Layup schedule help

Discussion in 'Fiberglass and Composite Boat Building' started by Scuff, Sep 5, 2017.

  1. jorgepease
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    jorgepease Senior Member

    Stiffness is not the problem, all is good till you hit something then what. A single layer of glass doesn't provide much impact protection for a boat with that much mass.
     
  2. fallguy
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    fallguy Senior Member

    If you want to improve impact results; I'd build in corecell M vs pvc. As for hitting things; gotta ask where. Didn't op say double at bow n keel somewhere further down? Why double the whole boat for impact? Just asking; sorry if there is a tone to it; not the intent.
     
  3. Scuff
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    Scuff Junior Member

    Hi I chose epoxy since I'm familiar with it. The designer said I should not deviate from the layup specified regardless of which resin. The layup information is from 1992 so may be good to update or review it with a composites expert? It also specified airex r63 which doesn't appear to be available in the US anymore. Designer did say divynicel worked well and corecell m looked good so I will choose one of those. I've built one stitch and glue dinghy and am about a third of the way through a seaclipper 16 so my experience is with wood as the core and the glass is just for abrasion/waterproofing. Would you recommend using an alternative to the 1.5 oz mat if using epoxy? Thank you all for the insight and information.
     
  4. Scuff
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    Scuff Junior Member

    The layup at the keel is two additional layers of the DB one 16" and the other 8" the bows to receive an additional layer of 7 1\2 oz fiberglass.
     
  5. jorgepease
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    jorgepease Senior Member

    Go for it ))
     
  6. fallguy
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    fallguy Senior Member

    No mat with epoxy. No substitution needed if the designer says so, but some might prefer an epoxy fill coat to reduce print through.

    I am sorry, but I misread to my bias. If the designer says no deviation, but you want to use epoxy; it would seem to be an unresolvable conflict.

    Can't you ask/tell designer to redo the schedule for epoxy?
     
    Last edited: Dec 6, 2017
  7. gonzo
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    gonzo Senior Member

    Mat is structural, so it can't simply be deleted from the laminate. With epoxy, you could use roving or stitched biaxial. Remember that the mat is by square foot and the fabrics by square yard.
     
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  8. TANSL
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    TANSL Senior Member

    All the material of a laminate (except the gel-coat, the painting and, perhaps, some other), even the resin, are structural. If not, why put it ?. What happens is that the mat has much less resistance than the fabrics and putting it (with its low resistance) in the outermost or innermost layers of a laminate, which is where maximum stresses occur, makes little sense. Unless, as previously stated, the mat is placed on the outside "to reduce print through". Therefore, if this objective is not pursued, the mat, even being structural, could probably be eliminated. In any case, it would be necessary to make some calculations, and check the composition of the laminate, before affirming one thing or another.
     
    Last edited: Dec 7, 2017
  9. Scuff
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    Scuff Junior Member

    My very basic understanding of composites is probably making this painful for you guys. It was my understanding that the csm used next to the core was to improve the bond between core and fabric when using polyester. Epoxy adheres much better so no csm is technically needed.

    I tried to Google replacement of csm for epoxy and got a thread from 2012 .. in there it sounds like the binder doesn't dissolve like it would with polyester but is still OK for epoxy?

    CSM and epoxy, the two can not be done together? https://www.boatdesign.net/threads/csm-and-epoxy-the-two-can-not-be-done-together.45456/

    And an epoxyworks article with similar findings

    Chopped Strand Mat and Epoxy http://epoxyworks.com/index.php/chopped-strand-mat-and-epoxy/

    If it is OK would I be adding additional weight using csm and epoxy with no actual benefit?

    Thanks again!!
     
  10. TANSL
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    TANSL Senior Member

    That's correct. The same goes for fabrics. It is not advisable to place more than 2 or 3 consecutive layers of fabrics. It is preferable to separate them with a mat that helps the resin to impregnate all the layers well.
     
    Last edited: Dec 6, 2017
  11. Scuff
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    Scuff Junior Member

    I see. So at the keel where multiple layers are required I may need the mat. I'm going to make samples using the layup as specified and then another without the mat and maybe a light cloth to reduce print through and then compare them. I did a rough calculation of weight added using the 1.5 oz mat and for the main hull that comes to ~160 lbs just for resin so a significant reduction in weight if the mat can be removed
     
  12. TANSL
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    TANSL Senior Member

    I can help you in the calculations if you give me the data of the panels you want to analyze as well as the general data of the ship. I usually use ISO 12215-5 standards for scantling small boats.
     
  13. gonzo
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    gonzo Senior Member

    The mat is used to increase adhesion between layers of roving. Also, it is used as a bulk material to increase stiffness. I am not sure what you call "resistance" since it is not an engineering term; perhaps you can define it more clearly.
     
  14. TANSL
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    TANSL Senior Member

    Thank you, Gonzo, I am glad that you are so aware of me, helping me to express myself correctly. You are my spelling corrector. Your language dominance and my technical knowledge would make us an invincible couple;).
    Of course, "resistance" is a translation error, I should have written "strength". For the rest, I see that you agree with me on what is one of the reasons for using the mat (only one of the severfal reasons), because in many occasions it is more efficient to use the mat than fabrics. Congratulations, that will help not to confuse the OP. If you wanted do some calculation (engineering as you like to say) for him, it would also be of great help.
     
    Last edited: Dec 7, 2017

  15. Scuff
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    Scuff Junior Member

    That would be great. What specific information would you need? I do have the theoretical strength and stiffness calculations for the two layup schedules that was provided by the designer so I think we would just need the calculations for a layup not using mat?

    Gonzo if the mat does provide stiffness to the structure would there be another material that would use less resin and cut down on the resin and weight? I think my estimate of 160 lbs for the main hull may have been low I figured just the mat but the fabric specified also has a mat backing as well.
     
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