends are fixed to something
If the block fell back through a loop it would be hard to sort in an emergency, or at night etc
Do you need a tackle with the winch?

 

[William_H]

So what happens when the load goes on the line as you start to lift the casualty

Quite so you need a tackle yes 4 to 1 is best to hang off the end of the boom with the topping lift holding the boom up. It is likely that the topping lift will be strong enough to take the weight of the person but friction in all the pulleys will make it difficult to raise the boom by the topping lift. Certainly on smaller boats a main haliard can be difficult to use to simple raise a person up the mast because of friction. You need to test the system in anger with a wet person on the end. No don't rush down to the boat right now just wait till summer before you throw him or better her into the water. (advice to my UK friends) olewill

 

[KellysEye]

We had a six to one block and tackle attached to a halyard and left it permanently rigged. We did test it with full wet weather gear and Jane and I could haul each other up. I've never seen another yacht with that. However the chances of a two handed crew getting a MOB back in heavy weather are slim to nil, they disappear very quickly and furling the genoa, turning round and starting the engine takes time. If you go below deck to press the MOB button on the GPS then its even more time.Thus our objective was to never have that situation and always wore harness and tethers at night and in bad weather. We had tape jackstays along the deck tied to fore and aft cleats.

Was the block and tackle necessary? Probably not but it gave, with hindsight, a false peace of mind. Now I probably wouldn't fit one but stick with the harnesses etc.

 

[nigelmercier]

I've been in discussion with Graham Wright regarding the use of a MastaClimba, he says:

With a weight on the end of a line (to give it some tension) a MastaClimba hung over the side would help a conscious MOB to help himself aboard. It would still need someone lifting with a sling of course but the major effort would be substantially reduced.

Sounds like a plan to me. No connection, just a happy customer.

http://www.mastaclimba.com/

 

[duncan99210]

The only realistic option for recovering a MOB on our boat is over the stern, especially with only the two of us on board. Yes, I understand the problems of rising and falling stern meeting MOB head, but it is more likely that this can be managed than reaching down a metre or more of freeboard to clip on a line to the casualty. We have a permanently rigged four to one handy billy rigged from the backstay which can be led to the genoa st winch. Frankly the main objective is to haul the MOB on to the boat, get them down below and start treatment, accepting the risk of additional injuries caused by the recovery than taking time out to rig complex systems from the boom or mast. However, that's for our boat, which has a sugar scoop and open passage from stern to saloon: other boats with a solid transom will need to look at over the side recovery systems, all of which are more complex and time consuming.

 

[AntarcticPilot]

With any block and tackle, you have to consider several issues when designing it. You have to look at the force available for pulling on the fall, the weight to be lifted and the speed with which the object is to be lifted. The point is, if you have a low force available - and those of us with lightweight crews need to consider this - then you can EITHER lift a large weight OR do it quickly - you can't do both. Now, I am nearly twice the weight of my wife, and she has weak shoulders. So, to get my weight down to a load she could exert would need at least a 6-1 tackle; possibly even 8-1. But of course, a 6-1 tackle means that she has to pull in 6 feet of rope for every foot I rise. So, whatever happens, she isn't going to lift me quickly! And because of the number of sheaves involved, there will be some loss in the tackle so in fact, the load will be higher than indicated by my weight and the ratio of the tackle. On the other hand, I can lift her weight without too much trouble, and a 2-1 tackle would probably work, and a 4-1 tackle would make it easy.

One answer is to have a 4-1 tackle, and my wife would use a sheet winch to haul on the tail. But it's not ideal if there's a sea running and I'm being thrown against the hull!

Incidentally, there are good and bad ways of reeving a tackle - the good ways lessen the friction in the tackle quite significantly by ensuring the parts of the tackle don't rub on each other. The Ashley Book of Knots is your friend there!

The other issue is going to be ensuring that a tackle with a lot of parts is ready to use. As others have suggested, a tackle kept in a locker somewhere is highly likely to come out of the locker in a tangle! And if it is stored with the blocks tight against each other to lessen the tangling, you have to pull a LOT of rope through before it can be used. Remember the old Haltrac Hoist? About a 10-1 ratio - but usually taking ages to set up because it had to be untangled and then stretched out!

I think that on the whole, I'd rely on using the winches with a low ratio tackle.

 

[jac]

Antarctic pilot makes a good point.

Whilst others have mentioned using a 4:1 or 6:1 you need to get a ratio that works for you. Your weakest likely member of crew needs to be able to lift your heaviest. Practically that is your wife lifting you.

You need to know what she can lift - do you have children/ grandchildren that she can easily move around. Use that as a starting point. If she can lift a 3 stone child and you weigh 15 stone then MINIMUM of 5:1 is needed. You also need to factor in your weight in full kit and soaked in water. Your 15 could become 20 making something like 6 or 7:1 needed.

Do remember that you don't need to have the handy billy able to be attached from boom to the casualty. If your boom is say 3 feet higher than guardrails then you don't need to lift the casualty those last 3 feet. Make the handy billy 3 feet shorter and use a 3 foot tail which will reduce the length of rope that you have to pull in to lift the casualty.

Finally, (and best done when safely moored up) test it. If you are the heavy person, can you sit on the pontoon and be lifted aboard. Your wife will need to be able to reach the tail and heave, she may need to be able to make it fast somewhere, how will she do that. She might need to lead to a winch, how can that be done. These can only be tested in-situ.

 

[saltylegs]

I have practiced lifting with the boom, the main sheet has a high load snap shackle to attach it to the traveller, this can be clipped on to the lifting strop.
the topping lift is strong, led to the cockpit and a winch if needed.
One advantage is that when pulling in you are always pulling the casualty towards the boat as the lead is from the bottom of the purchase.
Over the stern is not really an option for me.

 

[Stork_III]

I have practiced lifting with the boom, the main sheet has a high load snap shackle to attach it to the traveller, this can be clipped on to the lifting strop.
the topping lift is strong, led to the cockpit and a winch if needed.
One advantage is that when pulling in you are always pulling the casualty towards the boat as the lead is from the bottom of the purchase.
Over the stern is not really an option for me.

Put a snap shackle at each end. When you need it, reverse it on the boom, then you can pull down using your body weight.

 

[KenMcCulloch]

We have a similar spare purchase kept in the aft cabin and easily brought on deck to use in conjunction with the lifesling in the same way Old Bilbo describes. Something none has mentioned is using the liferaft. Depending on the circumstances, deploying a liferaft has always been high on my list of possible actions in a serious MoB incident.

Of course the most likely scenario for an MoB is not in the dark in big seas when everyone is far too scared to go over the side, it's picking up a mooring or leaving an alongside berth on a calm sunny day! One of the times we insist on LJs being worn is for such manouvres.

 

[nigelmercier]

You need to know what she can lift ...

No, you need to know what she can pull. Big difference.

 

[LadyInBed]

Put a snap shackle at each end. When you need it, reverse it on the boom, then you can pull down using your body weight.

I have put Snap and Swivel Shackles ( http://www.s3i.co.uk/SSswivel.php ) on both ends of of my main sheet blocks and my kicker blocks, it makes them very versatile. Easy to remove, main reversed for lifting mob or anything else, kicker with a snatch block on as a barber haul.

 

[knuterikt]

I agree that staying on the boat is best, but we know that sometimes the best intentions won't help.
So having a plan to recover a MOB would still be a good idea.

Some comment's to you statements in the quoted text in blue.

We had a six to one block and tackle attached to a halyard and left it permanently rigged. We did test it with full wet weather gear and Jane and I could haul each other up. I've never seen another yacht with that.
However the chances of a two handed crew getting a MOB back in heavy weather are slim to nil, they disappear very quickly and furling the genoa, turning round and starting the engine takes time.
Furling main and starting engine would not be my first choice you can turn back under sail faster. More secure no propeller to catch MOB or rope in water.

If you go below deck to press the MOB button on the GPS then its even more time.
The MOB button should be in the cockpit.
I think you will find that there are equipment that can have a external MOB button.
A DSC radio can be used to alert others with you position so having a DSC radio at hand in the cockpit seems like a good idea.

Thus our objective was to never have that situation and always wore harness and tethers at night and in bad weather.
And what if the weather is not that bad, a MOB situation can happen in good weather also.

We had tape jackstays along the deck tied to fore and aft cleats.
Problem is that there have been cases where the tethers have left the crew hanging over the side this can be as critical as a free floating MOB.

Was the block and tackle necessary? Probably not but it gave, with hindsight, a false peace of mind.
I would regret it if I lost a MOB because I did not prepare.

Now I probably wouldn't fit one but stick with the harnesses etc.

 

[BlueSkyNick]

This is always an interesting topic because the Simple Answer is that there is NO Simple Answer !

whatever system is preferred, I always suggest that the liferaft can be deployed if the MOB is conscious. If he/she can climb in, it buys time for their safety and might make it easier to reboard the mothership.