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Old 03-14-2019, 07:54 AM   #1
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David crane

Does anyone have a gouge on how to figure how much weight a deck crane can handle? I have a Hyatt Fantail 50 and there is not a lot of data available on this model since only 11 were imported to the US and that was twenty years ago.
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Old 03-14-2019, 08:03 AM   #2
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Do you have a name plate or photo of the davit ?
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Old 03-14-2019, 10:16 AM   #3
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I thought you were looking for someone!
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Old 03-14-2019, 10:54 AM   #4
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I'm going to guess he meant "Davit Crane"?..... and is looking for a gauge on the working and max limits of the crane.

The make and model of the crane would be needed to answer that question.
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Old 03-14-2019, 01:13 PM   #5
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Installation would probably matter, too. A crane with its foot on deck would likely be much less capable than one with an extension down into the main level or even into the bilge.

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Old 03-14-2019, 01:29 PM   #6
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Quote:
Originally Posted by Shrew View Post
I'm going to guess he meant "Davit Crane"?..... and is looking for a gauge on the working and max limits of the crane.

The make and model of the crane would be needed to answer that question.
Davit
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Old 03-14-2019, 01:58 PM   #7
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Make model specs needed then likely engineer would have to calc after he or she inspects. Assuming this was not a factory install. If it was fsctory then mfrs rating ought to be on file somewhere.
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Old 03-14-2019, 03:43 PM   #8
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Or maybe David knows!
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Old 03-14-2019, 04:53 PM   #9
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Or maybe David knows!
Okay, let's give this guy a pass.
I am hard of hearing and sometimes ....
Could also be another of the "spellcheck" errors.

But it is so much fun to tease him. LOL
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Old 03-14-2019, 04:55 PM   #10
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I looked at three different Fantail 50’s on YW, and none of the listings provide any specs on the davits.
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Old 03-15-2019, 02:32 PM   #11
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I also looked at the three boats on Yachtworld and enlarged this photograph of the only unit clearly visible. The unit in the photo looks very close in size and design to another one I have for sale, rated by the builder at 600 lbs.. My unit is of 3.5” aluminum construction and is designed to use a 2.5” solid bar aluminum standpipe. If the one you are asking about is the same as in the photo, it could also be of stainless steel construction instead of aluminum, making it stronger still. Nick Jackson also makes a similar pipe style crane.
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Old 03-15-2019, 04:09 PM   #12
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If your standpipe is only 2” in diameter and is solid, then it has a fairly low rating. My 6’ MarQuipt rated at 1500lbs had a 4.5” diameter pipe and a 1” wall thickness. The replacement 10’ unit with the same rating uses a 5” pipe with a 2” wall thickness.
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Old 03-15-2019, 05:03 PM   #13
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Here is a spec’ chart for Nick Jackson aluminum pipe davits that may help for some comparison. Column to the far left is capacity in pounds. Be aware that the 300 and 500 models do not have backbone reinforcements.
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Old 03-16-2019, 04:27 PM   #14
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Here is a spec’ chart for Nick Jackson aluminum pipe davits that may help for some comparison. Column to the far left is capacity in pounds. Be aware that the 300 and 500 models do not have backbone reinforcements.


Yes, I was asking about the crane (I challenge you to enter d a v i t and not have the site spell correct you)
It is a pipe design, apparently steel since it shows a little rust, 4” diameter going thru the top deck and into the main deck, with the added backbone rail also in steel. The winch is rated at 2000 lbs and it has 5/32 stainless cable. I’m sort of thinking that they would not have installed a 2000 lb winch on a mast that could not support something close to that. Unfortunately, I don’t think the original builder specs are available. I need a 700 lb working load for the new tender. Guess we’ll find out one way or another.
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Old 03-18-2019, 02:23 PM   #15
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Davit crane

Quote:
Originally Posted by healhustler View Post
I also looked at the three boats on Yachtworld and enlarged this photograph of the only unit clearly visible. The unit in the photo looks very close in size and design to another one I have for sale, rated by the builder at 600 lbs.. My unit is of 3.5” aluminum construction and is designed to use a 2.5” solid bar aluminum standpipe. If the one you are asking about is the same as in the photo, it could also be of stainless steel construction instead of aluminum, making it stronger still. Nick Jackson also makes a similar pipe style crane.
Thanks, very useful. Your photo is actually of a sister ship to mine. We have a beefier crane-3 1/2 diameter steel with exoskeleton at curve. I’m hoping to raise and lower a 650 lb RIB. Thinking I’ll use a pulley block, at least initially, to spread the load and not stress the winch motor as much..
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Old 03-22-2019, 01:01 PM   #16
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Cranes

Its best to get in touch with the crane manufacturer to determine specs of any kind. FWIW, a properly sized crane for that boat would be at least 800 lbs but more likely 1000lbs or more.
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Old 03-22-2019, 01:39 PM   #17
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Quote:
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Thanks, very useful. Your photo is actually of a sister ship to mine. We have a beefier crane-3 1/2 diameter steel with exoskeleton at curve. I’m hoping to raise and lower a 650 lb RIB. Thinking I’ll use a pulley block, at least initially, to spread the load and not stress the winch motor as much..


Just friendly warning: if you add a pulley block, with say a 2 part line, you will NOT reduce the vertical load on the davit structure, but you will double the force that the winch is capable of putting on the end of the davit. As you note the two part line will halve the tension on the rope, and hence the winch, but will not “spread the load” on the davit.
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Old 03-22-2019, 02:48 PM   #18
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And a second to Island Cessna's warning. Winch ratings aren't necessarily what you might think they are. A "winch" is designed to PULL something, not HOIST something. So a winch (like on the front of a truck or ATV, or on a trailer, and on many marine davit systems) rated at 2000 lbs. cannot HOIST 2000 lbs., but only pull that load, up some (typically unspecified) incline. When used in a davit application, be aware that the line load that winch can supply is usually only a small fraction of the rated capacity of the winch.

In davit applications, usually a HOIST is used, which truly can provide it's rating as a line load, at full drum. Hoists also are required to lock the load upon removal of power, something winches usually cannot do. And yes, hoists cost more than winches!

Attempting to determine the hoist capacity of any marine hoisting apparatus is very complex, and well beyond the DYI capabilities of most. As has been suggested, engagement of a licensed professional engineer to make such an assessment is money well spent. Unfortunately, failure of a hoisting system aboard a boat can, has, and not infrequently resulted in dire consequences. And as always, your money, your boat, your choice.

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Old 03-22-2019, 05:05 PM   #19
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Investigating the availability of winches and hoists, we found a DRAMATIC increase in the price of "hoists" over similar sized winches. And we found that pretty much all the winches available will more or less "brake" when power is removed. If you are going to be lifting significant loads over head, by all means, go hoist. If you are merely lifting a couple hundred pounds of inflatable AND can assure yourself nobody is ever going to be in the way in the remotely possible event of a failure, do consider a winch.
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Old 03-24-2019, 02:13 PM   #20
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David thanks you for your thread and watching his shows.


https://en.wikipedia.org/wiki/David_Crane_(producer)



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