Forming round chimes on flat bottom aluminum boat

Discussion in 'Boat Design' started by Shawn_Laughlin, Aug 5, 2019.

  1. Shawn_Laughlin
    Joined: Jul 2019
    Posts: 7
    Likes: 0, Points: 1
    Location: Groves,Texas

    Shawn_Laughlin Junior Member

    Okay I’m looking into building an aluminum airboat hull, but I’m stuck at how I will form the round/radius chines. There only 3 logical ways I can think of I forming them and I actually work on one of those machines,a set of plate rolls. I roll cylinders for all size pressure vessels and can’t see how it’s done with a set of rolls being how the left and right sides mirror each other perfectly.
    2 bending in a die the same radius and
    3 bend like above in a press break but laying out line 1” apart and breaking a small amount at each segment and that will eventually make it round but not smooth and a smooth radius is what I’m going for.

    Any suggestions or anyone know how the big boys do it?
     
  2. kerosene
    Joined: Jul 2006
    Posts: 1,037
    Likes: 59, Points: 48, Legacy Rep: 358
    Location: finland

    kerosene Senior Member

    How thick material?
    If I understood right you can get the U shaped profile but bending that to a compound curve (curved both ways) is the problem.
    I don't know how boat shops do it but in body work a shrinker/stretcher is used.

    It takes small bites and greates gradual enough results.
     
  3. kerosene
    Joined: Jul 2006
    Posts: 1,037
    Likes: 59, Points: 48, Legacy Rep: 358
    Location: finland

    kerosene Senior Member

    FSM-16-sheet-metal-shrinker-stretcher-Metal-plate-shrinking-machinery-tools.jpg_640x640.jpg
     
  4. messabout
    Joined: Jan 2006
    Posts: 2,947
    Likes: 176, Points: 63, Legacy Rep: 1279
    Location: Lakeland Fl USA

    messabout Senior Member

    Why do you want round chines on your air boat? Hard chines will likely allow it to plane at a somewhat lower speed. Round or softer chines are at least a marginal advantage on boats not intended to plane, such as a canoe, rowing boat, or sailboat.
     
  5. Barry
    Joined: Mar 2002
    Posts: 1,097
    Likes: 65, Points: 48, Legacy Rep: 158

    Barry Senior Member

    If you are familiar with rolling pressure vessels, just roll a half cylinder and cut the length at say 80 degrees then 160, depending on the angle that you want the sides.
    Canadian Airboat sells plans with the rear of the hull rounded. I would expect that there is less chance of catching a chine. But there are many airboats
    that use a hard chine over the entire length.

    If you decide to roll twice the circumference that you need and cut half, you could leave the side length attached to form the side of the hull. It would save some time
    and distortion. You could also roll a tapered cone to make the front of the boat an easier fitment, ie keep the larger radius at the rear of the hull.
     
  6. Mr Efficiency
    Joined: Oct 2010
    Posts: 7,491
    Likes: 240, Points: 63, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    If the idea of the round edge is to lessen the risk of tripping, a bevel edge should work well enough. And not require compound curvature.
     
  7. Shawn_Laughlin
    Joined: Jul 2019
    Posts: 7
    Likes: 0, Points: 1
    Location: Groves,Texas

    Shawn_Laughlin Junior Member

    5173EA88-0DF6-43CA-AB8C-8F91406CB4C7.jpeg BC2E40C6-4542-41D7-A15A-E952D816C665.jpeg im Sorry I thought I posted these pictures along with my original post.
     
  8. Shawn_Laughlin
    Joined: Jul 2019
    Posts: 7
    Likes: 0, Points: 1
    Location: Groves,Texas

    Shawn_Laughlin Junior Member

    3FE32F3F-57B5-40C4-9528-CDD4D9EBFC9F.jpeg I actually had thought about rolling and then cutting but ion shooting for a one piece hull and with the plate rolls I use there is no way I would be able to make both side mirror each other. These are the rolls I use and they barely roll a tank shell bc every bearing,plain bearing to be exact, are so wore out from not doing any kind of maintenance.
     
  9. Barry
    Joined: Mar 2002
    Posts: 1,097
    Likes: 65, Points: 48, Legacy Rep: 158

    Barry Senior Member

    Nice looking work.
    I would have used an I beam for the stringers if you could have riveted them instead of inverted T bar. More strength. Or Z- bar if you needed access to the lower flat for
    riveting.
    More strength, same weight
     
  10. Shawn_Laughlin
    Joined: Jul 2019
    Posts: 7
    Likes: 0, Points: 1
    Location: Groves,Texas

    Shawn_Laughlin Junior Member

    Messabout, I’m not exactly sure why my friend wants it to have round chines? I will text him now and find out. I know it will be used in Texas and Louisiana marshes,south east Texas mostly, and I have read that round chines is better for turning in grass and well,running dry vs a hard/semi hard chine if there is such a thing as a semi.

    He just had a one built from a place down in Florida, Hamant Airboats I believe is the name or something like that , that has chines similar to a diamondback or air ranger ,if I’m not mistaken. Hes still trying to finish it up,but’s it’s going to be a beautiful boat when he’s finished.
     

  11. messabout
    Joined: Jan 2006
    Posts: 2,947
    Likes: 176, Points: 63, Legacy Rep: 1279
    Location: Lakeland Fl USA

    messabout Senior Member

    To be sure, the round chined boat will turn better in grass or mud. It will also slide in high speed turns in clean water. If you let the after 80 percent, more or less, part of the hull have those pretty round chines, then you can gently transition from round to flatter as the bow sections turn upward. You can torture the material into shape that way. In that case the foremost sections of the chines will turn spray outward, whereas the continuously rounded section will not.

    A beveled chine will do almost as well when turning in grass or mud. Bevels will also divert spray outward better than a round chine might. Bevels are easy to build but agreeably, not nearly as sophisticated in appearance.

    The picture shows a beautifully done structure both in appearance and execution. If your client insists on what he wants, then the machine that Kerosene showed, is the secondary operative. You can, with some perseverance and skill cause that round section to curve as you choose with that machine...........or even better, with an 'English Wheel". If you have race car builders near you, check out their methods for making compound curved body panels. Google English Wheel. It is what it says it is, a wheel, but not necessarily English. In the hands of a skilled operator it can make some pretty fancy metal parts.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.