Ramp Maximum Inclination

Discussion in 'Boat Design' started by majaregielou, Mar 25, 2013.

  1. majaregielou
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    majaregielou Junior Member

    what is the maximum inclination of the ramps as guided by IACS society.
    Thanks and kind regards.
     
  2. gonzo
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    gonzo Senior Member

    Ramps for what?
     
  3. majaregielou
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    majaregielou Junior Member

    for vessels.. the typical maximum inclination of ramps in vessels.
     
  4. michael pierzga
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    michael pierzga Senior Member

    Im sure that the angle is recorded. If the angle is too sharp cars and trucks will bottom out on the ramp to ship and ramp to dock interface. .

    I see it many times at the local ROW ROW terminal. When the new port is busy modern ships are forced to use the Old port. The old port is low so when the Row Row lowers its stern door the angle is to sharp. A separate temporary platform Wedge must then be forklifted in reduce the angle so the cars and trucks can depart.
     
  5. majaregielou
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    majaregielou Junior Member

    but what is the usual angle of inclination in vessel's ramp sir..
     
  6. TANSL
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    TANSL Senior Member

    The slope of the ramp may depend mainly on the size of your ship and the number of vehicles that you want to transport.
    I do not know if the Classification Societies, or Drivers' Unions, place limits on the slope of a ramp. What I do know is that a normal land vehicle can attack 5% or 7% ramps without difficulty. I have worked for boats, with ramps slope around 5%.
     
  7. gonzo
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    gonzo Senior Member

    Is this a ramp for vehicles, and if so what kind? Military vehicles have a larger maximum incline. This link has a fair amount of information on grades and curves. The incline of the ramp alone is not the only limiting factor. The angle of the ramp and the dock is also a limiting factor.
    http://www.fao.org/docrep/006/T0099E/T0099e03.htm
     
  8. Petros
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    Petros Senior Member

    the thing that limits ramps is entrance/exit angles where you might drag the frame or bumpers. This can be accommodated with multi-stagged ramps where the differenace between adjoining angles is keep small.

    for conventional driveways and road ways, 20 percent is the maximum practical limit for short distances. Most highway standards for local roads is 16 percent, and for major highways it is more like 7 percent (but I think that is so heavy transports can keep their speed up when going up hill, not applicable for short boarding ramps).

    20 percent is on the steep side but most vehicles can climb it without issues, even heavy loaded trucks, the only consideration is the entrance angle and this is too steep to start and stop for most vehicles without spinning the wheels. If they do have to stop, it means backing back down to the bottom and climbing it at a constant speed. A 15 or 16 percent grade is the maximum practical grade for ramp for motor vehicles if there is the possibility of having traffic stop on it and having to get moving again.

    It might be interesting to note that in the USA, the maximum wheel chair ramp is about 8 percent (12:1), with short segments being allowed to be up to 10 percent (10:1). So if this ramp is also expected to be used by pedestrians including those in wheel chairs, than 10 percent is the maximum you will want to consider.
     
  9. TANSL
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    TANSL Senior Member

    Petros, surely you're right but I find that more than 15% is too much. I'm talking about civilian vehicle transport.
    Another issue: the access ramps to the boat from the dock are usually milder than the ramps between decks of the ship, for obvious reasons of space. In a port, if no space, you can always create it.
     
  10. gonzo
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    gonzo Senior Member

    The maximum allowed on highways in North America is 10%. However, that is for long stretches. Many access and utility ramps are much steeper. I think that ground clearance may be a more critical thing to look at.
    TANSL: what do you mean by creating space? Could you give an example?
     
  11. PAR
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    PAR Yacht Designer/Builder

    These building regulations vary from place to place. The federal park system uses 6 degrees as their ramp inclination and having launched large (long) boats from them, it's a sweet, shallow angle to work with, though does require a longer concrete pad to be poured. When you get into state, county and municipal ramps, this is where you'll find huge differences. I've seen them as much as double the federal requirements, which decreases the pad length, but also can make hauling a boat out very difficult once slime gets all over it. 6 to 8 degrees are ideal, with anything over it progressively being more difficult to use, but cheaper to install.
     
  12. Petros
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    Petros Senior Member

    six degrees is a 10.5 percent grade, do you mean degrees or grade?

    Local county road standards for arterial roads is 15 percent max, private driveways can be up to 20 percent grade. Highways would be less than that. I think the steepest federal highway I have seen is 8 percent, where the interstate passes through the Colorado Rockies known as the Eisenhower tunnel.
     
  13. PAR
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    PAR Yacht Designer/Builder

    I mean degrees. 10% to 12% grade is about what you want, steeper again is cheaper to build, but harder to launch. I've launched my 28', 30" draft skiff from 20% grade ramps, but had trouble clearing them without dragging the jack or getting enough traction to haul back up the ramp.
     
  14. TANSL
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    TANSL Senior Member

    I think the question of majaregielou refers to the internal ramps, and perhaps also to boarding ramps, on boats ro-pax or ferry type. Am I wrong?
     

  15. daiquiri
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    daiquiri Engineering and Design

    He said VESSEL's ramp. which I also intend as boarding ramp.

    If it is for cars, then it has to allow modern low-clearance and long-overhang models to engage the ramp. For example, in the attached drawings (angular quotes added by myself, hence approximate) of two Audi models you can see that the max angle should not exceed around 10°. The drawing actually shows 12.5° as minimum angle, but that should be considered as the ideal value. In reality, the inflation pressure of the tires can vary by 10-15% (depending on tire temperature, maintenance etc.) and car can be loaded with people and baggage, which will diminish the ground clearance and angles.

    Cheers
     

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