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Old 23-01-2018, 08:13   #1
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Can I "hang" a swim platform off the transom?

So bear with me, have been trying to think of different ways to do this.

Backstory: giving very strong consideration to adding a swim platform / boarding platform to our 1988 Gulf 32. While it would be a plus to my not-so-tall wife as far as getting in and out of the dinghy, main reason is to make it easier to load and unload our 100 pound dog (she was really small when we got her, I swear!). Right now we can ape hang on the stern ladder and haul her out of the dinghy by her PFD, but it's not pretty and will eventually end in disaster (blown backs, unplanned swims).

Caveats / assumptions: I'm mostly looking for some input on my (current) plan to mount the swim step, not so much on whether a swim step is a good idea or not. I get the potential aesthetic negatives (although I believe form follows function, and have seen other Gulf 32's with platforms and think they look quite burly), potential for higher slip fees, and I understand the potential for mayhem in large following seas, but for the foreseeable future we are a coastal cruising bunch so not expecting green water over the stern to be a regular thing. That last being said, my current plan would make the step reasonably easy to remove if needed.

Sourcing the step: After nearly choking on the $5k+ quote from the yard, figured it was time to try to do it myself. I have looked at prefabbed steps from Plasteak (https://www.plasteak.com) and am leaning that direction for ease of maintenance and custom build / shape. An alternative would be to make it myself out of fiberglass over plywood, but that still doesn't solve my issue with mounting.

The challenge: is mounting... we don't have a lot of space on the stern, and there's an exhaust for the Wallas diesel heater that is a factor as well. I'd prefer not to drill a million holes in the transom either, but the big problem I'm having with standard style swim platform brackets is that they stick down too far below the platform... this is an older school wineglass style hull and so we don't have a big flat transom, it curves up off the centerline and doesn't leave much/any room for a bracket.



Any bracket that extends 18" out tends to be at least 10" tall, a 10" tall bracket out near the outboard sides of the step would put the whole platform much too high to be of any real use. Also only real way to get a bracket to sit right is to have it custom made to the correct angles both vertically and horizontally to the exact spot on the transom... spendy and challenge with boat far away.

My "plan": So, what I'm thinking of doing is "hanging" the swim step from padeyes above the step. Basically, the plan would be to build a metal frame for the plastic swim step to sit on (it needs to be supported every 2 feet per manufacturer, a metal perimeter frame would do that)... I would weld that up out of 2" (or maybe 1 1/2") square tube that I would have hot dip galvanized by a local company (or might just use stainless square tube and bolt it together... I don't right gas/wire setup for welding stainless). Then I would use stainless eye bolts on the four corners of the platform (bolted through the platform itself AND the frame) and use either galvanized wire or even dyneema to connect the eye bolts to pad eyes mounted on the transom with BIG backing plates. Not sure if I would want one pad eye on each side of the boat or two (one for front one for back) on each side. I think with appropriate size pad eyes, appropriate backing plates, and strong enough galvy wire / dyneema this would be more than sufficient to carry, say, 500 pounds (both of us and dog, not that I see all three of us being on there at the same time).

I realize that just hanging the step would allow it to bang all over the place, not good, but I think then I could use square tube on the outer sides of the platform run back and bolted to the transom - also with big backing plates - to keep the platform in place... my goal here is to have attachment to the transom mostly just keeping the platform from swaying around while the lines/wires take the actual weight of anyone stepping on the platform, so I wouldn't need big angled brackets that are seriously weight bearing just simple bolts through transom to backing plates to keep the whole thing in place.







Any input on this appreciated... if you think I'm being a jackass hack ("hackass"?), so be it, let me know... better than having my wife and dog fall in the water someday. I can't really afford a multi thousand dollar custom job, and the local metal guys aren't marine oriented at all and I don't have any faith in their ability to help with a job like this, and my boat's 725 miles away, so I'm feeling a little limited on my options.

As always, thanks in advance.

-- Bass
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Old 23-01-2018, 08:52   #2
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Re: Can I "hang" a swim platform off the transom?

Howdy.
I read your post, and looked at the photos.
My comments that follow are offered in a friendly tone of voice and with the sole intent to help you.

Many of the boats I have looked at (and thought of owning) do not have a swim step on the stern, and it is a nice feature to have.

I have admired (looked at online) boats with swim steps for years, and considered what I would do to add one, if possible, to a boat.
__________

Looking at your suggested design (with hanging and mild steel) and looking at how little it extends past the boat's stern, I think the current design you have is impractical and possibly risky for causing injury.

I assume the "swim step" or "boarding step" or "boarding or swim platform" would need to be wide enough to stand on or to hold a person who is seated on it. That may not be what you have in mind, but it is what I would want as a minimum.

Also, based on my own experience boarding boats (such as when SCUBA diving) it is rare that a boat will remain flat. If you are on the ocean or in a bay or lagoon, there will be some form of swell or waves, so even if the boat is anchored, it will be pitching or rolling or rocking.

I think it would be better to either:
1. Buy a prefab swim platform and add it on, accepting more properly made holes in the transom

2. Make a deeper (extends further from boat) platform that is lower to the water, for easier boarding.

When I look at your second photo illustration and draw a plumbed vertical line from the part of the boat that is furthest aft, that line shows there is not much (none) of the swim step extending past that vertical line. So, your draft line looks impractical. How could a person or dog stand there?

3. Avoid a swim step or platform that can move if the boat moves. I would want the swim step or platform to be secure, so that I could "pull up" myself from the water if there were some small waves rocking the boat. I would not want anything that swings or moves on me (or others) trying to board the boat in any kind of swell or waves, etc.

4. consider building a semi-permanent "scoop" shape swim platform from fiberglass, that has adequate holes for drainage of following seas, etc. Mount it on brackets of some type, and consider it a "breakaway" item in extreme conditions. Possibly removable when wanted and if next boat owner does not like it. Or have it fold up in the marina and fold down when needed at anchor. Securely mounted on the bottom edge, possibly using your "strap" to help support weight when in used position. But, not allowed to close up by itself, prevent that with some kind of locking pin, etc.

Hope that helps.
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Old 23-01-2018, 09:07   #3
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Re: Can I "hang" a swim platform off the transom?

Thank you for the input, appreciate it. I will insert a few comments into yours.

In general, let's just say I hope my build skills are better than my photoshop mockup skills. The mockup images aren't particularly to scale. I intend the step to be 18" - 24" deep, hopefully deep enough to stand on easily, otherwise what's the point?

Quote:
Originally Posted by Steady Hand View Post
Also, based on my own experience boarding boats (such as when SCUBA diving) it is rare that a boat will remain flat. If you are on the ocean or in a bay or lagoon, there will be some form of swell or waves, so even if the boat is anchored, it will be pitching or rolling or rocking.
Definitely some pitching and rolling even at anchor on our boat, she hobby horses a bit, so certainly a factor.

I think it would be better to either:
1. Buy a prefab swim platform and add it on, accepting more properly made holes in the transom
I am generally leaning towards the prefab, and don't really mind the holes in the transom, it's how high the platform would have to be if I used the usual angled brackets such as these:
https://www.marinedepotdirect.com/sw...g-bracket.html


2. Make a deeper (extends further from boat) platform that is lower to the water, for easier boarding.
As I mentioned I definitely want this to be deep enough to be useful, I think the issue here is more my crappy mockup, I'm definitely NOT proposing a 10" deep swim platform. Lower to the water is actually what I'm trying to go for by mounting it differently.

When I look at your second photo illustration and draw a plumbed vertical line from the part of the boat that is furthest aft, that line shows there is not much (none) of the swim step extending past that vertical line. So, your draft line looks impractical. How could a person or dog stand there?
Again, mockup sucks, but you make a good point about making the step deep enough not just for standing on but to also compensate for the inward rake of the transom.

3. Avoid a swim step or platform that can move if the boat moves. I would want the swim step or platform to be secure, so that I could "pull up" myself from the water if there were some small waves rocking the boat. I would not want anything that swings or moves on me (or others) trying to board the boat in any kind of swell or waves, etc.
I agree completely. Moving swim platform would be worse than no platform. What I'm hoping I could accomplish would be having the platform bolt directly to the transom (but not with mounts like above) to keep it from moving, and then having the support lines be actually taking the weight, so I get away from the 10" tall support brackets like linked above.

Hope that helps.

Every thoughtful comment helps, appreciate your taking the time.
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Old 23-01-2018, 09:17   #4
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Re: Can I "hang" a swim platform off the transom?

Probably a better scale mockup of the side view:

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Old 23-01-2018, 09:25   #5
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Re: Can I "hang" a swim platform off the transom?

Well, some thoughts.

I went on a touristy snorkeling/kayaking excursion once on the Appledore Star, where they used a large, removable swim platform off the port beam, amidships. In previous years they'd used a rope ladder but customers had trouble with it. Anyway they used some of the same ideas.

Use only one kind of metal. A combination of stainless and galvanized will corrode and fail.

You will need some means of adjusting the length of the diagonal supports, such as turnbuckles, unless you measure and cut the lengths to very close tolerances.

You would want to mount the supporting eyes as high on the transom as possible, for strength. Perhaps even above the boot stripe.

You should consider the effect of upward force on the platform, such as in following seas, because with flexible diagonal supports the platform may break off the lower mounts. An alternative to consider would be to leave the lower mounts off entirely, and stow the platform when not in use. You could just use some sort of pads where it contacts the transom. You would want to extend the diagonal mounts as far out on the swim platform as possible, perhaps slightly beyond it, to counteract the tendency for it to flip up from weight on the lip.
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Old 23-01-2018, 09:30   #6
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Re: Can I "hang" a swim platform off the transom?

Here’s something similar:

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Old 23-01-2018, 09:31   #7
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Re: Can I "hang" a swim platform off the transom?

Sorry, ignore the clickbait thumbnail. They do build a swim platform.
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Old 23-01-2018, 09:44   #8
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Re: Can I "hang" a swim platform off the transom?

I would find a different method of anchoring the strap to the platform, eye bolts can be very easy to trip a foot or lie on if someone slips.
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Old 23-01-2018, 10:05   #9
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Re: Can I "hang" a swim platform off the transom?

Quote:
Originally Posted by 1000 islands View Post
I would find a different method of anchoring the strap to the platform, eye bolts can be very easy to trip a foot or lie on if someone slips.
Thanks... I have been thinking about this, and another thought is eye bolts don't leave an easy way to attach the line/cable. I'm now thinking u-bolts on the platform itself as well, much lower profile and you can thread a spliced dyneema or stainless turnbuckle onto the u-bolt before securing it from underneath.
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Old 23-01-2018, 10:14   #10
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Re: Can I "hang" a swim platform off the transom?

Quote:
Originally Posted by jibstay View Post
Sorry, ignore the clickbait thumbnail. They do build a swim platform.
Click bait AND bad 80's music ;-)

But they do seem to be onto something. That is not exactly a giant transom either and they make it work.

What do you think one would even call the brackets they mount to the transom... that's part of my issue right now is I don't even know how to search for what I might want.

One thing easier for them is they have what appears to be a completely flat transom (at least from side to side) whereas ours is more curved.

Thanks for the vid link, that's very useful.

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Old 23-01-2018, 12:15   #11
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Re: Can I "hang" a swim platform off the transom?

We had a similar swim platform issue after our 40 year old ss swim ladder died.

Here's what we settled on...

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Pretty sturdy. Makes a nice platform from the dinghy too.

West Marine carries these. You can also find them on eBay (search for " teak swim platform").
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Old 23-01-2018, 12:36   #12
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Re: Can I "hang" a swim platform off the transom?

A whole bunch of links and pictures. Not of your transom, but may have some ideas you could use. Good luck.

Swim Platforms 101 swim platform added
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Old 23-01-2018, 12:53   #13
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Re: Can I "hang" a swim platform off the transom?

Quote:
Originally Posted by jeffatds9 View Post
We had a similar swim platform issue after our 40 year old ss swim ladder died.

Here's what we settled on...

Pretty sturdy. Makes a nice platform from the dinghy too.

West Marine carries these. You can also find them on eBay (search for " teak swim platform").
Hmm, interesting thought. Unfortunately the platform itself is not wide enough for our use (planned use is to be able to stand on the platform to one side while the dog / water jug / groceries / whatever are on the other side, so things have an intermediate step between dinghy and cockpit.

However, West Marine also has a version of this just with the plastic step... it's almost worth it just for the brackets themselves and then have a wider (side to side, not deeper) step made for those brackets... would be a pretty easy install compared to some of the other things I've been contemplating.

Thanks.

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Old 23-01-2018, 14:13   #14
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Re: Can I "hang" a swim platform off the transom?

Hi, Bassears,

What I want to do here is help you think about the problems involved before you start spending money, and I am concerned that the swim platform idea isn't what you need. To be used as a swim platform, it needs to be accessible from you being in the water with your head out, like a swimmer, and should be easy to get up on for the swimmer with the least upper body strength. It might not be much of a step upwards from a dinghy, on the order of 4-6 inches above the water.

If the boarding platform is for the main purpose of helping the dog to board, then is the dog limber enough to stand on it facing forward? The dog needs to be oriented so it can get to the cockpit. You might do better to make a hoisting sling you can buckle on the dog and hoist it aboard with a halyard. (Be sure to reward the dog afterwards, it most likely won't like it. My 125 lb. dog hated to be lifted.)

Again, still thinking about your dog, the drain holes in the platform need to be small,and many--no claw nor paw snaggers, and you'll need some kind of non-skid on it that will work for dog feet, and that will still work if it is wet. (Dog will go for a swim sometime, most likely.)

Platform is going to have to be big enough for both you and the dog on it at the same time, so you can help it board. Even if it can make the jump now, as it ages, it will need your help. And, I think you will want the platform to fold up flush with the transom while you are under way.

If you're going to use line to support the weight, one way to do it is to have the line come down through a hole you drilled for it, and use a stopper knot. This will be softer than eyes when folded up.

I am not sure that you are going to be able to do this, but I think if I were to try to do it, I'd make a mockup first, out of something as inexpensive as possible.

One more issue for your consideration. If that is a boarding ladder I see on your stern, how are you going to be able to use it with the [as yet imaginary] platform? It may be that a boarding platform for Fido might work better amidships. Also, amidships, bobble at anchor is minimized, and access to the deck could be easier for the dog.

I would even consider using the halyard on the doggie lifejacket to hoist the dog aboard, much easier in the long run. My concern here is that the boarding platform, to be usable by the dog, will not be a suitable swim platform.

Good luck with the project.

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Old 23-01-2018, 15:58   #15
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Re: Can I "hang" a swim platform off the transom?

Thanks Ann, I always appreciate your thoughtful comments (this time and on many other threads).

I put "swim platform" in the title because that's what everyone seems to call it. To be clear, though, I really envision this as a boarding platform. Our cruising grounds are the Pacific Northwest, we don't swim much, so it's more of a waypoint between dinghy and cockpit. (That being said, if this gets built it will eventually include some sort of ladder with as many rungs as possible below water to allow someone to climb from water to boarding platform).

Current setup requires both of us, always. To load dog into dinghy I stand in dinghy, with death grip on ladder, and "sling" the dog down from the cockpit to dinghy in one (back wrenching) swoop. Dinghy back to boat involves my standing one foot in dinghy, one foot on ladder, one hand on stern pulpit, and hauling on strap on dog's PFD to get her high enough for my wife to grab the handle.

Other comments inserted into yours.

Thanks again,

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Quote:
Originally Posted by JPA Cate View Post
Hi, Bassears,

What I want to do here is help you think about the problems involved before you start spending money, and I am concerned that the swim platform idea isn't what you need.
As noted above, I misspoke when saying "swim"... really a boarding platform.

If the boarding platform is for the main purpose of helping the dog to board, then is the dog limber enough to stand on it facing forward? The dog needs to be oriented so it can get to the cockpit.
She won't be able to face forward unless the boarding platform is probably 3+ feet deep, which doesn't seem reasonable. I envision the platform more as my standing to one side of the gap in the stern pulpit, dog standing next to me on boarding platform (facing me), and then I can lift her from there to the lip of the cockpit coaming, which is about distance I lift her into the pickup truck all the time (we lift her in and out of higher vehicles to preserve her joints).

You might do better to make a hoisting sling you can buckle on the dog and hoist it aboard with a halyard. (Be sure to reward the dog afterwards, it most likely won't like it. My 125 lb. dog hated to be lifted.)
Have thought about a hoist (could use the PFD) but sounds very involved, and can't be done with just one person on board I don't think.

Again, still thinking about your dog, the drain holes in the platform need to be small,and many--no claw nor paw snaggers, and you'll need some kind of non-skid on it that will work for dog feet, and that will still work if it is wet. (Dog will go for a swim sometime, most likely.)
Oddly for a lab mix she's not a swimmer, but certainly wades, and the platform would get splashed plenty, so both good points above.

Platform is going to have to be big enough for both you and the dog on it at the same time, so you can help it board. Even if it can make the jump now, as it ages, it will need your help.
Yes, this is exactly what I hope to be able to do.

And, I think you will want the platform to fold up flush with the transom while you are under way.
I am leaning that way now too... an earlier comment about the stern dropping and water pressure blasting up from underneath the platform I hadn't considered, folding would solve that.

If you're going to use line to support the weight, one way to do it is to have the line come down through a hole you drilled for it, and use a stopper knot. This will be softer than eyes when folded up.
Nice!

One more issue for your consideration. If that is a boarding ladder I see on your stern, how are you going to be able to use it with the [as yet imaginary] platform?
That ladder would have to go, unfortunately, to be replaced by something either amidships (I do have a midship gate) or attached to the boarding platform. Unless I could lower it halfway down and that might be usable in some sort of ramp form...

It may be that a boarding platform for Fido might work better amidships. Also, amidships, bobble at anchor is minimized, and access to the deck could be easier for the dog.
We have a midships gate on one side, sure there's less movement there (our boat hobby horses quite a bit), but it's still a very high freeboard to do all in one move. Have considered some sort of ramp on the midships gate (gangway? passarelle? not sure what they're called, basically ramping down to the water like you see on larger boats) but couldn't work anything out... although that's something I should reconsider now that I've put more thought into how to design a boarding platform.

Good luck with the project.

Ann
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