wood planking on aluminium frame

Discussion in 'Boat Design' started by bertho, Aug 16, 2006.

  1. bertho
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    bertho bertho

    why not use to traditionnal plank on steel frame using aluminium, perhaps glue with polurethane and bolt with aluminium bolt on the first layer (can be strip plank half the thinness of the final planking, and two layer cold molded 45deg , with a sheet of fiber with epoxy to finish outside.. i have this system on my mind for a new 50 "sailing boat, did some expert have sugestion about this system??
     
  2. Syed
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    Syed Member

    I am not an expert, but I know that very dissimilar materials should not be jointed as the different thermal expansions will ultimately affect the joints. Concrete and steel have very close coefficients of thermal expansion; therefore the combination is widely used for building structures.

    Regards,
    Syed
     
  3. Richard Hillsid
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    Richard Hillsid Senior Member

    My advice is to forget it, I have refused every “can you aluminium frame my old wood boat project” and always will. Why would you want to use aluminium frames on a wood boat, cost, strength or some other reason, it can’t be that they would be easier to set up.
     
  4. bertho
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    bertho bertho

    gents,
    wooden planking on steel frame have been , and stil use, since years, only problem is metal corrosion, why don't use aluminium to avoid corrosion and save weight?? bolting can be improve with gluing ( elastomere/sika) and have a more stable planking using laminated wood ? i don't see any problem with dilatation with steel frame, this system have been use by william fife for "small yacht" until clipper 100'++ !
    bertho
     
  5. MikeJohns
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    MikeJohns Senior Member

    The traditional wood/iron framed composite was framed with either Iron or heavily galvanised steel, and a gasket between the frame and the planking. The fixings were commonly screwed from the inside and not through bolted except at the topsides and the keelson. Often frames could be individually removed for maintenance in the better designs. They did have some advantages in a smaller frame hull contact area and less wood rot and greater fastening strength.

    Aluminium has some inherant problems itself. It is prone to much more rapid corrosion than steel when it does corrode. Its relatively lower strength also dictates a larger frame than a steel one.

    The thru fixings will need to be fully isolated the frames will need painting in the bilge areas and they will need to be very well gasketed to prevent pockets of moisture. Welding the alloy causes a large drop in strength (40%) and fatigue issues are a problem so the frames will need to be well engineered.

    It's possible but these days there are better alternatives to wood metal composite construction. All metal or all wood cold moulded is considerably more reliable than a plank on frame design.

    What sort of vessel did you have in mind?
     
  6. bertho
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    bertho bertho

    Hi mike,
    thanks for your input, i'm also still wondering about this option, my project is a 50' schooner, i like wood,(have a "new" traditionnal 66' wooden plank now, very happy by, but it's heavy!) but it's so difficult now to find proper timber for a new project, and in all case, final weight is hight and labour is rare.. also a lot of poket and expensive fastening(silicon bronze), option of fully laminated, cold molded hull is probably the best on my point of view but labour and hour of work is very hight,
    as i see some shipyard in US still doing plank on steel structure with succes, i was just wondering why not use to aluminium instead of galvanized steel, aluminum is sensible with electrolize, but this problem can be managed, it's clean and lighter than steel, but i don't have data regarding corrosion wood/alu?? and about the best fastening between both..
    i'm aware about the problem between some wood and steel/zing, mostly due to the "tannin" in some timber.
    as i'm leaving in asiae, we have classe 1 wood as chengal, malaysian teck, rot and worm resistant, not to heavy, and with good glue caracteristic, but only in strait plank, no curve..
    anyway, I's still on project for next year! whatever the construction method !
    it's probably the best stage of the project!
    bertho
     
  7. Tanton Yachts
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    Tanton Yachts Yacht Designer

    " Artica". Wood on Aluminum frames.

    The yawl Artica, designed by Aero Marine for the italian Navy in the 50's, had such a construction scheme. L.H.T 12.8m; L.Fl. 10.04m; Beam 3.48m; T.E 2.19m. The boat is still going strong.
     
  8. MikeJohns
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    MikeJohns Senior Member

    Tanton

    Was that steel or alloy frames?
    Cheers
     
  9. Tanton Yachts
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    Tanton Yachts Yacht Designer

    Artica 2. Body Plan. All members in Aluminum Alloy to British std.
    B.S 1470 for sheet or strip, or plates.
    B.S 1473 Rivets.
    B.S 1476 Sections.
    B.S 1490 Castings.
    B.S 1474 Welding Wire.
    1 1/2" x 1 1/2" x 3/16" Angle Frames.
    7/8" Mahogany Planking.
     

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  10. bertho
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    bertho bertho

    Tanton, Thank a lot!
    i will give this indication to my designer as info, i guess the result is not too heavy, they use rivets? it was in 1954 ! aluminium marine grade was already existing?? or they use aeronautic grade..
    i try to find more info about this boat, but it's classified under "italian navy"!, i'm curious to understand why this construction sheme is not more popular..
    rgds
     
  11. Tanton Yachts
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    Tanton Yachts Yacht Designer

    It is not simple to build with aluminum and wood. Different kind of material, skills and know how. Bevelling is a *****. Frames and Beams have to have radiused root. In bevelled frames the non bevelled heel of the angle can be ground off without seriously weakening the section. In the case of Artica 2, the construction called for transverse framing. Fifty frames in all!
     

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  12. CDBarry
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    CDBarry Senior Member

    Actually, wood over metal composite is a very neat method of building boats, especially since the metal parts are what would otherwise be the heavy wood members that are hard to get (since they have to be laminated or cut out of bigger pieces). Beveling is only needful if you are using metal transverse framing (I would use wood longs and metal web frames), but even then, CNC the external flanges as developables, and weld them on the webs, and they will be forced to take the right bevel automatically.

    A number of fairly large minesweepers were wood over aluminum, but there is very little weight advantage between aluminum and steel (for framing, not for the shell), and fasteners are a problem in aluminum (unless, of course, you are sweeping magnetic mines).
     
  13. bertho
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    bertho bertho

    barry,
    thank a lot for your input, your comment is usefull !
    i was also thinking about cnc possibility to ''prefabricate all frame, also regarding the problem of '' multiple skill knowhow"" not available on a normal shipyard, it can be a solution to sub contract a set of web frame in aluminum yard, and do the planking in another one.. as i plant to built this boat in asia, it can be a solution,
    remaining is the fastening PB , how it's bolted on stell frame ?? with hot did galvanized bolt? as now we have also all the polyurethane .. why we can't use aluminium bolt + elastomere adhesive ?
    i dont want to sweep magnetic mine, but just to avoid corrosion..! i don't like rust on board !!
    cheers
     
  14. yachtsmanbill
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    yachtsmanbill New Member

    Need Help !!

    What a neat forum. I too plan on rebuilding the deckhouse on my 58 foot HATTERAS using aluminum frames with either alum plate or FRP over plywood sheeting. I have aluminum welding equipment and already own an aluminum ROAMER so I understand the ramifications etc., but I do need some design ideas. Raised pilothouse forward with a walk around deck seem to hit the spot.:idea: Any input or shoves in the right direction are appreciated !! CHEERS !!
    Capt. Bill @ yachtsman36@comcast.net 630 388 8882
     

  15. CORMERAN
    Joined: May 2006
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    CORMERAN Junior Member

    Alum. and wood

    To: - Yachtsmanbill
    - bertho

    Why not.........

    - Steel and wood are much closer in behaviour than Alum. and wood.

    - I've heard tell; that Alum. conducts heat 400 times better than wood !!

    (That's why Alum. always feels so cold to the touch
    and wood always feels warm.)

    - Therefore Alum. is a much greater risk re: fire, than wood OR steel.

    - Wood beams connected to a wood hull are INHERENTLY stonger
    and requires a lot less engineering to do.

    - Carbon fiber beams would be my choice.

    As carbon fiber is closer to the behaviour of wood than ALL
    the above.

    - Also if saving weight is your largest concern,
    then carbon is hard to beat.

    - I suspect the presumed extra cost of carbon - at the end of the
    day - will not exceed the extra time and money to get around
    all the complications inherent in trying to make alum. and wood
    work together in harmony.

    However, dont let us discourage you.
    Let us know 5 yrs after sea trials how well your vessel is standing up.
    Maybe you are onto to something that we have overlooked.

    Cheers !
     
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