Installation of Swim Platform w/Davit

[richardoren]

Trying to dilute the grizzly repairs with hopeful improvements, I located a tender hoist which mounts to a swim platform at the transom. It would be great but I first have to make sure that an after market fiberglass swim platform could withstand the weight of the dinghy. The hoist accepts up to 650 lbs, and it would be holding that weight during rough seagoing. Here's a picture of it in operation:

http://www.davitsystem.com/hydraulic_demo.htm

Thanks for letting me know if you think this would work at the back of a Hatt with only a couple of portholes in the stern. I would need to find a way of making a sturdy support under the front edge of the platform, using the access under the two lower drawers of the aft master stateroom. It would be great not having to disassemble more than that, especially not removing the fuel tanks under the aft cabin twin bunks.

All suggestions appreciated, as well as leads to a sturdy used swim platform.

Rich

[Beckytek]

I have been considering the same system for my boat. It looks like a problem solver for me. My dingy only weighs about 150 lb so I wouldn't do any re-enforcing of my platform. Let us know how it works out if you do decide to get it. Ron

[richardoren]

Hi Ron,

Of course I'll post back here and let others know what gives if I follow through with this idea. I'm thinking of this seriously, since my former now lost system had large davits with hand maneuvered pulleys lifting the dinghy:



PROS: The Sea Wise setup seems to afford both privacy at dock (when the dinghy is up it masks the master cabin port holes from view when stern docked) and would improve docking visibility from the deck when backing up (versus my previous higher lift setup). It would also be less prone to collecting water from rain or ocean spray. Its hydraulic power assist would enable one to easily use a semi-rigid boat with a heavier higher hp motor for better coastal roaming seaworthiness.

CONS: It might be a less solid system given that the davit would be mounted on an external leveraged platform, making it possibly more prone to being torn off if a following sea pounds against the dinghy bottom. Water may also be captured by the bow and stern of the dinghy when waves rush past the sides of the Hatt into the tender, making it less than suitable for high sea crossings. This could make disassembling the heavier dinghy a burdensome task before attempting a crossing. From the South of France to Corsica I had to remove the dinghy in the above picture and stow it under deck, not an easy task with a heavy semi-rigid boat.

ANY SUGGESTIONS on how this setup would work out or how to make an added accessory swim platform sturdy enough to hold the setup would be much appreciated. Wild guesses are as welcome as considered opinions.

Rich

[REBrueckner]

I do NOT know that specific system but I'm quite sure from the video the weight is held via the vertical portion of the lift bolted to the stern...it's NOT likely the swim platform carries any weight at all....So installers must have internal access to the stern to be able to securely fasten the lift to the stern.
(Opps, edit note: Trojan, next post, is correct...I was so busy looking at the arm I did not even notice the hinges on the platform.)

Just make sure the dinghy bow and especially the stern does not stick beyond your stern beam width if you move in heavy seas...especially the lower stern side WILL be subject to buffeting from big waves....you can guess how I know!!

[Trojan]

The dingy weight is supported by the two hinges mounted on the outer edge of the swim platform. The lift arm only lifts about 50% of the dingy weight. This is due to the side mounted hinges. In the up position the lift only supports about 50% of the motor weight. The motor weight is suspended between the dingy and the lift in the upright position. The greatest weight on the lift mechanization is in the first foot of lift. Once over center the stress is continuously reduced until the dingy is vertical. Under way the swim platform supports all the weight of the dingy plus the weight of the lift mechanization. This weight distribution on the swim platform could change depending if any or all of the lift is bolted to the transom. I would think the dingy would ride quite well providing the dingy bow end top side had some type of support similar to the lift end and attached to the transom to keep the dingy from twisting. Looks like a nice system. Simple.

BILL

[GaryNW]

Trojan's description regarding the loading is exactly correct. I have this system on my 31' EC- the PO had it installed. In my case, it is the manual hoist; dinghy is a 9.5' catamaran type fiberglas with a 6 hp 2-stroke.

Stress points must be properly addressed. My swim platform is oem based on the quality and material of the brackets (quality-high, material-copper alloy weldments). Yet I must address sagging in the cored platform where the brackets are attached, especially the outboard motor end. I have already had to reinforce the dinghy where the bracket is attached as it was getting ready to just break out a piece of the dinghy. And yes, I have a quick-disconnect rod at the bow end for stability in any kind of seas.

I have Weaver dinghy brackets, which are well made and can be quickly hinged inbd of the dinghy gunnel so they can't possibly damage the yacht. If Seawise brkts don't look like that, then use the Weaver brkts and get the rest from Seawise.

BTW, I like the system. Looks good, easy to launch/retrive and should be almost zero maintenance once debugged.
Gary

[aquacraig@shaw.ca]

There are alot of Seawise systems used here in the PNW as they're made in BC. They really are quite slick and appear to be reliable and long lasting. A more robust design is the Nick Jackson which can be manual or electric. They bolt to the stern and lever out over the swim grid to deploy the tender. A stainless cable supports the weight bolted to the transom and coaming area. Hope this helps.
Craig