Steel-made hull with fiberglass-made radius chine ?

Discussion in 'Metal Boat Building' started by xarax, Jul 5, 2007.

  1. xarax

    xarax Previous Member

    If we could fasten (somehow...), to the outside surface of a multiple chine steel hull, between two pairs of chines, longitudinal sections of two tubes made of fibreglass...We could have our constant radius chine steel hull with much less rolling, fairing, welding...
     
    Last edited: Jul 7, 2007
  2. Wynand N
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    Wynand N Retired Steelboatbuilder

    :eek: :confused: :?: :!:
     
  3. jehardiman
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    jehardiman Senior Member

    What Wynand said......Why on ever would you want to?
     
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  4. xarax

    xarax Previous Member

    Thank you jehardiman,
    Wynand is obviously as confused as I am on this crazy idea...The Achilles heel of amateur steel boat builder is his inability to produce fair double curvature surfaces, unless he is prepared to do the extra work, (more rolling, welding, fairing...) that a radius chine hull requires. It seems easier to me to just build two long plastic "bananas" and fasten them to the outside surface of the hull with bolts from the inside, alongside the turn of the bilge where one really needs the double curvature. If you are satisfied with constant radius curvature you can even use sections of commercially available flexible tubes as moulds. You can fill the bananas with foam and take them out easily when you have to repaint the hull. The same can be done on plywood-made hulls. Just an idea... I would like to have a few words from Wynand or any other with knowledge of steel boat construction about the varia problems that such a hybrid steel-fibreglass hull is bound to pose....
     
  5. Raggi_Thor
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    Raggi_Thor Nav.arch/Designer/Builder

    Then, why dont you build in wood and epoxy, like Didi 34, 38, 40 for example?
     
  6. timgoz
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    timgoz Senior Member

    If your idea was practical and/or feasible, it most likely would have been done long ago.

    I do not think Wynand is confused one bit, but visually expressing his opinion.

    Two main things I see that would rule out this idea.

    1. Bolt holes through a steel hull defeat many of it's inherent advantages.

    2. Corrosion would find a happy home behind such a setup.

    I would never consider such an arrangement. If I wanted to attach anything to a steel hull though, I would not through bolt, but employ welded on threaded studs.

    Steel pipe split lengthwise would allow a radiused chine while maintaining the integrity of all steel construction.

    Take care.

    Tim
     
  7. M&M Ovenden
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    M&M Ovenden Senior Member

    Could I add that a radius chine is really not that hard to achieve, even more so if it is constant radius. It's just more work compared to hard chines but not difficult. Trying to fit a composite banana sounds like orders of magnitude more difficult.
    A hull with small amount of double curvature will most likely be more fair than a hard chine all single curvature hull, less fighting with the hungry horse. Double curvature is not all bad for the steel boat builder.

    Murielle
     
  8. jehardiman
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    jehardiman Senior Member

    Timgoz and M&M have basicly said it. To insert a composite radius chine is more work and less effective than just rolling up one. Setting aside expansion/contraction, fastening, and modulus issues; most modern hulls are constructed using conic sections and/or local/minimal furnace heating. You can put an awful lot of double curvature into 3/16 plate with a 0-0-0 rosebud, a 10 pound sandbag, and a comealong.
     
  9. xarax

    xarax Previous Member

    Thank you guys, it is really polite to respond to such a bizarre vague idea as a hybrid steel-fibreglass hull...
    Didi 34, 38, 40 are fine hulls made of plywood, but radius chine hulls nevertheless. To achieve a fair double curvature you have to use many pieces, and that means a lot of work and a lot of seams, points where something can go wrong...If you look carefully you notice the transverse seams - as they reflect the light with a different angle. There is an obvious difference between any radius chine and the genuine double curvature surface of a fibreglass hull, although I believe that the difference is not functional at all and it may only lie in the eyes of the beholder...
    The argument that any practical or feasible idea would have been done in time when it becomes practical or feasible does not sound very convincing to me. :) The world is not the best and only world that might exist, unfortunately Mr. Leibniz... :) I don’t see any offence in visually expressing one s opinion, especially when it comes from a master of the craft like Wynand.
    The holes through the steel hull need not be as many as to defeat any inherent structural steel advantage. One could also find other ways of fastening the plastic parts on the metal surface...The task is to be able to detach them when you are to repaint the hull. I guess that the hull, being painted underneath the plastic parts, wouldn’t corrode more than the other parts ot it, although I am not so sure about that...
    Steel pipes can not be used as they don’t be bend lengthwise, a plastic pipe used for the mould could easily be bent...
    Double curvature is not all bad for the experienced or professional builder, but for the amateur is simply out of the question, as one can see around marinas...I am not convinced that to attach a plastic radius chine would be as impossible for the amateur boat builder as a genuine round bilge hull is, or as difficult as a metal radius chine. The work to cut, roll, weld and fair all these radius chine metal parts, (and remember, they have to be quite many if you are to present a fair double curvature surface that doesn’t play nasty games with the light...), this amount of work is evidently excessive for the amateur, and this explains the fact that most amateurs do not build radius chine hulls at all. You can put an awful lot of double curvature into 3/16 plate with a 0-0-0 rosebud, a 10 pound sandbag, and a come along, but I can t, and so do the majority of inexperienced amateur boat builders... :)
    The modern hull can use any developable surface, not only one that is composed of conic sections - it could well be composed of developable helicoids, for example...But it is the double curvature parts that we are talking about here, which fortunately need not be so extended as to inhibit the use of these plastic parts I am thinking about. It is only a small part of the whole surface, at the proximity of the turn of the bilge, where one really needs a double curvature part, but this part happens to be visible from the marina, and clearly distinguish the men from the boys of metal construction. :)
    Now, the expansion problem...This is a real problem indeed, but I thing it can be somehow solved if the chosen method of fastening permits a limited movement along the chines. The fibreglass is more flexible than the steel hull, so I don’t see a modulus problem, but I may well be as mistaken there as on the whole thing...
     
  10. Raggi_Thor
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    Raggi_Thor Nav.arch/Designer/Builder

    I think the main issue is that mixing mmaterials is asking for problems.
    If you make the rounded chine of polyester(?) and glass, why do you want steeel in the topsides???
     
  11. Wynand N
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    Wynand N Retired Steelboatbuilder

    Cut any steel pipe in half longitudinally with an oxy-acetylene cutting torch and see what you end up with....a perfect banana shaped radius section;)

    xarax, I suggest you take a look at my website (below my signature)
    which, incidentally is aimed at the amateur steel boatbuilder.
    BTW, if you are so bend on plastic chines, why not just build a plastic boat - much less hassle and more practical.
     
  12. jehardiman
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    jehardiman Senior Member

    Xarax, just a question....I understand that you are an "amateur builder", but just how much real experience do you have working with steel and how much working with composite?

    You see, some of your statments show that you have a very strange view of the effort required to complete some basic tasks in the design and construction of the two materials.

    Anyone can bend a slit steel thin-wall pipe to the curvature needed for radius chine, and I'll say most can do it with one hand because of how you fit it. Not only that, you'll get a fair curve if you're careful, which is something a slit plastic will never do without buckling. And you greatly underestimate the work needed to drill thousands of edge fastening holes (There is a very real reason that riveted construction was abandoned) or the engineering work necessary to make that joint both tight and as strong as the rest of the hull. And you do not seem to understand the amount of work needed to fair ANY one-off hull to glass smoothness.
     
  13. xarax

    xarax Previous Member

    Thank you Raggi Thor,
    Mixing materials is a very difficult (and some times even dangerous...) task in any type of construction, I agree, and I happen to witness that in "land" structures as well, so I guess it would be many times more difficult in sea structures, with the erratic movements of elements and floating bodies. But a great part of modern materials engineering is just about that, about solving problems posed when mixing the most diverse materials suffering of the most demanding structural loadings. Now, one does not have a real mixing of materials here, just problems of fastening together three quite simple formed structurally in depended floating bodies, made of two different but well known materials, i.e. problems of joints. I think these are problems that could well be solved with today’s engineering materials, skills and computing power.
    Dear Raggi Thor, I don’t want a boat made of steel at the bilge, of GRP at the turns of the bilge and of steel at the topsides !!! I just want a normal multi chine steel boat where a really small part ot the outside surface of its steel hull, less than one sixth of it I reckon, at the turn of the bilge, is "covered" with two plastic curved hollow bodies made of GRP and filled with some foam. These plastic bodies can be made very easily and very inexpensively. Thus the outside surface of the hull would present no hard chines to the flow of water or to our aesthetics...
     
  14. xarax

    xarax Previous Member

    No, even if you try hard, you end up with a simple curvature developable surface, composed of simple or multi apex conical or of cylindrical sections. To bend this metal surface, to torture it so its outer surface becomes a fair double curvature surface, this would be very hard indeed, at least for the amateur boat builder. What I tell you is simply, after you have finished your beautiful multi chined steel hull and you have painted it, you order two long plastic bananas from the local fibreglass boat builder, you fasten them along the sides of your hull with a dozen of bolts, so at the end you have only two narrow longitudal seams visible, you paint the outside surfaces of your bananas with a similar colour, and there you go! :)
    Now seriously Wynand, are you telling me that a steel boat with some quite small fibreglass-made attached hollow bodies, fastened along its hull, is such a really impossible task? I have hoped you would have pointed out the real problems that I can not even imagine...One can always order and build a carbon hull, you know...
    I really love the simplicity of a steel hull that, at least, doesn’t t smell as a GRP one! :) I am just trying to figure out a way to have less transverse seams, less welding and fairing, and a smoother radius chine hull that an amateur builder can easily accomplish.
    I can present one more arguments, a real killer, about the merits of such a hull:
    If, at the end of the day, you don’t like the outcome, you can always get rid of your bananas and sail with your beautiful multichine hull, just a little lower on water. You can cut the inside surface of the bananas and use them as two nice long curved flower pots. You can even carry these pots on board!:) :) :)
    P.S. I have visited your nice site many times, and it was a source of great pleasure for me, and I am sure for many others, to read all these useful details of amateur boat construction. It seems that I have not been a really good student of yours! :)
    I have only one last comment on the difficulty of radius chine construction for the average amateur boat builder: If it was so easy, given that a round bilge-like steel hull is so much desired, why we see so few radius chine steel boats (made by amateurs, of course), around the marinas?:)
    Thank you for your comments and your beautiful site.
     

  15. M&M Ovenden
    Joined: Jan 2006
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    M&M Ovenden Senior Member

    Well Xarax, we are looking forward to seeing in picture the result of that simple building method...
     
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