New GRP boatbuilding method?

Discussion in 'Materials' started by FAST FRED, Sep 21, 2008.

  1. FAST FRED
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    FAST FRED Senior Member

    Years ago we built one off cruising/passenger boats with the "Franz Mass" method.
    A male plug , covered with AIREX , a hand laid outer skin , remove the plug and lay up an inner skin.
    Was fine , even for USCG sub T boats for carrying passengers , but OH ! what a labor intensive building method!

    I observe the modern method of creating a production mold plug by carving it out of a hunk of foam and am indeed impressed with what a 3 axis cutter can do.

    I wonder with modern computer files and all the resin advances if a on off could be directly built.

    LLoyds GRP is based on an all chopper boat ,and many solid glass boats are 40+ years old and still going strong.

    My proposal would be for a lay up head for that 3 axis machine ,that would lay down (say, GRP rope for example) a layer that is 1/2 or 3/8 inch thick , starting on the shop floor.A chopper head with movable side rails for hull thickness could also work.

    The unit would simply lay fast hardening "rope" that was infused with resin and hardener.

    The outer shell could simply be built on itself , the "rope" having hardened as the layup head installs it.

    I have seen articles on NZ boatbuilders that could computer cut a ply interior that locked together (egg crate) and in some cases were even pre-finished , before being dropped in the hull.

    Perhaps the rope boat builder could create outside a pre made interior , so there would be a relatively ready to finish boat on completion of the hull forming.

    The exterior might require sanding and filling , in the old way , but with some of the newer spray fairing compounds , and yet a different head (for surface finishing) could be installed on the 3 axis machine.


    Interesting concept , a crew would assemble the interior , start the machine and simply watch as a hull is created.

    Except for the computer guy the labor could be low skilled.

    The disadvantage is very light weight construction would be hard to do, but for a large number of cruisers hull weight is not that much of a disadvantage .

    There would be almost ZERO waste , and the air pollution requirements should be easier to meet .

    Anyone think this would work? Anyone got a spare 3 axis machine and a yen to innovate?

    If it works , almost any boat could be custom built as desired , no more COOKIES!

    FF
     
  2. marshmat
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    marshmat Senior Member

    I think it's a great idea, and one that- given enough engineering and design- could become feasible.

    We have a very small version of exactly such a machine in one of the shops on campus- a 3D dimensional rapid prototyper. Most 3D printers work by injecting pigmented adhesive into a powder bed layer-by-layer. The result is pretty, but weak, and needs manual post-treating to strengthen it. The "dimensional" type builds up the shape out of a high-density polymer (they won't tell us exactly what the proprietary polymer is, of course). The result is pretty durable and accurate.

    Extending the same technology to a full-size boat could certainly be done. Just replace the quick-hardening polymer of the 3D RP machine with the epoxy-infused fibreglass rope Fred suggests, and scale it up. Some of the major obstacles would be:

    - Cost (development would run a few million at least, and a commercially useable setup would likely be a few hundred grand on top of the price of the 5-axis CNC and its building- which is already a million plus)

    - Chemistry (would need to develop a cheap, zero sag, 10-second-set epoxy; perhaps ultraviolet- or infrared-accelerated? Or would this open the door to even stronger, more advanced chemistries?)

    - Structural properties (would need to re-think the way we engineer composite hulls. The material laid down by the machine would be very directional in its strength characteristics, unlike chop-strand which is equally lousy in all directions. Perhaps build a hull out of multiple, very thin, passes in different directions?)

    Various forms of automated hull production have been talked about on here for a while, but I think we might be starting to hit on something useful here.
     
  3. Ilan Voyager
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    Ilan Voyager Senior Member

    Hi Fast Fred,

    How much would cost the form in foam? A lot will be needed, and in good quality.

    How do you take out the air bubbles from the "ropes"? How do you roll the composite to get a correct ratio of fiber? Finishing would be a nightmare. And the composite obtained will be of low quality.

    The machine gun (devilish invention if used on boats) has resulted on thousands of poorly built boats. Ok 30 years later if the engineer took a security coefficient of 2, even 3 sometimes, the crap will float, always far too heavy. What a waste of materials! What a waste of energy to move that! in France it is called "frozen cod". The LLoyds scantlings are the worst, too heavy and not strong. Have you read the nosense of their scantlings for sandwich?

    Triaxial is more interesting to use, and very fast to wet. Good surface also.

    The true fast methods use finished panels first; placoplastic (an old method using finished fiberglass panels for hard chine hulls), also Kellsal or Hughes systems. There are a lot of variants.

    Finishing is the killer, that takes time, and even your health.
     
  4. FAST FRED
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    FAST FRED Senior Member

    "Finishing is the killer, that takes time, and even your health."

    The 3 axis machines NOW finish a putty to a reasonable surface .

    Skills with a long board are EZ to train low priced help to do.

    The directional factor in a "rope" might be cured with a created product for this style of lamination.

    "Ok 30 years later if the engineer took a security coefficient of 2, even 3 sometimes, the crap will float, always far too heavy. What a waste of materials!"

    Most cruising boats frequently are happy with a 3X safty factor.

    The USCG requires 425% for Sub T passenger boats so overbuilt may be a horror to an engineer , but for an owner /operator its not a big deal.

    The boat's COST is a big deal (as well as longevity) so the ability of using less expensive (no reason for Epoxy) resin/ glass and the ability to have a true custom hull with out the cost of a mold is grand.

    Yes, the Kelsall system would do a similar low cost hull, but the shapes are very limited to developed near flat.

    FF
     
  5. kengrome
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    kengrome Senior Member

    Fred, I had a friend in college who used to smoke marijuana and when he was stoned he would come up with some of the most unusual ways of doing things that you could possibly imagine. But when you sat down and actually thought about it, you could see that some of his concepts were really good ones.

    You haven't been smoking lately, have you? :)

    I think your concept has a lot of merit, but like marshmat said it would cost millions to develop. Then again, with only one machine to serve the world demand for such boats you would have a monopoly for a while -- and given the available supply of money from rich people who can afford to have what they want when they want it I'm guessing that such a machine would pay for itself in no time.

    I also agree that the finishing could be done by the machine instead of directly by humans. It seems the whole idea here would be to replace costly human labor with the computer controlled machine work, not only to save huge sums on labor but to improve quality at the same time.
     
  6. marshmat
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    marshmat Senior Member

    The idea also raises the possibility of previously unheard-of structural systems. If you're able to build pretty much any shape directly via CNC, you may as well throw out conventional notions of constructability. Bulkheads, stringers, structural frames, tanks, cross-braces, etc. could all be built directly by the Machine. In a single operation. But this is still all solid-composite work; if you wanted to integrate cored composites.... I can see that getting a bit ugly.

    The mechanical and control side of it is ready to go today; there are a few 5-axis mills around that can cut a 40' helicopter body mould to millimetre precision or better, and plenty of larger but less precise ones. The difficulty would be mainly in the chemistry. All bonds would be secondary- you would need a resin that is waterproof, strong, zero sag, sets extremely quickly, and can form a near-perfect chemical bond to the cured layer under it without losing any strength. I don't think this would be cheap, at least not at first.
     
  7. TeddyDiver
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    TeddyDiver Gollywobbler

    It could use "bird bone" structure to form a core inside solid surfaces. The same base compound or possibly several ones depending on the structural demands.. Something like 4 colour printer.
    With thermosetting material no secondary bonds..Like welding with less heat?
     
  8. bntii
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    bntii Senior Member

  9. FAST FRED
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    FAST FRED Senior Member

    "Bulkheads, stringers, structural frames, tanks, cross-braces, etc. could all be built directly by the Machine. In a single operation. But this is still all solid-composite work;"

    Yes but ,there would be the ability to use far lighter and less costly "squirt" for low load interior surfaces.

    Realistically finishing the hull will be a challenge , a ply interior at least would need little finishing and is probably going to be cheaper , even with the assembly required.

    Only aircraft seem to be built to 110% , and experienced crews and radar try like heck to keep them in smooth air with out extra structural loading.

    A cruiser built to be beached or hauled by an indifferent crew NEEDS to be "overbuilt". 30 to 50 years of service life is expected.

    The question then becomes one of "how BAD" is the extra weight caused by simpler , lower cost construction.

    Would a displacement cruiser be able to recover the 200% or 300% higher construction cost of Lightweight high tech building?

    Would the repair of the light weight hull be within the ability of a boat yard or owner?

    FF
     
  10. spiel_mit_feuer
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    spiel_mit_feuer Junior Member

    ive seen some newer 3d printing technologies that uses a 2D axis to build a structure layer by layer, something like that using the same software as the smaller machine, but calibrated to operate the motors and controls of a larger 2D machine wouldnt be all that difficult or expensive to build, and you could essentially print a hard plastic hull from a goo, which could then act as a mould for fiberglass, carbon fiber, etc, or even itself be the hull since hard polymers i would trust as much as i would fiberglass... so if you wanted to search for that sort of technology, and adapt something similar, its possible.
     
  11. gonzo
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    gonzo Senior Member

    How about a CNC female mold? In foam it would be farily cheap. However, it would probably distort somewhat with the heat and weight of the laminate. The CNC could then fair the hull to tight tolerances.
     
  12. marshmat
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    marshmat Senior Member

    CNC female moulds can be done.... I've seen this done a few times. It works for smaller things but for big parts like a hull there are problems. The foams aren't rigid enough and so need to be heavily reinforced; there's also a durability issue there. If you switch to a tooling material like Renshape or TEPIC, the mould is stiff enough and can hold a decent finish, but is insanely heavy. What is needed is a material that is light, stiff, dimensionally stable and can be polished to a smooth surface. Some new materials based on foam TEPIC look promising but do not seem to be widely commercialized yet....
     

  13. FAST FRED
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    FAST FRED Senior Member

    Sounds like the dream of installing a computer code in a boat creating machine and coming back in the AM to finish it is still a ways away.

    Then the pre formed foam , Kelsall type system would still be the cheapest and fastest , for a hull with fair curves.

    Any building system faster , cheaper , "better" in someones view?

    FF
     
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