Davits for a RIB - help please

[stiknstring]

Anyone used the Plastimo davits on a sailboat? At the risk of being told that you get what you pay for, I am curious that while Cooney's (Whittal, Simpson etc)manage to sell davits (150kgs) for £2,500, Plastimo are selling similar looking davits and capability at only £370! Perhaps the S/S is inferior? Must be a story there.....

 

[oceanfroggie]

Important thing about davits is how they are anchored to the boat and supported. If carrying a small 3.5m rib weighing about 200kg (inc motor), the anchore points have to be heavily reinforced with extra GRP matt, blocks, and perhaps small truss behind transom to spread the load. Sometimes a vertical support pole is placed under the davit arm and fixed either to the transom bathing platform, or the transom. Otherwise over time they will just crack the GRP and rip out. Factory install davits are done this way, but often retro fitted ones are just bolted through existing GRP.

Not an issue for a small 3.5m inflatable with an air floor and a little 5hp outboard mounted on a transom bracket.

Also it is imperative that you can winch the dingy right up to the davit arms and strap it firmly in place. If there is the slighest bit of movement out in a blow the stress loads on the davits are collosal. Cooney (ie Simpson) took over Whitall as far as I can remember. The plastimo are possibly snap davits (ie not davits), but anchor points for a bathing platform where you rotate the dingy 90 degrees sideways for storage against the transom.

 

[Swagman]

Hi,

Agree with Ocean Froggie you might not be comparing apples with apples.

We fitted Simpson removable davits last year which cost circa £700 in UK. The alternate same spec but telescopic ones were made by Osculati are about the same price.

The Simpson ones were rated to carry our 3.4m inflatable plus 8 hp Yamaha.

We were also advised to do more than just bolt the mounting plates to the flat part on our transom, so had stainless 'extensions' made to distribute the plates load further. In our case these extensions fitted below the base plates down to another flat surface below.

IMHO I'd recommend this additional support as even very minor flexing at the transom by the boat / davit / plate will lead to gelcoat crazing.

If you want pictures of what we ended up with on our yacht, I've got some, so just PM.

Cheers
JOHN

 

[Talbot]

I have the plastimo 60mm (larger) davits. I cant comment on how good the deck flex bit is, cause I heavily modified mine so that they are permanent and have an additional support from halfway up the davit. The bases have been welded solid, and cut off so that it just goes through the deck, through the ply panel in the deck, and then through another reinforcing ply panel under the deck to spread the load. But I do have a BIG solar panel on the top of it.

 

[DaveS]

I've used the smaller sized Plastimo davits for a number of years with no problems. I made up GRP "bottomless boxes" which are bolted to the transom and into which the sockets are mounted. I don't normally lift up my o/b, but it's electric so not much weight anyway - the battery's a different matter, though, but it has to come aboard for charging anyway. I've attached a 3:1 tackle to one davit for battery lifting.

One suggestion if you use external boxes or cantilever brackets is to drill a small hole in the bottom of each socket to let water run out.

I would strongly agree with the need to keep the dinghy well tied down. I pass the bight of each fall through a D ring on the dinghy then wrap it round the davit and jam the last bit in the cleat. Avoids the need for extra ropes. When the dinghy fills with water I undo these lashings and, without disturbing the main lifts, shove the near tube down and back using its oar until the dinghy's past vertical and all the water runs out.