Construction of a cutter

Discussion in 'Metal Boat Building' started by dskira, Oct 4, 2010.

  1. dskira

    dskira Previous Member

    I don't know if you remember when I posted the lines of the steel cutter. Anyway her it is again.
    The boat is now in construction in England, and I asked the owner builder to send me pictures.
    It is just for information purpose I post them, and I hope the owner will continue to send pictures until completion. It will be an interresting story.
    Well will see.
    This is not an infomercial and the plans or the boat are not for sale :)
    Daniel

    [​IMG]

    [​IMG]

    [​IMG]
     
  2. Skovian
    Joined: Aug 2008
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    Skovian Junior Member

    Nice

    Hey Daniel,

    I had the original drawing as my desktop wallpaper for a while after first seeing it. She should look spectacular once she's done.

    Take care
     
  3. M&M Ovenden
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    M&M Ovenden Senior Member

    And a lot has been forgotten.

    Cheers,
    Mark
     
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  4. Ad Hoc
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    Ad Hoc Naval Architect

    Looking very good Daniel. :)

    Only comment i would make is that i would advise that the plate butt in the frame webs to be some distance away from the change of section shape, ie not at the "corners". I know this way it saves plate/money (as each part is shape depth and not complex shape)...but the location of the highest stress in the frame, is usually at these locations.

    Just a thought.
     
  5. dskira

    dskira Previous Member

    Ad Hoc, you have the Eye :)

    You are absolutely right, I will advise my customer about these butts, and will revise the design in accordance.

    Thank you.
    Daniel
     
  6. dskira

    dskira Previous Member

    Thank you. I saw the video of your wife cutting the insulation with the Beetle song in the background.
    Quite a ship you are doing you both, a beauty.
    Daniel
     
  7. daiquiri
    Joined: May 2004
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    daiquiri Engineering and Design

    Hi Daniel, so nice to see someone still wants to build one of these old-style beauties. I just love the look of the old british cutters. :)

    Completely off-topic:
    Found this image of Genesta at the Corbis Images site. Just look at those gentle lines (and also admire the drawing ability of the author - no CAD software back then):

    [​IMG]

    Cheers! :)
     
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  8. Ad Hoc
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    Ad Hoc Naval Architect

    Thanks for sharing D :)

    Draughtsmanship at its finest....a fine example in every respect :p
     
  9. dskira

    dskira Previous Member

    Oh no it is not off-topic, it is my kind of boat. I love them, I studied them to death, I collect old books of naval architecture about this amazing period.
    Thank you for showing this picture. What a draftsmanship.
    Daniel
     
  10. apex1

    apex1 Guest

    Phantastic picture D. Thank you.

    Richard
     
  11. yipster
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    yipster designer

    belive it or not, i too like those boats and take it in steel the chance of sections can not be double plated
     
  12. M&M Ovenden
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    M&M Ovenden Senior Member

    You are showing your ignorance of sailing history Brent. Those are typical shapes of pilot cutters. The purpose of pilot cutters was to get out to sea short handed, as fast as possible, in any possible weather. The pilot would get out to meet incoming ships and certainly couldn't pick the weather to do so. On smaller units a young boy would be on his own to bring back the cutter back to safety after dropping the pilot at the ship. Those are extremely seaworthy vessels which have sailed in the toughest conditions imaginable.
    In early age of pleasure sailing the pilot cutters have been very popular, not only because they are gorgeous but they are also reliable seaworthy boats.

    Murielle

    edit: Wow Brents posts disappear fast! My reply was in response to Brent second guessing these hull shape seaworthiness.
     
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  13. TeddyDiver
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    TeddyDiver Gollywobbler

    :D I noticed the same thing, and wanted to flag to mod but it disappeared faster than an origami is folded together..
    Back to topic.. Just a few weeks ago reread a couple of gaff books again.. wonderfull boats..
     
  14. MikeJohns
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    MikeJohns Senior Member


    Daniel
    I'll add :

    Or add the rider that the welds in those locations are critical, ie should be defect free with no stress risers, But it looks like you might have a bit of overkill in the web width anyway. Class rules are usually pretty forgiving as well.

    in the ballast area the inner end of the floor-frame weld will be in tension when the vessel is heeled. This is the fatigue load that needs consideration, either a doubler plate or a bracket might be advisable in high load areas with that 90 degree butt.

    An alternative is to cut the floor straight across the top and bevel the joint. This staggers the welds rather than having them all in line, Particularly if there's a flange (face bar). Sometimes a little more welded join obviates the need for another part (like a bracket). See the pic below.


    But steels much easier to detail than alloy or wood which would have (messy ;)) joins overlapping and tapering all over the place.
     

    Attached Files:


  15. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    Indeed this is a critical area. This was addressed in this thread here:
    http://www.boatdesign.net/forums/metal-boat-building/metal-frame-detail-28371.html

    But unfortunately the image that was in the first post is no longer there, it is ostensibly the same as that shown in Mike's above.

    Personally i don't recommend a doubler, for the reasons noted in the thread, despite the debate being about aluminium (different characteristics). In this instance, steel, because you still have a sudden change of modulus, despite the forgiving nature of steel, compared to ally. The stiffness in the side frame changes too quick over a short distance.

    Even though most Class societies say any joint greater than 150 degrees is considered continuous, thus may obviate the need for a bracket, i still recommend it, as does LR too, in these regions:
    LR guidance notes corner joints.jpg
     
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