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 Post subject: SC lifting rig?
PostPosted: Mon Mar 01, 2021 3:57 pm 
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Joined: Sat Jun 13, 2020 9:43 pm
Posts: 12
Location: Victoria, BC
Hi All,

New SC owner and I am super excited to get on the water this year!

My boat will be at a club with primary crane access. Well, there are ramps but they are steep and the SC is a bit heavy!

Has anyone used a crane to launch a 21? If so, can you share some design ideas and/or best practices?

The only method I can think of is 2 straps from Bow Tangs to the rear Rear Tangs (Genniker Tang on rear cross member).

- Is this a good Idea?
- How long should these straps be?
- Any better ideas out there?

One of my requirements at the club is that the lifting rig is "certified". The certification is not really well defined but I have been told that the simplest option is to buy straps from a marin supply shop with published ratings.

Kind regards,

Jordan


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 Post subject: Re: SC lifting rig?
PostPosted: Mon Mar 01, 2021 6:07 pm 
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Joined: Tue May 27, 2003 12:44 pm
Posts: 14063
Location: Oceanside, California
The Cat Cabin poses a challenge.

I have hoisted my Hobie 16. I use lines to the 4 pylon posts. The forward lines were short and the aft lines long as the center of lift weight was just aft of the mast. If you could remove the Cat Cabin you could get to the crossbar outer ends.

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 Post subject: Re: SC lifting rig?
PostPosted: Mon Mar 01, 2021 9:16 pm 
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Joined: Sat Jun 13, 2020 9:43 pm
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Location: Victoria, BC
Hi Matt,

Thanks for the quick response.

Yes, the Cat Cabin is the big issue. In a perfect world, I would lift from the cross beams although removing the cabin is not practical every time we launch.

What do you think of lifting from the bow tangs and tangs on the rear cross beam? Is this wise?

At 600 lbs I don't see any issues. However, with gear in the cabin and a little water in the hulls after a days sailing I worry the weight may become an issue.


As I type this I think I could make straps for under the front hulls and straps to go around the rear crossbeam. That would certainly take any weights that would be involved...


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 Post subject: Re: SC lifting rig?
PostPosted: Tue Mar 02, 2021 8:01 am 
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Joined: Mon May 09, 2005 10:25 am
Posts: 3964
Location: Jersey Shore
I would be leery about lifting from the bow tangs. The angle of the tang really isn’t appropriate for a vertical lift.

An option for lifting by the front crossbar would be to attach your hoisting strap to the cord loops at the ends of the crossbar which are used during mast raising (the loops that the trap wires connect to to stabilize the mast). Those loops pass around the front crossbar bolts, so the attachment should be plenty strong. Just make sure the cord you use is up to the task, you might need to use something a little larger diameter than the stock line.

sm


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 Post subject: Re: SC lifting rig?
PostPosted: Tue Mar 02, 2021 9:25 am 
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Joined: Tue Dec 10, 2019 8:15 am
Posts: 13
This maybe unconventional, but a certified sling is probably pretty small for a boat this light. I’m imagining something no larger than a beefy ratchet strap. Could you pass a sling line through the front and rear crossmembers and have all four ends attach to the crane hook slightly behind the mast as Matt described? You would have to remove or modify the crossmember endcaps but given a long enough sling the angle would be enough to minimize inward pressure on the catbox. There’s a good chance this would get your sling’s connection point close to the front to back center of mass behind the mast. You could potentially just tie the ends of the sling together and leave it attached to the boat 100% of the time, reducing prep time and a chance that it’s improperly configured in the future. I’m not an engineer, just throwing ideas out there.


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 Post subject: Re: SC lifting rig?
PostPosted: Tue Mar 02, 2021 11:27 am 
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Joined: Sat Jun 13, 2020 9:43 pm
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Location: Victoria, BC
srm,

Thanks. I was not thinking about angles. I was originally worried about fastener strength. Between angles AND fasteners, I will rule out lifting from the tangs.

NikNok,

Interesting! I like the idea of threading something through the crossbeams. Maybe a long loop of stainless cable with a sheath could provide the attachment points on each end of the beam.

Does anyone know if the end cap castings from another boat will fit? If I have to modify anything, I would prefer to use "sacrificial" parts and not the OEM.


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 Post subject: Re: SC lifting rig?
PostPosted: Tue Mar 02, 2021 12:22 pm 
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Joined: Tue Dec 10, 2019 8:15 am
Posts: 13
Jordan124 wrote:
srm,

Thanks. I was not thinking about angles. I was originally worried about fastener strength. Between angles AND fasteners, I will rule out lifting from the tangs.

NikNok,

Interesting! I like the idea of threading something through the crossbeams. Maybe a long loop of stainless cable with a sheath could provide the attachment points on each end of the beam.

Does anyone know if the end cap castings from another boat will fit? If I have to modify anything, I would prefer to use "sacrificial" parts and not the OEM.



If it were me, I would remove the endcaps and set them aside for safe keeping. Other than aesthetics, I don't see a need to keep them on the boat if there's a risk they could be damaged. I suspect a nylon lifting sling would do a better job of dispersing the pressure on the very ends of the crossmember. A thin stainless wire would probably dig into the aluminum and potentially damage the wire itself. Just looking on Amazon, a 2" wide nylon lifting sling has a 6,400 lbs capacity.


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 Post subject: Re: SC lifting rig?
PostPosted: Thu Mar 04, 2021 12:54 pm 
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Joined: Sat Jun 13, 2020 9:43 pm
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Location: Victoria, BC
Quote:
If it were me, I would remove the endcaps and set them aside for safe keeping. Other than aesthetics, I don't see a need to keep them on the boat if there's a risk they could be damaged. I suspect a nylon lifting sling would do a better job of dispersing the pressure on the very ends of the crossmember. A thin stainless wire would probably dig into the aluminum and potentially damage the wire itself. Just looking on Amazon, a 2" wide nylon lifting sling has a 6,400 lbs capacity.


More good advice.

I will focus on a strap through the front crossbeam (stays in place at all times) and 2 removable straps that wrap around the rear crossbeam and hook to either end of the strap through the front crossbeam.


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 Post subject: Re: SC lifting rig?
PostPosted: Sun Mar 07, 2021 12:36 pm 
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Joined: Wed Aug 08, 2007 10:20 pm
Posts: 272
Location: South Boardman, Mi
Unlike most cats the 21SC has a front crossbar to support the front tramp. I would lift the bows from straps on this crossbar. The lacing for the front tramp will keep the straps from moving laterally. Lift the rear with the rear crossbar. Again the tramp lacing should keep the straps from moving laterally. If the lifting angles are vertical this should be sufficient. If the lifting angles pull the straps inward you may need to brace them outwards with a pole (2x4?)

Alternatively just trailer it down the ramps. 600lb hobie cats launch way better than 3,500 lb sport boats.

Mast up storage out of the water is the best. Get good sail covers and leave the boat 95% rigged. Once upon a time I had lake front trailer parking for my 21SC and I could be sailing within 15 minutes.


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 Post subject: Re: SC lifting rig?
PostPosted: Sun Mar 07, 2021 8:41 pm 
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Joined: Sat Jun 13, 2020 9:43 pm
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Location: Victoria, BC
Quote:
I will focus on a strap through the front crossbeam (stays in place at all times) and 2 removable straps that wrap around the rear crossbeam and hook to either end of the strap through the front crossbeam.

Back at the boat for a little more exploration and measuring this afternoon. I am drifting back toward my idea of 1/4" stainless cable with a strong UV-resistant coating.

The crossbeam endcaps on both front and rear have approx 1/2" openings with nice radiused transitions. The idea is to run the cable through the existing holes and swage a thimble on each end. A 4 strap lifting rig will attach to each thimble with hooks. The cable will exert pressure on the extruded end cap that will transfer the load to the upper half (I guess?) of the crossbeam extrusion.

Concerns
- What to do with the thimbles that are sticking out when not being lifted?
- The hook/thimble joint may rub on the Cat Cabin.



Quote:
Unlike most cats the 21SC has a front crossbar to support the front tramp. I would lift the bows from straps on this crossbar....

I would certainly prefer this! 4 choker straps with a common lifting ring and I am golden.

My concern is the front tramp crossbar is only attached with a small plate and 2 bolts on either side. This looks appropriate to take the load of the tramp as it is transferred down through the plate and onto the top of the hull. My impression is that these 4 bolts (2 on each side) would take at least half the weight of the boat when lifting. This force would be pulling up, like a claw hammer removing a nail, and is a lot to ask for anything threaded into fiberglass.

Page 10 of the parts guide appears to show machine-style screws for the mounting plate which leads me to speculate that a nut or threaded bar is integrated into the hulls somehow. Unless I have missed it, neither the assembly guide nor the parts guide details this section of the hull.

Does anyone know what is inside the hulls? If the hull has something approximating a chainplate or significant backing plate I would love to know.



Quote:
Alternatively just trailer it down the ramps.

The boat will be stored mast-up with most rigging during the summer months. I have a fantasy of being able to jump on my bike with the kids, ride the club, be sailing in 20 min! The crane and lifting rig makes this possible.


Thanks again for all the thoughts!


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 Post subject: Re: SC lifting rig?
PostPosted: Tue Mar 09, 2021 6:38 pm 
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Joined: Wed Aug 08, 2007 10:20 pm
Posts: 272
Location: South Boardman, Mi
The front crossbar is held on by the same hardware that supports the bridal wires. It is plenty strong.

Here is some math to make you feel more comfortable. Imagine your boat fully rigged with no rig tension or sheet tension on a calm day. Then sheet in hard on the main. The downward force from the blocks acts on the sail, mast and rigging. The mast step becomes the fulcrum of a lever that runs from your bow tangs to the mainsheet. The ratio of the vertical component of loads on the main blocks (MainBlockForce_Z) to the vertical loads on the bow tangs (BowTang_Z) for a rig with minimal mast rake is equal to:

MainBlockForce_Z*L1/L2=Bowtang_Z

L1 is the length between where the main block attaches to the boom and the mast. On the 21SC this is equal to the length of the boom, or about 9.5ft.
L2 is the fore-aft length between the mast and the bow tangs, or about 7.5ft.

The 21SC has a 7 to 1 mainsheet, so the force you feel in your arms sheeting in is 1/7th the force acting on the boom. In total the ratio works out to 8.87:1.

Going back to the imagined example, if you were able to pull with a force of 100lbs*, the rear crossbar would see 700lbs of vertical force and the bow tangs would see 887lbs of vertical force (plus some aft force). The mast step would see 1,587 lbs of vertical force (plus a forward force equal to the aft force at the tangs plus the weight of the mast). As you can see the bow tangs are plenty capable of lifting the 300lbs required to get the boat out of the water. This example also illustrates the importance of a dolphin striker under the mast as 1,587 lbs in the middle of a 7' span is a tough load to carry.

*Disclaimer: I would not recommend sheeting this hard on a 21SC. https://www.hobie.com/forums/viewtopic.php?f=45&t=61361&hilit=+mast


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 Post subject: Re: SC lifting rig?
PostPosted: Wed Mar 10, 2021 8:33 am 
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Joined: Sat Jun 13, 2020 9:43 pm
Posts: 12
Location: Victoria, BC
Quote:
Here is some math to make you feel more comfortable.


That does make me feel more comfortable!!! Thanks.

Hooks through front crossbeam tangs and strap around rear crossbeams is nice and simple. I will explore some appropriate straps.


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