Dinghy davits and lifts?

stubones99 said:

Are the upper clevis pins going through the tubing? If so, that would weaken the tubing somewhat. By making the clevis pins go outside the vertical tubing, it would still be full strength right to the curve.

Also, a brace would add more strength than a gusset.

Still, pretty good solution for carrying the dink!

Stu

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OK...I'll bite because I am only a backyard guy and no engineer...

Do you have any numbers to show how the holes reduced any required strength? (webbed designs, trussing, etc...are all designs with material removed and occur without serious loss of strength)

And depending on the gusset size and brace design...there is no way to say one would be stronger than the other.

But thanks...it is OK and could be better in other respects.

You are right, to a degree.

A gusset is typically shorter than a brace, and the span is what makes the difference.

Drilling a hole in a cylinder removes metal, and introduces a weak point. Whether the weak point is enough to introduce a stress fracture, I don't know. I don't know the tubing size nor its alloy.

As long as it works, it works...

Lifting harness ideas...

dhays said:

My soon to be new boat has SeaWise Davits on the stern, which I think is great. However, I am also going to want to be able to lift the dinghy up onto the boat deck with the crane. I think the dinghy already has factory eyebolts but I will need to create a lifting harness.

Anyone have any good suggestions on how to design a lifting harness or suggested materials?

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I'm going to assume there's two lift points at the transom and one near the bow of the dinghy. You could take three ratcheting cargo straps, one on each eyebolt, and run them to a single ring. Shorten up on the straps until the ring is over a point approx. 3/4 of the way to the stern, and the ring is at the height you'd like. When the dinghy can be lifted by the ring and remain level, the strap lengths are correct. You could also use chain and s-hooks to determine the leg lengths, but either way it's just a trial and error thing to find that sweet spot over the CG of
your particular dinghy. I guess there's three choices for the bridle material...chain, webbing straps, or rope. Personally I'd go for the webbing straps or rope and avoid chain......no experience with hoisting dinghies but have moored close to those with chain hoists, and been woken up by the noisy chain when they make the early-morning trip ashore with the dog

tachyon said:

I'm going to assume there's two lift points at the transom and one near the bow of the dinghy. You could take three ratcheting cargo straps, one on each eyebolt, and run them to a single ring. Shorten up on the straps until the ring is over a point approx. 3/4 of the way to the stern, and the ring is at the height you'd like. When the dinghy can be lifted by the ring and remain level, the strap lengths are correct. You could also use chain and s-hooks to determine the leg lengths, but either way it's just a trial and error thing to find that sweet spot over the CG of
your particular dinghy. I guess there's three choices for the bridle material...chain, webbing straps, or rope. Personally I'd go for the webbing straps or rope and avoid chain......no experience with hoisting dinghies but have moored close to those with chain hoists, and been woken up by the noisy chain when they make the early-morning trip ashore with the dog

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Great idea on using the straps to determine the proper location.

For the harness I was thinking of using some Amsteel line that I have. I can splice SS hooks to the ends and bring them together and splice each to a SS ring. At least that was the best idea I could come up with.

dhays said:

Great idea on using the straps to determine the proper location.

For the harness I was thinking of using some Amsteel line that I have. I can splice SS hooks to the ends and bring them together and splice each to a SS ring. At least that was the best idea I could come up with.

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That's what I have. Works just fine.
I used spring loaded carabineer type hooks though.
My amsteel is 5/16" which is way oversized for a 600# dink but I wanted some substance to hang onto.

mbevins said:

That's what I have. Works just fine.
I used spring loaded carabineer type hooks though.
My amsteel is 5/16" which is way oversized for a 600# dink but I wanted some substance to hang onto.

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Yeah, the Amsteel is so strong that if sized appropriately it is too small to handle. I have Amsteel that I have used to make soft shackles for the boat. I think I have enough for a harness.

I just saw your homemade davit system. I also have a 390. I was considering a Hurley system, but now I may make my own.
I'm thinking I would like to have removable brackets....I'm still working on how to do that.

Thank you for sharing.
Ron

Wmiii said:

We have a 2007 Mariner 40 Sedan that is similar to many of the Mainships. I am looking for options for dinghy placement. Currently, I lift our 10' Mercury light weight dinghy and 15hp Yamaha motor (separately) to the top deck with a Garhauer lift.
That works good, but I would like to be able to launch the dinghy more quickly when we are cruising with daily stops.
I've looked at davits like Forespar, and Kato as well as swim platform mounted like Trick or Hurley.

What is the preferred method used my you Mainship owners?

Thanks,

Wm Mayberry
OPTIMYSTIQUE

Mariner 40

Ft Myers Beach, FL

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We installed " dinghy ramp " allows us to keep the motor on and I can launch or load in under 5 min. but you need a wide ( deep ) enough swim platform as half of the dinghy beam will be on it. .... FB

Ex Sailor said:

We installed " dinghy ramp " allows us to keep the motor on and I can launch or load in under 5 min. but you need a wide ( deep ) enough swim platform as half of the dinghy beam will be on it. .... FB

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I was also considering the "dinghy ramp". It's very similar to the Hurley system. I'm going to try to use a removable mounting system like " the dinghy ramp"

My swim platform is about 32" deep, so I think I'll have enough room.

Ron

0025 said:

I was also considering the "dinghy ramp". It's very similar to the Hurley system. I'm going to try to use a removable mounting system like " the dinghy ramp"

My swim platform is about 32" deep, so I think I'll have enough room.

Ron

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Ron, we have a hard covered sundeck so I ended up putting a 4:1 rope purchase ( c/w jam cleat ) from the back roof of the sundeck, long enough to reach the dinghy. As result, the better half can lift the thing by herself and all I do is position the dinghy on the ramps. I wish I had photos ... but we love the way this worked out. FB

Ex Sailor said:

Ron, we have a hard covered sundeck so I ended up putting a 4:1 rope purchase ( c/w jam cleat ) from the back roof of the sundeck, long enough to reach the dinghy. As result, the better half can lift the thing by herself and all I do is position the dinghy on the ramps. I wish I had photos ... but we love the way this worked out. FB

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I plan on doing the same thing. I currently have davits on the upper deck but it's a PIA. I want something my better half can use with ease.

I having alittle trouble finding HDPP that's thicker than 1".
Any suggestions?

Thanks

Hdpe

Excellent discussion! Seems to me that davit preference seems to come down to three variables.

1. Desire for ease and frequency of launching and retrieving
2. Tolerance for hassle dealing with motor tilting, unlocking or removing
3. Concern over security in heavy seas

Quite possible that I'm not reading these right as my only experience with launching and retrieving small boats comes from aluminum fishing boats at floating docks, but learning from y'all's experience is why I'm here. Here goes.

First, I see the dinghy as a daily use vehicle, so easy of launching and retrieval is really important to me. While I don't anticipate doing much swimming from the swim platform unless the dinghy is already launched, I do see a fair bit of fishing from the cockpit and a dinghy in Weaver davits would seem to create a lot of line and rod interference.

Second, I don't see myself removing a 100 pound outboard too often, if ever. Having spent a career dealing with mechanical stuff, those hinging motor mounts seem like a weak point and I would prefer to have the motor securely mounted to the dinghy transom. Same with gas tanks and batteries and anything else that stays in the dinghy. The less packing and unpacking involved in each launch and retrieval the better.

Third, once the dinghy is retrieved, it better not leave or move until I'm ready to launch at the next stop. The Weaver system seems like a real winner in this category. The hinged mounts on the swim platform look like a great idea, but leaning out over the corners to strap the three "corners" down look difficult at best, especially in poor conditions.

We had a Sea Wise system on a previous boat and loved it. The motor is permanently mounted on a hinged bracket on the transom. As the dinghy is recovered the motor bracket hinges and locks into the winch stand. About 1 minute to launch and about 2 minutes to recover.

Comodave said:

The motor is permanently mounted on a hinged bracket on the transom.

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I watched the Sea Wise videos and it does look like a solid system. Leaves the swim platform largely uncluttered. Anyone know the weight capacity of the 390 swim platform? Will it hold 600-700 pounds of dinghy, motor and davit hardware?

You can always add some supports under the swim platform if you think it needs it.

I just realized you said a 390 Mainship. Doesn’t it have the semi molded in swim platform? There were some issues with them taking on water if I remember correctly. Seems like they recalled some of them to rework the way the platforms were attached??? We looked at one that had a bilge pump in the swim platform.

HeadedToTexas said:

I watched the Sea Wise videos and it does look like a solid system. Leaves the swim platform largely uncluttered. Anyone know the weight capacity of the 390 swim platform? Will it hold 600-700 pounds of dinghy, motor and davit hardware?

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Beware of the attachment points for the SeaWise to a 700# dinghy. Mine is a Caribe 12 with a console and a 40 Honda. I bought it from a guy who had a Seawise on it. The fwd attachments were solid, but on the stern, the port side atachment was to the molded FG well a few inches fwd of the transom. That part of the dinghy was not robust enough for the weight it was then required to bear when tipped up on the SeaWise. It likely survived just fine through the installation process and until the first time out in heavy conditions. When I got the dinghy, that part of the attachment had been repaired, so I didn't notice the cracks right away, but within a year, the failure of the structure of that part of the well was obvious.
I use a davit system that lifts the dinghy without tipping it, so I don't stress the weakened area and it has not caused me any problems.

I wouldn't recommend putting a heavy dinghy to the test of either Weaver or SeaWise.

koliver said:

I use a davit system that lifts the dinghy without tipping it, so I don't stress the weakened area and it has not caused me any problems.

I wouldn't recommend putting a heavy dinghy to the test of either Weaver or SeaWise.

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So you gave up on the Seawise system and went to something like the Kato or Olsson approach?

The Seawise davit manual system is rated for 450 pounds so maybe that was why you had a problem with a 12 dinghy and a larger outboard. I did not have any problems and knew several others that had one without any problems. I would suspect it was either installed improperly or overweight. It is built very robustly and custom built for each installation. On mine the stern bracket went to the transom. Quick check online a 12’ Caribe weighs 425# and the Honda 40 was 214#. So unless the Seawise system was the hydraulic system, yours was overloaded.

Comodave said:

The Seawise davit manual system is rated for 450 pounds so maybe that was why you had a problem with a 12 dinghy and a larger outboard. I did not have any problems and knew several others that had one without any problems. I would suspect it was either installed improperly or overweight. It is built very robustly and custom built for each installation. On mine the stern bracket went to the transom. Quick check online a 12’ Caribe weighs 425# and the Honda 40 was 214#. So unless the Seawise system was the hydraulic system, yours was overloaded.

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To be perfectly clear, I never had a Seawise. My observation is not a comment on the quality of the Seawise system, rather on the dinghy itself.

I bought a dinghy from a boater who overloaded a Seawise with my dinghy. My boat came to me with a pair of davits that lift my dinghy straight up, one at the bow, the other at the stern. They are load matched to the weight they need to lift. The damage to my dinghy had been repaired and didn't become obvious until I removed the Seawise arm, but once I had done so and inspected that area it was obvious that the dinghy was not built strongly enough to support its own weight on the Seawise arm that attached to the side of the well just fwd of the transom.

I doubt any brand of dinghy weighing more than 500# is built to be stowed on its side, supported only by a pair of Seawise arms and survive rough water in that position. It is the dinghy, not the Seawise that will fail

I agree with the above noted weight limit of 450# on a Seawise. I think Weavers are for lighter loads still.

We have Trick Davits on our 2005 Mainship 400, installed them about three years ago. Our dinghy is a Caribe 11 light with a 20 hp Suzuki. We used two extension arms for the installation, though our swim platform is very deep. The extensions make loading a little easier, but I snug the dinghy up against the transom when under way, so they don't allow walk around space.

The Trick davits make the dinghy easy to load and unload. If you use criss crossing ratchet straps the dinghy is very secure on them. We haven't had a problem with shipping water into the dinghy, even with following seas. I tilt the motor up.

I have to be careful when docking as the dinghy is a little wider than the transom.

The one major problem we had with the trick davits is that the center plates are not very robust. We had two sets fail where the pin goes through the plates, there just isn't enough allowance there. It's hard to explain but easy to see in person. I ended up having four plates machined out of 5/8 inch aluminum, it cost about $250. Much, much stronger, no failures since.

Shoot me a PM if you have questions.

The weight of your dink is the main consideration when considering a davit system. My dink is 820#. Too much for a Sea Wise.

What do you use with an 820 pound dinghy?

I hope to be more like 500 pounds.

People
Season Greetings!
Long time no see!
I had my rubber duck on the upper deck. For the admiral and me it was a nightmare to lift it up as we both are pushing 60.
Therefore, I went to the drawing board and designed/built the one on the pictures. The boat is 12' with a 25 HP Yamaha. Boat, engine and gear weight 250 lbs. I pull them up with the boom winch
I hope you liked it!

The drawing is in centimeters
The big pipe is 2" thick wall
The transverse pipes are 1 1/2" tick wall
The small pipes are 1" standard

HeadedToTexas said:

What do you use with an 820 pound dinghy?

I hope to be more like 500 pounds.

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Olsson Davits.

Builders of Boat Davits - Pioneers of Transom Davit Technology

Here is a pic of my set up. Worked great all summer long in the Inside Passage.

Beautiful set up, ASD. Again, my experience is limited mostly to smaller center console outboards where bouncing over wakes and chop really strains things like battery and fuel tank mounts. I suppose the forces are completely different at the stern of a 20,000 pound boat running at hull speeds. Is that what prevents the 820 pound dinghy from tearing its lift eyes out? Perhaps I'm over-thinking the davits issue?

HeadedToTexas said:

Beautiful set up, ASD. Again, my experience is limited mostly to smaller center console outboards where bouncing over wakes and chop really strains things like battery and fuel tank mounts. I suppose the forces are completely different at the stern of a 20,000 pound boat running at hull speeds. Is that what prevents the 820 pound dinghy from tearing its lift eyes out? Perhaps I'm over-thinking the davits issue?

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I trim the motor up and the wake never hits the swim platform.