Immovable rod on a ship or air ship?

[MarkVIIIMarc]

You'll probably see where I am going with this quickly......So what happens if you click an immovable rod while on a ship or air ship?

Does it lock in some kind of geosynchronous orbit to the planet's core or move with the vehicle?

If it locks in fixed / stationary orbit to the core then the movement of the ship should cause it to contact the back wall or engine or rudder at whatever speed the ship is moving.

So if the rod takes 8,000 lbs of weight or force to deactivate it then it should break through a modern 4x4 of any length.

What are the most vital components of a D&D era ship of air ship I can expect to have this rod tear through?

[JellyPooga]

Given that a wooden sailing ship would weigh somewhere in the range of 200,000lb at the low end, even the smallest airships would plink an immovable rod into off-mode as soon as it came into contact with the ship. So no, anything critical to the function of the ship that's secured would be just fine. I might let the rod destroy some cargo or light fixtures, maybe some superficial damage to fixed furniture, but I certainly wouldn't allow it to be ripping holes in the superstructure or collapsing bulkheads or anything.

There are, of course, other uses for reducing the forward momentum of a person or object to zero whilst aboard a fast moving vessel...

[Mastikator]

D&D operates on an absolute and fixed coordinate system. Relativity does not apply, it's not even Newtonian physics. It's closer to Aristotelian physics (fire is an element? vision is "invisible fire" based? space is magic realm of gods? astral plane is platonic ideal?)

I'd say it punches right through the hull as the ship moves.

[Kane0]

What are the most vital components of a D&D era ship of air ship I can expect to have this rod tear through?

Rudders and masts i imagine would be a pretty big deal, or any part of the hull keeping the water out/gas in if you can make the hole big enough.
Other then that cargo holds or the captain's cabin? Not so much to damage the ship but to wreck the most valuable things within it

[JellyPooga]

So if the rod takes 8,000 lbs of weight or force to deactivate it then it should break through a modern 4x4 of any length.

I suppose it does depend on whether you're treating the ship as a whole, or its constituent parts. Does it belong to Theseus, by any chance?

[Unoriginal]

Does it lock in some kind of geosynchronous orbit to the planet's core or move with the vehicle?

Depends on what you lock it to/with.

Same way as if you cast a Wall spell in the space just ahead of a ship, it would be locked on the spot and the ship will hit the Wall, but if you cast it on the deck of the ship the Wall would move with it.

[Oramac]

My kids group did exactly this around 6 or 8 months ago. They were on a ship traversing a large magical lake and through various circumstances they activated their Immovable Rod while inside one of the passenger compartments of the ship.

I ruled that the rod stayed in place and began to crack the walls of the compartment, but not any major superstructure of the ship. Basically any non-load-bearing wall would be broken. Anything load-bearing would deactivate the Rod.

[Darth Credence]

This is, to me, a DM call that all that matters is consistency. I find it easiest to make it such that it remains stationary to whatever frame of reference the button pusher was in when they pushed the button. If you're on a ship and push the button, the rod remains stationary in relation to the ship. The main reason I go with this is that if you say that it remains in an absolute position, you need to either change the movement of planets to make the planet everyone is on the center of the universe with no rotation, or you need to have the rod move out of reach pretty much instantly any time it's used. If you even allow the planet to rotate at Earth speeds, then the rod would be about 1500 feet away one second after pushing the button if it is an absolute compared to the universe. This probably doesn't matter in most campaigns, but I use Spelljammer, so it matters in mine. Even if I fixed the main planet, that would just mean that when they travel to the moons, I would have to account for that movement.

For what it does to the wall of the ship, there is no way I would get into the weeds on what materials are strong enough to stand up to the amount of force it takes to disengage the rod. If I rule that it will punch through a wooden ship, what does that mean for an ironclad ship? How about a flying castle made of stone? I'm not getting into strength of materials for my game. So it either stops something, or it gets turned off, based on the force it applies - I am willing to make some basic force calculations to see which of those two happens, because the overwhelming majority of the time it is so far on one side or the other that it's an easy call. (FTR, an airship or large sailing ship moving at a cruising speed is easily enough to turn the rod off.)

I realize that the ruling on this is such that some players would dislike that we have effectively disallowed some things like destroying a ship with it. But I stand by it as what is best for the game. There are a ton of things that the rod can be used for, that I have bent the rules a bit to allow to happen, like one of my players uses one to do a salmon ladder to climb things. It's useful as a fulcrum, an anchor for block and tackle, door bar, to prevent an object from being stolen, mountain climbing aid, clothes hanger, perch, and so on.

[Biffoniacus_Furiou]

I'd agree that it's a DM call. If it were me, if at least 7,999 lbs of horizontal force could break through the ship, then the immobile rod would do so.

However, the engine or mast is built and attached strongly enough to move the ship's full weight, and would be able to withstand that. Likewise, crucial support structures inside the ship would be built to support its weight and just end up shoving the rod aside.

[Darth Credence]

I'd agree that it's a DM call. If it were me, if at least 7,999 lbs of horizontal force could break through the ship, then the immobile rod would do so.

However, the engine or mast is built and attached strongly enough to move the ship's full weight, and would be able to withstand that. Likewise, crucial support structures inside the ship would be built to support its weight and just end up shoving the rod aside.

I can see why one would reason that if 7,999 lbs of force would break through it breaks through, but I think that causes more problems than it's worth. Let's take a sailing ship approaching an immovable rod that has been locked in place.

You have your ship there, and someone puts the immovable rod in front of it, expecting it to hit the ship and punch through. Now, when the ship hits it, where does it hit? Does it hit the figurehead? If it does, does it break through? That may be a quite thick piece of wood, which would take a lot more force than that to break through, or maybe the carving has made it weak and it goes through easily. I have no idea which. Does the ship have a ram? Would the rod hit the ram? Which would win? If no ram, does it hit the beak? Which wins? Does it hit a thin part of the ship? How do we know? Is it an attack roll by the person planting it? A saving throw for the person piloting the ship? Do we need to figure out how fast the ship is going to get how fast it can turn to see how likely it is to maneuver out of the way of this thing? If they turn the ship enough, what does that do to the applied force? If it doesn't hit head-on, do we end up calculating whether it takes more force to push the ship to the side or for the rod to punch through? Do we have to figure out the angle the ship contacts the rod at to know that? How confident am I that 7,999 pounds will actually break through? Does the DM need to define the material ships are made of in advance and know the strength of the materials in tension and compression? Does it matter where along the length of the board that it hits? What is the actual size of the rod? It is described as flat with a button on one end, and the picture has a couple of carvings of armored horses on the end, but no note on dimensions. That will definitely change things - if it comes to a point on the end it will go through a lot more things than if it is the size of a 2x4. Is that a constant among rods, or is that something that needs to be thought through for every rod? Can you attach a sharp point to the rod to make up for it not being sharp?

I'm sure more things could or should be considered when asking the question "Does this exert 8000+ pounds of force when it encounters the rod?", but those are more than enough for me to not want to ask the question.

[NecessaryWeevil]

I'm seeing a lot of references to planets and orbits in this thread.
Do most D&D cosmologies really assume spherical planets in heliocentric orbits? I'd have thought not.

[MarkVIIIMarc]

I'm seeing a lot of references to planets and orbits in this thread.
Do most D&D cosmologies really assume spherical planets in heliocentric orbits? I'd have thought not.

In the material plane I always have imagined a mechanical universe similar to our own.

For the other planes all bets are off so to say.

[Unoriginal]

Do most D&D cosmologies really assume spherical planets in heliocentric orbits?

They do.

5e cosmology in particular assumes that most inhabitable-by-humanoids worlds in the Material Plane are spherical and orbit a sun.

However, said "solar systems" are just bubbles floating in the Astral Plane, aka the Plane of Thoughts.

In other words, if you take your spaceship and go far enough from your homeworld, you'll enter the collective uncounscious of all sapient beings.

[Lord Vukodlak]

I think you all over estimate the strength of 8,000lbs of force, that's about twice the energy you need to hit a Homerun in major league Baseball, and that's bare minimum. baseballs that are knocked completely out of the park are hit with just over 8,000 pounds of force. So I don't think a immovable rod is actually strong enough that it rip through a ship. More likely it'd embed it self into a wall then deactivate. I couldn't find how much force a cannonball would hit a ship with, but I'm guessing its way more then 8,000 pounds of force.
In any event, the rod doesn't withstand 8,000 pounds of force it can hold 8,000 pounds of weight and can be moved by a creature with a DC 30 strength check. Trying to figure out the newtons of force is going to be headache. So I'd run it as, if the thing weights less then 8,000 pounds hits the rod it stops. If it weighs more the rod fails. The ship weighs more then 8,000 pounds so a rod isn't going to stop it.

[Chronos]

A while back I was DMing and wanted to add a few extra magic items to a published adventure, but it made sense for the reward at one point to be a book, and just another spellbook was kind of boring, so I decided that it was a book of schematics for making an immovable rod. And any magic item schematic should have at least one component that's rare or hard to get, so it can't be mass produced, and I decided that the rare component of an immovable rod was a piece of stone that had been at the uppermost pinnacle of a mountain for at least 50 years.

I wasn't even thinking about this at the time, but in retrospect, this neatly solves the question of "immovable relative to what?": The specific immovable rod that my group has, is immovable relative to Mount Waterdeep.

[MarkVIIIMarc]

I think you all over estimate the strength of 8,000lbs of force, that's about twice the energy you need to hit a Homerun in major league Baseball, and that's bare minimum. baseballs that are knocked completely out of the park are hit with just over 8,000 pounds of force. So I don't think a immovable rod is actually strong enough that it rip through a ship. More likely it'd embed it self into a wall then deactivate. I couldn't find how much force a cannonball would hit a ship with, but I'm guessing its way more then 8,000 pounds of force.
In any event, the rod doesn't withstand 8,000 pounds of force it can hold 8,000 pounds of weight and can be moved by a creature with a DC 30 strength check. Trying to figure out the newtons of force is going to be headache. So I'd run it as, if the thing weights less then 8,000 pounds hits the rod it stops. If it weighs more the rod fails. The ship weighs more then 8,000 pounds so a rod isn't going to stop it.

Very interesting!

I think a lot of it depends on piercing vs stopping. The ship is just plum capable of dragging an immovable rod.

BUT

With the rod's pointy end first hitting the an interior wall it is the rod vs the wall. Can that part of the wall withstand 8,000 lbs per contact area of force?

8,000 lbs can't stop my car if it is going 60mps. It bet CAN puncture my grill and radiator possibly cracking itself and whatevr part of my block or front end accessory it hits?

[Kane0]

Having consulted a fellow DM, he had a novel response: when you activate the Rod it becomes immovable in relation to whatever you place it in contact with. So if you are placing it against the ship it 'sticks' to it, but if you are just holding it in the air it defaults to the center of the planet/plane and 'moves'

[Damon_Tor]

By RAW:

We use the Ghost of Saltmarsh crashing rules to determine what happens when a vehicle strikes an object. Nothing about the immovable rod implies that it's invulnerable or even resistant to damage, and we use the rules in the DMG to determine how many hit points the rod has.

We can look this up if you like, but I'm pretty sure that the rod will be destroyed by the impact while the ship's hull will be unharmed (as an impact with a tiny object won't do it enough damage to overcome its damage threshold.)

[Darth Credence]

Having consulted a fellow DM, he had a novel response: when you activate the Rod it becomes immovable in relation to whatever you place it in contact with. So if you are placing it against the ship it 'sticks' to it, but if you are just holding it in the air it defaults to the center of the planet/plane and 'moves'

I see a fundamental problem with this - it is always in contact with the person who sets it.

[MarkVIIIMarc]

By RAW:

We use the Ghost of Saltmarsh crashing rules to determine what happens when a vehicle strikes an object. Nothing about the immovable rod implies that it's invulnerable or even resistant to damage, and we use the rules in the DMG to determine how many hit points the rod has.

We can look this up if you like, but I'm pretty sure that the rod will be destroyed by the impact while the ship's hull will be unharmed (as an impact with a tiny object won't do it enough damage to overcome its damage threshold.)

Haha, I did not think about the Rod being damaged but I better be careful.

For game night I will ready a statement that my rod is contacting whatever vital part of the ship is handy. If it goes farther my point will be the rules of smashing down a door in a ship applies. You need to destroy the door not the whole ship. Micro over macro.

[Vogie]

You can also use the concept as a way to mimic how things work in real life by incorporating it into the designs. A ship might have a bunch of immovable rods that can be activated simultaneously to bring it to a halt.

There's a scene in the first season of Black Sails where the pirates drag their ship up on the beach and tie it to trees so they can do repairs... then some of the ropes break and it tries to right itself, while the crew is running around to help the scene. There's someone trapped underneath the hull, they've got to release the ship before the remaining ties break the mast and other important pieces of the ship. It's very dramatic, as we hear the creaking and groaning of the ship as they are doing it.

If the ship or airship has these immovable rods incorporated in them for one reason or another (maybe as an anchor analog, maybe there's a strong arm they can extend, then activate the rod as a way to turn on a dime), then the hardpoints at which the rods are going to be incorporated would be able to withstand a bunch of the force. If a handful of the rods are turned on independent of the others, you could have those moments where the craft lurches to a stop, and you hear that crunching and creaking as the ship is fighting the immovable rods.

[Segev]

My rule of thumb is to ask what the battle map looks like.

Is the ship moving relative to the map, or is the map the ship?

This can lead to corner cases, but for the most part, this will maximize the system working as intended. Basically, if you're trying to abuse it in a way that relies on counterintuitive behavior, or relies on overthinking it, it probably won't work. Unless it feels right, and the game will take it.