Anyone fitted a flettner style rotating vent for vans to boat cabin?

[Keshvane]

Looking at cabin ventilation on a merry fisher 805 on a swing mooring. Wondering whether anyone has tried the flettner type of rotating vents designed for vans and campers? Thinking it might a.so keep gulls away. Thoughts welcome.

 

[Poignard]

I haven't tried them but as they have a stainless steel spindle they should be fine. Here's some information:

http://www.flettner.co.uk/applications/boat-ventilation/