Tabbing advice

Discussion in 'Fiberglass and Composite Boat Building' started by Skua, Nov 27, 2017.

  1. Skua
    Joined: Apr 2013
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    Location: Hunt's Pier WW NJ

    Skua Senior Member

    A couple years back I gutted out a 28 ft cabin cruiser, down to the stringers. Originally the the only bulkhead /transverse frame, was the cabin entrance. On early models the was another bulkhead /frame forward at the vberth entrance. I am remodeling the boat to the early design. My question is this, the forward frame will support the forward weather deck as well as form the inner walls now, what would a sufficient tabbing schedule be? Currently thinking 2 layers of 1700 biax and epoxy, at 8 and 6 inches wide. Original construction was mat tabbing and poly. There were no structural failures, a lot of spider cracks from flexing, just rot from poorly sealed fittings and such.
    Boat was powered by an anemic 350 Chevy and moved at 32 kts flat out. The new power will be 454/502 Chevy. Cruising speed is hoped to be 25-28, and WOT at 38-40. This will be used mostly for weekends out.
     
  2. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    A little vague, but I like your plan. All based on not much more than my current build.

    I wish there were real solid rules on tabbing, but have not seen them. If they exist; maybe my statement will pull them out. PAR or Rx will know best.

    My boat primary structural bulkhead tabs are 6-6 and the vessel is similar in size. Minor bulkheads are 4-4.

    Sounds like anything you do will exceed the prior configuration.
     
  3. Skua
    Joined: Apr 2013
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    Location: Hunt's Pier WW NJ

    Skua Senior Member

    A pic of the forward bulkhead/galley counter assembly IMG_20171119_221937.jpg
     
  4. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Whats the plywood thickness? This usually determines how much tabbing is necessary, though you schedule sounds okay for 1/2". It's hard to screw up if you go heavier, on a boat like that.
     
  5. TANSL
    Joined: Sep 2011
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    Location: Spain

    TANSL Senior Member

  6. Skua
    Joined: Apr 2013
    Posts: 142
    Likes: 5, Points: 18, Legacy Rep: 73
    Location: Hunt's Pier WW NJ

    Skua Senior Member

    I'm using 3/4 Arouco, which is a pine based exterior. It's actually quite a bit better than a lot of the MDO and "marine" I have seen in my area. I am leaving 1/4 to 3/8 gaps between the hull and, frames/bulkheads.

    Original tabbing was CSM, about 1/8-3/16 thick but only a single layer, and 2-3 inches of bond surface.

    In TANSL's diagram, if, BHD= bulkhead diameter , bw1, bw2 =bonding width, what is tbh??

    And thank you all for the assistance!
     
  7. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

  8. Skua
    Joined: Apr 2013
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    Location: Hunt's Pier WW NJ

    Skua Senior Member

    TBHD = total bulkhead diameter then? If so I understand the formula thank you again.
     

  9. TANSL
    Joined: Sep 2011
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    Location: Spain

    TANSL Senior Member

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