Inexpensive hull construction materials

Discussion in 'Boat Design' started by fpjeepy05, Dec 9, 2019.

  1. ondarvr
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    ondarvr Senior Member

    I actually did say this was an option very early in this discussion.

    The problem is that it increases the cost. It also doesn’t increase the strength to a point where it’s of much value. Short fibers are easier to work with, but lack the desired strength. Long fibers do a better job on strength, but make the putty hard to work with.

    You still end up with a very low glass content and a more difficult product to form and shape.
     
  2. ondarvr
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    ondarvr Senior Member

    This is from an earlier post of mine suggesting how you can increase the physical properties.
     
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  3. fpjeepy05
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    fpjeepy05 Senior Member

    How is foam lamination different? It resists compression and shear. That is what the core is there for.

    I excepted wood as the best solution. I've stated that multiple times. You are grasping for straws now.

    The stack of cards is something that people are familiar with and helps to understand what people mean when they say "shear strength." You would be surprised how many people use that term and don't understand it.

    The stack of cards is not a good visual representation of sandwich construction. But that was not how I was using it. Single laminates don't fail in internal shear like sandwich construction does, because the outmost skins are the same strength as the inner laminations, therefore the outer lamiates will fail first. In a sandwich construction, the internal area is made of weaker material. The cards are all the same strength in the plane of the cards (which would not be the case in a sandwich construction) But the weak glue is weaker than the top and bottom laminates like in sandwich construction, and the orientation of the cards is aligned with the orientation of the shear that the core experiences. So it fails much analogous to the way a weak core material will fail.
     
  4. fpjeepy05
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    fpjeepy05 Senior Member

    I'm in agreement with you. I just wanted to identify possibilities in this thread before evaluating them. You have already done the evaluation and jumped the gun a little.

    If plastic/poly putty cost less than $1/lb in material. (Let's say $0.60/lb) Then the next thread topic would be can raw plastic and polyester be processed into a usable product for hull construction for less than $0.40/lb. You would say no, and I have no evidence to the contrary.
     
  5. fallguy
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    fallguy Senior Member

    This is a thread that never ends. It just goes on and on my friends. Some people started it not knowing what it was, and it will continue on forever just because.

    <repeat infinitely>

    ~adapted from Lamb Chop's Sing Along/Play Along by Shari Lewis

    When you have no hard facts; it heads quickly to polemics.
     
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  6. Rumars
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    Rumars Senior Member

    You need to stop thinking in pounds and start thinking in volume units to be able to make economic sense.
    Handlaid FRP is 35% glass fibers and 65% resin by volume. If you want to cut resin use by 50% of that used in handlaid laminate you need to go to 67.5% fibre ratio (prepreg territory).

    If you replace the glassfibre with shreded milkbottles or microballoons, etc. you still need to keep the same volume ratio and the filler should not be more expensive (per volume unit) then the glassfiber. If you want to use this as a core you need to see if the 67.5% shreded milkbottles/32.5% poly resin mix has the required properties. Then you add the required thickness skins and calculate the total cost of the panel then compare it to the handlaid solid panel you are trying to replace.

    Now I will say that a putty that is 60-70% shreded plastic/40% poly resin by volume will not have the required properties as a core, and you can prove me wrong by making one and testing it. Then we can talk about what resin ratio you actually need to achieve to be cheaper than the solid panel, given that the cored panel is always thicker.
     
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  7. gonzo
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    gonzo Senior Member


    Let's return to replying the original premise.
    PVC pipe is a terrible material for stiffening a fiberglass panel. Firstly, it won't adhere to polyester for any structural application. It is possible to use very expensive adhesives, but that negates the low cost requirement.
    Wood is the answer, but the OP for some reason refuses to accept it.
    The other reduction is to use hollow sections. Cardboard was proposed as a form, which has been used successfully by large manufacturers like Chris Craft. Again, the OP has objections, which are not based on any facts.
    In short, this whole thread is about an OP that refuses any facts based on decades of boat construction. He wants to hear that PVC is the magic solution and claims that anyone contradicting him is too stupid to see the truth.
     
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  8. waikikin
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    waikikin Senior Member

    Hi Gonzo,
    I've had the odd stick up with polyester & pvc so it can stick- I occasionally mold gelcoated internal corner moldings off it and usually rely on a few heavyish shots of PVA to guarantee release- if it sticks or not could be irrelevant as acts as a non organic form. Pricing at the local bunnings hardware is $16 per 6 metres of 90mm straight off the shelf which yields 12 metres so maybe $1.30 per metre which sems cheap to me and ends up split as"roughly" trapezoidal though probably not ideal in depth, I've used it occasionally to add stiffness to cockpit hatches, under the aft deck of my Seawind cat hat was feeling a little too springy and to as below to interface ply rolling frames to some hull tooling mostly to minimise print of the elements. Generally I'll add a cap of 880 gram uni by a layer or two sandwiched between choppy, probably far from perfect but a useful material at least & think I was getting it at about 6 or 8 bucks a length for seconds straight from the manufacturer about 15 years ago so low cost. If I'm applying it a few dabs of hotmelt glue hold it prior to laminating, I feel it's most suited in the longitudinal orientation as would require very careful heat forming to take a curve of much tightness... though I remember a sparky building a boat using 20 mm conduits making very quick templates for transverse floors in his cat by heating to floppy and setting to shape in situ. The material has some worth in consideration.

    Regards from Jeff



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  9. Mr Efficiency
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    Mr Efficiency Senior Member

    Did anyone ever discover how they put those bubbles in the Aero chocolate ? If fpjeepy finds out, we may finish up with a new core material made from drink bottles !
     
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  10. fallguy
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    fallguy Senior Member

    A good time to close thebtr
    How would the bubblified core be stronger than its solid nemesis?

    All kidding aside, I am serious.
     
  11. Mr Efficiency
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    Mr Efficiency Senior Member

    I guess for the reason that if it has adequate physical properties, it could be a light enough core, but I think someone pointed out the material is already made into foam. It is all about cost, and you are paying a bomb for those bubbles in PVC core, so obviously it is no small task to put them there, the cost of the basic raw material is not that great, but you could say that about a lot of manufactured items.
     
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  12. fallguy
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    fallguy Senior Member

  13. waikikin
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    waikikin Senior Member

    It's the bubbles that make foam special ..... next time I have some spare resin I'll mi some bicarb or mix it with a mentos & coke:eek:... what could possibly go wrong... maybe some Q babies to thicken too..... I suspect could be quite brittle.

    The drink bottles are pretty durable & the PET ones seem particularly so. One of my boys did a plastic recycling project & produced a paddle blade with steel tooling, used milk jugs and IBC plastic- hdpe with a few bottle tops thrown in for a visual effect- really took some heat/energy to process & form..

    Jeff
     
  14. gonzo
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    gonzo Senior Member

    Yes there is an additive for that. For polymetrs it activates with heat. It is gets mixed at the hopper in the extrude. Mostly it is CO2
     
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  15. Mr Efficiency
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    Mr Efficiency Senior Member

    Carbon Dioxide ? That would make it similar to bread, that rises from the yeast making CO2
     
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