Disabling the Hahskyn-Varna Canal? (HFQ Spoilers)

What does it take to disrupt traffic (even temporarily) in a canal? I admit to being pretty ignorant of the mechanics involved, but I would think it couldn't be so difficult for a saboteur, much less one with the resources of the "Inner Circle," to throw a wrench in the works capable of stopping passage, even if it didn't cause permanent damage.

The reason I ask is that, assuming I'm not missing something, if the Hahskyn-Varna Canal that Captain Ahbaht led his squadron upriver to destroy was to suffer a mischief that put it out of commission for a five-day, the "screw-galleys" wouldn't have been in a position to threaten Ahbaht as he retreated. Whether that would have made enough of a difference in the subsequent battle might be debatable, but I can't imagine it would have hurt.

Is there a reason why this couldn't have been done, or if it could, why it wouldn't have been done?

It's really a pretty good question. We know that in matters of surveilence and spying, Merlin uses TF tech pretty freely. But otherwise, he exercises restraint, with a few rather notable exceptions.

Some of it is probably to avoid giving the Temple any more proof than possible that he is a demon. Sometimes he would be trying to avoid bringing the Temple's wrath down on the people in the area surrounding an act of unexplained sabatoge.

But mostly, he wants his allies to solve their problems with only an occasional hint or nudge from him...although to be fair, he has been pretty liberal with nudges and hints. But still, he usually avoids being the silver bullet for every issue that comes up which is wise because he doesn't want to be promoting dependency. That, in turn, means that his allies still face the risks of war based on the realities confronting them.

Don

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n7axw wrote:It's really a pretty good question. We know that in matters of surveilence and spying, Merlin uses TF tech pretty freely. But otherwise, he exercises restraint, with a few rather notable exceptions.

Some of it is probably to avoid giving the Temple any more proof than possible that he is a demon. Sometimes he would be trying to avoid bringing the Temple's wrath down on the people in the area surrounding an act of unexplained sabatoge.

But mostly, he wants his allies to solve their problems with only an occasional hint or nudge from him...although to be fair, he has been pretty liberal with nudges and hints. But still, he usually avoids being the silver bullet for every issue that comes up which is wise because he doesn't want to be promoting dependency. That, in turn, means that his allies still face the risks of war based on the realities confronting them.

Don

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Assuming the mechanics allowed it, I can't see the response from the Temple being of a factor. If it couldn't be disguised as a accident, natural disaster or the result of poor maintenance, I would think it could easily be made to look like the work of ICN Marines, given the close proximity of the ICN raiding force.

Regarding your other point, that line of reasoning isn't really in-character for Merlin. Letting things "play out" is one thing, but given the extraordinary inconvenience that led to this event, and the possible loss of life resulting from inaction, and the insignificant risk it posed to himself or his goals, I can't see him sitting this one out, if he had the opportunity.

Hellmer wrote:Regarding your other point, that line of reasoning isn't really in-character for Merlin. Letting things "play out" is one thing, but given the extraordinary inconvenience that led to this event, and the possible loss of life resulting from inaction, and the insignificant risk it posed to himself or his goals, I can't see him sitting this one out, if he had the opportunity.

It's possible he might have chosen to intervene if circumstances had been otherwise, but you've got to keep in mind the timing here. Specifically, the screw galleys had already left the canal before it became apparent that any help would be needed.

Ahbaht gives the order to turn around and head back downriver on June 24. He estimates that Hahlynd and the screw galleys would reach the river on the 27th, but immediately after we learn from Sarmouth and Hektor's discussion that the galleys are actually more than two days ahead of schedule, so they would actually reach the river the very next day.

However, at that point they still think that their galleons will be able to escape fairly easily. They estimate that Ahbaht would pass Ki-dau back into the open bay the morning of the 25th (at the same time as the screw galleys are only just reaching the river), that he would have joined up with Dreadnought before he ran into Rohsail's galleon fleet, and that the two ironclads operating in company would be amply capable of cutting a path out for the ICN force. In other words, even though things didn't go their way, crapping out on this throw of the dice isn't going to actually cost them and there's no need for Merlin's 'supernatural' assistance.

Thunderer doesn't run aground until the night of the 25th-26th, after the ICN force is well out onto the bay and *after* the screw galleys are already out of the canal onto the river. Until that point, there was no reason to expect that the screw galleys had any chance of catching up to the ICN force. If Merlin was actually worried enough after all to want to do something to help, until that point he would have been looking for ways to sabotage *Rohsail's* galleon fleet, not Hahlynd's screw galleys. And by the time Thunderer ran aground and anyone could have realized the screw galleys might catch up to them after all, it was too late to trap them in the canal.

Great points muonneutrino. Plus if Merlin is going to jump in every time the Alliance get in a bit of a fix anywhere on Safehold he is soon going to need a lot more hours in the day. NTM that much 'luck' on the alliance's part would have plenty more people than Rayno believing in demonic intervention, especially ear!y on

To answer your actual question, since everyone has ignored it:

you have to either drain the canal or disable the locks.

Draining canals is generally impractical: you can only do at points where the canal bed is higher than the surrounding terrain, and only section by section between locks. Nothing the other side of a lock will be affected, although of course you can't get through them until that side is refilled. Since the cumulative elevation changes at locks are often more than the depth of the canal, destruction of the locks themselves can drain the canal upstream. Many canals also have sections where the bed is above the surrounding countryside, so splitting the wall will empty that section. Doing either takes a very big and very precisely placed boom indeed.

Disabling locks, especially manually-operated locks, is not actually all that easy. While the _structure_ of a lock can be quite sophisticated it is also, like most heavy engineering, quite resistant to damage. The operating controls can typically be replaced in anything from minutes to a day or two by a local blacksmith and/or carpenter. Anything more permanent also requires liberal quantities of explosives, and even then you have to blow up the right bits or it can be back in operation in a week.

Not the sort of thing that a quick raid by a platoon of Marines is going to be able to accomplish.

Hellmer wrote:What does it take to disrupt traffic (even temporarily) in a canal? I admit to being pretty ignorant of the mechanics involved, but I would think it couldn't be so difficult for a saboteur, much less one with the resources of the "Inner Circle," to throw a wrench in the works capable of stopping passage, even if it didn't cause permanent damage.

The reason I ask is that, assuming I'm not missing something, if the Hahskyn-Varna Canal that Captain Ahbaht led his squadron upriver to destroy was to suffer a mischief that put it out of commission for a five-day, the "screw-galleys" wouldn't have been in a position to threaten Ahbaht as he retreated. Whether that would have made enough of a difference in the subsequent battle might be debatable, but I can't imagine it would have hurt.

Is there a reason why this couldn't have been done, or if it could, why it wouldn't have been done?

Louis R wrote:To answer your actual question, since everyone has ignored it:

you have to either drain the canal or disable the locks.

Draining canals is generally impractical: you can only do at points where the canal bed is higher than the surrounding terrain, and only section by section between locks. Nothing the other side of a lock will be affected, although of course you can't get through them until that side is refilled. Since the cumulative elevation changes at locks are often more than the depth of the canal, destruction of the locks themselves can drain the canal upstream. Many canals also have sections where the bed is above the surrounding countryside, so splitting the wall will empty that section. Doing either takes a very big and very precisely placed boom indeed.

Disabling locks, especially manually-operated locks, is not actually all that easy. While the _structure_ of a lock can be quite sophisticated it is also, like most heavy engineering, quite resistant to damage. The operating controls can typically be replaced in anything from minutes to a day or two by a local blacksmith and/or carpenter. Anything more permanent also requires liberal quantities of explosives, and even then you have to blow up the right bits or it can be back in operation in a week.

Not the sort of thing that a quick raid by a platoon of Marines is going to be able to accomplish.

Thanks for the answer! It sounds like it would be more difficult than I assumed to pull off. If that precludes a man-portable quantity of "Lywysite," much less gunpowder, from disabling the locks even temporarily, I would think that anything that could be passed off as a "natural" or "accidental" event would be insufficient to do the job.

Aside from the time table considerations, I suppose that the gear mechanisms for the lock are probably made from iron/steel. If so, then thermite is a sensible solution. Destroy the gears, disable the lock, and be off. Depending on the circumstances, a job for a squad with diversionary action.

Hellmer wrote:

Louis R wrote:To answer your actual question, since everyone has ignored it:

you have to either drain the canal or disable the locks.

Draining canals is generally impractical: you can only do at points where the canal bed is higher than the surrounding terrain, and only section by section between locks. Nothing the other side of a lock will be affected, although of course you can't get through them until that side is refilled. Since the cumulative elevation changes at locks are often more than the depth of the canal, destruction of the locks themselves can drain the canal upstream. Many canals also have sections where the bed is above the surrounding countryside, so splitting the wall will empty that section. Doing either takes a very big and very precisely placed boom indeed.

Disabling locks, especially manually-operated locks, is not actually all that easy. While the _structure_ of a lock can be quite sophisticated it is also, like most heavy engineering, quite resistant to damage. The operating controls can typically be replaced in anything from minutes to a day or two by a local blacksmith and/or carpenter. Anything more permanent also requires liberal quantities of explosives, and even then you have to blow up the right bits or it can be back in operation in a week.

Not the sort of thing that a quick raid by a platoon of Marines is going to be able to accomplish.

Thanks for the answer! It sounds like it would be more difficult than I assumed to pull off. If that precludes a man-portable quantity of "Lywysite," much less gunpowder, from disabling the locks even temporarily, I would think that anything that could be passed off as a "natural" or "accidental" event would be insufficient to do the job.

Adding to Louis R's comments, replacing the Lock doors is not easy, but just about any community should be able to pull it off within a week.

I live up at the northern end of the Miami Erie Canal, and the 2nd "Sidecut" from the Canal to the Maumee River is literally 100 feet from where I am sitting at the moment. Many of the old locks are visible to walk through and on, as are many miles of the towpath trails.

About 15 years ago, the Local Metroparks repaired one of the locks and rebuilt the Lock doors. To build the 4 doors they asked for ~50 volunteers to pay $200 each and help for 2 weekends to build the doors - they brought in 20 early 19th century craftsmen to teach and guide the construction work (The money from the Volunteers paid for the lumber and the craftsmen), and the group built the 4 lock doors in the 2 weekends just using tools available in the 1830-1860s.

The Miami Erie locks are made of Limestone blocks 3-4 feet thick, by about 5-6 feet long, with notches cut in the sides to fit the doors so the open doors are flush with the walls. The timbers of the doors are 10-12 inches thick. The door panels were thinner (6-8 inches thick?) with sluices built into the doors to allow water into/out of the lock. Some locks has side sluices built in channels in the walls as well. The doors "locked" closed in a chevron shape pointing up flow to reduce pressure on the doors (The water pressure forced them closed if the water height was not balanced).

The Miami Erie had no pumps to pressurize the canal - at the highest points several man-made lake were built by damming minor river valleys, and they were used to top off the canal's water. (One, Grand Lake St. Marys, was the largest man-made lake in the world until the 1930s). Other early canals use pumps (usually in the form of windmills) to top off their water levels if high elevation water sources were not available.

Each side of the Canal was topped with a towpath trail about 10-12 feet wide, and when the Canal was above the surrounding terrain, the earthen berm sides were usually ~20 feet thick at the top of the water. So while possible to breech - a considerable amount of dirt would need to be removed to do so.

It must be said, the Miami Erie is a considerably smaller canal than those discussed on Safehold - the locks can only accommodate ships ~14 feet wide and 90 feet long - so given their longevity, they are probably built to a stronger level than what I mentioned here.

chickladoria wrote:Aside from the time table considerations, I suppose that the gear mechanisms for the lock are probably made from iron/steel. If so, then thermite is a sensible solution. Destroy the gears, disable the lock, and be off. Depending on the circumstances, a job for a squad with diversionary action.

Most of the early canals were not even that advanced. The Miami Erie locks I referenced above used ~15 foot long beams to open and close the lock doors - there was some gearing on the sluices, but even that was usually pretty primitive, and easily worked around or replaced.

Stopping the sluices stops traffic from moving through the lock because the doors cannot open - but You can still transship cargo around the lock manually if necessary. However, destroying the lock doors keeps 2 segments of the canal unusable - the water level on the up flow section will be too low to be navigable, and the down flow section will have too much water for the next lower lock to open it's doors and have too fast a current for the tow teams to pull against.