Vacuum infusing wood that has been CNC'd to fit a mold

Discussion in 'Fiberglass and Composite Boat Building' started by Dejay, Mar 30, 2018.

  1. Dejay
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    Dejay Senior Newbie

    Haha thanks for sharing that video. That does put a bit of a damper on all my ideas. I can see how quickly they can work with all the materials prepared. Only a small percentage of material needs to be custom fitted. So all my CNC ideas really don't save much time in the first place.

    Maybe a female mold station would still have advantages because veneer strips get pushed better into a curved shape instead of trying "lift off" the male mold?

    And can you vacuum infuse cold molding without any special "flow channels" in the wood?

    So how much slower is cold molding or ashcroft using 3-4mm veneer compared to strip planking or plywood? Is it like 2 or 3 times slower than strip planking simply because you have 2 or 3 layers? From what I understand it allows to reduce the amounts of stringers and bulkheads you need which would be nice.

    And thanks for that build thread, that looks gorgeous and so clean. It's probably a rather slow build by a perfectionist?
     
  2. gonzo
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    gonzo Senior Member

    Using 3-4 mm veneer requires very close molds or several stringers to keep the shape fair.
     
  3. Dejay
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    Dejay Senior Newbie

    Stringers just on the mold stations or do they remain as part of the hull structure?

    PS: Don't say it depends on the design ;) Lets say in general when creating a more rounded compound shape.
     
  4. gonzo
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    gonzo Senior Member

    You can do it either way.
     
  5. Dejay
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    Dejay Senior Newbie

    Besides more cost for OSB sheets and CNC to make the mold stations, are there any relevant downsides to increasing the number of mold stations?

    I also figure you could CNC cut the stringers as well out of OSB so they are slotted into the mold stations.
     
  6. gonzo
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    gonzo Senior Member

    The stringers are usually cut on a table saw and the edges routed if they are part of the hull. The downside of more stations, is that you need to fair more of them. CNC is OK, but they are not more precise than the output of a computer program. In my view, they are seldom pretty curves and is why I always loft by hand. Also, thicker planking will fair itself, which makes the job much easier and faster. With stringers, you get the advantage of keeping the same amount of stations, and having long battens that fair the curves.
     
  7. Dejay
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    Dejay Senior Newbie

    Thanks again!

    Ok, another crazy idea :) I've been interested in 3D printing for a while, but plastics are heavy and filament expensive and fiberglass or carbon fiber extruders are tricky. They are done already with nylon afaik.

    But you could 3D print with continuous wood fiber filament.
    Imagine you would make thin veneer from wood and cut it into about 1mm x 4mm strips and glue two of these strips together to make a continuous wood fiber strand and put them on a spool (maybe you'd have to keep this spool wet). You'd need to develop a machine to do that. Something that uses computer vision to notices knots or weak spots in the wood and doesn't use those parts.
    Now you could use a thermoplastic resin or plastic and 3D print with this. You'd extrude the wood from a spool, apply glue on one side and have a roller push it on the previous surface. You'd need something to cut the wood strip.
    The "glue" would set very quickly and help make the wood waterproof. You'd need a 5D tilting and swiveling head that can swap from 3D printing to some milling head to smooth the surface. Then you could apply additional layers contouring the first layer in a different direction. Then fair again, apply another layer. You wouldn't need a mold but you'd probably need to turn the hull over half way to "print" and fair the inside bulkheads.

    Of course you'd need complicated machines to do this and high development costs. But together with a machine producing the continuous wood fiber filament material costs would be pretty low.
     
  8. gonzo
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    gonzo Senior Member

    Can you explain how the material costs would be pretty low. Keep in mind you are talking to engineers and we will call you on any unsupported claim.
     
  9. Dejay
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    Dejay Senior Newbie

    Well this could be made to work...
    Ignoring investment costs and development, you could build a machine that makes veneer out of tree logs. Either a CNC controlled saw mill or ideally a giant planer that slices off veneer from a log. If you can automate most of it, there shouldn't be much labor involved.
    Including the machine, long term and in mass production the amortized material costs should be similar to the costs of non-marine grade plywood since you can make better use of the wood. Your production volume wouldn't be as high than the high volume industrial peelers and machines, but it wouldn't have to be.

    I've looked a bit around and I haven't found anything about continuous wood fiber 3D printing. You probably could also 3D print houses or RV shells this way.

    I mean if you put in 2000 hours into a boat building project, with a few people collaborating you could probably amortize the time spend on developing the veneer and filament machine and 3D printer.

    If this could be made to work... and there are no patents encumbering this technology.
     
  10. Rumars
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    Rumars Senior Member

    So what you basicly want is using an automated fiber placement machine to lay 3D-veneer in a mold instead of carbon prepreg. Yes it's doable. 3D-veneer is already invented (basicly narrow strips of veneer stiched togheter on the back, same thing as unidirectional fiberglass fabrics), and AFP machines you can buy. Danzer will sell you the veneer 3D-Veneer https://www.danzer.com/en/products/sliced-wood/3d-veneer and several companies make AFP robots. You just have to find a suitable glue, but I'm sure that the producers will oblige.
    As for economic sense no it's not worth it. For true mass production there are cheaper options than buying an AFP robot, and big dollar superyachts do just fine with paying a salary to the guy laying the veneer.

    Material costs are low as it is. Just get on the phone with any veneer producer and tell them how much you need, you will be surprized at the prices you get when buying hundreds of square meters of the stuff. Even thick sawn veneers are cheap in quantity, you buy the log and have it sawn to order. Epoxy you buy in 200l barrels, it does not get much cheaper until you order in cubic meters.
    Transfering labour costs is only viable for specific situations like true mass production or quality requirements.
    The best thing an amateur can do is pay for a really good set of plans tailored to his needs. You can't loft and cut accuratley with a jigsaw? No problem, pay the NA for lofting and fairing the plans full size, than digitizing the station molds for CNC milling. Then you pay the guy with the really expensive and precise 5-axis machine to cut them. You have just transfered the labour costs in order to achieve quality. Did it make sense? Well if you count the hours needed to learn lofting and fairing and developing the motor skills to use a jigsaw and apply your standard hourly wage you make against the costs incurred you find out. Similarly if you hire a pro to sand and paint your hull.
     
  11. Dejay
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    Dejay Senior Newbie

    Oh that's a cool product. And yeah you're right about the veneer and labor costs. But the market for boats should also be driven by supply and demand. If you sell a yacht for a million you can spend the money, but as soon as someone can produce the same yacht without drastically reduced labor costs (or at least the hull), boats could become much more affordable and demand would rise.

    I meant FDM 3D printing though, not a 3D veneer. Using a filament of thin wood strips. Fused deposition manufacturing, but with continuous wood fibers maybe 3mm x 3mm cross section. Strips cut off from veneer that are stitched together on a roll. At least that machine doesn't exist I think. Well actually you wouldn't really need to stitch them together since you'd have to frequently cut and restart anyways.

    Usually you build up 3D prints in horizontal layers, but you could print the hull of a boat upside down (printing supports that are later removed), carefully mill the surface smooth and then 3D print on that surface with a 6 DOF robot arm. There'd be limits on the shape and max curvature though.
    You would build up a "3D plywood". If you can retain at least most of the physical properties of wood and don't use too much glue it might be equivalent to cold molding.

    And yeah it's another crazy ideas with lots of difficulties! :) The wood filament could break, shrink after printing, need to find the right glue, slow print speeds, a complex 6 DOF robot arm etc.

    You could also look at other plants like maybe thin bamboo stems or reeds. Anything that has good tensile strength, low density and good impact resistance.
     
  12. gonzo
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    gonzo Senior Member

    Once more, where is the economic analysis? I understand this is your idea, but it is not fact. You can do just about anything if you have enough money and time. However, it doesn't make it cheaper than usual methods. For example, what is the initial cost, maintenance cost, salaries, overhead, life expectancy, etc.?
     
  13. fallguy
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    fallguy Senior Member

    I smell a fishy school project.

    The diseconomy of the suggestions borders on comedic. I thought my 30% resin losses on $9k were horrid enough! (They are!)

    OsB makes a terrible frame. Its uses in construction are well appreciated.

    Boat frames in pressed board are more stable. Pressboard takes screws well if needed, but is any helpful comment even relevant dejay?
     
  14. Dejay
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    Dejay Senior Newbie

    Sorry I stretched your good will to listen to silly new ideas! I sometimes enjoy dreaming up new (unrealistic) ways to solve a problem more than actually solving the problem. I agree you'd need a ton of research and development to even see if any of this might become viable in the future.

    But I've learned a lot from this thread so your comments are definitely helpful. Thanks!

    I plan to read a few books and start by building a small skiff to gain experience. A big boat project is probably 3-4 years away.
     

  15. Steve Clark
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    Steve Clark Charged Particle

    Assembling a female assembly gig out of CNC cut parts. Then use the plating programs available in many CAD programs to pattern whatever planking system you chose. Two layers of plywood +/-45 cut 90 degrees to the face grain is a pretty nice basic skin.
    One thing to consider is to build the entire boat before taking it out of the jig and finishing the outside of the hull.
    SHC
     
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