HELP! Hull is Sagging! I don't know what to do!

Discussion in 'Boatbuilding' started by CatBuilder, Mar 21, 2011.

  1. rberrey
    Joined: Oct 2010
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    Location: AL gulf coast

    rberrey Senior Member

    Hoytedow shows a spreader beam in picture #2. Picture running this spreader beam from bow to stern , with as many straps hangging down to the boat as you need.
     
  2. CatBuilder

    CatBuilder Previous Member

    Gotcha, Rick. Thanks. What you're describing is in Ct's drawing too.

    I know what you mean about time. I'm actually pretty upset doing all these temporary bulkheads and beams and stuff. Complete waste of time and budget.

    It almost makes the case for just standing your bulkheads up on a (floor) strongback and foaming that in. I was originally looking at doing it that way, but heard this way I'll have a more fair hull and glassing would be easier. Glassing was pretty easy..

    Digressing... anyway... I was also thinking of these beams:

    [​IMG]

    You're right though. Whatever is fast and works...
     
  3. rberrey
    Joined: Oct 2010
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    rberrey Senior Member

    I think Hoyte and I both think you should move your pick points (where your straps are that hook to your hoist) more toward the center. With the strongbacks I think you will be fine. Find the center bow to stern, move 25% to the bow and 25% to the stern and this is where you need to start for pick points. Pick up slowly and adjust toward or away from center as needed, you only need to pick it up an inch or two to see if its balanced. rick
     
  4. rberrey
    Joined: Oct 2010
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    Location: AL gulf coast

    rberrey Senior Member

    A male form is within my skill level, I will use a different form method other than battens to get a fair hull. rick
     
  5. CatBuilder

    CatBuilder Previous Member

    I can only do that if I use a "longitudinal spreader bar" to lift with many straps. There is nothing in the center to grab onto, which is why I'm having this problem to begin with. I'm as close to the center as I can get. Any closer, and there is only a bilge there, no topsides and no deck.

    Here is a picture of the part I have in the mold. The green highlighted half of the port hull on this old catamaran is what I have coming out of the mold. See where the bridgedeck attaches? See how there is no topsides there, and as you can also imagine no deck? Just the area down by the waterline, which is then connected to the bridgedeck? That space is all wide open with nothing except a bilge and a little bit above the waterline. That's why I can't move the pick points into that area without a longitudinal spreader bar.

    So do I go with the longitudinal spreader bar or the L beam? I'm getting a bit more confused now that all the options are on the table. Or... do I need both?
     

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  6. CatBuilder

    CatBuilder Previous Member

    Me, too. :)

    I can see now, after having all this experience, that the easiest (best) way to build a boat would be to position your actual bukheads on a strongback, then do regular strip planking (not bead and cove). After, you could just use your grinder, then a longboard to get out imperfections in the foam, then glass, finish, and roll over.

    That's how I was going to do this in the first place.

    WTF am I doing all this stuff for?... I'm in it now, though.
     
  7. CatBuilder

    CatBuilder Previous Member

    Thinking a bit more, the strongback "L beam", etc... will be necessary no matter what, because when I flip the thing over to go turtle, I'll still need that support...
     
  8. cthippo
    Joined: Sep 2010
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    Location: Bellingham WA

    cthippo Senior Member

    How far apart are your cranes now? At an absolute minimum the beam should be that length, the more the merrier. Your first lift has shown that the boat can handle having the ends unsupported for the distance from your straps to the ends.

    Just think how much faster the next one will go! :p
     
  9. Brian2009
    Joined: Jan 2011
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    Location: Sun Valley, Idaho

    Brian2009 Junior Member

    Not sure if this helps, (it may be an unnecessary distraction so read it with a grain of salt):

    Regarding the strong back you need to construct for lifting the hull -

    at some point won't you need to build a boxed mast beam (runs transversely from one hull to the other) for the king post to sit on? Could you construct this beam now, and use it for the strong back? Obviously you wouldn't want to damage it. . . just thinking what you could build now that you might be able to use later?
     
  10. hoytedow
    Joined: Sep 2009
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    hoytedow Wood Butcher

    The suspended bar longitudinally would not be a spreader, because it would serve a different purpose; support. Spreader means just that, by spreading the sling so it can't compress the hull beam-wise. Spreaders placed between the L and R side of the straps just above the strongback would work well and need only be 1.5 x 1.5 inches(nominal 2x2) x width at strap meets top of bulkhead. Compressive strength of 2x2 is more than adequate.
     
  11. michael pierzga
    Joined: Dec 2008
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    michael pierzga Senior Member

    Well Cat ? Hows the coffee ? and did you get your lift sorted ?
     
  12. Herman
    Joined: Oct 2004
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    Herman Senior Member

    If your hull is 136 kgs, 8 beers get your boat lifted easily. Building a boat singlehanded is OK, but for some jobs a helping hand is easy.

    We once WALKED a 35ft boat hull (upsidedown) through the city (some 2 miles) with a bunch of people. OK, we caused a traffic jam, but nothing serious for the rest.
     
  13. CatBuilder

    CatBuilder Previous Member

    I think I have said this many times, but you can't lift this hull out with people.

    It was constructed inside a mold in the shape of a "basket" that is a little higher than a human shoulder. What would you grab? How would you lift it up the .5 meters to clear the top of the mold, which is just above your shoulder? It has to be .5 meters above this to clear.

    Anyway, it is going... slowly. I am working on the strongback. It takes hours for me to get lumber, because I am in a remote location, so I am just back from getting 2x6's and 2x4's for the strongback.

    I did not find any lifting equipment to make 4 slings. I have only two.

    Also, if I use 4 slings, I think 2 of the slings will crush my hull. I have the existing slings on bulkheads. If I use more slings, they will not be on bulkheads and will crush the hull when I lift.

    So... I think I have to use 2 lift point, not 4.

    I may also be cutting the sides off my mold to make for less of a lift, if the cranes don't work.

    Not really enjoying "boatbuilding" here. This sucks.:confused::(
     
  14. cthippo
    Joined: Sep 2010
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    cthippo Senior Member

    Take some of those straps you are using around the bulkheads and use them for lifting straps. In fact, I think you could route all of them around your lifting bar and they would work exactly the same way they are now.
     

  15. hoytedow
    Joined: Sep 2009
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    Location: North of Cuba

    hoytedow Wood Butcher

    They can't crush your bulkheads if you use spreaders. You by now have plenty of wood in the form of 2 x 4s.
     

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