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Old 28 July 2007, 08:58   #1
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Lifting a RIB with slings

I have just come back from 10 days in Spain where we keep our RIB.

When we are not there it is stored in a yard undercover and is only left on our mooring afloat whilst we are in residence so to speak. (sounds posh). The yard, which has no water-frontage, trailers the boat to a public slip and launches for us all of which is common practise with many yards in and around the harbour. Next to the slip are two cranes also used by the various yards to launch boats.

From what I can see there is not the culture in Spain of trailering your RIB in the morning to a slip to launch it and then trailering it back out in the evening. There a quite a few versa docks or equivalent down there and those who donít have them tend to antifoul. We are a little unusual in keeping our boat ashore when we are not there as most keep their boats afloat for the season which is what I have done with previous sailing boats.

I have noticed that with a growing number of RIBs in the area it seems to be more and more common for these to be craned in using slings not lifting eyes. I have always insisted to the yard that our RIB must be launched by trailer down the ramp and never lifted in a sling and was very surprised to see within an hour or so 2 Valliants and a big Osprey all launched by crane and sling.

I suspect that as RIBs are becoming more popular nobody has thought about this and they are just treating them as if they were rigid hull boats.

The yard has now told me that after this year they will replace all their trailers with ones with hydraulic adjustable chocks and fancy electrics that must not be submerged and so will no longer be able to launch by trailer and slip unless I buy my own trailer. At the moment I only have a storage cradle with dolly wheels which we used to ship the boat down on and storage whilst in the yard.

I have always understood that you should never lift a RIB in a sling and this is even mentioned in the XS manual that came with the boat.

What do other RIB users think and have they ever lifted using slings?

Sorry no pictures but I can get some when I am down again in a few weeks time.
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Old 28 July 2007, 09:10   #2
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Every launch I have done for the past four years has been by crane and slings. All that's needed is a spreader bar and hard tubes.
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Old 28 July 2007, 09:52   #3
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Thanks Richard

They do have good wide spreaderbars.

I have also noticed that when yard get my boat ready they always seem to have the tubes harder than I would which may be thier normal procedure. I then tend to let some air out.

I must say I am still a bit nervous though.

Jon
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Old 28 July 2007, 13:00   #4
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Slings vs. Eyes

Does your boat have lifting eyes? My Avon SR 4.7 has factory eyes fore and aft although I have never used them. I trailer in and out. I'd need to go look but I think the eyes on the SR are through hull and are very beefy. Even if one has them they would need to have the proper bridle to connect the boat to the lifting device. Even with the proper bridle, one would need to insure the bridle was properly connected to the eyes...another opportunity for bad things to happen.

I would agree that if spreaders are used to avoid a lateral "pinch" on the hull/tubes, slings should be just fine. The hull would surely be capable of carrying the dead weight of the boat, the force of which would be exerted on the keel.

I've been around a lot of "travel lifts" which use slings to launch larger vessels and they provide the spread required due to their inherent design. Again, a crane with a single lift point would demand spreaders. The trouble with sling lifts ocurrs when someone doesn't get the balance points right; I've seen a 30' center console dropped that way.

Having said all that, anytime a boat is airborne risk is present. I would always want to be present during such an operation unless I knew the crew to be bullet proof.
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Old 28 July 2007, 13:22   #5
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Thanks Tomas

We dont have lifting eyes fitted and they would have needed to be put in during the build. I got the boat as an ex demo so I got what they put on but had I the option I would have specified them.

It is not so much the concern of droping the boat out of the slings more that it is damaged by the lifting process. I understood that the point where the tubes are attached to the hull can be weakened over time by lifting with slings. Lawrence at Barnet Marine indicated that you would not notice anything immediately but it would in time cause problems. I would have thought that this would show first around the transom.

I have noticed that there is a thread about a new Ospery on the south coast and it shows pics of it being launched in a sling which i think is suspended betwwen the forks of a fork truck (dificult to see). The sling is hardly compressing the tubes so i doubt if that is causing a problem.

I'm interested to know if anybody has had problems.
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Old 28 July 2007, 15:17   #6
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Quote:
Originally Posted by Richard B View Post
Every launch I have done for the past four years has been by crane and slings. All that's needed is a spreader bar and hard tubes.
A lot depends on how much the tubes stick out. On my boat they jut out a long way so wouldn't fancy lifting slings. What about deflating the tubes altogether???
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Old 28 July 2007, 17:25   #7
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They've lifted plenty of Prosports out of the water where I keep my RIB. They reckon that deflating the tubes is the worst thing you can do as there's a risk of pinching the tubes adainst the hull attachment. Keeping them hard spreads the load.
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Old 28 July 2007, 23:05   #8
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Originally Posted by codprawn View Post
A lot depends on how much the tubes stick out.
A spreader of greater length than the beam of the boat with tubes inflated would exert little or no force on either the tube or hull at the point where the tubes are connected. The weight is carried by the keel. There is no difference between such a lift, force wise than placing the hull on the ground, with support stands to keep her upright. That is why a travel lift is always the best way to sling a boat, if such a machine is available. If the vessel will fit under the machine frame, the lift points are always greater than her beam. A spreader length equal to or less than the beam will exert "pinch" force proportional to how much less than the beam its length is.

Were one to use a single point sling lift using a crane without using a proper spreader, even on a rigid hull, one would risk damage to rails and exert unhealthy pinch forces on the hull/deck joint.

Tomas...king of the twelve oz. lift
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Old 29 July 2007, 05:26   #9
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When i had my previous RIB lifted out i but LARGE FENDERS (sausage type) between the sling and the hull this stopped the slings collapsing the tubes, you might have to get in the water to do this
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Old 29 July 2007, 07:07   #10
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When i had my previous RIB lifted out i but LARGE FENDERS (sausage type) between the sling and the hull this stopped the slings collapsing the tubes,
Not to beat a dead horse but using this method would amplify the pinch force on the hull in an area that the hull is not designed to be pinched, even as you "protect" the tubes from compression. Spread the lift point of the slings outboard of the tubes and viola...problem solved. I would think that most conventional rigid hull pleasure craft have a beam equal to or greater than most ribs so therefore a properly equipped boatyard should have the equipment to sling without compressing the gunnels, tube or no tube.

The further complication with a proper spreader is to be able to position the fore and aft sling in the correct location to balance the lift. A non-adjustable spreader for lifting a 18 meter vessel will not be correct for a 4 meter vessel in terms of fore/aft placement.

It comes down to competency of the boatyard and most who are actively handling a large assortment of lifts probably have the awareness and equipment to avoid problems. There are however some pinchmeisters out there, I'm quite sure.

Any hull builders out there who care to comment? I'd be interested as to how much or little the shell of a hull is affected by compression or what design thought goes into the eventuality that these hulls will be slung. I don't think there's any argument that severely compressing tubes is not a good idea at all what with their mechanical joining to the hull. It ain't natural which brings to mind Mr. Natural who says, "Get the Right Tool For the Job"
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