Model Boat Mayhem

Please login or register.

Login with username, password and session length.
Pages: [1]   Go Down

Author Topic: what are cowl vents for?  (Read 1772 times)

MikeA

  • Guest
what are cowl vents for?
« on: September 07, 2011, 08:08:42 am »

sorry for stupid question but what are they for engine in takes?
Logged

dodgy geezer

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,920
  • Location: London
Re: what are cowl vents for?
« Reply #1 on: September 07, 2011, 08:26:10 am »

Some may have provided air to the boiler room, but I suspect that the majority are just for good old fresh air.

Remember that a boat (if built correctly) is watertight, so it must be airtight as well. Under those conditions you would suffocate if you hadn't got a positive method of pulling air in and out.

Oh, and many ships would also have a large number of sweaty sailors crammed into a small space.....
Logged

Colin Bishop

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 10,946
  • Location: SW Surrey, UK
Re: what are cowl vents for?
« Reply #2 on: September 07, 2011, 08:53:08 am »

Larger vents provide air to the bigger interior compartments such as engine/boiler rooms, the smaller ones to various other internal spaces. The cowl serves as a wind collector using the wind or forward motion of the vessel to force air down below. Most cowl vents have an upper rotating section so that they can be angled to catch the wind or even turned away from the weather in bad conditions. They could also be shut off to stop water getting below.

Cowl vents were particularly important in the days before forced ventilation systems. Most larger ships are now air conditiond so you don't see them anymore.

They are a bit of a pain to make for modelmaking purposes though!

Colin
Logged

DavieTait

  • Full Mayhemer
  • *****
  • Online Online
  • Posts: 1,130
  • Location: Fraserburgh
Re: what are cowl vents for?
« Reply #3 on: September 07, 2011, 11:21:03 am »

The ones we had on the David John A169 were for cooling the engineroom , boats built later have forced air cooling so don't need them. As you say a bit of a pain to make for a model




Logged
Davie Tait,
Scotland

MikeA

  • Guest
Re: what are cowl vents for?
« Reply #4 on: September 07, 2011, 01:29:01 pm »

thanks very much very informative
Logged

davidm1945

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 350
  • Location: Worcestershire UK
Re: what are cowl vents for?
« Reply #5 on: September 07, 2011, 03:58:18 pm »

Also with blocked vents (happened on subs when the snorkel would go underwater for any length) the engine would start to feed on internal air causing pressure changes etc which was very uncomforable, should imagine the same would be for surface ships, certainely enough of a pressure change rapidly to make a mess of somebody cuaght in a door ... Would often become foggy apparently once pressure is equalised..
Logged
Never worry about theory as long as the machinery does what it's supposed to do. Robert A Heinlein.

pugwash

  • Guest
Re: what are cowl vents for?
« Reply #6 on: September 07, 2011, 04:08:01 pm »

Darren back in the day when we went to action stations the citadel was completely closed up and air recirculated
but citadel  air pressure was always kept slightly higher than atmospheric pressure. The idea being we would not
take in any nuclear fallout if there was a slight air leak.

Geoff
Logged

Bryan Young

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 6,893
  • Location: Whitley Bay
Re: what are cowl vents for?
« Reply #7 on: September 07, 2011, 06:09:04 pm »

Further to the previous answers.....in many cases an observer would look at these things and wonder why they were all apparently randomly positioned. Not so....unless it was a lazy ship. The Engineers were generally quite keen on keeping as cool as possible so some vents (remotely wound from the engine room) would be facing into the wind, and others would be turned against the wind. One sucks and the other blows. The more awkward ones were the vents serving the cargo holds. Generally manually operated, which meant that some poor sods had to get out there at all hours to "trim" them. Then either the wind would change or the ship would alter course and the whole rigmarole had to be gone through again. Not a pleasant task at 2am in the middle of a SW monsoon. But it was just another accepted piece of life at sea. BY.
Logged
Notes from a simple seaman

davidm1945

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 350
  • Location: Worcestershire UK
Re: what are cowl vents for?
« Reply #8 on: September 07, 2011, 07:38:15 pm »

Hi Geoff,

That makes sense. :-))

I was thinking more on the u-boat's Schnorchel to be honest, I read they were a constant problem, the diesels when running on the surface would take air direct through the sub.

The intake pipe did not lead directly to the diesel engines. This was to prevent unnecessary stoppages as it was common for the intake valve to open and shut as the ocean waves swept over the snorkel head, periodically submerging it. Instead, the intake pipe led to the inside of the boat, providing breathing air for the crew as well as the engines. The engines would draw air from the interior of the boat as usual, where the entire volume of the boat itself acted as an air buffer. In the event that the valve was suddenly closed, the diesels could run on for a short time, but this cannot be sustained for long. If the air supply was lost, the diesels had to be immediately disengaged to prevent the entire internal air from being extracted. Obviously, this would have catastrophic consequences for the crew. Thus, during the initial installations, the air supply was constantly monitored in order to stop the diesels whenever the valve closed, but this was later automated.

Apologies, it's not quite the topic Cowl Vents...
Logged
Never worry about theory as long as the machinery does what it's supposed to do. Robert A Heinlein.

Tug-Kenny RIP

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 7,670
  • Location: Newport. S Wales
Re: what are cowl vents for?
« Reply #9 on: September 07, 2011, 07:46:24 pm »


Very interesting answers  Thanks for that.   :-))


ken


Logged
Despite the high cost of living   .......... It remains popular
Pages: [1]   Go Up