Installing a swim platform on an Attalia
This project began to eliminate the annoyance of getting people and gear up a stern ladder from a dinghy. On more modern Jeanneaux, there is usually a cut-out transom, incorporating a boarding platform and swimming ladder. Our design began with a year of daydreaming and pencil sketches and computer (CAD) designs, long before the frame was welded up. With no existing model, the CAD designs were invaluable, because they allowed 3D viewing.
For my Attalia, Coup de Vent, the platform became a trapezoid about 40”long at the hull, 30” at the back and 19 inches deep. It would sit about 12” above the water – a good height for a dinghy and dangling feet.
The frame is 1” square aluminum tube, anodized and powder coated. It attaches to the hull with two stainless bolts that are also the hinge pins for folding. We chose aluminum for cost, weight, ease of modification (which wasn’t required). The white marine-grade finish is very nice, but was more expensive than anticipated. The platform is 3/8 UV stabilized polyethylene with anti skid and “Coup de Vent” engraved by CNC machining. The plastic platform was extended an inch in each direction after mocking up a cardboard version. Yes, we felt silly standing on a piece cardboard with a jerry can in the middle of the winter! We also extended the hinge depth on gut feel – a good thing. A telescopic swim ladder slides under the platform. The ladder was purchased cheap over the Internet, but it needed a bit of beefing up with some extra welds.
The transom needed extra fibreglass and big backing pads to support the load. Who knew that transoms are only really thick where they meet the hull and deck? As you can see in the photo, Shipwright Service opted to glass in ¾” plywood knees, inboard of the large stainless backing plates.
The hinge design worked well, but we didn’t count on (ie didn’t notice) the sideways curvature of the transom. It just folds without binding. We also needed to add a mid transom step with a handhold. This attached using the bolt holes for the old ladder. This makes a nice seat when standing on the platform – so nice, that I’m considering making it wider for two people.
All in all, I’m pleasantly surprised that it is a total success. It meets a whole bunch of criteria:
* Fairly light weight due to design and aluminum construction (about 30 pounds)
* Visually not too obtrusive (white colour helps)
* Doesn’t drag under sail or power
* Seems to be a good size for 2 people and gear being transferred
* The (slightly reinforced) stock ladder stows nicely
* Can be folded to reduce boat length for marinas
* Can be taken off entirely with 2 bolts
The same approach should work on any similar boat with of an inboard rudder, from about 25 to 36 feet. For larger boats, the triangular bottom support under the platform wouldn’t work, because the platform would end up too high. I’ve worked out two alternative designs to keep the platform about a foot of the water, but that’s another story!
Ralph Booth - Attalia - Coup de Vent - www.aproposmarine.com