Swim Platform Design ideas/help for steel hull truller

Discussion in 'Boatbuilding' started by sandog, Jan 30, 2021.

  1. sandog
    Joined: Jan 2021
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    sandog Junior Member

    Hello. I hope I am posting in the right forum here. I am in contract to purchase 63', semi-displacement, steel-hulled boat. The biggest concern with this for the use I want it for, is the swim platform. Currently, there is none.

    I could do the simple teak deck, and have a ladder going down to it, but am greatly against this idea. What I am thinking of is adding stairs to go down to a swim platform (maybe adding 2~3' to the length of the boat), and then have a 30~40" swim platform that would fold up.

    Secondary would be to have the whole swim platform fold up as well as stairs that go down to it. Maybe have 18" or so that does not fold up. The distance gives room to store scuba tanks and inflatable paddle boards, etc, without taking up deck space or room space.

    I will upload two photos of the back of the boat, and two photos to show the two different ideas, sorta, in concept.

    Any input, incite, help, etc would be highly appreciated. Thank you in advance.

    imgur.com https://imgur.com/a/oGl9VVU (I have trying to link a gallery, but have been unsuccessful)
     
  2. bajansailor
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    bajansailor Marine Surveyor

    Welcome to the Forum Sandog.

    Re the first two photos in your link above, are these of the actual boat that you are purchasing?
    If so, she looks like she is in pretty good condition - but I hope that you have still had a thorough survey carried out, including ultrasonic hull thickness testing (unless this was done relatively recently).

    Have you got a yard in mind for building a hull extension? This would add some extra buoyancy at the aft end, but also give you extra waterline length, and add a bit of lift.
    It might be easier to simply build a fixed platform, rather than try to have a 30" - 40" platform that can fold up - this would be a big heavy beast.
    Many fibreglass production boats now seem to have relatively large platforms built in - the Fairline Squadron 68 is a typical example.
    Squadron 68 | Fairline Yachts https://fairline.com/en/yachts/squadron/68/

    Re stairs, would they intrude into the hull (like the Fairline in the link above), or would they be completely 'outside'?
    If the latter, they would take up a lot of space on the platform?
    Would it be feasible to just have a ladder going up from the swim platform?
     
  3. missinginaction
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    missinginaction Senior Member

    First things first. Before I'd do anything I'd take a good look at the transom. Make sure that it is engineered to take the loads that will be placed on it by the platform. I can't speak for metal boats but in the case of my fiberglass boat the original equipment transom was about 1/8" in thickness. It served it's design function just fine, but needed considerable work before a strong platform could be installed. I'll post a link that will give you an idea.

    New swim platform for a 1973 Silverton Sedan https://www.boatdesign.net/threads/new-swim-platform-for-a-1973-silverton-sedan.56033/
     
  4. sandog
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    sandog Junior Member

    Survey has been done on it, and hull thickness is in great shape.

    I was not trying to "extend" the ship length. I was thinking, in a basic sense, picture a platform that is 24~30" fixed, and then another 24~30" that folds up. So in the Fairline link, the first bit would be fixed, and have stairs, but then where the line is, it would fold up. A ladder would be simpler, but no where close to as convenient, or safe, with kids goofing off on it.
     
  5. sandog
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    sandog Junior Member

    I am not trying to intrude into the current hull at all.
     
  6. sandog
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    sandog Junior Member

    I could also do a fixed platform, but would be more limited to 48" or so in total add on length and would need to incorporate stairs into that as well.
     
  7. bajansailor
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    bajansailor Marine Surveyor

  8. sandog
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    sandog Junior Member

    Those are definitely very cool, but look insanely expensive, and do not understand how they would integrate into this boat. Also, thank you so much for putting the photos into the messages.
     
  9. bajansailor
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    bajansailor Marine Surveyor

    It might be worthwhile making some inquiries re cost - you might be pleasantly surprised.
    It should be fairly straightforward to attach a hydraulically raised platform to the transom of your boat?
     
  10. sandog
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    sandog Junior Member

    @bajansailor, are you talking about having it attach to the back in a vertical fashion and come down? If so, that is a great idea!
     
  11. bajansailor
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    bajansailor Marine Surveyor

    Yes, that is basically what I am thinking about - you could build a short (say about 3'?) fixed platform first, for the steps or ladder from the aft deck to land on.
    Or you could perhaps attach it directly to the transom (you might have to locally add some extra stiffening on the inside to cope with the loads).
    But if the latter, then the staircase or ladder would end in 'mid air' when it is lowered.
     

  12. sandog
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    sandog Junior Member

    Anyone else have any other ideas?
     
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