A question about underwater demo charges

[Marc]

Bon dia!

Here I have a question for any of you with some knowledge about explosives.

First a little background. In our last game, the mission assigned to the characters in my pre-Kalisz campaign was to investigate the suspected presence of a handful river barges and two tugs in the old fluvial port of Torun. Once the presence of the barges confirmed, the primary objective was to prevent the barges to flee when elements belonging 5th Infantry Division assaulted the city. The secondary objective was to capture as many of the crewmembers as possible, with the 5th ID HQ thinking about trying to explode the possibility to transport supplies and materials by river, from Chelmno to Włocławek.

Anyway, the solution adopted for one of the groups (I have two groups running simultaneously the same campaign with very different results) was to infiltrate by night to the surrounding high buildings near the port one day before the attack. Once satisfied with the obtained information, two tried to sabotage the barges and tugs setting little demolitions charges to cause easily repairable damages. The charges must detonate little before the first combats in the city, to prevent the crews to have enough time to repair their ships. I have not any knowledge about explosives, so, in a few words, I let them (setting the tasks needed and the difficulty levels), to put little charges underwater one in the rudder of each barge/tug. Each charge was detonated by a timer set on the hull and over the water level. All the process was done by night. So…once the game finished and without taking into account the chances to render useless a barge with this system: 1. Can the normal explosive charge listed in the demo kit be set underwater? 2. Can the connections, the wires and the blasting cap be isolated enough to allow the timer to detonate the underwater charge? Have I allowed them to make an impossible task in the real life? :o Thanks in advance.

[pmulcahy11b]

I only have very basic explosives training, but I do know that the task the player's tried can be done -- explosives can be set and detonated underwater. (Just ask the crew of the Rainbow Warrior.) I believe you need special wiring and blasting caps, but you could logically assume that these are in the basic demolitions kit in T2K. The person directing the setting of the charges also might need special training to make the explosives go off just the right way to do what the players want to do -- I know I'd have no idea of how to do it.

[jester]

Okay, the TnT and C-4 or other plastique type explosives will do nicely. So will some of the more modern dynamite type explosives <I said type not real dynamite> other things like blackpowder, guncotton and such NO! I would imagine even some old artillery shells would do the job.

Oh yeah, detcord!!!!! Lots of it!

Those fuse igniters will be a tool you would need since matches and cigarette lighters won't work in a water enviroment. Also, yes timers will work well too.

Both blasting caps will work, solutions to make sure they work is paint them with gasket sealant, that plastic stuff used to dip tool handles in to give them a rubber cover and grip, plastic and electrical tape. The more time in the water the longer the water has to work its way into your stuff. <modern time fuse does burn in water though and blasting caps also are pretty waterproof>

I again recomend DET CORD!

Okay those are the tools you can use. An electrical timer would be your really weak link.


As for the mission, you say, BARGES, what kind? How thick of steel? Any form of stearing or rudders or power or control?

A puncture above the waterline is useless, if they are that desperate they will move them out since they will be little risk of them taking on water and even with some splashing it could be managed with pumps.

Barges as I know them seldom have control or power. So those are out.

A small leak or slow leak is not bad, but again if it is realized to be a minor slow leak they can put temporary repairs to hit and get underway using pumps or bailing to keep it under control.

As I understand transporting barges the greater problem with them is their running aground, or them fouling. Those are harder tasks to remedy and take more time but often do less damage. I would have put some detcord on their mooring lines prior to the attack and when the attack took place or before the barges got underway BOOM! Blow the cables/chains anchoring them or tethering them. And then the vessels will be drifting on the current, this will hazard navigation for other vessels as well, add to the confusion and the vessels will either run into another vessel at slow speed causing minor damage, or run aground either on shore or a sandbar where recovery can be made later.

Another evil option:

rig some additional anchors or even a underwater sail or something to drag along the bottom or just act as a catch. Imagine the frusteration of the crew trying to manuver the barge and the tow vehicle when they have a couple anchors that they do not know about. But, your team knows about them and a simple 15 minute dive with a heavy pair of bolt cutters, a wrench or a large sharp knife is all it takes and of course your team knows where to look which makes it much more easier.

Another idea is to block the channel out of the port. Take one of the barges or another vessel and anchor it or even sink it at the choke point of the exit channel where it is shallow enough to not allow any vessels to exit the harbor <much like the Japanese attempted to do with Pearl Harbor with the few ships that tried to get out into the open sea> That would put a bottle in the port without doing any damage to the vessels.

The down side of disabling a vessel where it can not be sailed, or bottling the harbor as the city is about to be taken is the forces in the city destroying all equipment and assets that they can not take with them, or before they are forced to surrender.

Now for the tugs.

Det cord around the rudder or propeller shafts but can you repair them? Will you have the parts to do the job? Its simple and will do the job, but can it be repaired and will the enemy sink the vessel to deny it?

I would do the following myself:

Contaminate the fuel or damage the fuel line and fuel filter since most tugs are diesel. Clog the fuel injectors, steal the glow plugs or just foul them.

That way, the vessel can get underway with the cargo, then shortly after the vessel will DIE and be adrift and ripe pickens. At that point you just have to take the vessel and clean the glow plugs or fuel line. I personaly would do two or three things to the vessel.

Another thing would be to put a short or kill switch in the electrical system so the engine will not be able to run, or even loosen or disconect the cables to the primary controls, nothing like them making a run and then not being able to control their vessel.

The problem is not so much the fix, but finding and diagnosing the problem which will take much more time than the actual repair.



And then we also have the whole piracy thing.

Have your team members hide on the tugs. When the attack happens they either man the tugs and sail out, or wait for the crew to board and get underway. Then when that happens your team(s) emerge and sieze the tugs that are hauling the barges. You gain the vessels without damage, and they are all ready to sail. This also has the benefit of giving your team(s) a means of getting out of a town that is about to be under seige and suffering all the issues one would encounter in a town that will be filled with urban fighting.

But, the biggest issue that I see is the enemy damaging the vessels and supplies to make sure that they are not captured and usable by the aproaching forces.

[Legbreaker]

Oh yeah, detcord!!!!! Lots of it!
ABSOLUTELY!
With enough det cord, almost anything is possible. Placing a charge underthe waterline with the det cord running up to the detonator above water level is just one option, and has the benefit of keeping more of the moisture effected elements dry. You might have some issues with water penetrating the end of the det cord submerged in the water, although if the charge isn't there more than a few hours and/or measures are taken to minimise this, it shouldn't be too serious.

I certainly like most of Jesters ideas too, some of which don't even require explosives (awww, no fun).

[Targan]

I've arrived a little late in this discussion and much of what others have said is true so I won't double up. But I will say this: depending on the nature of the timer and how you want to set the explosives off you can use just about anything explosive as long as you put it in a plastic bag and seal it. The steel hull of a barge is a pretty tough item, if the explosive isn't tamped in some way and/or is not a shaped charge it will have to be a pretty significant blast to penetrate.

In my campaign the 2IC of the PC group is a USN SEAL officer, Tadeusz Jones (Polish mother/Welsh father), and he led a very exciting mission at the end of the Pirates of the Vistula/Ruins of Warsaw modules when the group wanted to steal a Shershen-class torpedo boat from the bad guys. To create a diversion and reduce the risk of being chased Jones and the group's combat engineer put together several self-forging shaped charge underwater limpet mines. Their design was quite clever I thought - for the copper self-forging plates they used the sort of copper bowls you find in many kitchens for fluffing up egg whites, and to attach the mines to the hulls of the target ships they used magnets from hi-fi speakers.

[Legbreaker]

Yup, with a bit of intelligence and access to some scrap, you can make all sorts of fun things like that.
Improvised charges along with booby traps and precision charges (cutting sheet steel for example to size with explosives) were one of my favourite things back in the day. Home made claymores, stake mines, shaped/directional charges are all easily made as long as you've got the explosives and a bit of time. Take the Gallipoli campaign in WWI for example - hand grenades or "bombs" were constructed from empty jam tins and any shrapnel to hand - cut up pieces of barbed wire, previously used shrapnel, stones, anything really.

[Targan]

Absolutely Leggy. Some C4, a fuse and detonator, a solid back plate and whatever you would like to use as shrapnel and voila! Improvised claymore mine. Not particularly hard or dangerous to put together and frighteningly effective.

Sounds like you and I have similar tastes in loud entertainment! In a suitably secure, safe and controlled environment of course.

[Legbreaker]

Anyone can create a big bang blowing the crap out of the countryside. It's the little stuff that requires true skill!

[headquarters]

you know what they say in military demolition class-"use this and that formula to calculate meticously the exact amount of TNT needed -and than double that "

[Legbreaker]

For us it was "if in doubt, add more".

[jester]

ABSOLUTELY!
With enough det cord, almost anything is possible. Placing a charge underthe waterline with the det cord running up to the detonator above water level is just one option, and has the benefit of keeping more of the moisture effected elements dry. You might have some issues with water penetrating the end of the det cord submerged in the water, although if the charge isn't there more than a few hours and/or measures are taken to minimise this, it shouldn't be too serious.

I certainly like most of Jesters ideas too, some of which don't even require explosives (awww, no fun).


Well, I do my damnedest to keep my PC's alive, and I have found the less shooting and things going bang and boom in their vicinity, and the more distance they can put between such things while they are riding, the better chances they have to accomplish this :)

Here is another idea:



Have the PCs take one of the barges and anchor it in the center channel, and just lay up with automatic weapons and sniper rifles. They engage anyone who gets close to any other vehicle. Think of the thorn in the side of the enemy that would make?

[Marc]

Thanks for the feedback! Great information for my future games.

Jester, I think that you have mentioned nearly all the options considered by the players of both groups. For more information, here are some notes that conditioned the tactics of the groups playing the adventure:

- The HQ of the 5th ID had been able to reunite a group of German and Polish citizens (NPCs) that assured to have enough experience to act as crew the embarkations of the Torun port. This people have been convinced by members of the 5th ID of the inevitable success of the current offensive. Once the NATO controls all the way from here to the Baltic coast, and depending of their collaboration with the military they could receive the embarkations in property, trading in the newly zone controlled by the NATO. The group of characters could choose to take these NPC’s with them or keep them in reserve with the main force, entering the scenario with the first troops trying to link with the characters in the port.

- Among the embarkations in the port the we have (some of the information was provided previously by Polish collaborators):

o 1 heavily armed (3x HMG’s) tug (1), property of the council of Torun and crewed by locals. The tug acts as escort of the barges and tugs near the city of Torun and tugs the non-motorized barges that are property of city. The crew sleeps in Torun.
o 1 lightly armed (3 x MG) tug (2), property of a family that lives from the commerce between Torun and Warsaw. The crew sleeps in the ship.
o 1 lightly armed (4 x MG) self-propelled barge (3). A private embarkation, hired by the different locations along the Vistula. The crew sleeps in the ship.
o 1 towed barge (not loaded)(4), property of the crew of the independent barge.
o 3 partially or fully loaded towed barges (5,6,7)property of the council of Torun and the council of Plock.

The map below is with the GM map, wiht all the "hidden" elements.
600

Both groups of players choose a similar approach, advancing concealed among the destroyed industrial zone, until they reach the damaged high buildings surrounding the port. One of the groups (B) chooses to infiltrate the crewmembers until the industrial zone and pick three of them (Polish) to act as translators. Group A considered mainly three options: Sabotage the embarkations causing them easily repairable damage just before the beginning of the main attack; Take one of the barges and block the port entrance, defending it; Take one of the barges and block the port, sinking the ship in the entrance. The two last plans were discarded, one because enemy patrols were discovered in both sides of the entrance and the group considered too difficult to defend the blocking barge and the other because the players were not sure that the engineers of the 5th ID had enough resources to refloat the sunken barge. The fear of a delay in the linking forces was an important point, too. So Group A chooses finally to set an observation post in the building, controlling the enemy patrols and guiding the movement of the two remaining members that, with the help of a little two floating device improvised to transport the demolition material, were designated to sabotage the embarkations from the water, in the middle of the night. Although two other characters with sniper rifles were covering their movements, being discovered implied nearly a certain death. The mission (with some incidences, like the loss of one of the floating devices with all the material) was a complete success.

Group B chose to try to take the independent barge and the independent tug by surprise, hijacking both ships with the help of the polish sailors that they took with them. They assaulted both ships simultaneously, entering unnoticed in the port until they reached the embarkations. The barge was successfully taken after a short firefight with one crewmember (a sentry). The rest of the crew was trapped inside the barge and they were finally convinced to surrender the ship, with the help of one of the translators. The other ship was alerted by the shots in the barge, and the family owning the embarkation tried to defend their home and the way they earn their living. One of the teenage sons became dead in the firefight. The head of the family ordered the rest to surrender the ship. By this time all the militia patrols had hear the shots. The plan of group B was to take both embarkations to the center of the port, covering the rest with automatic fire. But, for the moment, they are in pinned down in the slowly moving ships, going to the center of the port (with the non-motorized barges) and under intense automatic fire from three sides. And the bigger mistake: still one hour for the main attack. And the head of the family of the independent tug is trying to find the time to regain the control of his ship… A delicate situation… The next session could be a bloody one. :D

Mmmmm... a long post... Ahhhh...the enthusiasm of a GM :)

[jester]

Oh so simple!:


Lots of diving here!

Three or four underwater chains or cables just below the waters surface should bottle up that little bay nicely.

Also, cut the moorings of the unmanned barges and vessels. That will keep the people from the maned vessels trying to get close and control them, and prove very difficult for anyone to do anything in the area.

And last,

A boat, or even a bus or large truck, drive either to the narrowest part of the channel the bus will sink when it is run into the channel thus blocking it. A boat will have to be scuttled. The teams make it to the islet and conduct a fighting withdrawl to other vessles on the seaward side that will meet them there and take them out of the area. Like I said most of the operation will be conducted underwater so it will be out of sight and sound.

[headquarters]

Thanks for the feedback! Great information for my future games.

Jester, I think that you have mentioned nearly all the options considered by the players of both groups. For more information, here are some notes that conditioned the tactics of the groups playing the adventure:

- The HQ of the 5th ID had been able to reunite a group of German and Polish citizens (NPCs) that assured to have enough experience to act as crew the embarkations of the Torun port. This people have been convinced by members of the 5th ID of the inevitable success of the current offensive. Once the NATO controls all the way from here to the Baltic coast, and depending of their collaboration with the military they could receive the embarkations in property, trading in the newly zone controlled by the NATO. The group of characters could choose to take these NPC’s with them or keep them in reserve with the main force, entering the scenario with the first troops trying to link with the characters in the port.

- Among the embarkations in the port the we have (some of the information was provided previously by Polish collaborators):

o 1 heavily armed (3x HMG’s) tug (1), property of the council of Torun and crewed by locals. The tug acts as escort of the barges and tugs near the city of Torun and tugs the non-motorized barges that are property of city. The crew sleeps in Torun.
o 1 lightly armed (3 x MG) tug (2), property of a family that lives from the commerce between Torun and Warsaw. The crew sleeps in the ship.
o 1 lightly armed (4 x MG) self-propelled barge (3). A private embarkation, hired by the different locations along the Vistula. The crew sleeps in the ship.
o 1 towed barge (not loaded)(4), property of the crew of the independent barge.
o 3 partially or fully loaded towed barges (5,6,7)property of the council of Torun and the council of Plock.[/INDENT][/INDENT]

The map below is with the GM map, wiht all the "hidden" elements.
600

Both groups of players choose a similar approach, advancing concealed among the destroyed industrial zone, until they reach the damaged high buildings surrounding the port. One of the groups (B) chooses to infiltrate the crewmembers until the industrial zone and pick three of them (Polish) to act as translators. Group A considered mainly three options: Sabotage the embarkations causing them easily repairable damage just before the beginning of the main attack; Take one of the barges and block the port entrance, defending it; Take one of the barges and block the port, sinking the ship in the entrance. The two last plans were discarded, one because enemy patrols were discovered in both sides of the entrance and the group considered too difficult to defend the blocking barge and the other because the players were not sure that the engineers of the 5th ID had enough resources to refloat the sunken barge. The fear of a delay in the linking forces was an important point, too. So Group A chooses finally to set an observation post in the building, controlling the enemy patrols and guiding the movement of the two remaining members that, with the help of a little two floating device improvised to transport the demolition material, were designated to sabotage the embarkations from the water, in the middle of the night. Although two other characters with sniper rifles were covering their movements, being discovered implied nearly a certain death. The mission (with some incidences, like the loss of one of the floating devices with all the material) was a complete success.

Group B chose to try to take the independent barge and the independent tug by surprise, hijacking both ships with the help of the polish sailors that they took with them. They assaulted both ships simultaneously, entering unnoticed in the port until they reached the embarkations. The barge was successfully taken after a short firefight with one crewmember (a sentry). The rest of the crew was trapped inside the barge and they were finally convinced to surrender the ship, with the help of one of the translators. The other ship was alerted by the shots in the barge, and the family owning the embarkation tried to defend their home and the way they earn their living. One of the teenage sons became dead in the firefight. The head of the family ordered the rest to surrender the ship. By this time all the militia patrols had hear the shots. The plan of group B was to take both embarkations to the center of the port, covering the rest with automatic fire. But, for the moment, they are in pinned down in the slowly moving ships, going to the center of the port (with the non-motorized barges) and under intense automatic fire from three sides. And the bigger mistake: still one hour for the main attack. And the head of the family of the independent tug is trying to find the time to regain the control of his ship… A delicate situation… The next session could be a bloody one. :D

Mmmmm... a long post... Ahhhh...the enthusiasm of a GM :)

I love it .Great looking set up for a GM .Also team B has a major problem now , and I have to say that the session with the outgunned,outnumbered and out of time party are the GREATEST .get them desperate and have them bitingtheir nails while they wait for their phase..All of them leaning in to see if this or that diceroll that the other player made was a success - because by now they are in the same boat (!) and need eachother to get out alive so every good roll counts .

team a ? good luck .

here are some ideas I got for team b ..

1) vengance/hostage situation gone bad. A resourceful family of armed sailors in T2K - maybe they have a hidden knife ,a Tokarev pistol ,some hidden latch to lock a steel door/bulkhead inside the boat ..

2) sniper duel : the militia on land doesnt want to ruin the precious cargo or boats so they get their best marksmen to sneak up and start manouvering to get fire superiority -that is with so much harbour around them there are 900 000 sniper positions to choose from ,but on the barges there are only that much space to take up position .Once the snipers/marksmen get into position they all dont shoot in the same phase,but some wait and aim to get optional fire .
If they can cover the whole armada and force eveyone to take cover they can rake the windows and deck forcing everyone to keep down so that a militia bording crew can get out there and storm the barges etc ..Too dark you say ? flares from mortars ,GL or handheld can brighten up the harbour and do away with any advantages the players had there ..hehe

3) Butch Cassidy& Sundance Kid : end scene of the movie where the Bolivian federales have them surrounded in the small house and shoot a hundred thousand holes in the walls until they try to maje a break for it and find eternity .Alternatively "The wild bunch" end scene with the extremely long and very brutal slaughter scene at the end -also fit nice since the boats have some MG mounts on them .

looks like fun I have to say .

Cant wait for our next FtF after reading this .Only 2 months away:D

[Marc]

Oh so simple!:


Lots of diving here!

Three or four underwater chains or cables just below the waters surface should bottle up that little bay nicely.

Also, cut the moorings of the unmanned barges and vessels. That will keep the people from the maned vessels trying to get close and control them, and prove very difficult for anyone to do anything in the area.

And last,

A boat, or even a bus or large truck, drive either to the narrowest part of the channel the bus will sink when it is run into the channel thus blocking it. A boat will have to be scuttled. The teams make it to the islet and conduct a fighting withdrawl to other vessles on the seaward side that will meet them there and take them out of the area. Like I said most of the operation will be conducted underwater so it will be out of sight and sound.

Sadly (or happily), the mission was assigned to the group while the division was yet advancing from its starting positions. In fact, the group received their new orders shorter after the completion of another mission, the capture and holding of what remained of the Chelmno Bridge to allow one M1 AVLB to launch its bridge over the destroyed part;
So, no time for long preparations, and no chance to acquire specific material for the mission (scuba, chains…). The “sailors” hastily summoned by the HQ of the 5th ID are, for the most part, a group of opportunist. And both groups, although the information provided by the Polish informants, acquired their own information performing their own recon on the target area. Then, they decided what to do with their available equipment. No assistance from the division was possible.

Another point is the dimensions of the entrance. Although it seems narrow, the “neck” of the corridor is nearly 50m wide and I considered that the depth was enough to let a comfortable margin for a loaded barge.

[Marc]

1) vengance/hostage situation gone bad. A resourceful family of armed sailors in T2K - maybe they have a hidden knife ,a Tokarev pistol ,some hidden latch to lock a steel door/bulkhead inside the boat ..
That is happening right now!!! A hidden pistol on the command bridge of the tug...the head of the family is "helping" to maneuver the ship. He is with one of the Polish "sailors" and with one of the characters, but all three are pinned down by the small arms fire that is sweepping the control room. Everything is possible in the first turns of our following game.


Alternatively "The wild bunch" end scene with the extremely long and very brutal slaughter scene at the end -also fit nice since the boats have some MG mounts on them.

For the moment, I consider it the most probably end...

[rcaf_777]

Ok if case anyone is intrested I posed this question to combat diver I work with and it will work

If you need to know about demo ask the engineers