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TNT platform issues

Discussion in 'Technical Discussion' started by Pascal, Apr 1, 2022.

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  1. Pascal

    Pascal Senior Member

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    We ve been having a lot of issues with out TNT swim platform, 2004 vintage, on the 110 lazzara. This thing has been a nightmare

    i ve been in touch with TNT but I can’t say they ve been helpful. Apparently they don’t have a technician who could come take a look at it. Anybody knows someone familiar with these in SoFl?

    1)- the platform isn’t high enough so at hull speed we get a massive amount of water washing over and shooting thru the holes. TNT suggested adding a second stage to gain another foot or more but a second stage also raised the platform by 3” from the frames. Even though our chocks are as low profile as they can be, the dinghy will not float if the platform is 3” higher in the down position

    2)- we keep loosing bolts… I think that’s coming from the major vibration and shaking going on under way. What can be used to stop this from happening? 4200 in the threads? Get bolts with holes for safety wire? Right now I had to use a socket extension held with clamps to replace one of the big bolts. Tonight I noticed the platform is a little low on the port side and can see something else is loose. Will Investigate in the morning before raising anchor in cat cay to cross to maimi

    3)- unlike Nautical Structure, TNT doesn’t use locks and relies on hydraulic pressure to keep the platform up. Simple, cheaper but… if a hose fails, platform goes down. Happened to us on the way to Exumas luckily on the bank in good conditions so we were able to launch the dinghy so we could tow it. I use the deck winch to raise it as high as I could. Another lucky break is that I found a used 12’ hose on board so I was able to restore hydraulics… obviously I m replacing all the hoses next week after we get back.

    Any contact for a specialists, any tip or suggestion appreciated.

    this thing is driving me nuts and the slow ineffective response from TNT is frustrating.
  2. Pascal

    Pascal Senior Member

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    Picture. You can see the socket extension held with clamps…

    Attached Files:

  3. Slimshady

    Slimshady Senior Member

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    Those lifts are always trouble, old mate used to work on them and had stories a mile long.
    The way I see it is this. Large platform that tender rests on is close to water and gets dunked regularly when underway especially when rough. Can't elevate higher or tender won't launch.
    Having a large deck so close to water surface is a safety hazard in my eyes. It can easily be torn off in rough water. That happens because of its large surface area for water to push against. If deck was redesigned to minimize surface area by making it largely pervious that could help but not reduce cyclical loading. Even with that done the tender will still try to disembark in rough seas. That's not fixable unless tender is relocated or towed. Tremendous forces involved with that platform being forced thru water repeatedly. Photos of platform might help.
  4. Pascal

    Pascal Senior Member

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    The 84 I ran before had a nautical structure which was very reliable. It also had mechanical locks actuated with their own pistons. It was actually lower to the water than this one

    for some reason there is a lot more water being pushed up behind the hull on this boat, either because of the length or the transom shape and it hits the rear of the platform instead of coming up behind the boat. Once we hit 14/14.5 kts the problem goes away.
  5. Capt Ralph

    Capt Ralph Senior Member

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    Could this be a hint?
    :rolleyes::rolleyes::rolleyes:
  6. Slimshady

    Slimshady Senior Member

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    Every hull is different and how the water flows back to fill the hole. Dealing with a broken lift or partially launched tender underway is never good. Can the platform be modified to significantly increase the number of holes to allow free flow of water thru it? Cut out hatch size sections, reglass and add grate in its place like ones used in road trench drains. Obviously custom made from marine grade materials. Just brainstorming.
  7. Pascal

    Pascal Senior Member

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    Well Hull speed is about 11.5kts and that s our preferred cruising speed unless we have a reason to go 20

    for some reason, TNT built the platform with a removable oval cut out on stbd side close to transom. And just 3 sets of smaller holes and the aft end. I thought about making them removable as well but it feels like a band aid
  8. mapism

    mapism Senior Member

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    You previously said that the problem goes away as you hit 14/14.5 kts, so I suppose that anywhere from 11.5 to 14.5 is just a transition speed on your way to full planing speed - and as such, only momentary.
    Now, pretty sure there is also a lower speed under which the problem goes away, and I'm wondering what such speed is.
    I mean, at hull speed, a tiny variation can change the boat wake significantly.
    So, I wouldn't be surprised if just half a knot or one knot less than 11.5 could prove a good enough workaround...
    And cruising at say 10.5 kts can only mean an even quieter ride and an even lower fuel burn, with an acceptable increase in passage length.
    Well, it would be acceptable for me, anyway! :)
    Of course, if the problem would already materialize at 7 or 8 knots, it would be hard to tolerate, on a 110 footer.
    But I'd be surprised if it would take such a big slowdown...

    PS: that aside, I don't see any trim tabs in your photo.
    If you don't have any, it's likely that some large tabs plates along the transom borders could fix the problem.
    Last edited: Apr 2, 2022
  9. Pascal

    Pascal Senior Member

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    I am familiar with what hull speed is :) On this boat it is 12.5kts (typo in my previous reply). The problem starts at about 9.5kts so unfortunately it is not a transition issue. It s worst at our most used cruising speed.

    this 110, like pretty much every Lazzara, doesn’t have trim tabs and doesn’t need them. The boat gets on plane easily with minimum bow rise. Adding stuff to the hull is a non starter. We need to address the platform issue

    so I m looking for recommendation for someone who works on these in SoFl and also I d love to see pictures of TNT second stage lift system which I know has been installed on many boats.
  10. Capt Ralph

    Capt Ralph Senior Member

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    Formula Yacht had a nice cylinder inside a square tube inside another square tube, out of the water lift system hidden in the aft hull sides that I keep dreaming about.


    In the back of my mind, I keep thinking of this set up behind Bertie.

    No hinges or articulating arms.
    Last edited: Apr 2, 2022
  11. mapism

    mapism Senior Member

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    That's not what I meant when I mentioned "large tabs plates".
    I've seen several boats with overhanging swim platform where fixed tab plates (in neutral position, i.e. aligned with the hull bottom) were enough to radically reduce the platform wash at low speed.
    Of course, with a lifting platform, it could be tricky to fit such things without interfering with the platform movement.
    But if feasible, it could be the easier and more effective workaround.
  12. Slimshady

    Slimshady Senior Member

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    Sorry pascal I don't know anything about the company my old mate worked for so I can't recommend them.
  13. Capt J

    Capt J Senior Member

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    Replace the swim platform. TNT's were junk when they were new, and having a 16 year old one, well........
  14. Rob Greenwood

    Rob Greenwood Member

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    What is the best swim platform available today?
  15. ranger58sb

    ranger58sb Senior member

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    Can't speak to "best" but GHS (General Hydraulic Solutions) is another maker.

    -Chris
  16. mapism

    mapism Senior Member

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    In Europe, most builders would agree that they are those produced by these folks.
  17. Pascal

    Pascal Senior Member

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    Can’t beat German engineering!
  18. Pascal

    Pascal Senior Member

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    I contacted them them but they don’t have a lift that woudl fit the boat
  19. Capt Ralph

    Capt Ralph Senior Member

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    Custom work?
  20. Pascal

    Pascal Senior Member

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    Apparently they re not interested.