Gym Sulkinson Fork wrote:
On Thu, 25 Oct 2018 17:11:41 +0100, Nightjar
wrote:
On 25/10/2018 16:07, Gym Sulkinson Fork wrote:
On Thu, 25 Oct 2018 16:03:22 +0100, wrote:

On Thu, 25 Oct 2018 15:47:48 +0100, "Gym Sulkinson Fork"
wrote:

Why are these fitted instead of just a stationary vent like you
see on caravans?

http://www.flettner.co.uk/van-roof-vents/

I don't see the point in using the wind to power a vent, when the
air was already moving. Surely that's like fitting a generator
to your bicycle to power a motor to make you go faster?

They are just more efficient than a simple hole in the roof with
sufficient cover to keep the rain out. If there was a better mouse
trap, somebody would have made one in the last 200 years.

Yes I know they claim to be more efficient, but why? How can you
take power from the wind to then give it back to make it faster? Isn't
that breaking the laws of physics?

They are a Savonius rotor, which uses the wind to rotate a shaft.
There is a fan attached to the shaft, which, unlike a simple hole,
actively extracts air from the vehicle. They are also widely used on
boats, to keep them ventilated while sitting at their moorings.

I'd just open the window (with a rain guard of course).

Another Hucker troll.