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From: Nick Finnigan on 11 Jul 2010 12:44 Steve Firth wrote: > Nick Finnigan <nix(a)genie.co.uk> wrote: > >>> I would like to find >>> per vehicle ferry figures, as per passenger make little sense, as its the >>> vehicle load that determines a ferries carbon footprint. A few extra car >>> passenger - pasengers are marginal in effect. >> Cars and even HGVs are marginal in effect on ferries - they'll travel a >> yard an hour faster, but otherwise be exactly the same. > > I hope, although I'm not sure from your syntax that what you are saying > is that a laoded ferry has a slightly higher speed due to the longer LWL > than a lightly loaded ferry. I'm saying that the only difference will be a negligible change in speed. A more lightly loaded Seacat may be able to go (very slightly) faster.
From: Steve Firth on 11 Jul 2010 13:44 Nick Finnigan <nix(a)genie.co.uk> wrote: > Steve Firth wrote: > > Nick Finnigan <nix(a)genie.co.uk> wrote: > > > >>> I would like to find > >>> per vehicle ferry figures, as per passenger make little sense, as its the > >>> vehicle load that determines a ferries carbon footprint. A few extra car > >>> passenger - pasengers are marginal in effect. > >> Cars and even HGVs are marginal in effect on ferries - they'll travel a > >> yard an hour faster, but otherwise be exactly the same. > > > > I hope, although I'm not sure from your syntax that what you are saying > > is that a laoded ferry has a slightly higher speed due to the longer LWL > > than a lightly loaded ferry. > > I'm saying that the only difference will be a negligible change in speed. > A more lightly loaded Seacat may be able to go (very slightly) faster. Hmm, catamaran ferriea especially wave piercing designs tend to be trimmed to always ride at the same height, and the hull form tends to have vertical bow and stern sections so I doubt that loading makes any difference. I would expect SWATH type hulls to be unaffected by loading since the wetted surface is more or less constant. A displacement hull ferry tends to get slightly faster as it is loaded because its length at the waterline is longer than when lightly loaded.
From: Steve Firth on 11 Jul 2010 14:56 Phil W Lee <phil(a)lee-family.me.uk> wrote: > Try comparing a car ferry with a foot passenger ferry for the same > number of passengers, (or a car ferry with the vehicle deck converted > for passenger accommodation) and the vehicles make a huge difference. > Maybe 2 or 4 times the number of passengers for the same ship, and > therefore fuel burn. I can't find real world figures that support your beliefs. The worlds largest passenger ship (Oasis of the Seas) burns 200ml per passenger mile (ppm) when operated in third class mode with 6296 passengers its normal complement is 5400 passengers (two to a room). Condor Express a high speed catamaran with 776 passengers and 200 cars has the same fuel consumption, 200ml ppm. The Pentalina ferry to the Orkneys which carries 350 passengers is claimed to burn 80 ml ppm. The Pont-Aven Ro-Ro ferry with 2400 passengers and 650 cars burns 70ml ppm. Of course if your'e proposing operating a slaver-type solution with passengers chained to the car decks you might get better ppm figures, but then the ferry wouldn't attract many passengers. It's very difficult to find any passenger only ferry - the only modern one I'm aware of is Ambulu a 920 passenger only ferry. However the Indonesian government treats fuel consumption as a state secret. Probably the same fuel consumption as a Seacat since it has similar engines and speed. So around 180-200 ml ppm. Ferry operators accomodate cars because doing so makes profits. I can't see that abolishing the car decks in favour of new cattle class transport will make those ships noticeably more efficient.
From: Mrcheerful on 12 Jul 2010 04:32 Phil W Lee wrote: > Ian Jackson <ianREMOVETHISjackson(a)g3ohx.demon.co.uk> considered Thu, 8 > Jul 2010 10:02:43 +0100 the perfect time to write: > >> In message <i14384$ug5$5(a)news.eternal-september.org>, Mike P >> <privacy(a)privacy.net> writes >>> On Thu, 08 Jul 2010 09:37:49 +0100, Chelsea Tractor Man garbled: >>> >>>> On Thu, 8 Jul 2010 08:36:48 +0100, Mike P wrote: >>>> >>>>>> thats as good a proof as we need. I can move a loaded narrowboat >>>>>> on the end >>>>>> of a rope, I cannot keep that weight up in the air. >>>>> >>>>> It's the lift innit? >>>>> >>>>> I bet if you had a good strong wind providing some lift, you >>>>> could pull a glider on the end of a rope along in the air ;-) >>>> >>>> yes, a very small one. >>> >>> That would be a kite... theory is the same though, if you had a >>> 150mph gale, you could pull a glider along, or a Cessna. >>> >> Errrrr... >> No. >> An aeroplane would have to be moving forward THROUGH the air with a >> differential (airspeed) of at least 60mph. > > A bit lower than that, but in the right order of magnitude. > The sort of speed that could be provided by the good strong wind > already mentioned. > A 150mph gale would actually be a category 4 hurricane, and would pull > the wings off most Cessnas unless they were aligned exactly into the > wind. > Goundspeed is irrelevant to aerodynamic lift, and you get the first > part of your airspeed by taking of into the wind, if you have any > sense. > If the windspeed is higher than the stalling speed of the aircraft, it > will fly if suitably tethered (to give the right angle of attack for > the wings), even without starting the engine.. > I once had to add power to avoid landing in reverse! > I then had to await aid to get the aircraft to a tie down - it was > well beyond my ability to taxi without becoming airborne again in a > 55kt wind - at below walking pace. Not something you want to do > sideways :) >> If you towed an aircraft >> with a kite, you would simply have the aircraft dangling vertically >> beneath the kite (unless the kite was at a different altitude, where >> the air was moving much faster - say the jetstream?) > > I think you're confused - in the case being mentioned the aircraft IS > the kite. > A tethered kite flies because the ground is towing it through the air. > without airspeed it becomes a rather clumsy parachute. >> >>>> The power needed to push an aerofoil through the >>>> air and generate enough lift to get a narrow boat's weight off the >>>> ground is large, >>> >>> Flying narrow boats? Cool. I want one ;-) >>> > Fit four turbines and enough wing area, and you can have one :) when I was very young I was at an air display and got to sit in the cockpit of something from the raf, naturally I pushed and pulled the stick and foot controls till there was a thump and I was told to stop!!, as it was a windy day I had made the tail lift off the ground !! (presumably it was pretty closely balanced with a tail wheel)
From: Albert T Cone on 12 Jul 2010 04:33
bugbear wrote: > Albert T Cone wrote: >> boltar2003(a)boltar.world wrote: >>> Chernobyl is the worst case. Its very hard to make something that'll >>> go off >>> in a thermonuclear explosion which is why north korea took so long to >>> do it >>> and Iran still hasn't managed. If all it took was sticking a load of >>> refined >>> uranium in a large lump then Luxembourg would probably have nukes by >>> now, never mind all of the middle east. >> >> That is all it takes > > IIRC, you have to make the lump before > the lump has time to explode, which adds > a bit of difficulty. I think that normally two hemispherical shaped charges are used to compress a spherical sub-critical mass and in doing so increase the neutron flux above the criticality threshold and then...Pop! I think the difficult bit is getting your shaped charges to produce a spherical compression wave of good enough fidelity |