Material conversion question

Discussion in 'Materials' started by mcdc, Apr 5, 2013.

  1. mcdc
    Joined: May 2012
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    Location: North Carolina

    mcdc Junior Member

    I have a stringer that has a schedule as follows:
    1. 4 OZ CSM
    2. 18 OZ woven
    3. 4 OZ CSM
    4. 18 OZ woven
    made with VE resin.

    I am making the repairs with epoxy and 17 OZ double biaxial so the question is, how many layers should be used.
    I was thinking since the total that was removed was 108 total OZ's per yard, I could replace with 7 layers of 17 double biaxial????

    The thickness that was removed was really thick with resin at the bottoms so it is hard to replace the same thickness , around 7 to 10 mm.

    Thanks
     
  2. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    More info may be needed. Is this a total replacement or just a small repair to the stringer?

    The original laminate was rather weak for its weight and thickness, but possibly somewhat stiff, so it wouldn't take much of an epoxy laminate to equal the strength, getting the same stiffness may require more material though.
     
  3. rberrey
    Joined: Oct 2010
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    Location: AL gulf coast

    rberrey Senior Member

    On the scantlings of my build I have the option of replacing the 24oz woven with 17oz biax, and doing away with the csm as it is there to give better bonding and thickness. I will use a layer of 17oz 45/45 and 18oz 0/90 as I will be using foam. If the stringer is ply then 0/90 would not be needed.
     
  4. mcdc
    Joined: May 2012
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    Location: North Carolina

    mcdc Junior Member

    This is a complete engine stringer replacement on a 30 foot dual I/O with a mid stringer section also being replaced. The engine stringers are two 3/4 ply each with the before mentioned schedule ( 4 OZ CSM/18 woven/4OZ CSM/18 OZ woven). The MID stringer section is 4 OZ CSM. I have replaced all the wood and bedded. I have started with covering the mid section with 5 layers of DB 17 OZ. I have been advised to use some milled fiber in the resin to give me back the stiffness.
    So, will the 5 layers I have already covered the mid section be ok and then use milled fiber when wetting out the engine stringers and use 6 layers on them. Thanks for the replies
     
  5. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    I was hoping someone that does more epoxy construction than I do could chime in with a good laminate schedule. But I would think what you plan to do should work fine
     

  6. mcdc
    Joined: May 2012
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    Location: North Carolina

    mcdc Junior Member

    Thanks. I was able to contact PAR and he suggested using the milled fiber with the resin and reduce the number of layers to 5 versus 8.........just not sure I am skilled enough to pull that off......but 8 layers in that tight space seems tough also!!!
     
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