Swim Platform- Height Above Water

[scottinsydney]

I am wondering what the best practical distance is for a boat's swim platform base to be above the water?

We are halfway rejuvenating the boat's old hydraulic swim platform mechanism and can adjust this setting.

At present the board's base above water is a huge 18" which makes boarding the platform difficult from a RIB. The RIB also gets stuck under the platform.

The swim platform is 17' wide and 5' deep. What would be the best compromise height for most sea conditions allowing easy access and protection from the boat's wake and the sea conditions?

[Pascal]

The fixed platform on my 53 is about 12" above water. I ve run boats with platforms set much lower, as low as 6". You dont want the dinghy to get stuck under the edge. Most lower platforms have slats or opening to relieve water pressure

[racclarkson@gmail.com]

The fixed platform on my 53 is about 12" above water. I ve run boats with platforms set much lower, as low as 6". You dont want the dinghy to get stuck under the edge. Most lower platforms have slats or opening to relieve water pressureMake the slats bigger.

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[Photolomy]

Mine is about 6", which seems pretty good. It is right above the exhaust, so it can't go any lower.

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[Passages]

I'm at 12" and I wish it were a few inches less. (Maybe 3)

Our 13' Whaler gets pinned under if the waves hit it wrong.

[scottinsydney]

The second last American owner installed a TNT Goliath hydraulic platform system in about 1998. It’s a set of twin sliding boxes boxes using an elaborate 3 cylinder 3 stage mechanism to lower the platform. Each section noves 13". The platform is massive being 17 x 5’ wide, maybe more than 600 lbs. The Goliath is overly complicated and has too many parts that could fail.

The cockpit extension's transom was strengthened internally with metal braces. Big job.

1st Australian owner removed the platform in 2010 due to broken hydraulics and put everything in storage. After I bought the boat I reused the original Goliath Aframe transom bracket and had made a fixed bracing for the platform. The original TNT rode 18” above the water and thats what the bracketing is now set.

At the machine shop yesterday we found rebuilding the Goliath and 2 x 3 sets of cylinders for each support too daunting. We have decided to use one new aluminium marine grade ram for each mechanism to lower the first stage only by 13”. Although still above water by 5" the platform will still be better for swimming and launching and retrieving the inflatable dinghy. We will investigate if the platform's initial height can be set to 12" above water level. (Hence my original question about swim platform height.

Photos show cutting off the old parts that had locked up. Also, the Aframe transom bracket now supporting the fixed platform supports.

I will soon have 6 x stainless 13" throw TNT rams that will need new seal kits $150 each for sale. New US$2500 each. For sale in one lot $5000 or $1000 each.

[Toolsntoys]

I have a tnt lift on my cruisers. The rams are 48” and work great for lowering a couple feet below the water line. I find that leaving the platform close to or at water height isn’t good. A couple good waves and it feels like its going to get torn off. If however I leave it 8-10 inches below the water line all is good and can leave it like that all day which is usually what I do. It’s great for swimming and just hanging out in the water

[scottinsydney]

Is this a single ram? Would you have a photo please?

[Toolsntoys]

I don’t have photos but I have had them out for rebuilding. Basicly my set up is a 48” stainless steel ram that has about 36” of throw It fits inside of three boxed channels each with bushings and rollers. The inside channel has brackets connected to the swim platform. It’s a really basic set up that I think can be easily fabricated. The boat is out of the water and shrink wrapped I’ll see if I can get pics. The platform was added to my boat in early 2000 and I know tnt has discontinued that model.

[Toolsntoys]

Sorry I should have clarified. It has two rams each inside it’s own channel

[R D Young]

My lower rub rail is about 9 inches above the water line, so it worked well to build in the swim step at that height - low enough so this old guy can get back on board from daily swim. I built the two posts for temporary dinghy tie ups and to help the needy to climb out of the dinks. The posts also go 6 inches below water line to keep dinghys from sliding beneath. They slip into a smaller square tube attached under the swim step and can be removed with one spring pin.
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