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-   -   Lifting a Heavy RIB using Spinnaker Pole Setup? (http://www.cruisersforum.com/forums/f117/lifting-a-heavy-rib-using-spinnaker-pole-setup-120061.html)

TMT2 03-02-2014 12:19

Lifting a Heavy RIB using Spinnaker Pole Setup?
 
Anyone out there with experience lifting around 350lbs of dinghy with a spare halyard/spinnaker pole rigged like a crane?

I am "cogitating" on the physics of lifting my Avon 10 footer onto the foredeck of my Gulfstar M53 Ketch. The RIB has a steering helm and Yamaha 25 four stroke + 10gal tank + battery...total weight about 350lbs.

I have heavy duty, hydraulic davits for local lifting and quick deployments but want to put the RIB up on the foredeck for open water passage to avoid the following seas and heavy weather swinging/chafing issues.

My idea: Crane the dinghy (fully equipped) (fair weather) from water, over lifelines to center of foredeck (pre-formed chocks) using crane action of the spinnaker pole and a 7-1 purchase for lifting 350lbs of dinghy weight.

The rig:
(1) Spare halyard (5/8in dyneema) to top-side of spinnaker pole (as topping lift) controlled by 2-speed Barrient 16 on the mainmast.
(2) Snatch block on lower-side (outboard) of spinnaker pole with "lifting" line (1/2in polyester) using a 7 to 1 purchase block to handle lifting (hand pulled).

Has anyone done this kind of thing out there? Any suggestions/ recommendations. I have tried this rig with a smaller 80lb water-tender (8.8) and the mechanicals seem to work but I am concerned about the integrity of the spinnaker pole - especially at the mast contact point and the slide track base with an additional 230 lbs?

I'd welcome any advice/suggestions?

TMT2
Gulfstar M53
s/v TAKE ME THERE!
Tampa, FL

toddedger 03-02-2014 14:53

Re: Lifting a Heavy RIB using Spinnaker Pole Setup?
 
I've done something similar. I used to build spin poles, no problem for the pole and fittings. The trouble is when swinging in with the load. The boat will heel a bit, and change heel as you come closer to the centerline. You need several hands to control the guys to keep load under control.

Dsanduril 03-02-2014 15:29

Re: Lifting a Heavy RIB using Spinnaker Pole Setup?
 
Our dinghy is somewhere between your two examples in total weight and we've used pretty much the system you describe with no problems/issues. If you think about the loads on spinnaker sheets and halyards when the wind is up then 350 pounds is really very little.

TMT2 04-02-2014 09:02

Re: Lifting a Heavy RIB using Spinnaker Pole Setup?
 
Appreciate the comments - I will attempt the lift of the new RIB (350lbs) in the next few weeks and post my "lessons learned" along with a few photos or video for others if it works out well. I have literally "crawled" the web looking for records of others' experiences and there is very little on the "how to" on this one with accompanying video - seeing it work is priceless.

TMT2
Gulfstar M53
s/v TAKE ME THERE!
Tampa, FL

Cheechako 04-02-2014 09:12

Re: Lifting a Heavy RIB using Spinnaker Pole Setup?
 
I'd take the motor off.

Jd1 04-02-2014 12:54

Re: Lifting a Heavy RIB using Spinnaker Pole Setup?
 
Quote:

Originally Posted by Cheechako (Post 1458697)
I'd take the motor off.

I'd use a bladder filled with water and adjust the water to simulate an overload.

a64pilot 04-02-2014 13:20

Lifting a Heavy RIB using Spinnaker Pole Setup?
 
Engine weight is 170 lbs, 10 gl of fuel is 68 lbs without tank, battery maybe 20 lbs? Thats 258 lbs just there. Maybe total weight is more than 350? Dinghy and steering helm is how much?

boatman61 04-02-2014 13:34

Re: Lifting a Heavy RIB using Spinnaker Pole Setup?
 
I'll second the remove engine and secure separately.. same with the fuel tank.. having that much weight lashed on the foredeck is asking for trouble in a seaway if it kicks up... adopt a more seamanlike approach.

FlightPlan 04-02-2014 14:06

Re: Lifting a Heavy RIB using Spinnaker Pole Setup?
 
I have done this often, and each time made modifications to the system. I will preface with the following equipment on board my boat:

Electric primary winches
2 spare halyards
4 spare snatch blocks
2-1/2" diameter spinnaker pole
deck chocks
11' AB inflatable with 25 HP Yamaha
16 gallon fuel tank

I use one halyard as a topping lift to the outer pole end. (my pole attaches to the mast track ball and socket and has a hand winch with continuous line that raises it to vertical and latches to the mast when not in use) The important thing here is to set the pole at a level high enough so you don't have to raise it during the process of hoisting.

I run a line tied to the outer tip of the pole to a block attached to the other end which is measured to be centered over the ring of the hoisting bridal. I then run the second halyard thru the block and attach the halyard shackle to the bridal ring. This allow me to hoist straight up from the chock. The pole is actually not taking the boat weight which is around 800 pounds, the halyard is doing the work.

I have a spare line that is 30 feet long that I actually run thru the centering block on the pole to the halyard itself and it gives me enough tail on the halyard to run thru a snatch block that is on a pad eye used to secure the baby stay on the outboard rail. Then the halyard is led back to the electric primary winch.

The final step is to take another spare line tied to the pole tip that leads back to the unused primary winch. This line swings the pole outboard with control and compensates for the issue caused by heeling of the boat. Once the boat is outboard and clear of the shrouds, I square the boat up with the dingy mooring lines by tying them to the lifeline on the boat. I then start easing the boat down with the halyard on the primary winch.

It takes about 15 to 20 minutes to load or offload the dingy with this method and I have done it by myself. I prefer to have one other hand to assist with keeping the dingy pushed off the boat which is navy blue and will show white scuffs every time the dingy rubs it going up or down.

john540 04-02-2014 14:08

I always took the motor off first. (25hp) My Achilles RIB weighed over 200 pounds, and I would crank it up with the spinnaker halyard. Usually one person would stand on the foredeck and lean out, holding the halyard outboard so the dinghy wouldn't catch on the side of the boat. Once the dinghy was to the lifelines, they would push directly on the dinghy until it was over the lifelines, then let it swing in to the center. We would tip the dinghy onto its side, and lower it upside down onto the deck. It was tricky to do when it was windy, but I was able to do it by myself many times.

CDunc 04-02-2014 15:04

Re: Lifting a Heavy RIB using Spinnaker Pole Setup?
 
My Thought would be to the compression the spinnaker pole would be exerting on the mast at the fitting, it seems the spinnaker pulls on the mast when in use and when it is too much the fitting gives way. I think I would rig a wire "stay" to the fitting and then to a chain plate or the toe rail when over the side and then rig it forward to one side or the other so the rib will clear when the boat is over the bow area to help with the compression loads. But that's just me.

Dsanduril 04-02-2014 15:22

Re: Lifting a Heavy RIB using Spinnaker Pole Setup?
 
Quote:

Originally Posted by CDunc (Post 1458951)
My Thought would be to the compression the spinnaker pole would be exerting on the mast at the fitting, it seems the spinnaker pulls on the mast when in use and when it is too much the fitting gives way. I think I would rig a wire "stay" to the fitting and then to a chain plate or the toe rail when over the side and then rig it forward to one side or the other so the rib will clear when the boat is over the bow area to help with the compression loads. But that's just me.

Spinnaker poles (properly designed) are intended for compression loading, and that is usually the largest determining factor in the sizing of the both the pole and the fittings. When the pole is far forward (on a reach) and the guy is pulling aft the pole is under tremendous compression loads (essentially the tension load on the guy = the compression load on the pole - even at an angle of 20 degrees between pole and guy the pole load is > 90% of the guy load), which are all transferred to the mast fittings. A 350 pound dinghy is nothing compared to 1000 square feet of sail with 10 knots of breeze on a reach.

TMT2 05-02-2014 10:03

Re: Lifting a Heavy RIB using Spinnaker Pole Setup?
 
Thanks to all who are commenting with good insights. I would prefer not to remove the outboard as this is an "involved" task.

Flightplan - You seem to have the nearest setup to what I will attempt. My spinnaker pole is on a track on the forward side of the mainmast. I have lots of height flexibility to set the spinnaker "crane" at the right level to clear lifelines, but the angle is what I need to bring the RIB to the center of the foredeck. That means I need two "lift mechanisms"...one to lift the RIB from the water (or deck) and one to raise the high end of the spinnaker pole (topping lift) to reach the center of the foredeck (for launch or stowing). I have that - 1 x 2-speed manual winch on the mast and the lift line on the 7:1 purchase rig...both can be tied off their own cleat on the mainmast - I do not have to "share" anchor points.

A64pilot - The AVON (plus helm) is probably in the neighborhood of 200lbs - so I agree...the lift will be more in the neighborhood of 425lbs. You can't turn this rig upside down due to the helm & bench seat...might as well keep everything else mounted for a "complete" lift.

Boatman61 - Yes...450 lbs on the foredeck is a planning factor to consider...this is a 53ft boat with a 16ft beam...I am more concerned about seeing over it from the center cockpit than the balance issues I think?

I still have to fabricate the lifting bridle and get the bow/stern balance right on the RIB when lifting - will work that this weekend. The I must also design the "cradle" and on-deck tie-downs so that the V-birth hatch will open for venting with RIB in place on the foredeck.

More to report later as I experiment with this - if it works to my satisfaction, I will post video. Thanks for all of your inputs!

TMT2
Gulfstar M53
s/v TAKE ME THERE!
Tampa, FL

boatman61 05-02-2014 10:23

Re: Lifting a Heavy RIB using Spinnaker Pole Setup?
 
Was not overly concerned with the 'Balance'.. was more concerned about a hard bottom rib sitting on the deck with just a lashing.. even upside down they'll move in a seaway..
Now you've stated your building a cradle that resolves some of my concerns.. have fun..

a64pilot 05-02-2014 10:42

Re: Lifting a Heavy RIB using Spinnaker Pole Setup?
 
Watch an episode of "whale wars"


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