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Lutz

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Everything posted by Lutz

  1. Judging by the weather forecasts that I’ve seen for France lately I can‘t understand why anyone would want to use an airconditioning unit. We’re in southern Spain at the moment and I would say the temperature here is just comfortable, about 25 to 27 degrees during the day under clear blue skies and nothing but sun, and under 20 at night. I wouldn’t want it any cooler.
  2. Two German states, Baden-Württemberg and Bavaria, have two weeks of half-term school holidays at the moment.
  3. I recall reading the results of a test published in a magazine some time ago that a caravan becomes more susceptible to instability once the difference in wheel load left to right exceeds about 75kg.
  4. The aerodynamic centre of pressure will not move appreciably and in any case it would only affect stability in crosswinds. Anyway, laminar airflow is less of an issue because it’s more or less a steady state. Turbulence and sudden gusts are much more likely to be a potential problem.
  5. Without a plausible reason supporting the anecdotal evidence one can only take it with a pinch of salt. There are so many variables involved that it is almost impossible to change just one without affecting anything else.
  6. 15cm height difference at the hitch (and that’s quite a lot) on a caravan of 7m overall length (fairly typical for a family size caravan) results in only about 1 degree change in attitude, certainly nothing like 3 degrees. Secondly, aerodynamic drag is proportional to the square of the speed, so a Boeing taking off at 184mph will experience more than 9 times the drag (and consequently lift) as when it is taxiing at the same speed as a towed caravan. In practice the difference will be a lot greater because the flaps that increase lift will normally be retracted when taxiing. Thirdly, simply by virtue of its geometry, a caravan won’t behave like an aerofoil section, so you are really comparing apples with pears.
  7. Lutz

    Van levelling

    I don’t use anything. If it looks about level and the drawers or doors don’t open or close of their own accord, that’s good enough for me.
  8. Far too much emphasis is being placed on airflow under the caravan when it should be obvious that frontal area of a big box like a caravan is going to influence the result a lot more. This is also borne out by the caravan’s drag coefficient of around 0.8 compared with that of a car (about 0.27) and even more so for an aerofoil section (about 0.05). Consequently, a towcar with a low roof line compared with that of, say a 4x4 which sits higher, is going to make a much bigger difference than the relatively small changes in attitude of the caravan.
  9. Kerbweight is not documented anywhere so I don’t know where the sources get their information from.
  10. There is a tighter speed limit on caravans without dampers in Germany than if they are fitted so they must have an effect.
  11. I agree, but depending on the lateral compliance and spring rate of the X-Trail’s rear suspension relative to that of the Mondeo, they may have more of an effect in combination with the X-Trail than with the Mondeo.
  12. That’s a bit far fetched. As if an inch or two up or down is going to make a noticeable difference. There is no laminar airflow under the caravan - far too much uncontrollable turbulence. What goes on in the exposed frontal area of the caravan above the roof of the towcar is much more important. I’m surprised no-one has mentioned lateral compliance of the X-Trail’s rear suspension or the aspect ratio of its tyres. To me that would be the first thing that comes to mind after the obvious. Possible lack of dampers on the caravan are another item.
  13. Yes indeed. If noseweight is too low it can even turn negative at higher speeds.
  14. If you say it makes a difference then you will surely be able to explain why. I have not yet come across an explanation that stands up to reason.
  15. Without any opportunity to carry out a first hand investigation it’s almost impossible to give the OP a categorical answer because there are so many possible variables. One can only suggest measures that have helped others in the past, but they may not necessarily apply in his case. We don’t even know whether his caravan is fitted with dampers, for example.
  16. Water, by virtue of its much higher density than air, has a much greater effect already at lower speeds, so you can’t compare a boat with a caravan. Besides, because of turbulence caused by the towcar ahead and the complex configuration of the caravan chassis, airflow under the caravan is anything but laminar. Because the exposed frontal area of the caravan is above roof level of the towcar the same will happen (decreasing noseweight) if the caravan is nose down.
  17. When I was a boy I once inserted a couple of meat skewers in a very old looking socket on the terrace at my grandparents’ place just to see whether it was still connected to the power supply. I shot from one side of the terrace to the other 🙂
  18. That’s right, David. One shouldn’t jump to conclusions that international standards and agreements are always an EU thing.
  19. A big box like a caravan doesn’t behave like an aerofoil section so one can’t draw any conclusions from that. Besides, caravans are normally towed at speeds well below those of an aircraft where aerodynamics play an important part. Noseweight is reduced at speed not because of airflow underneath, but because of the large exposed frontal area above the roof of the towcar.
  20. Why? How can the attitude of the caravan affect stability? Please explain the reasoning behind your statement. Of course, if you set the noseweight when the caravan is level and then raise the hitch to a nose up position it can affect stability, but then the noseweight wasn’t set correctly in the first place.
  21. So long as the noseweight is set correctly nose up or down is irrelevant.
  22. I can’t quite see why it should be criminal or why anyone should get killed unless they do something silly like removing their own plug and the sticking bare wires in the socket - but I’ve even seen that done. It would seem fairly obvious to me that if the plug doesn’t fit you need an appropriate adapter.
  23. BS1363 is a UK standard just like each and every country has its own standards. To commonise throughout the EU would involve enormous costs for relatively little benefit. It’s a lot cheaper to make do with adapters should the need arise. Having said that, for low power dual insulated equipment that doesn’t need an earth, the flat two pin Euro plug works almost everywhere and the two pin plug with earth, as pictured in Borussia’s photo is becoming increasingly common in Southern Europe, too. It has long been the standard in Northern Europe.
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