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Old 19-01-2012, 09:32   #1
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Davit Falls

Hi all
Next month hope to get a set of davits fitted to the transom for the dink.
What I would like to achieve is to have a set of falls (block and tackle) to lift and lower the dink, but with one hauling part only.
Anyone achived this with success and care to share the details, pictures or sletches would be good

Cheers
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Old 19-01-2012, 09:36   #2
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Re: Davit falls

Good question Nigel...looking forward to seeing the replies.
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Old 19-01-2012, 09:47   #3
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Re: Davit falls

I've not done it, but I've given it some thought, and I would run the blocks similar to how blinds are done.

bitter end >down to boat >back up to block >across to the other davit, block >turn thru block down to boat >back up to block >out

To reduce friction, I'd put blocks down at the boat some kind of way, maybe a block with a clip of some sort - just clip to the boat.

Hope this makes sense,
t.

edit: Husband tells me Harken makes just such a thing. The max on this is 200lb, but you could upsize the tackle.
http://www.hoister.com/
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Old 19-01-2012, 09:53   #4
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Re: Davit falls

Quote:
Originally Posted by nigel1 View Post
What I would like to achieve is to have a set of falls (block and tackle) to lift and lower the dink, but with one hauling part only.
I think you'd be making a lot of extra work for yourself with such an arrangement. I run 6:1 tackle on my davits, and there's no way I could lift both simultaneously without running the line to a winch.

Are you planning to haul the dink by hand? Will this arrangement be motorized on winch-powered?
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Old 19-01-2012, 09:59   #5
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Re: Davit falls

how heavy is the dingy? and will you be lifting with the engine?
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Old 19-01-2012, 10:03   #6
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Re: Davit falls

The pointy end of your dink is likely to be quite a bit lighter than the motorized end. Thus the lifting power required at each end will be different. Also, it's nice to be able to lift the pointy end up a little higher before snugging the whole thing up, to drain out water. I wouldn't do it how you are suggesting.
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Old 19-01-2012, 10:11   #7
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Re: Davit falls

Channel Islander is spot on. There are real advantages to separate block & tackle. Plus, you only need to alternate between the falls a few times as you hoist the dink, and with cam cleats this only takes a few seconds. - Colin
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Old 19-01-2012, 10:53   #8
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Re: Davit falls

You may be able to use a single point lifting harnes that already has the bow-up aditude setup in the sling....then use additional straping to secure it to the underside of the davits
Like this your choices for rigging may be greater.
Keep in mind that most "off the shelf" davits will most probably not be able to handle the additional and considerable lateral loads that this type of arrangement will result in.
Adding a truss/beam or compresion post across the top of, or between the davits may eliminate the lateral loads and min the case of the truss/beam may be used as the picking point...but now your getting into some seriose dicking around and certainly more weight....makes two sets of falls look pretty attractive.
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Old 19-01-2012, 10:55   #9
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Re: Davit falls

You are making it overly complicated. Many times you do not want the dink to drop evenly, especially when trying to drain it. I use 2 3part blocks on the engine end and 2 2 part blocks on the pointy end. I haul and drop the dink by myself (10'06" RIB and 15 hp Yamaha). When lowering I do both ends at the same time with half a turn around the cleats. Sit on the helmsmans seat, push the dink out with my feet to clear the transom and lower away.
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Old 19-01-2012, 11:23   #10
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I would go with 6:1 purchase

My boat came with 3:1. which is just not enough.
Sail Delmarva: Better Purchase for Dingy Davits
The cam cleats are nice.

I hoist with the engine on and secured. I can see no sensible reason, with my boat, to remove it. It is well secured to the dingy and the dingy is secure.
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If I removed the engine, the risk to my back or of dropping the engine (however slight), and the inconvenience of not have the dingy always ready to go far outweigh any perceived up-side.

I would not hoist level, for the reasons others have stated. Often I lower the stern near the water with the bow nearly up and drain the last of the water. I don't store it level except when sailing; I open the drain and leave the transom 10 inches lower than the bow.
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Old 19-01-2012, 13:20   #11
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Re: Davit falls

Quote:
Originally Posted by ChannelIslander View Post
The pointy end of your dink is likely to be quite a bit lighter than the motorized end. Thus the lifting power required at each end will be different. Also, it's nice to be able to lift the pointy end up a little higher before snugging the whole thing up, to drain out water. I wouldn't do it how you are suggesting.
This is correct. The line of action of a single line hoist will have to pass through the Center of Gravity of the boat. In theory one could set up a 2 or 3 leg lifting harness with a single point of connection above the CG; or, a lifting horse, with two leg harness straps fore'n aft and a single point of connection between the horse and the hoist, but you'd still have to deal with several lines that will be needed to keep the dinghy from rotating/swinging during the hoist.

FWIW...
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Old 19-01-2012, 17:46   #12
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Re: Davit falls

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Originally Posted by nigel1 View Post
OK, you have all convinced me, stick to separate falls. I had forseen the problem with one or the other end dipping.
They will be custom davits, with a cross brace to support solar panels. The dink is small, 3.6m with air floor, and the outboard will not be stowed on the transom.
Now to find some reasonably priced blocks, if there is such a thing
might want to incorporate a little lifting arm for the outboard as well,that swings outboard for taking the motor off the transom.

also have found that webbing straps that can be tensioned under the dinghy when stowed save a lot of chafe.
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Old 19-01-2012, 17:48   #13
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Re: Davit falls

OK, you have all convinced me, stick to separate falls. I had forseen the problem with one or the other end dipping.
They will be custom davits, with a cross brace to support solar panels. The dink is small, 3.6m with air floor, and the outboard will not be stowed on the transom.
Now to find some reasonably priced blocks, if there is such a thing
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Old 19-01-2012, 19:31   #14
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Re: Davit falls

I tried lifting the dinghy with some small bocks but it was never going to work. Too much friction and too little mechanical advantage.

So I went with a couple of small manual trailer winches. Single rope to one for the bow, double rope to the other for the stern.


Works like a charm. The ratchet on the trailer winch is a godsend. Means that we can stop and catch our breath at any time.

If I was doing it again I'd be tempted to use stainless steel and longer davit arms. Crew needs to kick the dinghy away from the stern as it comes up and down.

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Old 19-01-2012, 19:58   #15
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Re: Davit falls

Quote:
Originally Posted by atoll View Post
might want to incorporate a little lifting arm for the outboard as well,that swings outboard for taking the motor off the transom.

also have found that webbing straps that can be tensioned under the dinghy when stowed save a lot of chafe.
Hi Atoll,

can you expand on the webbing straps, how were they rigged. Webbing straps is something I am not short of.
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