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Old 06-11-2013, 13:42   #31
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Originally Posted by Ann T. Cate

^^ Dockhead, I think this is good advice. To me, the big question is whether one or both davits will need replacing, if you are committed to having the dinghy in davits under way, rather than lashed down on the foredeck. Questions I'd have are why did the crack develop there? Is there a microscopic mate to it on the other side? Is it at a stress riser from a weld?

If, as you suggest, you downsize somewhat with the dinghy, then the foredeck storage option becomes more doable. [On our smaller boat than yours, we actually dinsinflate the tubes, to make it fit better, and use an electric inflater to inflate.]

If you go to a 15 horse OB, which is what we have, it will be a simple matter to use a harness and a halyard to put it on the dinghy. We find we prefer to do this amidships, with the dink in the water. Takes only moments. However, I do wonder if you'd be happy with the 15 horse and the large crews (6 or 7, I believe you've reported), 'cause the 25 shall have had an easier time with their weight, not a problem, of course, if you're in the habit of moving them in 2 groups.

My 2 cents.

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The way I cruise now, I hardly ever have a chance to plane the dinghy, so the 25hp are completely wasted. I could make the 6 knot speed in UK ports with 5hp, I reckon, even with 6 onboard. But in the Caribbean? It's hard for me to guess. I can well imagine cursing myself for downsizing the engine and getting rid of the remote steering.

Foredeck is not an option no matter what I do with the dink, because I have a cutter rig with a deck-sweeping staysail - no place. I have a lovely big afterdeck which would take even my present 12' RIB, but here is also a downside - it's one of the nicest spaces on board, much used for other purposes.

I would not mind fitting and removing a tiller-steered outboard - did that for years on my old boat. If I go to a 15 horse tiller motor, I can leave the motor on the dink for coastal passages, and haul it up to the rail for further or in bad weather. Even with the motor on the dink, I will have significantly reduced the mass.

The dink is a RIB - so planes much more easily than a soft dinghy. I have a hunch that 15 hp is going to be enough to plane nicely with up to 4 on board. Hmmm. I do have up to 7 on board, but rarely more than 4 or 5 in the dink at one time.
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Old 22-11-2013, 18:50   #32
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You might want to try a stay (constructed like a heavy lifeline with turnbuckles) run from the top of your davits to the deck at about a 45-degree angle or smaller. After all, you just want to reduce loading on the davits themselves.
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Old 23-11-2013, 08:37   #33
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Originally Posted by DainyRays View Post
You might want to try a stay (constructed like a heavy lifeline with turnbuckles) run from the top of your davits to the deck at about a 45-degree angle or smaller. After all, you just want to reduce loading on the davits themselves.
Thanks, but my davits are above deck level.

I have about settled on just welding it back up
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Old 23-11-2013, 08:39   #34
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Originally Posted by DainyRays View Post
You might want to try a stay (constructed like a heavy lifeline with turnbuckles) run from the top of your davits to the deck at about a 45-degree angle or smaller. After all, you just want to reduce loading on the davits themselves.
Thanks, but my davits are above deck level.

I have about settled on just welding it back up, then unloading them with a halyard attached to the dinghy (not the davits) with a sling.
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Old 23-11-2013, 09:45   #35
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Re: Cracked Davit :banghead:

Dock my friend, I have a 10 foot RIB that planes with 3 with an 8 hr. OB. We have it on davits in bays, but out in on the big blue it goes on the front deck. I tie it down so it can be quickly used as a life raft if needed.
I initially removed it because I didn't like the windage, but recently seen davits crushed when the boat was pooped and the dingy filled with water, becoming a thousand pounds too heavy. It pulled the davits off and left holes in the deck- just saying....
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Old 23-11-2013, 10:04   #36
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Re: Cracked Davit :banghead:

I share Newt's concern about the sudden weight with a big following sea swamping my dinghy on my davits. I've not had it happen, but an occasional wave can look threatening comming from astern before I get the lift. I can easily remove my outboard and always store it on deck when offshore. I also, depending upon conditions, use a sling on a halyard from my mizzen to lift the side of my dinghy that is further from my tansom so that more of the bottom of my dinghy is facing the following sea and little water could remain in the dinghy at this new angle. If I were starting new, I would likely have designed my davits to suspend my dinghy a little higher, but as I said, I've only had the threat of a problem.
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Old 23-11-2013, 10:47   #37
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Re: Cracked Davit :banghead:

I appreciate y'all's concern, but there's not much I can do about that. The dink is a 12' RIB and cannot be accommodated anywhere else. The davits are rated for the load, and they are quite high above the water. They have survived about 15,000 miles or so in the English Channel and Bay of Biscay in up to Force 10 without incident, and other large cruisers in these waters carry their dinks the same way.

I might just ship a different and smaller dinghy when I venture off crossing oceans. On the other hand, I don't think I'm every likely to sail anywhere with conditions as tough as right here, so maybe not worth messing around with it. With part of the load taken to a halyard, should be quite a bit more robust than it is now.
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Old 23-11-2013, 11:04   #38
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Re: Cracked Davit :banghead:

Quote:
Originally Posted by Dockhead View Post
I appreciate y'all's concern, but there's not much I can do about that. The dink is a 12' RIB and cannot be accommodated anywhere else. The davits are rated for the load, and they are quite high above the water. They have survived about 15,000 miles or so in the English Channel and Bay of Biscay in up to Force 10 without incident, and other large cruisers in these waters carry their dinks the same way.

I might just ship a different and smaller dinghy when I venture off crossing oceans. On the other hand, I don't think I'm every likely to sail anywhere with conditions as tough as right here, so maybe not worth messing around with it. With part of the load taken to a halyard, should be quite a bit more robust than it is now.
+1

And if you do meet your 'once in a lifetime perfect storm', just cut the dinghy free and get a new one at the next port.

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Old 23-11-2013, 11:24   #39
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Re: Cracked Davit :banghead:

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Originally Posted by Dockhead View Post

What do you guys think?
I had a davit snap while carrying an engineless Zodiac C310 RIB (about 55 kilos). It was in perhaps force 5-6 on Lake Ontario with 1.5 metre waves...in other words, nothing much. I decided after dealing with all the mess and having to clear the fall out of the prop and rudder to say goodbye to davits and indeed the Zodiac (which was PVC and not long for this world anyway).

Instead I got a Portabote and a nesting dinghy. Both live on the foredeck and aren't in the way. Yes, I can't launch them as quickly, but a little planning takes care of that. Having two tenders that "compress" is actually less effort and, in windy situations, less trouble than trying to hoist a Zodiac on deck.

Now the steel braced pads for the davits hold a deck crane on starboard, and soon, a pole for a wind gen on port. Much better for weight and windage and peace of mind.

Just my two cents.
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Old 23-11-2013, 11:50   #40
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Re: Cracked Davit :banghead:

Quote:
Originally Posted by S/V Alchemy View Post
I had a davit snap while carrying an engineless Zodiac C310 RIB (about 55 kilos). It was in perhaps force 5-6 on Lake Ontario with 1.5 metre waves...in other words, nothing much. I decided after dealing with all the mess and having to clear the fall out of the prop and rudder to say goodbye to davits and indeed the Zodiac (which was PVC and not long for this world anyway).

Instead I got a Portabote and a nesting dinghy. Both live on the foredeck and aren't in the way. Yes, I can't launch them as quickly, but a little planning takes care of that. Having two tenders that "compress" is actually less effort and, in windy situations, less trouble than trying to hoist a Zodiac on deck.

Now the steel braced pads for the davits hold a deck crane on starboard, and soon, a pole for a wind gen on port. Much better for weight and windage and peace of mind.

Just my two cents.
How much I would love to have no davits on the transom which are, on top of everything else, ugly, ugly ugly.

I've looked hard at the Portabotes. So far I have not quite been able to let go of having the RIB.
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Old 23-11-2013, 11:57   #41
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Re: Cracked Davit :banghead:

Does the dink have a hull drain to the void between the inner and outer hull and is it full of water hence extra weight you may not be accounting for?

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Old 23-11-2013, 12:10   #42
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Re: Cracked Davit :banghead:

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With part of the load taken to a halyard, should be quite a bit more robust than it is now.
I would solicit the aid of a naval engineer before attaching a halyard to the dink. There could be a lot of shock loading that the forestay wasn't designed to handle. Not so much under sail but when motoring in chop.
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Old 23-11-2013, 12:14   #43
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Re: Cracked Davit :banghead:

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I am glad you have a large boat and I am sure you are proud of it. Still, I would reconsider the idea of Davits offshore or in anything above 20 knots. I have not yet seen any commercial davits that I would trust offshore with any kind of sea. One big wave can poop the whole boat. Even a big one like yours! And the question of "standard practice" surprises me, as no one I know that cruises seriously would carry a dinghy (WITH AN ENGINE,) on Davits offshore.

I can go from a dinghy deflated on deck to in the water with an engine on in about 10 minutes. I weigh about 120 pounds.



Apparently not strong enough if one is cracked and sagging. Sounds like you averted a disaster or are possibly headed for one. Davits with a dinghy and engine should not be used offshore in my opinion. Again, you already have your opinions as I suspected.
I am so with you on this one Windlove. Ditch the davits! If Dockhead has such a large boat then there must be space on deck, take the outboard off and stow it separately and possibly use the spinnaker pole and a 4-1 block and tackle and stow it on deck where it will be nice and safe.
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Old 23-11-2013, 12:40   #44
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Re: Cracked Davit :banghead:

This thread sounds a lot like the "Tow your dinghy thread".
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Old 23-11-2013, 12:55   #45
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Re: Cracked Davit :banghead:

Changing from a 25hp 2 stroke mariner to a 15hp mariner saves 13kgs (48kgs versus 35kgs).

Dropping to 10hp or 9.9hp versions doesn't help because the engine is based on the same block as the 15hp. You would need to drop to 8hp to make a real difference.

Perhaps just changing down to a 15hp would be enough as the engine weight is all on the Port davit.

Mercury Marine

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