I want to build a swim platform

I have a 48 foot Californian. 15'2" beam. I have a fairly narrow 2 foot swim platform. I am entertaining the idea of building a larger one of 4 foot wide. I have found a custom builder that wants 4200.00 to build one. How doable for the DIY'er? I'm fairly handy with tools and have the time. Now, wood core or divinycell? I want to build it stout. at least 600 pound capacity or better.

Any thoughts?

If you're willing to work in fiberglass you can do it yourself. Quick answer to your question - do not use wood core! Closed dell PVC is best.

1. Make a full size template.
2. Make a flat table bigger than template and cover with shiny mica
3. Fabricate a flange that matches the edge of template of appropriate depth (6"?) surface with your shiny mica.
4. Wax no less than 6 times. No more than two times per day.
5. Brush/spray on gel coat 18 mills thick.
6. Laminate as necessary.
7. Insert core into wet mat or appropriate cement. Weigh down or vacuum bag.
8. Laminate on top of core.
9. Remove and trim.
10. Paint/glue on non skid.

In the way of the SS brackets you may wish to replace the core with solid glass ( during lamination).

Use 3m 5200 to bed when thru bolting to transom.

knotheadcharters said:

I have a 48 foot Californian. 15'2" beam. I have a fairly narrow 2 foot swim platform. I am entertaining the idea of building a larger one of 4 foot wide. I have found a custom builder that wants 4200.00 to build one. How doable for the DIY'er? I'm fairly handy with tools and have the time. Now, wood core or divinycell? I want to build it stout. at least 600 pound capacity or better.

Any thoughts?

Click to expand...

doubling the width may present a few challenges, first off the brackets to handle the load vs. the moment arm related to the depth available on the transom to spread the load. also 4' may be a bit wide for the size of boat. keep in mind that at 60 sq. ft you can put a lot of load on the platform and the thing better be able to support at least 1000 lbs. if you really need that kind of depth to the platform you may need to look into a tank that is basically a hull extension.

Good Luck,
HOLLYWOOD

Ahoy knothead

Seems you are looking to have a fixed-in-place Swim Step. I may build a new, larger SS for our Tolly. I’m impressed with design of Mark’s Coot SS. Its retracting ability interests me. For our boat it appears I would need to have the starboard portion remain fixed in position to keep the boarding ladder in position. From that area to port I can visualize a 3’ 6” deep hydraulically operated platform with modified swim ladder. The construction of Mark’s SS also interests me. It appears to me relatively light weight in regard to its metal frame and planked surface. I’m not exactly rushing into things... but I do have my radar on for improved, considerably larger, yet retractable swim step alteration.

Thanks for this thread. Others’ swim step build-out input may get really interesting.

Happy Boating Daze! - Art

there is a very extensive older threat on this if you search it

Here are a couple good threads from recent past to start with. Dwhatty made a beautiful PlasTeak replacement last winter.

http://www.trawlerforum.com/forums/s32/alternative-swim-platform-materials-5368.html

http://www.trawlerforum.com/forums/s32/swimgrid-re-do-12049.html

hollywood8118 said:

doubling the width may present a few challenges, first off the brackets to handle the load vs. the moment arm related to the depth available on the transom to spread the load. also 4' may be a bit wide for the size of boat. keep in mind that at 60 sq. ft you can put a lot of load on the platform and the thing better be able to support at least 1000 lbs. if you really need that kind of depth to the platform you may need to look into a tank that is basically a hull extension.

Good Luck,
HOLLYWOOD

Click to expand...

Hear, hear. Not only static load, but the force of someone standing on it, jumping on it, lifting dinghies, occasionally bumping the dock, and multiple people. To double sounds a little unstable. (the platform not the owner)

Check out Butler Marine, Duryea, PA. Seems you can have one made for a lot less. Might be worth checking out. I have a lot of work done by them

http://www.butlermarine.com/transom_platforms.shtml

A heavy following sea at displacement speeds can allow the overtaking wave to ride up over the platform and potentially up and over the stern. Not a likely scenario under normal operating conditions, but something to be well aware of under those circumstances. I am in favor of retractable (or swiveling) platforms with good through drainage, that will be the route I take when I get to that project.

I added a foot to mine as it was only two feet long. I removed the old one and the brackets. I then went to the local exotic wood supplier and had them mill me some teak 2 inchs wide to match the old platform. starting on the inside (stern side) I added the new material. Next I purchased some stainless flat bar and built new heavier brackets. Looks like the original just wider. Have fun.

Take a look in Sailorman.com, I saw many used swim platforms to sell there.

hollywood8118 said:

doubling the width may present a few challenges, first off the brackets to handle the load vs. the moment arm related to the depth available on the transom to spread the load. also 4' may be a bit wide for the size of boat. keep in mind that at 60 sq. ft you can put a lot of load on the platform and the thing better be able to support at least 1000 lbs. if you really need that kind of depth to the platform you may need to look into a tank that is basically a hull extension.

Good Luck,
HOLLYWOOD

Click to expand...

I agree. Our platform, added by a PO, is 29" off the transom. The original was slotted teak and not as wide. When we are at anchor or on a mooring, the wake from a passing vessel will shake Hobo as the wave compresses under the platform. Under way, the seas have never been an issue. Maybe if the platform was perforated, the loading wouldn't be as big an issue? 4' is getting pretty big but then again, properly designed, you would have enough room for a couple of chairs.

Larry M said:

I agree. Our platform, added by a PO, is 29" off the transom. The original was slotted teak and not as wide. When we are at anchor or on a mooring, the wake from a passing vessel will shake Hobo as the wave compresses under the platform. Under way, the seas have never been an issue. Maybe if the platform was perforated, the loading wouldn't be as big an issue? 4' is getting pretty big but then again, properly designed, you would have enough room for a couple of chairs.

Click to expand...

Larry,
great picture!
it illustrates a couple possible issues.. on A KK such as yours there is not enough transom depth to get adequate support from the underside (most desirable) , also the above platform supports can be a trip hazard and are at times damaged when the stern swings wide (not a big issue on the KK as the platform is narrow in comparison to the beam. Also, below platform supports are mostly in compression under load (unless a wave is pushing up on them)... where the above platform support is in tension ad relies heavier on the hardware.
On the Krogen there is no other option and it is the best solution.

A vented platform really helps lessen the loading when waves push up under the platform.

HOLLYWOOD

Larry M said:

I agree. Our platform, added by a PO, is 29" off the transom. The original was slotted teak and not as wide. When we are at anchor or on a mooring, the wake from a passing vessel will shake Hobo as the wave compresses under the platform. Under way, the seas have never been an issue. Maybe if the platform was perforated, the loading wouldn't be as big an issue? 4' is getting pretty big but then again, properly designed, you would have enough room for a couple of chairs.

Click to expand...

I like your dink ropes pre-attached and ready. Very good idea!

I also have a swim platform on my list of projects. The more I think about it, the more I'm leaning to the Coot type retractible design. I'd have to add squaring ribs on the stern out to about 11 ft. or so to make it look right, but it seems to me that it would be no more expensive to go that way, so why not. The addition of a substantial swim platform would greatly enhance our man-overboard plan, and being able to retract the platform would help with dinghy retrieval (davits) and dinghy crane access to the stern.

I want to build it stout. at least 600 pound capacity or better.

A good sized wave or wake can easily be more than 600 lbs.

Thanks for all the input guys. Doug as far as coming up over the stern. If I had a wave overtaking my stern which is 8 1/2 feet off the waterline, I have bigger problems. The platform itself is 15 inches off the water line at rest. Underway a lot more, most of my cruising is done in the ICW had aspirations of the Bahamas but that will be a long way off there's a lot to see in the US first so not real concerned with heavy following seas. If I do go that large (4 foot wide) it will be vented to alleviate some wave pressure.

knotheadcharters said:

Thanks for all the input guys. Doug as far as coming up over the stern. If I had a wave overtaking my stern which is 8 1/2 feet off the waterline, I have bigger problems. The platform itself is 15 inches off the water line at rest. Underway a lot more, most of my cruising is done in the ICW had aspirations of the Bahamas but that will be a long way off there's a lot to see in the US first so not real concerned with heavy following seas. If I do go that large (4 foot wide) it will be vented to alleviate some wave pressure.

Click to expand...

Not sure if it would work or last or even be desirable....but....if I was worried about the size, some removable or lightly attached inserts would resolve the problem of not enough pressure relief/drainage for when you encounter dangerous weather/huge wakes unexpectedly.

These pictures are from a Selene that are factory made. My understanding is they no longer offer this option.

Here's a pictures of the underside. The platform was made with plywood then glassed. We had it off this year and it takes 2 people to manage because of it's weight. It will easily support 1000 lbs or more. The top is 11.5" off the water at rest.

PSNEELD,
When I say vented I mean a slatted design. Remember nothing is perfect and the case for following seas is a variable not a constant. My neighbors 60 Sea Ray has a 6 foot wide swim platform with a 12 foot Nova Rhib on it and his travels each year to the Bahamas he has never had an issue with following seas affecting the platform.

Here's the 3' wide platform I built for my 50' foot boat a year ago... (I can load more pictures of the building process).
- Total cost about $800 (incl fiber)
- Used 3 layers of 0.5" exterior plywood from home depot
- Screwed and glued
- Once sanded, recover with Fiber & epoxy (boat sides)
- installed it on top of the 2' feet wide old teak one (just a couple of bolts)
- re-installed the later (2" shorter)

We love it now and this is very secured for the wife & kids.
I plan to install the "SeaDek" product on top (some sort of rubber mat)

BTW, the color you see if after I applied the epoxy / Fiber (no color added)
Bye
Francois

Very good work ;-)

we chartered a nordic tug with a custom swim platform that had a cradle for the tender on it. It was bulletproof from what I could tell. The tender was pretty heavy as well..


It was made by some custom fabrication company in Washington, but I dont recall the name of the company.

bligh said:

we chartered a nordic tug with a custom swim platform that had a cradle for the tender on it. It was bulletproof from what I could tell. The tender was pretty heavy as well.. It was made by some custom fabrication company in Washington, but I dont recall the name of the company.

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Looks like a nice sturdy platform. the one flaw is it looks like aluminum, aluminum is the biggest pain to keep paint on. Definitely not good since it's going constantly be close to water and in the prop wash.

I am sure some you are correct and it was aluminum, but it had been anodized. I cant remember if any of it was fiberglass or not.

What was even better about it was the dinghy. It was all aluminum yet looked like a RIB and it was a beast. It was set up for fishing with built in fish finder, VHF, pole holders, storage compartments, bilge pump, running lights, and fish wells. It was a real treat to use that tender. I cant imagine how much it cost, but I imagine he had well over $25k into the dinghy alone.

bligh said:

What was even better about it was the dinghy. It was all aluminum yet looked like a RIB and it was a beast. It was set up for fishing with built in fish finder, VHF, pole holders, storage compartments, bilge pump, running lights, and fish wells. It was a real treat to use that tender. I cant imagine how much it cost, but I imagine he had well over $25k into the dinghy alone.

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Thanks for showing swimstep and "Robo Dink"! BA looking tender!!

You say "he had ... $25K into the dinghy" Was that a person or rental company you leased from?

Bet you had a blast!

More I look at pict of very heavy dink on davits at far end of swim step - more I wonder - how is that platform fastened?? Through transom I-Beams... just kidding, sort of!

Here is the Ipe one I built for our girl last year.

Nice one , Mark!