Split mold for hull

Discussion in 'Fiberglass and Composite Boat Building' started by Sam III, Apr 22, 2008.

  1. ratrace2
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    ratrace2 Senior Member

    Well, Sam, I got'ta tell ya, you do very neat, clean, precise work. Very nice.

    Now, a couple of things: 1st, this doesn't take advantage of the "work done".
    What does this mean? It means that if you had followed the design of a very long single piece (spelling don't count) it would have also helped stabalize the mold i.e. the resion and labor consumed would have counted toward the final result.
    2nd: too small, in my humble opinion. If you look at the (green model) you will see that it has a large hole in one end. This is so you can put a pipe in it and align the two halves much like a steel worker aligns to steel beams with a "drift"....ya need the leverage when this thing gets heavy...and it will.

    So, My solution is to double up on what you already have...just add another block on top of what you got and "putty" around it to make it smooth......
    Because: what we want is a mold the opens and closes much the same way that you open and close a large rectangle tupperware container.......ya get on edge started and that helps align and close the rest of the lid....

    Good effort, budd, Nice work...............Rat Out:) :)

    Oh yea, now build a really big table, cut a hole out for the mold, then cut the table in half where the mold seperates...then put wheels on it........your done..
     
  2. Sam III
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    Sam III Junior Member

    Well this is after the gel coat was sprayed.

    Will put first of CSM tomorrow.

    Sam
     

    Attached Files:

  3. ratrace2
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    ratrace2 Senior Member

    Slow down there cowboy. Where are the alignment/keys on the other flanges?:(
     
  4. Sam III
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    Sam III Junior Member

    Ratrace2,

    There are 2 alignment keys on the bow parting board, 4 more accross the centerline parting board and one on the stern.

    The other boards are just flanges for attaching vacuum bagging dum dum.... :)

    Thanks for looking.

    Sam
     
  5. ratrace2
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    ratrace2 Senior Member

    Sorry, I didn't see them.......good job.... Nice clean work....Appplaude, applaude......can you see me clapping.............
     
  6. Sam III
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    Sam III Junior Member

    Started on the other side of the mold this week. Parting board's came off very easily.

    First picture is of almost finished starboard mold and 2nd is the mold in the post cure oven.....

    Question now is after other half is done, how large should the bolts be to hold the flanges together and how far apart should they be?

    Sam
     

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  7. ratrace2
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    ratrace2 Senior Member

    SamIII,
    Start with a bolt every 2' ft, if the mold draws together real tight fine; if not, put a bolt every 1' ft if the mold draws toghether real tight, or as tight as you want it i.e. no gap at the seam, fine. Rinse repeat. 1/4-20 with big 2" fender washers and 2"x4" blocks of plywood is recommended: anything cheap and easy to keep the integrity of the geometry
     
  8. ratrace2
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    ratrace2 Senior Member

    SamIII.
    You glassed both sides of the plug before you removed any parts of the mold from the plug, right?
     
  9. Sam III
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    Sam III Junior Member

    Yeah, still in the process of doing the port side of the mold. Just finished the first 5 layers of csm last night.

    Will do balsa core tomorrow and Monday then more csm and woven roving on the hull and flanges.

    I figured I would trim the flanges and then clamp and drill before I take anything off.

    Pictures left to right;

    Picture of port side before gel coat, after gel coat and after .75 oz and 4 layers of 1.5 oz csm.

    More pictures to come.

    Sam
     

    Attached Files:

  10. ratrace2
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    ratrace2 Senior Member

    OK, finish the other side then read "the elements of boat strength"; Gerr, p.26
     
  11. eathena
    Joined: May 2008
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    eathena New Member

    You HAVE TO make sure you have positive draft angles on that locator pin or you will never get the thing out. Either add it with body filler or sand them at an angle to get the draft.

    We made some locators from wood and then made a mold of them so that we could make multiple locators from one original wood plug.
    [​IMG]
    [​IMG]

    For a hull mold I would suggest bigger locator pins just to ease the alignment process when you are putting the two halves together.

    Also, everybody here is talking about using some vinyl and other materials to place a flange on a plug. I just make a flat sheet of fiberglass, cut the profile I need, and hot glue it to the plug (there is masking tape between the hot glue and plug in order to allow removal). Its simple, available sine we are working with fiberglass anyway, and universal since you can make any size sheet you want.
     
  12. ratrace2
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    ratrace2 Senior Member

    I already told him to make bigger locator pins; he didn't want to.
     
  13. Sam III
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    Sam III Junior Member

    The locator pins I used were 1/2" tall and appx 3 inch's square. I rounded them over on the sides and corners. The parting boards with positive locator squares released very well.

    Sam
     
  14. ratrace2
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    ratrace2 Senior Member

    SamIII,
    Great job bud, really looks good. Sure, you got the postive draft on the pins, but, because they are so shallow (1/2)--I wanted you to make them 7-8"--they won't help you muscle this big Motha into alignment.
     

  15. Sam III
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    Sam III Junior Member

    Finished the last of the laminates for the 2nd half today. Yeah.

    Now to build and attach the support frame work.....

    Sam
     
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