Dinghy up level with flybridge

All,

I'm adding some dinghy davits to my 40ft Mainship and would like some feedback if it's a good idea.

I'm going to mount the davits on the aft flybridge, that will overhand the swim platform and bring the dinghy up to the level of the flybridge.

Advantage is that it's totally out of the way. Can get on the swim platform and it's above. Looking out the aft area from the lower helm, and it's above. Looking aft from the flybridge and it's below, but might block a bit trying to look down from the back.

With the same davits I could just hold it on the swim platform and tie it to the cleats to keep it from swinging aft. A bit of a crude drawing, but the idea is there.

Thoughts?

I would be concerned that, unless you stabilize the dinghy against port/starboard motion, the boat's roll, which is more pronounced at that height, will be exacerbated by the motion of the dinghy, which in turn will increase the dinghy's sideways movement. If you hit a resonant frequency . . .

Clipper 40s(sold in US as Mariner, but ? with this) have an OEM rack for the dinghy, cantilevered off the aft FB. As Mainship don`t have this as OEM you`d need to check support strength. Clipper fit a Davico crane to lift/launch the dinghy, pipe supported to the lower deck. This would have the dinghy locked in place, no movement.

The dingy will swing side to side no matter where you mount it. I use two tye down straps with ratchet tighteners in a cross pattern from bow of dingy to opposite davit and stern of dingy to opposite davit and that holds it in place with very little swing.

Thx,

Good comments. I saw a similar solution on line today. Looks like they have two arms that support the dinghy on a small platform, and got the dinghy and motor up there.

I sure like it out of the way.

Seevee said:

All,

I'm adding some dinghy davits to my 40ft Mainship and would like some feedback if it's a good idea.

I'm going to mount the davits on the aft flybridge, that will overhand the swim platform and bring the dinghy up to the level of the flybridge.

Advantage is that it's totally out of the way. Can get on the swim platform and it's above. Looking out the aft area from the lower helm, and it's above. Looking aft from the flybridge and it's below, but might block a bit trying to look down from the back.

With the same davits I could just hold it on the swim platform and tie it to the cleats to keep it from swinging aft. A bit of a crude drawing, but the idea is there.

Thoughts?

Click to expand...

Structural issues ...... just be sure the thing will not collapse. I assume your davits are powered and not manual. Manual will be a big PITA. Oh-- the picture shown has the dinghy well inside of the swim platform, so much so that lowering/retrieving will find that platform to be a good size obstruction.

Ill have to take a pic of my monstrosity.

I cant see how the fly bridge lip will be strong enough to mount the 2 davits without a massive amount of redesign and added strengthening . The mechanical advantage on the base bolts of the davits is your biggest concern .

gaston said:

I cant see how the fly bridge lip will be strong enough to mount the 2 davits without a massive amount of redesign and added strengthening . The mechanical advantage on the base bolts of the davits is your biggest concern .

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Good point, it's a matter of how big a back plate under the deck would work. I'll have a engineer friend of mine check it out.

The one with the supports a few posts up could be an idea.

Seevee said:

Good point, it's a matter of how big a back plate under the deck would work. I'll have a engineer friend of mine check it out.

The one with the supports a few posts up could be an idea.

Click to expand...

Im a design engineer

Its not what size plate under the davit its whats holding the davit up from underneath and where that extra weight is been transferred to . The weight should be transferred vertically to the deck but whats holding the deck up

We make a living from making simple things hard

I did look at doing the same on my IG32 the dingy gets in the way of casting when fishing but I binned the idea too much heart ache for so little gain

It looks to me raising and lowering past the swim platform is going to be problematic, needing someone down there "helping" with the dingy. If you do motorize it, have a remote switch so you don't necessarily need two people.

Here is an advert for a Clipper 40 with the dinghy where you would like it. They use a crane, supported through the FB to the lower deck, to lift/lower it. Go through the pics, some may be helpful. Used Clipper 40 for Sale | Boats For Sale | Yachthub. Note Clipper 40s are built solid, like the proverbial brick outhouse.

BruceK said:

Here is an advert for a Clipper 40 with the dinghy where you would like it. They use a crane, supported through the FB to the lower deck, to lift/lower it. Go through the pics, some may be helpful. Used Clipper 40 for Sale | Boats For Sale | Yachthub. Note Clipper 40s are built solid, like the proverbial brick outhouse.

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So very tempting
Bruce he will take less I have already asked LOL

gaston said:

So very tempting
Bruce he will take less I have already asked LOL

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I know, met him when I inspected, interesting seller. That dinghy hadn`t been used for a long while, but it was staying put,and the boat wasn`t bending under the weight. I`m thinking it could be picked from the side and swung into position using the crane.
My St. Croix crane(manual) picks up on the side, dinghy goes on the aft FB, no aft overhang, not much room on the FB either. I think we`re keeping the IG.

BruceK said:

I know, met him when I inspected, interesting seller. That dinghy hadn`t been used for a long while, but it was staying put,and the boat wasn`t bending under the weight. I`m thinking it could be picked from the side and swung into position using the crane.
My St. Croix crane(manual) picks up on the side, dinghy goes on the aft FB, no aft overhang, not much room on the FB either. I think we`re keeping the IG.

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We should go 1/2 in the Clipper 40 and then we would both be happy

BruceK said:

Here is an advert for a Clipper 40 with the dinghy where you would like it. They use a crane, supported through the FB to the lower deck, to lift/lower it. Go through the pics, some may be helpful. Used Clipper 40 for Sale | Boats For Sale | Yachthub. Note Clipper 40s are built solid, like the proverbial brick outhouse.

Click to expand...

Didn't follow your posted URLs but a crane is the way to go. I installed a crane on my boat (used from Sailorman in Ft. Lauderdale) right after I purchased the boat. I also fabricated aluminum chocks that I mounted onto our front deck in a manner to that didn't block an exit hatch. My dinghy sits perpendicular to the boat's rhumb line. The base of the crane is plate mounted to the deck along with a 4" aluminum support pipe that passes through the deck into an interior closet. I mounted a base for the pipe which absorbs the mechanical vertical forces; the deck plate transfers the horizontal forces to the deck proper.

I pick the dinghy up, fully loaded including the outboard, swing the crane over the water and lower the dink into it. REverse process for retrieving it.

I strongly prefer a davit crane.........but I am not the one with the OP's problem.

foggysail,on the advice of an engineer boat neighbour I have not supported the St. Croix from FB to main deck. We lift 30kg, the mounting is pretty much over the side house "wall", there is a large plate under the FB to distribute load, and the plate has a turn down screwed to the house "wall" longitudinal timber. The Europa design provides a support right opposite the mounting. And the "mast" tube is bracketed to the railings, as St Croix suggest, using fittings they provide.
I`m a little nervous about it and know it could be controversial, but deflection is minimal under load, I think it works, but I`ll be watching it.
But no way would I mount davits as the OP originally considered, the aft FB deck would likely fail. The link was to provide the OP pics of how Clipper did it, OEM.

FlyWright sans dinghy?:



Most elegant, dinghy atop master cabin, with a crane:

My setup.

gaston said:

Im a design engineer

Its not what size plate under the davit its whats holding the davit up from underneath and where that extra weight is been transferred to . The weight should be transferred vertically to the deck but whats holding the deck up

We make a living from making simple things hard

I did look at doing the same on my IG32 the dingy gets in the way of casting when fishing but I binned the idea too much heart ache for so little gain

Click to expand...

Geeze from an engineer! Give me more thoughts. I'd love to hear ideas from you, thx.

BruceK said:

foggysail,on the advice of an engineer boat neighbour I have not supported the St. Croix from FB to main deck. We lift 30kg, the mounting is pretty much over the side house "wall", there is a large plate under the FB to distribute load, and the plate has a turn down screwed to the house "wall" longitudinal timber. The Europa design provides a support right opposite the mounting. And the "mast" tube is bracketed to the railings, as St Croix suggest, using fittings they provide.
I`m a little nervous about it and know it could be controversial, but deflection is minimal under load, I think it works, but I`ll be watching it.
But no way would I mount davits as the OP originally considered, the aft FB deck would likely fail. The link was to provide the OP pics of how Clipper did it, OEM.

Click to expand...

Bruce-- you received fine advice. The deck plate for my installation acts as a fulcrum point for horizontal forces. The vertical force is transfered via a 4" aluminum pipe to a well supported plate located in the rear of an out of the way closet. I have had problems but with the winch only. I have replaced it once with the same as the one that failed. I intend to see what Harbor Freight has to offer (120vac) and purchase something for backup.

My arrangement has worked flawlessly for over ten years. I'll try to take pictures.

And Bruce, I agree with you about the OP's setup.

foggysail, the St Croix Junior is a work of art but basic. It has a 4 gang block to ease the work. No motor, no manual winch. It can lift 190lbs, we are not approaching that. The engineer`s theory is the load goes into the side of the house,and down, but he was watching carefully when we christened it.
Seevee,were the Clipper pics helpful?

Bruce--

ANYTHING that eases raising and lowering your dinghy from the water is all you need. My dinghy & 8hp outboard are in the 200lb range so a winch does help.

I had the same dinghy when I owned my Hunter 30 sailboat. It was not an enjoyable task back then lifting the dinghy with a halyard to store it on the forward deck. My outboard had to be removed first. I was overjoyed finding a used crane at Sailorman for less than $2K.

Maybe something like this, but with a longer frame and the hinge point mounted higher in the transom or even on the gunwale?

From my experience the lower the weight the lower the centre of gravity and the more stable the boat is in a rough sea.
A dinghy mounted off the F/B with supporting struts below to be honest would be a disaster to unship and mount a outboard in an emergency situation and frankly its not ship sweet, so why not secure it to the bathing platform.

BruceK said:

foggysail, the St Croix Junior is a work of art but basic. It has a 4 gang block to ease the work. No motor, no manual winch. It can lift 190lbs, we are not approaching that. The engineer`s theory is the load goes into the side of the house,and down, but he was watching carefully when we christened it.
Seevee,were the Clipper pics helpful?

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BruceK,

Yes, some good ideas out there. I realize that supporting it well would be necessary, but I really like to get it out of the way for most of the "day" cruising.

Irish Rambler said:

From my experience the lower the weight the lower the centre of gravity and the more stable the boat is in a rough sea.
A dinghy mounted off the F/B with supporting struts below to be honest would be a disaster to unship and mount a outboard in an emergency situation and frankly its not ship sweet, so why not secure it to the bathing platform.

Click to expand...

Irish,

Would agree about the high center of gravity, but if I were operating in rough weather, I'd lower it to the swim platform. For the vast majority of cruising, the 100 lb dinghy would not be and issue with the higher center of gravity. Would be less than adding one person on the flybridge.

When the weather gets rough, I prefer to secure the flybridge and operate from below. Some boats don't have that choice.

We've got a different Mainship, 370 Motoryacht, but I've seen other owners rig the boat to lift the dingy onto aft deck roof, which falls about shoulder height standing on the flybridge. (Photo below, not of our boat but of the same model with the dingy way up in the air.) The profile of your model probably isn't quite as tall as ours, but besides increasing the roll (moment arm, for those who like mech engineering terms) I'd be concerned about increasing windage too. Our boat is just a giant sail, a billboard in high winds and it's tough to wrangle. Our dingy and motor together weigh just less than 200 lbs. so I don't worry about the weight as much as increasing the boat's profile. We love our boat, overall very happy with it, but even at 26,000 dry weight and about 28,000 loaded, it gets knocked around like a Styrofoam cup in high winds. I understand the desire to lift the dingy high enough to get your swim platform back, but we finally resigned ourselves to removing the motor and lugging the dinghy up over the bow rail for longer runs. Didn't see a better alternative without increasing windage even more, and storing it upside down on the bow is a nice secure way to run. Always a compromise one way or another.

Lateral thought. Riviera and Maritimo boats usually locate the dinghy on a rack on the foredeck with an electric crane to do the work. Typically they lack a lower helm. Worth considering if vision from a lower helm is not affected.