Dinghy Crane?

wyoboater · 05-08-2015, 08:34 PM

Greetings
I just purchased a 1985 Mainship 40 double cabin. It has a fiberglass cover over the aft deck, supported by stainless steel stanchions. I'd like to get my dinghy off the swim platform and on top of the fiberglass cover. Any thoughts on whether it will support the crane/cradle/dinghy and motor? Or will I need to add more support? Any thoughts from people who have done or tried this?

Thanks in advance

Heron · 05-08-2015, 08:59 PM

Pictures would help..

Lutarious · 05-08-2015, 09:22 PM

The sundeck will probably hold the dink, if it's a normal size and weight, but the crane would need to be anchored with a stand pipe from the deck below, through the sundeck. Not so much a weight issue as a torque issue when the dink is out on the arm.

wyoboater · 05-09-2015, 05:54 AM

This is a better pic of the current set-up...I want to move the dink from the swim platform to on top of the overhead.

caltexflanc · 05-09-2015, 07:12 AM

I'd get the opinion of a good boat yard. While that top looks like it will hold the dink, but will it accomodate someone walking around on it as well as the side forces from the standpipe for the davit? It appears to be merely designed for cover. That particular dinghy looks like a pure inflatable, so I'd guess those forces wouldn't be too bad.

wyoboater · 05-09-2015, 07:19 AM

Good point. I had figured the weight of the dink and the motor, didn't even think about the fact that I'd have to walk around on it too....yeah, I think I'll get the opinions of a few pros..........thanks

DavidM · 05-09-2015, 11:50 AM

I think that there are several issues with putting a dink on top of that cover, which BTW looks aftermarket:

The fiberglass probably will not take the load of a dink, motor and one person. You would have to put several strengthening ribs of wood and glass over them. to make it stiff enough.

Several hundred pounds of extra weight rolling around in a sea way is going to put some serious side loads on that structure. I don't see any diagonal bracing. You would need to add some.

And as others have said a pipe davit will need to go down all of the way to the deck and be somehow braced against the side loads while lifting a dink.

I would leave the dink on the swim platform.

David

Bay Pelican · 05-09-2015, 11:57 AM

Determine if the cover is an aftermarket add on. If original then Mainship can probably tell you both the weight the cover can hold and any stability issues if 200 lbs are added to the cover underway.

If aftermarket you would need a pro, probably two to determine both the weight and effect underway. In this case it may be much cheaper and safer to go with davits off the stern.

Heron · 05-09-2015, 11:58 AM

As to weight, if it's a cored fabrication you may be OK...If not, I wouldn't. And, as David and others have pointed out, the crane Stanchion will need to extend to the lower deck and be suitably braced..

The dink really isn't in the way...I'd be inclined to leave it there..
You could put snap davits on it so it could be easily lowered into the water.

**Larry M** · 05-09-2015, 01:43 PM

It looks like you may drive from the fly-bridge? You could add a davit on the fore-deck and mount the dinghy there. I'm not sure how it would look but you see lots of sport fishers with towers doing it. You also would have the advantage of keeping the added weight lower.

wyoboater · 05-09-2015, 05:07 PM

Thanks to all...as far as leaving it on the swim platform, I just don't like it there. I hadn't thought of the bow, thanks....and I am looking at davits to hang it over the platform off the stern.....just some thoughts, but either way, I'm not going to leave it on the swim platform...thanks again for the thought on the bow, I'll consider that also. Might be able to get a swing over removable crane for that.

Gabe n Em · 05-09-2015, 05:17 PM

Wyoboater,
Please post pics of whatever you decide to do. We have almost the same boat with dinghy davits but it's the same - the swim platform is taken up by the dink. Another option would be good

wyoboater · 05-09-2015, 05:26 PM

Gabe n Em....will do....and that's a nice boat you've got!

BruceK · 05-09-2015, 09:43 PM

Wyoboater, Difficult to say, the extension looks more light protective roof than walk on surface, maybe kept light to not add weight up high. A pair of pulley/davits mounted at the aft edge might distribute the load and save a support tube, someone still has to be on the roof to pull the lines and secure the dinghy into place. I see multiple pipe stay supports, but is there any pipework or other strengthening built into the edges? I would remove the o/board for the lift.
I ordered a St. Croix Junior Crane to help me get my dinghy on the aft FB more easily, mine looks a more substantial platform and the crane is part supported off the existing railings. I`m with you, I don`t like the dinghy occupying the swimstep,fouling access, etc.

wyoboater · 05-09-2015, 10:29 PM

Yeah, I might end up going with something like this. I just really don't like the looks of it tied on the swim platform. Not professional. I have the swim platform davits on the boat, and a jr crane for lifting the motor to it's holding block on the rail, I just don't like it.

FORESPAR Nova Davit Dinghy Lift | West Marine

BruceK · 05-09-2015, 11:25 PM

I checked the West Marine davits, nice, but do you want it hanging on davits across where you sit outside? I was thinking of a pulley set up to get it to sundeck roof level, with a manual drag onto the roof, and securing.

**Pack Mule** · 05-10-2015, 04:58 AM

I fought with this dinghy storage thing a while myself . I wanted to put mine on the roof .Most of the guys here on TF talked me out of it and I'm glad I listened . I finally had some davits made . I' m fiddling around with my hardware and lifting blocks to get everything just like I want it .

wyoboater · 05-10-2015, 05:24 AM

Pack Mule, that's a nice set up there. And Bruce, I just don't know....I still think the roof idea is best, just trying to figure out what's most practical...dunno dunno dunno.

ranger58sb · 05-10-2015, 07:34 AM

Quote:

Originally Posted by wyoboater

Thanks to all...as far as leaving it on the swim platform, I just don't like it there. I hadn't thought of the bow, thanks....and I am looking at davits to hang it over the platform off the stern.....just some thoughts, but either way, I'm not going to leave it on the swim platform...thanks again for the thought on the bow, I'll consider that also. Might be able to get a swing over removable crane for that.

I know of a Silverton in that size range (slightly smaller) where the owner installed a serious davit for bow mounting, and she said it was entirely satisfactory. The davit mount extends through a fore cabin locker all the way down to the hull; she said rock solid. She could launch by herself, no issues...

As far as I know, Mainship never offered that kind of hardtop over their "boat deck" -- so would suspect (as others) that it's an aftermarket installation. Might work, might not, but in addition to boat/motor/crane weight... your weight while you're up there can be another big deal... and in any case, the hull may or may not be all that great (safe?) with that much weight that high. (Pendulum, righting moment, etc.)

Also... how would you get up there? Doesn't look like you'd have easy access...

And a bow mount would speak to all that relatively easily. We'd do that ourselves, probably, except I value the sight picture out the front windshield. OTOH, I could probably convince myself that when we're anchored, the dinghy would be in the water, and wouldn't be obstructing the view.

-Chris

wyoboater · 05-10-2015, 07:51 AM

Ranger, that's another good idea that has been brought up. I've been doing a little surfing for pics, and cranes that might allow that, but haven't found any yet. If you have any pics/info on the Silverton install, I'd appreciate it.