Swim platform construction material?

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rsn48

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Feb 18, 2019
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Capricorn
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Mariner 30 - Sedan Cruiser 1969
My boat is finally heading in the home stretch of a large refit and one of the items nearing completion is my new swim platform. The old platform was removed as it was too narrow and a new one a bit wider planned. Other than teak, does anyone have a recommendation for material to be used building the actual platform?
 
I could be wrong. but PM GFC (Mike) I believe he rebuilt his swim platform or knows of a company that can make one.
 
My original platform is wood cored fiberglass with non-skid on top. I personally wouldn't use wood core for it, but building one from foam cored fiberglass should be fairly practical.

I know some places build them out of the plastic artificial teak stuff as well. Starboard is probably an option too, although either of those has to be fairly thick with lots of supports to not be too flexy.
 
I forgot to add that Seawise davits are going to be added so the platform will be under some stress and the Rib and 10 hp Merc transition from vertical to horizontal so I need the platform to be able to handle the transition stress.
 
rsn48 said:
I forgot to add that Seawise davits are going to be added so the platform will be under some stress and the Rib and 10 hp Merc transition from vertical to horizontal so I need the platform to be able to handle the transition stress.
Click to expand...


That would push me more towards fiberglass, as it'll be easier to reinforce an area for the davits to mount and transfer the load to the platform to hull brackets.
 
I built platform partly with a SS fabrication shop and partly myself for the teak installation. Any shop that does quality marine stainless steel fabrication can do it. These can be found by asking around at local boatyards.

The perimeter was SS and so were the two diagonal supports. One middle crosswise support was added to support the teak and a band of SS was welded on each end to support the teak.

In your case where it will hold a dinghy plus outboard as well as a person or two, I would use large diameter SS tubing, probably 1-1/4" for the perimeter and the diagonal supports. The load from the Seawise attachment points should be right at the two supports so two should be adequate.

If I were doing it today I would probably use Plasiteak or similar.

David
 
I would use square or rectangular stainless steel tube for a frame and support beams and Ipe wood for the top.
 
The brackets to hold the platform were constructed locally out of some metal, I draw a blank and epoxied over. There are five L brackets with a support in the L forming a support triangle. These brackets have been installed.

I have suggested the Ipe wood to my refit guy after the above post discussing this material, haven't heard back.
 
I don't think this is perfect, but its what we did. The PO used 1" square stock aluminum... it lasted about 5 years and rotted off the boat. The boat use to have a davit system off the swim step so it was beefed up a lot at that time. I rebuilt what they did in 1" 1/4 wall SS with all stainless brackets. I took out the sheet metal screws the PO used and installed 1/4 ss bolts with lock washers and goop on each side to slow down the leaks. There are 5 braces, two are located where the davit system use to be. I think you would rip a hole in the transom before the swim step fell off...

If the boat did not have 20 screw holes that went all the way through I would have built something much different, but this works.

I have seen a few of the custom one off swim steps that S3 has done, and they are flat out amazing. Some are bolt on, some are built on and seamless.

https://www.s3maritime.com/

I have a friend that works for them we call him Mr.Glass
 

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Simi 60 said:
I recently got rid of the thin cracking teak and replaced it with plastic composite decking.

It is heavier being double the thickness but oh so very secure to walk on.


https://www.bunnings.com.au/ekodeck-137-x-23mm-5-4m-red-rock-composite-decking_p0120934
Click to expand...

I have Trex brand composite decking on my sundeck at home. I wouldn't recommend it for marine use. After a very few years it softens and changes shape, so the original spacing between the boards shrinks and in many cases just goes away, as the plastic sags. Also the support on my deck are 16" apart, and the decking sags a little between them. Finally the finish has deteriorated to the point that they look bad. I would paint, but due to many tall cedars close by, I have to power wash the deck at least twice a year to get the cedar droppings off, and I don't think paint would survive that. This is the place where Trex is more durable than wood

I would not hesitate to use Teak despite the high price, as it will outlast the rest of your boat (if you use a robust dimension), or Ipe.

The wood slat design is a proven design, with solid areas where you are going to mount your SeaWise and with adequate supports.
 
We'll see

The teak strips we had were a death trap.
New teak was going to cost silly money and this stuff, due to them sending out a grooved edge vs square edge, cost exactly $zero.

As we had planned on heading up to South East Asia at the end of the year if it didn't last there would have been plenty of exotic hardwood choices to be had cheap when there, but that's not looking likely now.
 
Contact Butler Marine, https://butlermarine.com

I had them fabricate swim platform for my GB36 Classic. Great workmanship, customer support, very fair pricing.
 
rsn48 said:
My boat is finally heading in the home stretch of a large refit and one of the items nearing completion is my new swim platform. The old platform was removed as it was too narrow and a new one a bit wider planned. Other than teak, does anyone have a recommendation for material to be used building the actual platform?
Click to expand...


Try this place:

https://www.myswimplatform.com/
 
Simi 60 said:
I recently got rid of the thin cracking teak and replaced it with plastic composite decking.

It is heavier being double the thickness but oh so very secure to walk on.


https://www.bunnings.com.au/ekodeck-137-x-23mm-5-4m-red-rock-composite-decking_p0120934
Click to expand...

Hi Simi

Ditto for us - Malagari came with a composite planked swim platform - - the PO was able to curve it to match the transom and laid it with the reeded side up which is great for non slip - its a light brown, sort of matching the colour of new teak and it still looks as if it was laid yesterday. Absolutely no maintenance needed
 
rslifkin said:
That would push me more towards fiberglass, as it'll be easier to reinforce an area for the davits to mount and transfer the load to the platform to hull brackets.
Click to expand...

Swim steps should be considered “stern bumpers” , and constructed accordingly.
I’ve seen several where stout metal brackets were pushed right through the hull with catastrophic results.
Consider making the whole thing an extension of the hull, and integral.
Your slip fees are usually based on LOA anyway, why not have that be all boat?
 
Since your boat is 29', weight of the swim platform may be an issue.

We built several platforms for clients using a foam core with plastic blocking covered in 1708 fabric and epoxy. Even a few that extended the hull and provide storage and/or live well and fish storage.
 
I built our last swim platform out of plywood and fiberglass. I am not particularly happy with how it came out, weight wise, and a lot of other ways. The next haul out, I think I am going to use it as a pattern to build a completely new one, probably with some kind of closed foam cell core, and again of fiberglass.

The plywood was cheaper, but I do regret using it now. I'm already seeing some water intrusion, despite my best efforts to seal up screw holes.
 
Take a look at plasteak.com. We had a bow pulpit made by them on a previous boat. Like it a lot. No affiliation.
 
Since your boat is 29', weight of the swim platform may be an issue.

We built several platforms for clients using a foam core with plastic blocking covered in 1708 fabric and epoxy. Even a few that extended the hull and provide storage and/or live well and fish storage.

I don't think there will be a problem. We were originally going to use three brackets and up them to five due to the Seawise davit system, with RIB and 9.9 motor sitting on the davits, and swim platform.

The boat was built with fiberglass over wood as original build. When the old leg and engine were removed and the new Merc 6.2 l and Bravo 2 let brought in it was quickly realized the old hole for the leg would have be reglassed in and recut which was done.

This allowed us to get a first hand look at the transom and I swear it is roughly 3 inches thick or more. We had to take a plug out for some reason that escapes me and my refit guy has kept it to show others how strong some old boats could be.

With the addition of the custom made brackets which definitely look stronger than some of the ones show in this thread, I don't think there will be a problem with torsional torque.
 
rsn48 said:


With the addition of the custom made brackets which definitely look stronger than some of the ones show in this thread, I don't think there will be a problem with torsional torque.
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I was referring to the weight of the platform changing the trim, not the strength of the structure. Glass/plywood, metal, solid plastics are heavy. A lot depends on where the engine is located and the current trim.
 
I guess that what you will use to build your platform will primarily a question of what you are seeking.
Do you seek for a warm look (or does it fit your boat)? If yes then it will be wood varnished or not.
Do you seek for lowest maintenance, well in that case it will be fiberglass sandwich (over wood or anything else).
Do you seek for a James Bond look? You may use carbon fiber :)

So for me first thing would be to ask myself how I want it to look.

L
 
Alaskan Sea-Duction said:
What about starboard?
Click to expand...

While I love Starboard, in this application it doesn’t shine. It is pretty heavy and needs a lot of structural support or it will sag over time. It would need some kind of stiffener and that adds more weight. Plasteak used Starboard like planks and puts them on edge with spacers. That may work much better structurally. But not a flat sheet of Starboard. I use Starboard for lots of things where structure isn’t a big deal. Love it that it never needs finishing, no varnishing. On a previous boat I replaced everything outside that was wood with Starboard except the swim platform.
 
How'd I miss this thread? I know you said you don't want teak, but...

Go here and talk to this man. Island Teak - Custom Teak Milling.

swim platforms Island Teak - Custom Teak Milling.

He gets butts of old growth or salvage wood from Asia, and sends them back to the island in a container. Has his own small sawmill and cuts and mills his own. Beautiful, beautiful wood. Careful where you park. If you drive a shiny car the peacocks may attack it. Get some of teak oil that he makes there too. Squeezes his saw dust with a cider press.
 
So I have talked with my refit guy and what he has come up with so far, until the plan changes is to use a marine grade plywood, slathered in epoxy all around, with the plastic resin or whatever its called decking material over the plywood, to create a finished look.

The platform won't be that much longer than the old one taken out which was 18 inches, the new one will be roughly 22 inches.
 
Are they going to use fiberglass or just epoxy?
 
Boat builder by trade, I would not be happy with that if just resin soaking even if it was swum.

If they are going to glass it different story, but quality marine ply ain't cheap and by the time they use quality marine ply, double bias and epoxy they could almost do it in divinycell, strucell, nidaplast , etc and polyester resins for the same cost.
Zero rot potential.
 
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