New Stringers

Discussion in 'Boat Design' started by helluvaboater, Feb 28, 2016.

  1. helluvaboater
    Joined: Jul 2015
    Posts: 50
    Likes: 0, Points: 6, Legacy Rep: 10
    Location: Maui

    helluvaboater Junior Member

    Installing new stringers in my 27 foot express cruiser fishing boat. Tons of pictures at...

    http://boat-building.wix.com/wrangler

    Boat was originally setup for twin stern drives. I built a new transom and I am converting to a single v-drive so the last 8 feet of the boat is gutted right now.

    I plan to install a 200HP Cummins 6BT engine but I might get a 370HP 6BTA one day so I am trying to build the boat strong enough for the 370HP option.

    The stringers I am installing are made 1.75" thick microlam LVL and are 8 inches tall. My question is in regards to the tabbing where the new stringers meet the existing stringers.

    [​IMG]


    The new engine stringers are in-line with the exsting stringers, which are made from 1/2 marine ply with some roving/mat over it. The existing plywood stringers run up to the deck. When I cut out the old plywood stringers, I only left 6 inches sticking out to "sister" the old stringer to the new stringers. In hindsight, I should have left more so I could sister them together for a length. Is it completely necessary to sister these stringers together?

    [​IMG]

    There are fuel tank glassed to the hull outside of the stringers that add some longitudinal rigidity to the hull. They pass past the bulkhead at least a few feet:

    [​IMG]

    I have begun strengthening the area where the new stringers meet the forward bulkhead. I so far did 4 layers of 1.5oz mat in all the inner corners to round them off. Then we laid 3 layers of staggered nytex 1708 strips in the following places on both of the stringers:

    [​IMG]

    I also did 2 more units of 18oz roving + 1.5 oz mat over the existing bulkhead which had maybe only 1 unit on it already.

    I also put in some smaller stringers outside of the engine stringers to add more lateral support. These are glassed in with 3 units 18oz roving / 1.5 oz mat:

    [​IMG]

    These run from the transom to the back of the fuel tanks that are glassed to the hull.

    My questions are:

    Is it OK to sister the new engine and existing stringers together with only a 6-inch "sister" joint like I am doing because the fuel tanks add the lateral support to the hull in this area?

    -What is the tabbing schedule for the engine stringers on the forward bulkhead and transom? Does mine look OK?

    -Tabbing schedule for non-engine stringers?
     
    Last edited: Mar 4, 2016
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