Transverse beam layup

Discussion in 'Fiberglass and Composite Boat Building' started by Jason Rodgers, Jul 28, 2022.

  1. Jason Rodgers
    Joined: Mar 2021
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    Jason Rodgers Junior Member

    I am building a transverse beam out of fibreglass with not a lot of laminating experience.
    I will be laying up the beam on a waxed piece of lumber shaped to create the beam dimensions, later glueing and tabbbing the beam in place after it has cured.

    Advice is to build the beam using 6 layers of 820 quadraxial.
    I will be using West's 105 and 206 slow harder. Daytime temps are reaching 68F (20C).

    - Is 820 quad difficult to wet-out and laminate - what ratio of resin to glass is needed?
    - Would it be easier to make the beam using more layers of 600 bi-axial?
    - To maintain chemical bonds, can this be laminated in one go? What methods will help do this?

    Thanks. Transverse beam dimensions.jpeg transverse layup.jpeg



     
  2. kapnD
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    kapnD Senior Member

    The beam will only be as strong as it’s tabbing, which is shown as a single layer.
    Nice drawings, but relevant to what?
     
  3. Jason Rodgers
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    Jason Rodgers Junior Member

    Any pro laminators on here who could chip-in on how they would go about laying this beam up?
    From a few practise runs, I found that the initial layers would tend to move when using a squeegee to remove the trapped air and excess epoxy from the final layers, even when waiting for tack off between layers.
     
  4. fallguy
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    fallguy Senior Member

    After building one cat, I consider myself semi-pro. The fabric will move a bit, so you'd need to oversize the part and cut it to final dimensions. No way will most any glass wetout easy enough to lay on top of itself on edges. So, oversize about an inch in all directions. Then cut after cured.

    The shape is a bit odd, as a general comment. I'd be concerned about the thing buckling in the middle under heavy loading is all. There is not as much resistance to buckling in this shape as a U shape, for example. But I don't know the application here.

    I have not used quadraxial glass, but have experience with biax and triax. The issue with quadraxial will be the difficulty in wetting through in hand laminating. The issue with biax is the strength for what you are building and tow direction is not good. You could cheat and lay biax unevenly at the cost of fabric and develop some strength. Also, you could lay it up with biax and uni and skip the 90 tows which offer little and it'd wetout easier. Stiffness os largely thickness, so you have to determine thickness needed if you change it to 6 biax and 6 uni if that is enough, etc.

    You can certainly hand laminate in a single go and of course infuse in a single go. Only way I'd do it for either method. It would be very difficult to wet bag this part. Maybe with a tropical two hour epoxy...but even then; I'd not want to.

    Another thing for the quadraxial is the direction you lay it. I think 3 of the pieces need to go zeros down and the other three zeros up, most likely.

    For cutting it out after cure, I like to use a carbide 4" circle saw. You can get a cheap chinese one for about $50 here and I have one that lasted for several years and a blade change.

    There are a few guys here who are much better at specifying a layup than my builder guesses...fyi. Whether they comment is another story.

    For handwork; it doesn't matter if the lower layers start to kick; in fact probably better to reduce heating. So, there is really no time restriction. You'd just want to pour half the resin on the bottom of each part as this stuff will not wet down through.
     
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  5. fallguy
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    fallguy Senior Member

    Another thing to keep in mind. Resins perform better at temps a bit higher than 68F. The concern is that you set the resins on a garage floor and the jugs get down to say 55-60F at night. This will make the resins flow poorly. Of course heating epoxy is generally not good either. But the best flow tradeoff through quadrax, triax, biax is going to be with 75 degree resins. So, avoid the stuff turning into honey overnite as well and keep in a warmer environment or off the floor at least. Cold resin is a pure nightmare for multi-layer fabrics and drives up resin content way above 1:1
     
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  6. Jason Rodgers
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    Jason Rodgers Junior Member

    Thanks for the very helpful advice and info.

    The beam is part of structural reinforcements needed after taking out a large rhode channel void, which had extended (load bearing) vertical walls. A vac panel was then installed under the deck and the deck laminated with 3 layers of 600g biax over the top of a G10 windlass plinth for a new windlass (RC10).

    The beam specs and other construction details have been provided by a N.A. - measurements are in millimeters. The beam design is perhaps a product of the limited space to fit the beam (pic attached).

    Appreciate the input on the direction of fiber layup. I have not found a primary source of how to layup to match the type of load.


    Deck dimensions.jpeg W-RC10 600g biax.jpeg RC10 install - barrier coated.jpeg
     
  7. fallguy
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    fallguy Senior Member

    The fiber layup I recommended may be incorrect. I was assuming the glass was standing alone, thus the former, and my comments on buckling.

    If you are attaching the glass to something, all 0's would be out, unless it is free between the hulls.

    I am a tad confused and need to see some drawings of the beam and the hulls to be more precise. The NA ought to have provided tow directions.
     
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  8. Jason Rodgers
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    Jason Rodgers Junior Member

    The N.A. advised to attach the beam to the hull walls (as well as to the underside of the deck). Other than those connection points, the beams base will be hanging. I can grab some pics from under the deck if this will help clarify.
     

  9. fallguy
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    fallguy Senior Member

    The concept is simple. The long fibers away from neutral axis. So, for a foam core, long fibers out on each side.

    If the part stands along out in space between the hulls, then 3 in 3 out for me.

    If the part attaches to something else on the bdeck, all long out I'd say.
     
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