(http://img838.imageshack.us/img838/238/whaleshoot12.png)
Oceanshoots is my last major 31.25 fortress, a fairly simple megaproject/experiment fortress set up for one purpose. To create a situation where a dwarf could harpoon whales with ballistae arrows.
It's a bit of a silly goal, but I wanted to see if it was possible.
Challenge #1: Catching whales.
In my earlier fortress where I set up a working sea serpent farm, I learned through trial and error several key points about how to capture non-vermin fish.
First, catching fish works best when you can get the fish to swim onto the cage traps under their own power. Trying to force the fish through a trap array with flowing water is not very effective.
Second, aquatic animals compete with surface animals for the number of groups of wild animals allowed to be on the map at once. Aquatic creatures also seem to be much lower priority when the game decided what group of wild animals to spawn next. If you want to spawn wild animals in the sea, you need to prevent them from spawning on land.
Third, even creatures like sharks or sea serpents will run away from war animals. Strategically placed war dogs can be used to drive fish into your cage traps.
I picked a 4x4 embark site that straddled two savage ocean biomes, to maximize the number of wild sea creatures that would appear. The embark site I picked meant that the dwarves were the only civilization that could reach my fortress, though I didn't realize that at the time I embarked. It didn't really end up making any difference anyway.
After setting up the basics of a self-sufficient fortress, I started making the trap chambers. The embark site was divided vertically by a nearly straight coastline. I dug chambers three tiles wide parallel to the ocean, separated by a one tile wide rock wall. On the side of the chamber facing the ocean I built raising drawbridges, so that the chamber could be sealed off from the ocean. The rest of the chamber was filled with cage traps. After raising the bridges, I channeled out the last line of rock from above to connect the chamber to the ocean.
(http://img109.imageshack.us/img109/575/onetrapdry.png)
On the surface one Z-level up, I built a windmill-powered pump to pump water out of the chamber. I also built a wall to prevent dwarves on shore from scaring or being scared by fish near the trap entrances. I also had hoped the wall would block ocean waves, but it was completely useless for that.
(http://img804.imageshack.us/img804/442/onetrapsurface.png)
The same lever was used to both open and close the trap, and to engage the pump which pumps water out of the chamber. I'd throw the lever one way to let water and fish in, wait for the trap to catch something, then throw it the other way to seal it off from the ocean and drain it so the dwarves could remove the cages and reload the traps.
I built six of these chambers, which covered nearly the entire shoreline from one end of the embark site to the other.
Now the trap wasn't catching much yet, since the local wildlife spawns were being taken up by camels and vultures and other annoying non-aquatic life. Step two was to build raising drawbridges lining the entire edges of the surface. Fortunately the embark site was nearly flat, so I was able to use maximum-length bridges for most of it. This also meant completely sealing the fortress from the outside world. No trade, no immigrants, no liaison. Didn't really matter at this point as I already had a Baroness and a self-sufficient fortress.
After that, I only had to eliminate the last group of camels wandering around on the surface for sea creatures to start spawning. They'd wander around the ocean and eventually get caught in the traps lining the shore.
(http://img813.imageshack.us/img813/6338/gettingcaptured.png)
The traps worked for a bit, until I ended up with a group of fish sitting offshore, not moving. Seems when you get one of those groups that moves in a line, and then catch the leader, the rest of the group gets bugged and doesn't want to move again. To solve this I built a series of platforms over the ocean, where I then stationed war dogs to scare the stuck fish into moving into the traps.
(http://img196.imageshack.us/img196/5260/scareplatforms.png)
I ended up with these spanning the entire ocean side of the embark, so that there was no place a fish could sit without being in sight of a war dog. The platforms were set up to channel creatures entering the map straight into the cage traps. This worked astonishingly well, groups of creatures would spawn and then almost instantly flee to the shore to be caught. The only downside to the scheme was that I ran through war dogs quickly, they kept getting into fights with sharks and drowning or bleeding to death.
Once I had the platforms in place, the fish catching system was almost too effective. I clear-cut the entire surface of the map repeatedly trying to build enough cages, and had dwarves working non-stop to move cages into storage and load new ones into the traps.
(http://img38.imageshack.us/img38/9496/catchd.png)
Soon enough I had a dozen whales for the next step, along with dozens of sharks and other fish. I also caught two sea serpents. Both were female, unfortunately. As an experiment I deliberately released one, and made sure it left the map without being recaptured. Later, a second sea serpent appeared, and was caught. This one was male. It appears that the game tracks local biome populations as numbers rather than individual creatures, so you can get a rare creature to reappear with a different gender by releasing it and then waiting for another of that species to reappear.
Now that I had my captive whales, I needed to set up a way to shoot them with ballista arrows. Siege weapons in DF can only shoot at something on the same Z-level as them. This makes it tricky to fire them at an aquatic target.
(http://img593.imageshack.us/img593/9854/overalldry.png)
I set up a target chamber sealed by raising drawbridges on the eastern and western sides. Above the bridges on each side were solid lines of pumps set up to pump water back into the chamber. When active they'd create a standing wall of water, keeping the water in the target chamber even when the sealing drawbridges were lowered. A ballista off to the side could then fire right through the chamber from the same Z-level.
(http://img546.imageshack.us/img546/7880/moseseffect.png)
The target chamber opens on both the eastern and western side so that ballista arrows which passed through the target would hit the far wall and then fall down into a collection area to be reused. The east and west sides of the chamber are also lined with wall grates, in an attempt to prevent creatures in the chamber from swimming out of the water and air-drowning. These are not entirely effective at this.
On the south side of the chamber is a drawbridge-blocked passage through which water is pumped in from the ocean. This is used to fill the target chamber. This passage also is lined with cage traps, which can be used to recapture the target animals.
In the center of the north side of the chamber is a sub-chamber which is used to let animals into the target area. Cages containing the target creatures are placed there, and then linked to a lever elsewhere.
The chamber is filled with water.
(http://img835.imageshack.us/img835/263/setup1r.png)
Once the chamber is filled, the lever is pulled to release the creatures. A war dog behind windows at the top scares the target animals into the main area.
(http://img692.imageshack.us/img692/1647/setup3h.png)
A floodgate is then used to seal off the passage, preventing the target creatures from leaving the main chamber.
The rest of the northern side of the chamber is lined with windows, behind which is are raising drawbridges and war dogs on chains. The bridges are usually kept raised, to hide the war dogs from the target creatures. If I want to recapture the targets, I'll open the bridge to the south, then open the bridges in front of the war dogs, scaring the targets into the cage traps in the passage to the south.
The entire floor of the target chamber was made of retracting bridges. On the Z-level directly below the bridges was a chamber lined with floor grates.
(http://img37.imageshack.us/img37/796/grates.png)
When the bridges were retracted, any corpses left in the target chamber would drop down onto the grates, the water draining away through channels under the grates, so that the corpses could be recovered for butchering.
Once the creatures are in the target area, the pumps are running, and the drawbridges on the eastern and western sides are lowered, the ballista can freely fire at the whales in the central chamber.
(http://img207.imageshack.us/img207/3955/whaleshoot10.png)
How well does it work? Not all that well, actually. Ballista seem to fire on a random path – there doesn't seem to be any actual correlation between where the arrows go and where the targets are. I have a Legendary Siege Operator running the ballista (he spent years firing rocks at a wall with a catapult while the everything else was being set up). I put a dozen whales in the chamber at once to increase the chances of the ballista arrows actually hitting something.
When one of the ballista arrows actually manages to hit, it does cause some damage.
(http://img827.imageshack.us/img827/5369/combatreport1.png)
(http://img268.imageshack.us/img268/6369/hurtwhale1.png)
Haven't actually killed any of them yet. Despite what you'd think, ballista arrows act less like harpoons and more like ranged warhammers, so rather than skewering any of the targets the arrows are just causing bruises and minor injuries. There is quite a lot of whale blood coming out of the test chamber, so maybe if I keep this up long enough they'll bleed to death, or die of infection.
I did notice one odd thing during an earlier test run with bluefin tuna.
(http://img405.imageshack.us/img405/6914/containmentfailure.png)
The eastern and western sides of the chamber are lined with wall grates. These were intended to stop creatures from swimming out the western or eastern sides of the chamber, breaching the Moses effect water wall, and air-drowning. Wall grates, unlike fortifications, seem to block creatures from deliberately passing through them even when submerged. They don't prevent creatures from being pushed through by moving water. I was concerned that the whales would swim into the wrong spot and get pushed through to air-drown. This didn't happen with whales, but when I put bluefin tuna into the chamber every one of them ended up air-drowned quickly. I don't know if the whales were simply stronger and better able to resist moving water, or if DF is actually taking creature size into account when deciding whether a creature is pushed through grates by moving water.
Fortress map is uploaded here:
http://mkv25.net/dfma/map-11026-oceanshoots
If you would please, can you post/PM me with a list of your good threads? It seems that Dwarven Relativity fails to do you justice. I'm now motivated to make you your own section, because every single thing that you do is amazing.
(http://i1022.photobucket.com/albums/af342/girlinhat/DSCN0075.jpg)
Rebuilt the trap chamber with two rows of grates.
(http://img192.imageshack.us/img192/2002/dualgrates.png)
I have also prepared a selection of copper and steel ballista arrows. Let's see how well this works.
(http://img6.imageshack.us/img6/7784/shootingfish1.png)
(http://img194.imageshack.us/img194/1223/bluefishhurt1.png)
(http://img51.imageshack.us/img51/6126/bluefishdead4.png)
(http://img525.imageshack.us/img525/8876/onedrowned.png)
Better, the ballista arrows are actually killing their targets sometimes. The dual rows of grates make it less likely that fish will escape, but they're not perfect. One bluefish managed to get through both grates and air-drowned anyway.
Now I'll drain the water and try it with whales again.
Now shooting metal ballista arrows at whales...
(http://img831.imageshack.us/img831/5476/whaleshot15.png)
(http://img20.imageshack.us/img20/5649/whalehurt2.png)
(http://img404.imageshack.us/img404/6156/whalehurt3.png)
(http://img850.imageshack.us/img850/3932/whalehurt4.png)
(http://img577.imageshack.us/img577/9274/whalehurt5.png)
It's starting to look like not even a steel ballista bolt to the head will actually kill a whale. I don't know if this is a testament to how tough whales are, or how useless ballista are as a weapon.
Also, whales can stand up.
It turns out I did have a fair amount of silver ore on site after all, so I have built a batch of silver ballista arrows. First I'll try firing them at a group of smaller targets.
The first arrow fires is very promising...
(http://img40.imageshack.us/img40/8369/fisharrowed1.png)
(http://img18.imageshack.us/img18/7286/fisharrowed2.png)
(http://img811.imageshack.us/img811/7951/fisharrowed3.png)
That's two fish killed by a single ballista arrow. Admittedly, they were small fish.
(http://img840.imageshack.us/img840/8049/fisharrowed4.png)
(http://img195.imageshack.us/img195/5474/fisharrowed5.png)
Still fairly effective against larger fish. Unfortunately, I'm still loosing as many fish to air-drowning as to ballista arrow hits. Two wall grates in a row just isn't enough to stop fish from being pushed through by moving water.
(http://img195.imageshack.us/img195/6964/fisharrowed8.png)
Now, testing silver ballista arrows against whales.
(http://img195.imageshack.us/img195/6461/silverarrow.png)
(http://img72.imageshack.us/img72/3694/silverarrow2.png)
Still not lethal, but at least they're bruising internal organs now. This confirms the theory that ballista arrow damage is dependent on density, and that silver is the best material for ballista arrows in the default game.
My copy of DF has several heavier metals that can be made (rose gold, thorium, uranium, wolfram, etc) but this embark site doesn't have the required raw materials to make any of them. I'll have to try something different next.
Next test: Firing through magma!
(http://img851.imageshack.us/img851/7178/magmawall.png)
I have created a second liquid-wall setup, using another pair of screw pumps. This one contains magma! In theory, the bolts fired by the ballista should catch on fire or something while they pass through the magma, right?
I admit I completely cheated to make the magma, using DFhack to add the magma in. I have reached the magma sea, and have a perfectly working magma force setup over a magma pipe, but the magma in this embark is just silly far down. I decided to skip a week of work by using dfliquids instead of building a hundred-pump pump stack. Meh.
The setup is just the same as the previous one, with a wall of pumps (these ones made from green glass) on each side of the liquid wall, pumping the magma back onto itself to keep it from flowing out.
(http://img41.imageshack.us/img41/2298/magmawallupper.png)
First, since I already have them set up and ready to go, I'll fire a silver bolt through the magma. It should melt or something, right?
(http://img690.imageshack.us/img690/1636/silverarrowmagma.png)
(http://img109.imageshack.us/img109/6204/silverarrowafter.png)
Huh. Nothing unusual result. My siege operator decided to fire a steel arrow through the magma next.
(http://img580.imageshack.us/img580/9203/steelarrowmagma.png)
Nothing unusual happened there, not that we'd expect it to. Ok, time to get serious. Forbid all metal arrows, fire some wooden ballista bolts through the magma.
(http://img834.imageshack.us/img834/2862/woodarrowmagma.png)
(http://img849.imageshack.us/img849/5163/woodarrowmagma2.png)
Half a dozen wooden ballista arrows fired through the magma, not a one of them caught on fire. And it's not that the water is putting the fire out, I'm pausing the game and examining each shot before it hits the water wall.
As an additional check, I dug up some graphite and set up a catapult. Let's see if we can get burning graphite boulders flying through the air.
(http://img600.imageshack.us/img600/5867/graphitemagma.png)
(http://img338.imageshack.us/img338/1955/graphitemagma2.png)
Nothing. A dozen graphite boulders fired through the magma, none of them caught on fire. None of them hit any of the whales, either. That was disappointing.
I'd try and figure out a way to set the ballista bolts or graphite boulders on fire before firing them, but I suspect the siege operator would either refuse to use burning ammunition, or bleed out in the process of trying to fire them. Still something I might test.
Save has been updated, for anyone who wants to do their own experiments.
http://dffd.wimbli.com/file.php?id=5632