I have designed these 2 useful parts with tinkercad and they are available by download.
You can adapt them to your needs with tinkercad
Designed for 1/400 or 1/350 scale and yet printed by shapeways.
Air Vent
https://www.tinkercad.com/things/gvcJ7Sp3ruL-airvent350
Anchor Winch
https://www.tinkercad.com/things/6eJ7Cak5Lfq-winde