Height of swim platform

[Beta Don]

You can see them in this picture - The boat came from the factory with smaller teak strips with stainless 'C' channel on them to protect the sides from pilings while docking. I replaced those with larger strips of Ipe wood and topped them with heavy, solid solid stainless rub rail - The same rail I wrapped around the swim platform I built. My rub rails are in the factory location . . . . same height. I lengthened them a little so they go a bit farther forward

We had sat the boat, fully loaded with about 2,500 pounds of gear and food for cruising, in the water prior to doing the bottom job - We had to raise the waterline at the stern by about 5 inches! Despite the extra load, the platform was still out of the water while underway, so on a lightly loaded boat, the height should be just fine. She tipped the scales on the Travel Lift at nearly 11,000 pounds!!!

Don

[Sunsetrider]

Minor hijack - looking back at my pics on the previous page, and noting the location of the brackets on Beta Don's also on the previous page: can I get away with putting a full-width platform on my existing struts? I need a better width to install davits but I am fearful of drilling more holes unnecessarily in the hull.

[JT48348]

I would never let drilling holes in a boat hold me back from installing supporting struts or whatever. God created 3m5200 for the sole purpose of installing things below the waterline. Your fears are unjustified in this day and age.

[Beta Don]

The wider you make it, the more likely you're gonna bump it on a piling while docking, so the better your brackets need to be! We saw several boats with platforms knocked off center by several inches and bent up flimsy brackets underneath. If your brackets are at all questionable, I would keep it 8 inches or a foot narrower than the transom on each side

Don

[Sunsetrider]

JT - you ignore the laziness factor.

BD - I don't have doubts about the strength of the materials or the installation of my existing brackets. The platform is quite strong and stable and supports my own 200-plus pounds without a whimper. My only concern is whether I can maintain lateral stability given a wider platform with the relatively narrow stance of the existing brackets. Two scenarios:
- a large person stands on one end - will it overstress the fittings to one side? If so, said large person could avoid the far ends.
- snap davits further off-centre for the 80 lb dinghy - in this case the weight at each end will be balanced, so perhaps not a concern.

Or am I just fooling myself? I would like to avoid the time-consuming step of locating the metal pieces and finding a welder to fabricate more brackets, and then drilling and installing, all before the marina launch timetable. Instead, I could jump right into designing and assembling the new platform. Then just bolt it on.

[Beta Don]

If you're going to make the platform wider, I would certainly make the brackets wider too. If your smaller platform only has two brackets, for sure I would use four on a platform as wide as the transom, especially if you intend to attach a dink to it

In my humble opinion, the static load of a couple 200 pound people standing on the platform shouldn't be what you're worried about - It's a given that it needs to support that. I've had 4 people on mine a few times. You saw my backing plates inside the transom. Of greater concern is the dink attached to the platform and what loads it will put on things when the boat gets really knocked around in a rough sea . . . . or, you knock it into a piling or something. A 6,500 pound boat moving at even half a mile per hour would be a real jolt if the platform was to hit something and you expected it to absorb that and come away undamaged. I think THAT would be a much greater concern than the static load of a couple people

Desert Albin lost a dink off his platform due to a large wave. We've all been in conditions which test the limits of things. If you think something may be questionable, those kinds of days will test it for you

But, I tend to overbuild things a bit, due to my past boating experiences and the problems I've seen others having to deal with away from their home waters - Things that are an easy fix in your own marina can be a challenge in a strange place where you don't know what resources are available or where to find them. Repairs away from home tend to get expensive

You could just bolt it on as it is, be real careful and hope for the best. I have seen platforms that don't look to be sturdy enough to stand on, yet they were still there . . . . probably been on the boat like that for years. Maybe the boat seldom goes anywhere, or only leaves the slip on nice days? I just don't seem to have the best of luck when I trust that approach, if you know what I mean

Don

[Sunsetrider]

Yes, I hear you, Don. And now I am thinking of a compromise: for the outboard pair, use "uppers" - bolted to the rear of the platform and partway up the transom.

[JT48348]

I think you need 4 brackets and 4 braces.
Two is not enough

[sail149]

I was poking about a marines in FL in November as saw a very strong swim platform on the back of a new Ranger Tug 21 . The platform was made to be a complete extension of the hull even if it was bolted on . It had railings and built in recess for fenders.
The other thing is how high the mounted it . I think probably to extended the boat length at a rub rail hieght so you can see it?

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They put them lower on the larger versions.

[Beta Don]

On my 33' sailboat, I extended the hull to include a 'sugar scoop' transom with a built-in swim platform and a built-in boarding ladder, which turned my 32.5 footer into a 34 - I got it redocumented as a 34. I left the original transom intact (that's it with the name and hailing port on it) and just added onto the hull aft of it. In the end, it pretty much looked like it had come from the factory that way *and* I gained another foot or so of waterline length, which I'm sure didn't hurt the hull speed any. Sure made it 10X easier to get in and out of the dink

I didn't paint the entire hull either - It's still factory gelcoat. Only the transom and the aft 3 feet or so is painted. I just blended it into the hull color. Pretty hard to detect even from up close

Don

[Sunsetrider]

Don - why register at the xtra length? Why pay more dockage fee?

[sail149]

Don
That's a cool modification . Looks like a hunter 32/34?
Years ago we used to race against a wood cold molded boat . They extended the hull by 2+ft like you to increase the planning surface and wl length It would disappear over the horizon.... They also sanded one layer of wood out of the inside to save weight!

I bought this cool little launch, 15', and would like to add planning plates because the boat hits hull speed at about 1800 rpm and the stern squats yet the engine is rated for 3600rpm.

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I'd like to add something like this.

What do you think?

[Sunsetrider]

I am going with 4 brackets after all (i.e., 2 new outside brackets), and looking to build a cedar platform 54 inches wide. The backing plates will be crucial, given that the supports are to be attached to a single-sheet fibreglass wall. I will replicate what Don did on the previous page as it seems to provide the backing with a large surface area. What would be the best adhesive for the backing plates - I want to stay away from the mess of epoxy paste. 5200?

[WillieC]

How about sikaflex 291. That is what I will be using. I dry fit my pieces, then mask the hull with tape and mask the part at the edge where all the splooge occurs. Then it is a simple wipe with screwdriver, knife or finger, don't cut yourself. Since the original backing plates on mine were 1/4" cut washers, I will be upgrading as well. I think I will use 2X2 strut washers, hot dip galv preferably, though I could use Don's wood backing to re-attach the previously solid glued paneling, with a little forethought.