"Effects on speed from Funnel hits." Topic

Hi all,

For years we have played rules that deduct speed from ships following a funnel hit, but whilst reading and re reading (after decades in some cases) a lot of sources for our Jutland project, I am struggling to find mention of it in texts.

Fundamentally shoving a reet big hole in your exhaust is not going to improve engine performance but what effect did it have. Do other rules factor this in ?

Interested to hear your thoughts.

Regards Ken
yarkshiregamer.blogspot.co.uk

My understanding of how it works is: The exhaust in a coal/oil fired ship actually creates a draft that pulls fresh air into the burners and works sort of like a carburetor for lack of a better description. If you start puncturing the funnel, it reduces the draft that is created, thus reducing the air getting in and making your engines less efficient.

I'm sure someone will come along with a more technical explanation, but in a nutshell, that's what I've been able to glean from my readings.

Related to that – how does the air get *too* the coal/oil fire? Intakes, but where are they located? How are they protected?

Any naval architects out there want to weigh in?

Do a google search on <natural draft> versus <forced draft> marine boilers.

The power output of a boiler was defined by two factors: fuel supply and availability of the amount of oxygen necessary to fully burn it within any given unit of time.

Boilers operating under natural draft basically draw incoming air at 14.7 pounds per square inch, i.e. – one atmosphere of pressure or so. The very tall and slander funnels seen on ships of the late 19th century are usually evidence of boilers operating under natural draft; they were designed to optimize the draft of exhaust gases, which in turn gave an assist to incoming air. Any damage to a funnel which interfered with its draw (think of a fireplace and chimney) would reduce the output of the boiler.

Boilers operating under forced draft appeared around the last decade of the 19th century or so. They operated at a much higher pressure of intake air (perhaps by as much as an order of magnitude). This was enabled by sealing the boilers or boiler rooms from the outside atmosphere and artificially increasing the atmospheric pressure of the intake air going to the boilers by means of large and powerful intake fans. The greatly increased amount of intake air (oxygen) available to a boiler under forced draft meant that much more fuel could be burnt in a unit of time, which meant higher temperatures, which meant greater steam pressure, which mean more power to the engines.

Damage to funnels or stacks produced little effect upon output of a forced draft boiler; their risk factor lay in their intake fans, but these were below decks and thus better protected.

Hope this helps

B

Cheers guys, I am quite happy with the fundamentals of the effects, but how do your rules reflect this if at all ?

The Funnel(s) on most ships is fairly prominent so I would expect a fair number of hits on it during a battle based on surface area alone. I'm not coming across much evidence of speed loss.

Regards Ken
yarkshiregamer.blogspot.co.uk

but how do your rules reflect this if at all ?

Most of the of pre-dreadnought and forward rules that I'm familiar with don't for the reasons well stated by Blutarski. Given the universal use of forced draft, funnel hits would not have any appreciable impact on a ship's speed.

One effect of a funnel hit that has not been mentioned is blow back. An explosion against a funnel will cause a pressure wave to travel down the funnel and the uptakes to the boiler. This can have several effects:

a) Extinguish, or partially extinguish, the fires.
b) Damage to the boiler resulting in a loss of steam pressure and thus speed.
c) Cause severe burns to boiler room crew.

During the Battle of the Barents Sea HMS Onslow was hit on the funnel. This damaged the casing of No 1 boiler and lifted the safety valves. This also caused a fire in the boiler room.

I would make a funnel hit cause a temporary loss of speed, if only because pressure would be reduced while the boiler room crew check for damage.

What would happen if the entire funnel were knocked down or destroyed? Would the boiler room need to shut down?

Wolfhag

My first ship was a DDG built in 1960 and the uptakes for the boilers were in the stacks. If you hit them you'd possibly affect airflow into the boiler. Fletchers and Sumners had uptakes in the stacks too. Not sure about other nations' DD's.

Here are some things I've come across that might be new info:

Uptake Armor
This was designed to keep "down the stack" deck hits from happening to the rather large holes in the deck for the uptakes. The armor stopped while still inside the hull, so it the funnel was holed above it or a hole punched into that heavy sloped armor, even if the projectile was stopped, the funnels inside the armor might be punctured by chunks of armor and/or the nose pieces of the projectile itself. Thus, the area around the funnels could still be flooded with super-hot, poisonous smoke during a gun battle with both sides having battleship-size guns. The more upper hull damage, the more the smoke would spread (it is under a lot of pressure and the wind kicked up by the ship as it moves would cause the smoke to move around a lot through any holes in the side, deck, and transverse bulkheads). Even though the bridge, control tops, and main armament are rather far away from the funnels, the amidships secondary mounts could be rendered out of action by this smoke if fragment damage allowed it to spread.

One of the US Navy TERRIER missile cruisers, then Destroyer Leaders -- I think DLG-18 USS WORDEN -- took a US "friendly fire" hit off of Vietnam circa 1970 when a US Air Force fighter mistook its AN/SPS-48 3D radar signal for a North Vietnamese radar and fired an anti-radiation SHRIKE missile at the ship (this is a rather small missile much like a SPARROW air-to-air missile, but with an explosive warhead that was jacketed with tungsten-carbide slugs to penetrate packed earth, rock, concrete, thin steel, and other light protection around a radar site). It worked perfectly (unfortunately for the ship) and exploded immediately above the huge 48 radar antenna just behind and above the bridge. The explosion knocked out every radar and electronic antenna in the fore part of the ship -- except for the AN/SPS-10 surface search and navigation radar (tough nuts, those!) -- and the damage reached most of the way to the aft superstructure. Very little damage extended below the weather deck level, though. Only a couple of people were killed, luckily, but the hit also riddled the funnel, which supported the 48 radar and other things and was called a "mack" (mast-stack). The hot engine gasses spewed out into the ship's superstructure, which was of course also riddled, and it had to be abandoned, requiring the ship shut down its steam engines and be towed back to port, even though the engines and boilers themselves were still in perfect condition and the hull was not breached anywhere below the waterline. Thus, the ship's propulsion system was completely put out of action by indirect damage. This is called a "mission kill" where the target (WORDEN, here) is out of action as far as its assigned mission is concerned (and for some time thereafter during extensive repairs).

Shrike warhead info:
Diameter 8 inches (203 mm)
Warhead

67.5 kg (149 lb) MK 5 MOD 1 (or MK 86 MOD 1) blast-fragmentation,or 66.6 kg (147 lb) WAU-9/B blast-fragmentation

Looks as if it would be the equivalent of an 8" HE round.

Wolfhag

What would happen if the entire funnel were knocked down or destroyed? Would the boiler room need to shut down?

In a heavy sea your boilers may be flooded with rather unpleasant results.

Wolfhag – Did you receive my email from today + 3 attachments?

B

Blutarski,
Yes, received and downloaded all three. Reading them now. Somehow I missed these. Thanks, I'll be in touch.

Did you fix your Windows 10 ransomware problem??

Wolfhag

Hi Wolfhag – Yes, I was able to recover my Windows 7 set-up. But I can promise you this: My next PC will NOT be a Microsoft Windows box. I am all done being jerked around by these corporate flim-flam artists.

The arrogance of Gates and his crew is just breathtaking.

B