Infusion VS Hand laid

Discussion in 'Fiberglass and Composite Boat Building' started by Jeffrey, May 19, 2014.

  1. Jeffrey
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    Jeffrey Junior Member

    I have successfully built a high performance boat using 1208/h 80/1208 with some additional reinforcement in critical areas.

    If I want to infuse the same boat does it need higher glass content because of the vacuum compressing the laminate?

    How many oz of glass can be infused at one time before it gets to hot (like the transom)

    Thanks
     
  2. ondarvr
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    ondarvr Senior Member

    An infused laminate "will" have a higher glass content, that's one of the main goals.

    You can infuse as many layers of glass to just about thickness you desire. 2" to 4" thick laminates can be done at one time with off the shelf products.

    The issue you need to work around is the infused laminate will be thinner than a hand laid one and the result can be a more flexible part.
     
  3. Jeffrey
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    Jeffrey Junior Member

    I understand the higher glass content ratio. Infusion is touted and saving up to 40% on weight. But if you just add back the weight with more glass where is the savings?

    Let me ask this another way. If I use my same lamination schedule via infusion you mentioned I'd lose stiffness. How much glass needs to be added to maintain the same stiffness. Is there some formula for this?
     
  4. ondarvr
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    ondarvr Senior Member

    You need to design in a core or shape the part so the flex isn't noticed. The other option is to overbuild with more glass, it will make the part similar in weight to hand a laid one, but significantly stronger. There are some products that can be used to stiffen an infused laminate, but they tend to act like a sponge and soak up resin to do their job.
     
  5. jorgepease
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    jorgepease Senior Member

    or use a little thicker core ??
     
  6. SamSam
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    SamSam Senior Member

    One big advantage with infusion is the containment of fumes and the limiting of human contact with the resins. I think that's becoming a big issue with the authorities like EPA, health insurance, etc.

    The economical and environmental advantages of using less resin are also a consideration.

    I've always wondered about the difference in the mechanical properties between an infused material and one that has been worked with a paint roller and a bubble buster or squeegee. In the photo, there are spaces between the warp and weft of the woven roving. When we hand worked that, the individual rovings would flatten out sideways so when done there were no spaces. If that was infused, I imagine there would be numerous pinholes in the laminate and numerous spaces of pure resin, which has little strength.

    Almost all fiberglass materials have spaces and voids and it seems it needs 'working' of some sort to allow the microscopic filaments to move around, fill in spaces and also to allow each filament to be encapsulated in resin.

    Two other questions...I also wonder if there is much infusion done with polyester resin and if when infusing or hand laminating, does a person have to use fiberglass materials that are specific for one or the other process?


    [​IMG]
     
  7. jorgepease
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    jorgepease Senior Member

    You wouldn't use woven, it would be stitched fabrics and low vis resins would be a must for sure.
     
  8. ondarvr
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    ondarvr Senior Member

    It's the opposite. In hand lamination the there is little consolidation of the glass, so while it does conform to a shape and can be worked around, it will spring back and the voids (areas with no glass) return leaving a very weak and resin rich laminate. When infusing those voids are almost totally removed, that's why you end up using so much less resin.


    90% of infusion is done with polyester resins, and while you can infuse with most types of glass, woven and CSM products will inhibit the flow and cause problems. So uni's and stitched products are more common.
     
  9. ondarvr
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    ondarvr Senior Member

    The physical properties for the same weight laminate are significantly better with infusion. The issue can sometimes be overcoming the difference in stiffness in laminates of the same strength. Extra thought, materials and design may need to be used to make an infused part suitable for the same purpose as a hand laid one if stiffness is an important factor.
     
  10. Jeffrey
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    Jeffrey Junior Member

    Thanks for the responses on this. I was hoping for and easier more direct answer I guess. Something like .... when you infuse a part you add "x%" of glass to maintain the same structural characteristics due to the compression of the laminate. Maybe its not that simple
     
  11. Stumble
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    Stumble Senior Member

    Jeffrey,

    Why would you add more glass, increase the core thickness and you retain the same strength, same stiffness, and save weight.
     
  12. ondarvr
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    ondarvr Senior Member


    Every aspect of it would change depending on the shape and contours of the part being made. An infused round ball would need little done to simulate the same stiffness of a hand laid ball, but a flat panel would typically need a core or significantly more glass, of which there are many choices, to even come close. Then you need to figure in the resin used and actual amount of vacuum used in production.
     
  13. FishStretcher
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    FishStretcher Junior Member

    I suspect a few people missed out on the H80 core bit.

    Generally speaking, if the core is of significant thickness, and the skins on the core aren't, then the overall stiffness will be similar. Infusion will make for thinner skins, given with the same amount of glass. There will be less resin. So the thickness goes down a little. But the reinforcement is tied together better. So it is likely to be a wash as far as you are concerned. Your parts will be lighter. In the areas where there is NO foam core, you will need more glass to get the section (thickness) back to where it was for hand lay up, as the distance from the outer fibers is what gives it the stiffness. Assuming the fiber materials and orientations are the same.

    So you could make it with a bit more glass in the non cored sides. And a bit more glass on the cored skins. And it would weigh about the same but be stronger and stiffer. Or you could skip the more glass on the core skins, keep the thickness in the non cored areas and save a bit of weight and have *about* equal strength and stiffness.



    Roughly speaking.

    If it were me, I would add some glass back to increase penetration resistance of the sandwich core. But I am rough on boats.
     
    Last edited: May 29, 2014

  14. Jeffrey
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    Jeffrey Junior Member

    Thanks Fish Stretcher!
     
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