I want to build a swim platform

Nice job

Have you thought about doing a hull extension instead of just tacking something on the transom like an afterthought?

Cats do it quite often for great benifit.


On a grander scale on a motor boat.


and on something smaller, though god only knows why they stepped it in half an inch instead of following the hull lines


I am yet to hear of a boat that hasn't benefited from a few extra feet of water line length and it makes for easier boarding, a "real" swim ladder can be mounted and its a secure place for offloading groceries, cleaning fish etc etc etc..

Mixing the first and third photo, if you made an hull extention, you can earn boat displacement

Parmenter

Thanks for locating and posting the three picts! Those stern additions look nice and would elongate the boat's LOA and WLL as well as being very useful during many stand-still events and for cruising dink storage... etc.

However, as you may notice in attached video, experiences that rule my sea keeping mind clearly tell me that following/conflicted seas of a really bad condition keep the upward fordable swim step design as my top priority. Bad water such as this only need happen once with too big a rear end platform on any boat and Davy Jones may well claim another submerged member! In boat design I believe “Be prepared for the worst – Plan for any event that might occur – Hope for the best!

Old saying: "When you least expect it - Expect It!

Also, finding dockage space and extra dockage charge keep the upward foldable swim step at top of my list for replacement on our boat that plys SF Delta.

Fishing boats in rough seas

http://www.youtube.com/watch?v=ByGSMmenPDM

Hull extension is not in the budget. I want a wider platform for a couple of reasons, one being I have a 12 foot Carolina skiff I would like to carry on the back. No Not going with davits and no not wanting to tow it. I have a 12 foot RHIB on the boat deck and I want to carry both. But primarily I just want a wider platform for hanging out while swimming.

Francois I like the idea of just adding with and using the existing platform but not sure about over hang strength, that additional unsupported 2 feet may not be able to handle a 350 pound Carolina skiff with a 35 hp motor.

knotheadcharters said:

Hull extension is not in the budget. I want a wider platform for a couple of reasons, one being I have a 12 foot Carolina skiff I would like to carry on the back. No Not going with davits and no not wanting to tow it. I have a 12 foot RHIB on the boat deck and I want to carry both. But primarily I just want a wider platform for hanging out while swimming.

Francois I like the idea of just adding with and using the existing platform but not sure about over hang strength, that additional unsupported 2 feet may not be able to handle a 350 pound Carolina skiff with a 35 hp motor.

Click to expand...

and planning for the unexpected.. if the skiff fills with either rain water or from seas the loading will be huge.. this happened on the SeaRay we had.. 12' zodiac filled when a rag left in the boat plugged the open drain and the damn thing filled to the brim.. the load on the platform was scary...
HOLLYWOOD

hollywood - That much weight on platform disturb/wrack the platform's braces? I take it the fill was from rain and not heavy seas...

Self bailing cockpit 2 scuppers and a cover, remember people this is ICW cruising. I appreciate all the following sea comments but apparently a lot of you are unfamiliar with the ICW in Florida. Very narrow never more than a 1 foot chop, slightly more in the rivers or near the inlets but only in heavy winds which means I will be laying up those days.

Rather than carrying the Skiff flat on the platform, consider Weaver Davits and a Weaver Hoist. If you're interested, talk to Don on Moonstruck. He just bought one. Don't think he's got it installed yet but he did a lot of research before he bought it.

You need to maximize the angle of your supporting brackets. To do so you need to know how deep you can make them, by measuring the distance from the new bottom of the swimgrid to the bottom of the transom. Having done that you can design your new swimgrid to whatever depth the new brackets can hold.
I also think lots of handholds along the aft edge are important. this will permit landings in your dinghy, tying things off, etc.
On a sailboat with a transom that resembled the KK above, I built one out of FG with a plywood core, multiple aft edge handholds, and the depth determined as I have indicated above. It was a great addition to a boat that came without.
The added 13" on Retreat's Swimgrid has been the best modification.
I recommend you go for the widest your transom depth will allow.
Make your SS supports good and strong, as you will frequently have a crowd on it and that crowd will often weigh over 1000 pounds.
Extending the old one by adding to its inside edge will likely be the easiest way to gain the extra depth. You may want to raise it up a little to get a better angle on the supports. I learned by trying to re-use the old supports that they were not robust enough for the movement of the weight away from the transom. That gave me a source of bronze for other projects when I replaced the old supports with robust, SS made properly.

Quick questions:

1. How do plan on mounting the skiff?

2. How do you plan on getting skiff on and off?

3. Is beam 62"? If snugged agInst transom, you can figure the total wright is out 32" aft of transom. This is where you'll need to calculate load weight.

The skiff brings in a whole set of extra considerations. Any budget for one of those lifting platform devices?

Knotheadcharters, the over hang on my 2" tick ply swim platform will not support the weight of 350lbs + outboard.

HopCar, we love this Weaver Hoist system you show. We had the opportunity to use one of these last year on a charter boat in Anacortes and was very please with this system.
On our boat, we store the dinghy (that I built out of plywood ) on the fly using an electric crane (and this works fine for us).
Francois

Francois, I like your dinghy. Is the other end pointy or transom type?
What plans did you use?
I'm building a 14 foot plywood skiff right now but would like to build a dinghy for my boat when the skiff is done.

Art said:

Parmenter

Thanks for locating and posting the three picts! Those stern additions look nice and would elongate the boat's LOA and WLL as well as being very useful during many stand-still events and for cruising dink storage... etc.

However, as you may notice in attached video, experiences that rule my sea keeping mind clearly tell me that following/conflicted seas of a really bad condition keep the upward fordable swim step design as my top priority. Bad water such as this only need happen once with too big a rear end platform on any boat and Davy Jones may well claim another submerged member! In boat design I believe “Be prepared for the worst – Plan for any event that might occur – Hope for the best!

Old saying: "When you least expect it - Expect It!

Also, finding dockage space and extra dockage charge keep the upward foldable swim step at top of my list for replacement on our boat that plys SF Delta.

Fishing boats in rough seas

Click to expand...

Technically, that video is breaking surf over a river bar. Extremely rare conditions that I doubt most trawlers would ever see during their service. Unless you are crossing sand bars, I think it would be safe to design your swim platform knowing you'll never be in breaking surf.

Art said:

hollywood - That much weight on platform disturb/wrack the platform's braces? I take it the fill was from rain and not heavy seas...

Click to expand...

mine was from rain... didn't go gown to the boat for about 6 weeks and Portland can get A LOT of rain in a short amount of time.

I guess the point I was trying to make is you HAVE to plan for the extreme's
and leave plenty of room for extra capacity.

On the sea ray the dinghy was on a homemade version of the Hurley Davit, I just wanted something more classy.. for protected waters they work very well. I did have " following waves" overtake the inflatable and lift it off the davit a couple times... the waves can get to 6'+ and be really square on the Gorge
The dinghy is on the platform in the attached pic.

HOLLYWOOD

Hurley Marine Rib or Soft Bottom Inflatable Dinghy Davits | Boat Davit

HopCar, the dinghy I built is called "Saboteer" and you can find the plans from the Glen-L web site. The bow is transom like and is setup for sail with a 16' mast (2 sections). The boat is great rowing and can accept an outboard up to 5HP (which is what we use most of the time for fishing).
Francois

bligh said:

Technically, that video is breaking surf over a river bar. Extremely rare conditions that I doubt most trawlers would ever see during their service. Unless you are crossing sand bars, I think it would be safe to design your swim platform knowing you'll never be in breaking surf.

Click to expand...

NEVER is a really BIG word (term) whose total meaning/context I believe can't be fully relied upon for items that at a moment’s notice could alter in their potentials for application, creation, development... or, even their very existence.

For many items that it may be loosely used for I see the word “Never” as a “self imposing” oxymoron in and of its own volition; i.e. Definition: 1. at no time in the past or future; on no occasion; not ever. 2. not at all.

Never, Always, and Forever: Three words I try not to use in relation to most items or events... cause... in previous decades I've repeatedly found - "When You Least Expect It - Expect IT!! Therefore I do my best to plan for whatever I feel “IT” may become, especially regarding the untold changes that can suddenly develop in marine conditions.

And, yes, although not in as severe a wave conditions as the cautionary video I linked to this thread... I have been in what I feel were some real hairy-ass New England seas in the 1960's and 70's while off shore and while entering inlets during inopportune times. Sea conditions that I feel could well have become disastrous if we’d had any type swim platform attached to our transom.

That said... If a boater actually never leaves protected waters then it is true that pretty much never will their boat become afflicted by tumultuous following or confused seas.

But, cha just never know, do ya!

PS: Although our Tolly came with its original swim step, and the step is surely fun to use, I still look forward to eventually replacing it with an upward folding platform.

One of our boat's greatest assets is how it handles in a following sea. While docked here in Stuart, FL along the St. Lucie River, I've had the opportunity to observe the different boats, all facing stern to the river, dealing with the various wakes coming into the marina. These wakes are no more than 100 ft. away and some of them really steep, perhaps 3 ft. difference from well to tip. Among those equipped with swim platforms have been an Ocean 48, Krogen 39, Great Harbour N-47, and Peaquad 36. After months of observation, I'm surprised to say that I haven't seen any issues with swim platforms at all. Each time a steep wake flows in, the transom of each boat simply lifts before the swim platform bottoms out.

There's no question that rough seas will will do whatever they want to do to your boat, but in all but the most serious cases (like Art refers to above), maybe the extra hang-over is not as much of an issue as I have imagined to be. Still, a retractible platform built from scratch is liable not to be much more expensive than a solid mount. Indeed, it would have to be built better. My Admiral and I realized two years ago that if our boat was equipped with a swim platform that made water access simple and easy for our aging frames, we'd have doubled or tripled our use of the boat. Having space for a couple of chairs and a thick ladder that had steps broad enough not to kill your feet would remove any doubts for us. Doing a quality glassed and reinforced squaring-off of the transom mounting area would provide not only the opportunity for a retractible unit, but later replacements or retrofits would only need be the same economical straight-across design.

The unit below the unapologetic example of a swim platform on an N-47 Great Harbour. It has space, strength, and a heck of a ladder. I'd probably want a couple of relief holes in it, but you can see what I mean. Yes, I know, it, such a platform adds to overall length and Marinas may charge you the extra bucks and so on, but if you're on this thread and you want a swim platform on your boat, that compromise is probably decided anyway. I believe a retractible version of this could be built, perhaps not this heavy, but do-able.

I think the biggest issue is the support. You can have them made or buy them.

The platform can be made of anything.

If using a solid sheet of some sort of plastic or fiber glasss. It would be
best if they are slotted to help prevent all the problems mentioned.

SD

I plan to build a new fiberglass swim platform with plenty of slots to redduce water loading from above or below. I am fairly familiar with fiberglass techniques, but I don't know how to form the slots. Any advice would be appreciated.

Probably building the core first, with holes in place and then overlaying the core with fiberglass. Fiberglass needs a core for strength or it flexes too much. First decision would be to decide what material you want to core the platform with. No experience with it, just a logical assumption.

Shoal. Here's how to make a fiberglass platform with slots and flange.

1. As I mentioned before, make a flat table a bit bigger than plat form and cover with shiny mica.
2. Using your template, set vertical pieces around the perimeter. These should also be faced in the same shiny mica. For radiused corners, score the flage pieces.
3. Layout the position of the slots.
4. Attach mica covered pieces the length. Width and depth of the slots. Make the depth if these pieces about an inch deeper than total thickness of lamination.
5. You now have the reverse image - fine female mold.
6. Using mold release paste wax, wax the heck out of it. No less than 6 times. No more than 1 time per 6 hour period.
7. Using modeling clay and a tongue depressor or you finger, radio us ALL the inside radiuses where the bosses meet the horizontal platform.
8. Spray with PVA or similar mold release agent.
9. Gel oat. Laminate. Insert core. Laminate.
10. Trim.
11. Release from mold
12. Sand the radiuses.
13. Prime with epoxy primer (with nonskid?)
14. Topcoat.

Thanks Doug and Reuben, that's about what I feared. I was hoping there might be a few tricks of the trade that would make constructing the mold a shorter job than makng the finished item. Sadly not so - guess I'll just have to bite the bullet.

If you spend more than a day making this one-time mold, you're doing something wrong. It does take some woodworking skills, not beyond the average do it yourselfer. The lamination lulu be picky depending on number of slots.