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Thread: 3D printed boats

  1. #11
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    Default Re: 3D printed boats

    Marc,

    Remember, both canoe hull and deck print as an integral shape, and print times and quality vary with different printers. That said, Selwyn just sent me this:

    "Just ran the data through the software. And this will be about right in reality.

    Based on normal flow rates/speed and fine layering to get the nice smooth finish.
    Nozzle of 0.3mm gives 20 hours
    Nozzle of 0.5mm gives 15 hours

    Mass of both come in at around 85 to 95g raw hull. Nice and smooth, rigid and strong."

    Here's a pic of Shrink being assembled:

    Click image for larger version

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    Bill

  2. #12
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    Default Re: 3D printed boats

    15-20 hours.... that's not far off a wooden hull.... but its time spent waiting and watching, not working...

    nice thing is that changing a design and reprinting is a few keystrokes away
    Marc

    S1M 1981
    Victoria 81
    RG65 181
    IOM 81, 681, 881

  3. #13
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    Default Re: 3D printed boats

    Actually for a prototype is rather interesting to modify the forms and the day after having the New Hull.

    For what concern the external finish, I'm not sure that will be the one I would search for. Reynolds will not be happy either !! hehe
    Thus sanding and painting are probably necessary.

    In terms of weight the Trap 65 hull was not far away from 85-95g and a good glossy finish is always welcome as on the 43" !
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  4. #14
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    Default Re: 3D printed boats

    Claudio,

    Again, I'm not quite sure what point you are making. We all know that a good hull can be made by carving a plug, spending a lot of time sanding and polishing, making a mold, and laying up a hull. It looks like you make very nice ones.

    The point of Selwyn's work is to demonstrate, so that others can also learn, how a competitive hull can be made without all that...using a technology that produces a light, rigid, pretty nice hull that can get from drawing board to water in a week or two at low cost.

    Do you have reference data that demonstrates a distinct advantage to a glassy hull surface at model boat speeds? I haven't seen that...but if glassy is what someone wants to get from the 3D printed surface, no problem...it won't take anywhere near as much work as it does to make a smooth plug. And you do sand and paint those glass hulls, don't you?

    Bill

  5. #15
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    Default Re: 3D printed boats

    Quote Originally Posted by mudhenk27 View Post
    Claudio,


    .............is to demonstrate, so that others can also learn, how a competitive hull can be made without all that...using a technology that produces a light, rigid, pretty nice hull that can get from drawing board to water in a week or two at low cost..............

    Bill
    Hi Bill,
    I spent more then 35 years in Space Technology and I'm very enthusiastic about everything is close to New Technology, but at the same time I like to think what is the benefit at the End of the Process.

    Reported your phrase "... a competitive Hull..."

    What do you means by that ?

    1 - in terms of costs
    2 - in terms of performances in the water, fluidity, friction, roughness ...
    3 - in terms of easy implementation of the process
    4 - in terms of strength/rigidity/twisting
    5 - in terms of weight
    6 - in terms of durability
    7 - in terms of manufacturing time

    About Reynolds Number and Frictional resistance the Web is plenty of information, too long to explain here, but as recalled from Book data about Roughness that induce Frictional resistance :

    - Gelcoat polished......1Ám
    - Car Body New..........5Ám
    - Brush paint.............20Ám
    - Rusted sheet...........250Ám
    - Concrete finish........1000Ám
    - Dirty Hull................5000Ám

    To note that 37% of the total Frictional Resistance is produced by the Surface finish

    As speed increases less shall be the roughness.

    So far, my understanding is that this technology allow a
    'fast construction' if the process is well understood and controlled
    Cheers
    Claudio

  6. #16
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    Default Re: 3D printed boats

    Claudio,

    By competitive hull, I mean one that can compete successfully in international competition against other entries. I don't mean that the boat has to finish in first place, but rather that it will show itself to be deserving of racing in the group, staying with the fleet and handling well.

    That is what I meant by competitive, but based on his results racing the GM RG65, I think the hulls that Selwyn is producing will show themselves to be competitive in all 7 of your categories.

    You seem to be focusing a great deal on surface, but clearly, winning performance is not all about having a shiny hull. I am well aware that there is evidence indicating that hull surface is important in big boats...what I was asking is if you have seen any research results on the effect of hull surface at the low Reynolds numbers at which our models operate. I have heard, but have no evidence, that the available research does not scale down to model size.

  7. #17
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    Default Re: 3D printed boats

    Bill,

    is not forbidden to dream, although I would like very much that this technology will become true.

    Most of the naval architecture books have plenty of pages dedicated to Frictional Resistance.
    True, my phobia is roughness and the pictures seen until now as well seen on Selwyn paper are justifying my remarks.
    The thickness evoked of 0.35/0.45 mm are not the ones seen in the pictures that seems closer to 1mm for a 65cm hull (see attachments).
    May be thicker and heavy for longer hull ?

    Most of the tests carried out are made with "scale models" in towing tank therefore the scale factor are included.

    Click on the web : "Reynolds Number" or "Frictional Resistance" and a lot of data become available.

    BTW, by performance I do exclude the modeler "Fingers".

    I do also consider for a modeler that the time spent to build a model is part of the game played with a great pleasure .... I do not refuse progress, but still I have some reticence to consider "a competitive Hull" in all terms if made with a the 3D printer.

    I hope sincerely that the time will prove it or not that I'm wrong !!
    May be with a different material then PLA who knows !

    For me the roughness is, in my opinion, the critical point of this type of construction that will require hours for sanding, painting, polishing on a surface that is not very sturdy to support manual pressure as seen in the picture and adds weights. My Hulls are supported by the mold.

    My regards to Selwyn that I do not have the pleasure to live closer, I will watch the printer working at my place !!!.

    Cheers
    Claudio
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    Last edited by claudio; 04-19-2017 at 10:07 AM.

  8. #18
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    Default Re: 3D printed boats

    OK Claudio,

    I understand that you are skeptical and not excited, you've made your opinions clear, and I'm not trying to convert you. The only reason I'm replying to your posts is to try to ensure that other readers are not mislead. You have not seen one of these hulls in person, have not handled one, and have not sailed one, so I think some of your concerns are unfounded.

    In my opinion, the technology has come true, as demonstrated by Selwyn's success...though these are the early stages, and it is likely to improve over the next few years.

    But enough opinions. Here are some facts:

    The finished hulls are as rigid as those built from other materials I have used such as wood, glass, and kevlar.

    The PLA material is easy to sand and paint if a glassy surface is desired.

    The thickness naturally varies with the size of the model, just as it does when laying up glass or carbon. The result is a hull as light as those typical in the class.

    Completed boats have been successfully sailed in three classes: Footy, RG65, and IOM.

    Enough said.

  9. #19
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    Default Re: 3D printed boats

    In an attempt to be factual, I've taken a couple of pictures that I hope will show the texture of one of Selwyn's Footy hulls. This is straight from the printer. The first is an overall shot. Note the bow, where you can see the thin 1/3mm printing (yes 1/3mm.) The second is a closer view.

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    To alleviate any concerns about being able to sand the PLA, or that the hull might not be rigid enough to hold up to sanding, I took a couple of hours this afternoon to demonstrate. I took the 26g (yes 26g) Footy hull that I had already coated with thinned epoxy. I sanded it with 220 grit, then sprayed it with rattlecan semi-gloss clear. After drying, I again sanded with 220 grit and re-sprayed. The result is in the following picture. The picture disappoints me, because the plastic shows a pattern underneath the clear, even though the hull is now quite smooth. I guess it is reflecting the pattern from the inner side, but I'm not going to paint it an opaque color just to prove a point...I like the orange. I'm not claiming this is a great finish, I got dust and dog hair in the paint. But it should be obvious that I could get it as smooth as I want by spending some more time...maybe even glassy. The hull took the stress of sanding without a problem...nothing broke or cracked, even though it has no internal supports.

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    Last edited by mudhenk27; 04-19-2017 at 06:26 PM. Reason: added dog hair

  10. #20
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    Default Re: 3D printed boats

    As I was taking those pictures of hulls yesterday, and admiring the finish Selwyn has achieved, it occurred to me that he has got it so tight now that we might not need the epoxy coating. So I threw a pound of weight in the hull (it's a Footy) taped up the ends, and floated it in the laundry tub...oops, I mean the test tank. Left it there for 12 hours. Opened it up this morning and there is not a single drop of water in it...not one drop!

    Awesome work, Selwyn.

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