Inexpensive hull construction materials

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

  1. ondarvr
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    ondarvr Senior Member

    I’ve been in composites for over 50 years, I’ve used, sold, and done tech service for just about every type of product being used in the industry.

    I’ve been through the “this is the best new low cost material craze” many times.

    Foam isn’t cheap, but it works when light weight and stiffness are desired over cost and weight.

    Make your putty for the core, test it in the real world and see how it works.

    How do you plan to make shapes with it, or shape it once in place.

    Can you make 4x8 sheets in thicknesses from 1/4” to 24” like foam?

    What is the weight per cubic foot of this product. Can a person lift a 2’x4’ sheet by themselves, trim it to fit with simple hand tools, bend it around a radius, then glass over it easily? Both wood and foam excel at that.

    So while the perceived cost of the raw material is lower, the actual build cost can go up significantly.
     
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  2. fpjeepy05
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    fpjeepy05 Senior Member

    Again I will agree to disagree. You can't even agree that polyester putty with ABS filler is stronger than 5lb density PVC foam. You already know everything. Not worth discussing. Thanks for your contributions.
     
  3. ondarvr
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    ondarvr Senior Member

    I didn’t say that, the two aren’t even that comparable as a core, if you test it you will probably see that.

    Your putty mix will be harder, but harder doesn’t necessarily make for a better core, each core is chosen for its properties in the exact application.

    Again, you need to bring up new ideas, not rehash old ideas that haven’t been found to be useful.

    I’m supplying you with the reasons why these products and methods didn’t work in the past, I was there, I experienced it. If you can create a different product or method, that’s great. Learn from history.
     
  4. BlueBell
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    BlueBell Ahhhhh...

    Ojeepy you're a jolly soul aren't ya.
    Good luck.
    Page 6 and counting.
    Oh, your hallow's crooked!
     
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  5. Mr Efficiency
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    Mr Efficiency Senior Member

    Jeepers creepers, ondarvr appears to have a wealth of experience in the field, always worth reading, it is all well and good to look for better ways, but the expectation that something novel will arise from your enquiries here, has to be low, if he can't offer a suggestion.
     
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  6. waikikin
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    waikikin Senior Member

    Thanks for the info Rumars... it was just a random thought though I quite like the fatigued appearance of the example... I'll probably just buy mine from Baines Masonry Home http://www.bainesmasonry.com.au/ as they've got a local plant and not expensive.
    Al the best from Jeff

    upload_2019-12-19_19-39-4.png
     
  7. fpjeepy05
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    fpjeepy05 Senior Member

    You're getting so close. Just say it. Polyester putty with ABS filler is stronger than 5lb density PVC foam. I think you will find it very freeing.
    I appreciate ondarvr's contribution. But I like discussions that seek common ground. I can't say I have learned anything other than "it can't be done." According to ondarvr there are no applications of any material that can be used in boat hulls of any type that is cheaper than CSM and polyester. I had no "expectation that something novel would arise" but I'm done offering my input.
     
  8. Mr Efficiency
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    Mr Efficiency Senior Member

    So what, the use of PVC core is not principally as the strength component, but to use the strength of GRP, particularly high glass content GRP, more effectively. What is you poly putty contributing to the build ?
     
  9. ondarvr
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    ondarvr Senior Member

    You keep putting words in my mouth.

    I said what you have suggested has been tried and not adopted by builders for various reasons, overcome those obstacles and it may be a viable option.

    Your putty mix, I asked you before how you plan use and apply it as a core...affordably.

    Please explain.
     
  10. fallguy
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    fallguy Senior Member

    How is poly putty with ABS filler not heavier than 5.3 lb core? I calculate ABS plastic at 1.03 grams per centimeter, which is more than water last time I checked. And that is about 66 pounds per cubic foot versus 5.3 lbs for a san core. I am gonna go out on a limb here and assume poly putty also sinks in good old H2O, and so you are talking about a core that is about 12 times heavier before you seam it. If your idea is that it doesn't require glass, that is interesting because polyester last time I checked is not absolutely waterproof. Let's assume I am wrong on the waterproof bit. It would still need to have engineering properties that beat a glassed san core which is unlikely. And since all components are denser than water, for pos buoyancy, you add the cost of buoyancy foams and lose those spaces.

    The two (san and the poly/abs) are not even close to comparable. You would use the heavier product where needed and not just as a general hull core to pick up some alternative engineering attribute. In my build, for example, I opted for plywood in a couple of areas where I really wanted more stiffness than san or plascores would offer, or had less distance for strength, for example. I did use plascore in my build, but only for the convenience of the sizes available. It was for timesaving largely and because I didn't have any way to vacuum 50" wide panels.

    I find these exchanges interesting, but missing elemental basics. There are less expensive cores out there than san. Honeycomb cores like plascore, for example, are far less costly. And plascore would not be denser than water.

    If I have made some invalid assumptions about weights, let me know. Perhaps those magic bubbles Mr. E mentioned are going in there at about 90%.. Is my last statement a shot? I don't know. Perhaps, but you can't just consider cost of raws.
     
  11. Mr Efficiency
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    Mr Efficiency Senior Member

    He said "stronger" though ? Anyways, I feel the reader decays IQ points by reading all the nonsense.
     
  12. fallguy
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    fallguy Senior Member

    Oh, I definitely lost some brain cells reading here. He may have said stronger, and lower cost, but I am pointing out a problem. These materials don't have a single engineering attribute that makes them. Solid steel is also stronger than a san polymer!
     
  13. Mr Efficiency
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    Mr Efficiency Senior Member

    STOP PRESS !
    When I was at the beach a while back, I noticed huge quantities of pumice washed ashore, I admit it did cross my mind, freeby-jeepy fashion, that maybe there was an application for that, in boats, other than for rubbing corns off your feet. I guess it isn't all that strong, but it is light.
     
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  14. rxcomposite
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    rxcomposite Senior Member

    "Stronger" is not the correct property to be used. It is shear strength plus the thickness of the material properties needed by the laminate to define the EI. The tertiary property needed is density. That is what defines the core material.
     

  15. fallguy
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    fallguy Senior Member

    does abs dissolve in esters?
     
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