Fuel Usage VIIC/41

[Osmium Steele]

Originally Posted by TLAM Strike

Aren't the vents always open? Since fuel oil is lighter than water dosn't it just sit atop the water as the water slowly fills the tank as the oil is used up?

I know the Russian Foxtrot had open fuel tanks.

I read an excerpt of a biography of an old uboat mechanic. He said when they decided to fill the tank with water after the fuel oil was gone, they opened the vents and heard loud clanging as the boat rocked. The screw (worm gear) that opens the vents had broken, and the vent was bouncing against the pressure hull and wall of the MB/FO tank. He had to crawl in the empty tank and link the loose ends together to keep the vent closed. I assumed from his account that the tanks were kept closed until empty.

The lower vents are huge and would likely cause some turbulence in the tanks as the boat was underway. This would inevitably cause some mixing of seawater and oil, especially in a tank filled with oil.

Is the foxtrot directly vented to the sea, or is it a rudimentary seawater compensating system like modern boats' diesel tanks?

On another note, every pic I've ever seen, except one, of a boat out of the water had the vents closed. I can think of myriad reasons to keep them closed while exposed that way, but still. You'd think there'd be a few of them lying around.

I tell ya, researching a boat of which seemingly no pictures exist, and precious few of her sister ships, is a pain in the butt.