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Post by Hardy on Feb 13, 2007 22:03:10 GMT -8
I understand what you are saying but, if the standard legal height limit is 4.15 metres, why is it that the Queen of Alberni has a clearance of 4.67m and the other four C-class vessels clearance are 10cm lower. The S-class vessels are 4.59m. Very good point. I often wonder this myself. There are time when a trucking company has to haul an overheight load. And there are options for doing this. You have to get proper permitting and licensing to be able to haul overheight loads and in addition, your pilot cars have to BE VERY ALERT and check for not only structrual clearances (bridges, overpasses etc), but also WIRES, BRANCHES, STEET LIGHTS etc. I would imagine that every now and so often that there are overheight loads that travel on board BC Ferries.
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Post by Hardy on Feb 13, 2007 22:09:49 GMT -8
If you drive a truck down an angled ramp on to the flat deck of a ferry, the actual clearance the truck needs is greater than the height of the truck. To get a sense of this, take a shoebox and put it on the counter. Measure its height from the counter surface at the center. Then tip one end up a little and remeasure the height from the counter surface at the center again. As you will see, the box is higher, therefore, more clearance is required. As Barnacle pointed out, you can cheat the geometry a little by angling the deck of the ferry a little as it puts surfaces closer to the same plane. The Alberni probably has more clearance as she was specifically designed to take truck traffic, and the greater clearance might allow her to take some over-height loads the other vessels could not accommodate. I agree wholeheartedly with your *EXCELLENT* description and the visual. I also move furniture, and even if a sofa (for example) stands up on end in a doorway, when you tip it, the measurements you need are on a diagonal, not just the height/length. This is a touch one to explain to someone who pulls out a tape measure and only measures L W H. My only point of contradiction to your post is that the clearances on BCFS ships are measured to the deckhead heights. The clearances at the loading doors of the ships are MUCH greater. At least all the current vessels anyways. So the angle of the ramp is a moot point in general. Once you are on the ferry, the deck is flat! Ramp angle affects (more often than not) the grounding out or high centering of loaded low-bed style trailers. Occasionally during high tides, some lower landing gear or belly boxes on underslung high-boys might cause issues. The actual HEIGHT of the load, to the best of my knowledge, has never caused an issue upon loading or unloading as long as the truck height was below the deckhead clearances. I look for correction if I am wrong on this. Can any of the avid ferry followers confirm that ALL current vessels in BCFS fleet have a large open overhead area (higher than the deck clearance) at the loading doors? The only overhead obstacle would be the loading ramp for the upper deck, which is usually way higher anyways.... Thanks in advance.
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