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Old 20-10-2015, 05:36   #1
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Will the cleats work as lift points for davit?

Planning to purchase a Boston Whaler Dauntless 170 as a tender/dinghy and store it on deck, at stern. Already have a hydrolic davit but may need to upgrade it. The question is, BW170 doesn't seem to have any points for tying up the davits cable, so I'm planning either to use the cleats (4 on sides, 1 on bow) or install several lifting points seperately. We're talking about around 2500lbs/1.25 tons here. Any ideas, past experience and/or suggestions?
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Old 20-10-2015, 05:44   #2
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Re: Will the cleats work as lift points for davit?

They aren't made for that in my opinion, but if any can handle it, it would be a little Boston Whaler. I'd use straps under the hull though, I wouldn't risk the cleats.
They really weigh 2500 lbs?
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Old 20-10-2015, 05:52   #3
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Re: Will the cleats work as lift points for davit?

8 inch cleats, they're beefy enough as hardware, however, my main concern is connection points/screws.

Straps are what I have in mind as a viable option too, however, if there's a more practical way (a.k.a. I'm lazy) that's preferred!

The weight is around 2000lbs; however, I'm planning to keep an additional life raft, some supplies etc. on that one as well, as a secondary boat in case of emergency (hence 17 feet instead of 13-15). Not to mention the fishing gear and other stuff that will accumulate over time and make it heavier.
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Old 20-10-2015, 06:15   #4
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Re: Will the cleats work as lift points for davit?

The BoatUS Foundation, in conjunction with the University of Virginia School of Engineering, set up laboratory testing apparatus to simulate the loads placed on cleats of different design configurations and materials.

Cleat (K) 6" Stainless Cleats, fastened with 4 - 1/4-20 bolts, tested to 6660 pounds, at 00 angle of pull (6560# at 45/450).

They did NOT test a dead lift configuration.

Foundation Findings #16 [Cleats]
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Old 20-10-2015, 06:22   #5
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Re: Will the cleats work as lift points for davit?

The clearts are not designed for lifting, you need through bolted lift rings with SS backing plates. The whaler is just foam and fiberglass. I hope your mother ship is large, you really need a hydraulic crane for that size whaler.
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Old 20-10-2015, 06:35   #6
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Re: Will the cleats work as lift points for davit?

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Originally Posted by GordMay View Post
The BoatUS Foundation, in conjunction with the University of Virginia School of Engineering, set up laboratory testing apparatus to simulate the loads placed on cleats of different design configurations and materials.

Cleat (K) 6" Stainless Cleats, fastened with 4 - 1/4-20 bolts, tested to 6660 pounds, at 00 angle of pull (6560# at 45/450).

They did NOT test a dead lift configuration.

Foundation Findings #16 [Cleats]
Like Tingum says; the weak point is not the cleat but the backing.

Mothership is no problem. The issue is with the weight, not size.
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Old 20-10-2015, 06:46   #7
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Re: Will the cleats work as lift points for davit?

Well... If it doesn't work.... At least you'll have some place to glass in rod or drink holders...
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Old 20-10-2015, 06:56   #8
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Re: Will the cleats work as lift points for davit?

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Well... If it doesn't work.... At least you'll have some place to glass in rod or drink holders...

Hurray!!!
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Old 20-10-2015, 07:20   #9
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Re: Will the cleats work as lift points for davit?

In my limited experience from owing one Boston Whaler they do not through-bolt the dock line cleats.
The bow eye is likely a U-bolt that's through-bolted, and you should be able to add your own U-bolts to the inside of the transom pretty easily. The bow eye location (just above waterline) is not ideally located for lifting, so you light want to add your own U-bolt that faces up/aft inside the boat. Make up a 3-point harness of load-rated straps and you're golden.
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Old 20-10-2015, 07:20   #10
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Re: Will the cleats work as lift points for davit?

From the Manual, Pages 2-20 & 2-21

... The bow and stern eyes may be used only for short term lifting of the boat.
Long term lifting with the bow and stern eyes or lifting with the bow locker eyelet can cause stress on the fiberglass and gel coat and is not recommended.
For long term lifting or storage, use flat, wide belt-type slings and spreaders long enough to keep pressure from gunwales ...

http://www.bostonwhaler.com/boat_gra...01352449PM.pdf
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Old 20-10-2015, 07:25   #11
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Re: Will the cleats work as lift points for davit?

Attached Eye Wide Sling Type 9 - Light Duty Nylon Lifting Straps

These seem to be the perfect solution right now.
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Old 20-10-2015, 09:20   #12
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Re: Will the cleats work as lift points for davit?

Consider also how your dinghy up in davits will BEHAVE when your vessel maneuvers in bouncy head seas, wallowing following seas. Will the dinghy bounce up and down, try to swing around? Will that motion increase the stress on the cleats? Are you going to launch and hoist your dinghy in an anchorage that has current? Things to consider when you rely on a cleat to do things it wasn't built for.
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Old 20-10-2015, 10:01   #13
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Re: Will the cleats work as lift points for davit?

I have an 18' BW Outrage that has been hanging in my boat house for 30 years (supported by 3 factory installed "lifting eyes") with no apparent damage or issues. All three eyes are thru bolted IE eye on both ends of a threaded rod. Having said that all lift cables are vertical and there are no dynamic loads (other than me getting in or out of the boat). I certainly would not consider lifting from eyes/ cleats only supported by skin and backing plates.

"Long Term Lifting With Bow and Stern Eyes Can Causes Stress on the Fiberglass and Gel Coat ...") is a nonsensical restatement of the definition of Young's Modulus" or maybe "Hook's Law". Probably crafted by BW's legal department as a poor excuse to CYA.
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Old 20-10-2015, 10:16   #14
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Re: Will the cleats work as lift points for davit?

Quote:
Originally Posted by MehmetCan View Post
Planning to purchase a Boston Whaler Dauntless 170 as a tender/dinghy and store it on deck, at stern. Already have a hydrolic davit but may need to upgrade it. The question is, BW170 doesn't seem to have any points for tying up the davits cable, so I'm planning either to use the cleats (4 on sides, 1 on bow) or install several lifting points seperately. We're talking about around 2500lbs/1.25 tons here. Any ideas, past experience and/or suggestions?
A couple of engineering considerations.

You need to consider both strength and strain.

Peak loads several times the dead weight will likely be experienced by the cleats, fasteners and backing plates due to dynamic loads.

A simple strength sizing approach is to use a factor of safety to size the cleat, fasteners and backing plate thickness. (Simple shear only). 4.5 x static weight is a good rule of thumb in this application. This will be very conservative but not so conservative that you end up with an odd looking solution.

Low cycle strain will be a more likely failure mode if you undersize a cleat, fasteners or backing plate. As little as a few hundred cycles can lead to strain failure.

In this case you'll likely see permanent deformation of one or more of the components. Probably the backing plate or surrounding structure. It will be visible and detectable by deflection if you substantially undersize.

Conduct a trial lift / load test looking for visible deflection. This will tell younwhether your close to the mark or not.

Lifting straps are also a good option.





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Old 20-10-2015, 11:02   #15
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Re: Will the cleats work as lift points for davit?

I have a small 16 foot motor boat at the dry storage yard here in the Los Angeles harbor. They lift with slings, rated 10 times the static load, and cross tied so they can't spread apart under load. Even though the crane is on the hard, they're concerned with wind and UV derogation of the straps. That said, the straps are slippery when wet, and I'd be concerned about that much weight swinging around without some fail-safe way of attaching the boat. Three point harness with rated pick point hardware, through bolted to backing plates is what I would choose.

Dave
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