Boat Design

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ast3r3xast3r3x
Posted:
in General Discussion edited January 2014
Another physics project for you all to help me with



We get .25 pounds of clay and we must make a boat that holds at LEAST 100 marbles. So I figured I'd inquire what are the best boat designs? I guess for the most part since barges seem to be flat on the bottom that it is a better recipe for displacement? Also is it better to displace all the water you can or leave some room for an air bubble to help hold the boat up? Any comments and suggestions you are willing to give would be much appreciated.
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Comments

  • Reply 1 of 33
    airslufairsluf Posts: 1,861member
    Kickaha and Amorph couldn't moderate themselves out of a paper bag. Abdicate responsibility and succumb to idiocy. Two years of letting a member make personal attacks against others, then stepping aside when someone won't put up with it. Not only that but go ahead and shut down my posting priviledges but not the one making the attacks. Not even the common decency to abide by their warning (afer three days of absorbing personal attacks with no mods in sight), just shut my posting down and then say it might happen later if a certian line is crossed. Bullshit flag is flying, I won't abide by lying and coddling of liars who go off-site, create accounts differing in a single letter from my handle with the express purpose to decieve and then claim here that I did it. Everyone be warned, kim kap sol is a lying, deceitful poster.



    Now I guess they should have banned me rather than just shut off posting priviledges, because kickaha and Amorph definitely aren't going to like being called to task when they thought they had it all ignored *cough* *cough* I mean under control. Just a couple o' tools.



    Don't worry, as soon as my work resetting my posts is done I'll disappear forever.
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  • Reply 2 of 33
    powerdocpowerdoc Posts: 8,123member
    I will made a boat shaped like the I cube



    It will be the best ratio between the amount of clay used to build it, and the holding capacity. However it will be a disaster in term of hydrodynamic.
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  • Reply 3 of 33
    smirclesmircle Posts: 1,035member
    Quote:

    Originally posted by Powerdoc

    I will made a boat shaped like the I cube



    It will be the best ratio between the amount of clay used to build it, and the holding capacity. However it will be a disaster in term of hydrodynamic.



    A half sphere would have an even better ratio.
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  • Reply 4 of 33
    ast3r3xast3r3x Posts: 5,012member
    I havn't decided if I want to fire it yet, if I do I was thinking it would add weight. Before we try it out he is going to wight it and it has to weigh .25lbs at most. If it is more we have to shave some off before we test it.



    I think my biggest question is if trapped air or just plain boat holds better.



    Somone want to check my thinking here? The boat will hold the weight of the water it displaces? So if I fill my boat with water and weight it that is how much water it should hold... minus the weight of the boat?
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  • Reply 5 of 33
    709709 Posts: 2,016member
    I'd go with the flat-bottomed approach. Probably very much like a pie-pan, but with the bottom slightly coned downwards towards the center so the marbles don't all roll to one side and tip it over. Heck, maybe even curl the edges of the pan downwards a bit to create a lip that traps a ring of air.



    Oh, and I can't imagine that firing it would add weight. I'd assume that it would decrease the weight by firing out the water in the clay. I know squat about this, so I could very well be wrong.
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  • Reply 6 of 33
    audiopollutionaudiopollution Posts: 3,226member
    Quote:

    Originally posted by ast3r3x

    I havn't decided if I want to fire it yet, if I do I was thinking it would add weight.



    Wouldn't firing it marginally lower the weight of the boat, since you are removing all moisture from the clay?



    [Oops ... didn't read 709's post before I hit reply.]
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  • Reply 7 of 33
    ast3r3xast3r3x Posts: 5,012member
    Hmm guess I didn't really think about that, I was thinking it was just bonding oxygen into it...faulty thinking I guess.





    I'm not even sure how much clay it actually is. If I have enough I will either make some imprints of the marbles to help hold them on place as I think I'll have to stack them.
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  • Reply 8 of 33
    powerdocpowerdoc Posts: 8,123member
    Quote:

    Originally posted by Smircle

    A half sphere would have an even better ratio.



    You are right, my mistake. Anyway a half sphere will quickly sink : absolute instability
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  • Reply 9 of 33
    fellowshipfellowship Posts: 5,038member
    Quote:

    Originally posted by Powerdoc

    You are right, my mistake. Anyway a half sphere will quickly sink : absolute instability



    Powerdoc with that G5 you have I can not believe you have not worked out 2 or 3 prototypes



    Fellows
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  • Reply 10 of 33
    curiousuburbcuriousuburb Posts: 3,325member
    fired clay might end up thinner with same or stronger strength



    maybe you could blow some air bubble foam into the clay for honeycomb effect



    is the "lake" stable or are ripples an issue for shallow freeboard boats?



    does the boat need to move, or just float?
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  • Reply 11 of 33
    powerdocpowerdoc Posts: 8,123member
    Quote:

    Originally posted by FellowshipChurch iBook

    Powerdoc with that G5 you have I can not believe you have not worked out 2 or 3 prototypes



    Fellows



    Unfortunately all my G5, and especially my dual are in my office. I have just a G4 533 in front of me.



    I suggest that ast3r3X take a grapefruit, remove the flesh, and make some test in his bathroom : there is nothing better than direct experimentation



    He can also try different shapes : lemon, concomber, banana ...
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  • Reply 12 of 33
    nebulousnebulous Posts: 193member
    I would think that it would be wise to fire the boat once it is shaped, as this would decrease the weight. However, if you fired it, then when it was in water it would quickly absorb water and may be more likely to sink because of that. Think of a terra cotta gardening pot or a chia pet when you add water to it. If you were allowed to glaze it after firing it then you probably should, as that would keep the water out.
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  • Reply 13 of 33
    ast3r3xast3r3x Posts: 5,012member
    No glaze or anything adding but clay.
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  • Reply 14 of 33
    andersanders Posts: 6,523member
    Half a dome just big enough to hold the marbles and at the bottom a lay just long enough to reach the bottom of whatever holds the water
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  • Reply 15 of 33
    scottscott Posts: 7,431member
    Quote:

    Originally posted by Powerdoc

    You are right, my mistake. Anyway a half sphere will quickly sink : absolute instability





    Maybe not. All boats can be considered an extension of the the spherical shell. If I'm not mistaken as long as the center of gravity is below the water line you're okay. Either that or you have to have good balance of a metastable boat.
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  • Reply 16 of 33
    powerdocpowerdoc Posts: 8,123member
    Quote:

    Originally posted by Scott

    Maybe not. All boats can be considered an extension of the the spherical shell. If I'm not mistaken as long as the center of gravity is below the water line you're okay. Either that or you have to have good balance of a metastable boat.



    Right for the center of gravity, but there is others conditions :



    The half sphere is terribely instable for a boat : more stable than a complete sphere who is totally unstable, but very poor indeed. In a complete sphere the center of gravity is at the same place than the center of the hull. I am not skilled enough to say if it's the same for a halp sphere but if they are not exactly the same (assuming that the hull has a constant thickness, they are very near).



    For those who are interested : see this link
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  • Reply 17 of 33
    airslufairsluf Posts: 1,861member
    Kickaha and Amorph couldn't moderate themselves out of a paper bag. Abdicate responsibility and succumb to idiocy. Two years of letting a member make personal attacks against others, then stepping aside when someone won't put up with it. Not only that but go ahead and shut down my posting priviledges but not the one making the attacks. Not even the common decency to abide by their warning (afer three days of absorbing personal attacks with no mods in sight), just shut my posting down and then say it might happen later if a certian line is crossed. Bullshit flag is flying, I won't abide by lying and coddling of liars who go off-site, create accounts differing in a single letter from my handle with the express purpose to decieve and then claim here that I did it. Everyone be warned, kim kap sol is a lying, deceitful poster.



    Now I guess they should have banned me rather than just shut off posting priviledges, because kickaha and Amorph definitely aren't going to like being called to task when they thought they had it all ignored *cough* *cough* I mean under control. Just a couple o' tools.



    Don't worry, as soon as my work resetting my posts is done I'll disappear forever.
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  • Reply 18 of 33
    ast3r3xast3r3x Posts: 5,012member
    I don't need it to move and it will be in steady water. I did ask and we can't add a full bag of salt.
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  • Reply 19 of 33
    scottscott Posts: 7,431member
    Quote:

    Originally posted by AirSluf

    ...



    More of an ovoid or egg shaped container may work to preserve the static stability a little more and also constrain the marbles to prevent shifting cg's. Still no good for moving, but this is how many buoy hulls are shaped and they float quite well.



    That helps on one axis of rotation but not the other. Also the point about an ellipsoid helping to constrain the marble is irrelevant. You can shape the bottom of the boat however you want. Make it a cup.
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  • Reply 20 of 33
    piwozniakpiwozniak Posts: 815member
    ast3r3x, you'll learn more here than at the school :-)



    Have you considered dual-hull or does it has to be mono-hull ?



    you can design something like U-U, it's super stable, but i don't know if that's something you can do.



    l8tr
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