Why is sleep comfort spoiled in an RV that is out of level?
On a tilted bed the body uses muscle all night and a low head brings on reflux; doors and drawers open by themselves and become a source of noise.
When the bed surface is tilted the body uses muscle all night to stay in place; when the head is low the blood pressure in the head region rises and reflux is brought on. Doors and drawers also open of their own accord, and even slight slopes turn into a source of noise that repeats through the night. Tilt has three separate effects on sleep comfort.
The physiological effect
Physiological: On a bed where the head end is low, the blood pressure shifts to the upper body and the stomach contents are pushed towards the oesophagus. To stop itself sliding, the body keeps the leg and trunk muscles slightly tensed all the time, and that leads to tiredness in the morning. For someone lying on their side, lateral tilt upsets the line of the shoulder and the hip; the person turns through the night looking for a position. The severity of the effect varies with the person and the direction of the tilt: at the same tilt one person may feel nothing while someone who suffers from reflux may be uncomfortable until morning. That is why the question "how many degrees of tilt is uncomfortable" has no answer that holds for everyone.
The mechanical and system effects
- Mechanical: Hinged locker doors, the toilet door and drawers open of their own accord, or fail to close, according to the direction of the tilt. Objects rolling about make a noise through the night.
- System: The same tilt applies to the fridge, the grey water drainage and the tank level sensors as well; the loss of comfort does not come on its own but along with the services.
- Perceptual: A small, steady tilt is not noticed in the first hour, but builds up through the night into restlessness.
Which axis upsets what
| Source | Symptom while sleeping | Correction |
|---|---|---|
| Front-rear tilt | Sliding towards the head or the foot end, reflux | Corrected in the front-rear stage |
| Left-right tilt | The shoulder line upset while lying on your side | Corrected in the left-right stage |
| Rocking (not tilt) | Shaking in the wind and with movement | A matter of stabilisation, not levelling |
The KTS200 measures on two axes and corrects the front-rear axis in one stage and the left-right axis in another; those two axes are exactly the ones that decide the sensation of sliding in bed. In the fine stage the system goes down to 0.025 degrees, which is a deviation too small to notice by eye. The spirit level indicator shows the two axes separately in the application.
What levelling does not solve
Levelling removes tilt, it does not remove rocking. The flexing felt while walking about inside the vehicle and the swaying that arises in the wind are a separate subject; levelling and stabilisation are not the same thing. The firmness of the mattress, the length of the bed and the ventilation are comfort variables unconnected with tilt as well. Because of body manufacturing tolerances the bed surface can stay tilted by a millimetre or so while the chassis is level; the system does not correct that, a thin wedge under the mattress does.
What to do in practice
Level as soon as you park, not just before you go to bed; every system you use during the stop draws on the same reference. If the stop is a long one, Wind Mode helps to hold the position against the shaking that arises through the night; when wind mode and fine mode are used is a separate question. If the sense of tilt has come back in the morning the ground may have settled, so repeat the operation.
Do not level by eye or with a bottle put on the table; a bottle shows only a coarse deviation, not the small, steady tilt that spoils sleep. If your bed does not run in the same direction as the axis of the vehicle, work out once which axis falls at your head; after that you will know which direction you have to correct first.
The full topic: RV automatic levelling guide