It was foggy with light rain, and it was very cold. There was no wind. Seth and Bjorn grunted as they dragged the latest prototype out of the workshop to avoid the risk of damage from engine testing. The new craft implemented the three-axis control scheme, with a stick between the pilot''s legs and a pair of foot pedals to control the rudder.


    "Do you think it will be safe out here?" Quinn asked.


    Seth pointed up to the red flags at the top of the nearby belfries, barely visible through the fog. They were limp against the flagpoles.


    "I will tie some bells into the rigging," Irene said. "If we leave the workshop door open, we will be able to hear the wind."


    The tables inside the workshop had all been moved to the sides to make room for the prototype, leaving an open area in the center of the room. A small pile of metal ingots were stacked in the center of the space, along with a handful of sturdy wooden blocks.


    "So we have two problems that I want to discuss today," Quinn said. "First, we need to figure out how the engine is going to work. Second, we need to design the propeller. I suggest that we discuss the engine first. Are there any objections?"


    "That sounds good to me," Vince said.


    Vince had volunteered to work on the propeller design, and Quinn assumed that he would be the only one in the club with an interest in the matter.


    "I have scoured the library searching for books relating to engine design," Quinn said. "I did not find a single book on the topic. There is plenty of training material describing how to operate a steam engine, but nothing describing how to design a new one. I asked the professors. Atlas vin Truscae was the only professor with any information on the topic. He told me that steam engines are designed at Spire Sophia, in the mountains between Zairo and Truscasia. Individual nations have factories for assembling and maintaining the engines, but Lyn does not have such a factory."


    "So where do the engines in White Chasm come from?" Seth asked.


    "Grael Nydia," Quinn replied. "Among the locks ascending from the lower river up to the city. It''s a six week journey by steamboat, so going there is not an option. Apparently there was a factory in the harbor, but it was destroyed generations ago. The order came from Empress Sasha after she killed King Redmond and took the city for her family."


    "What about the Theocracy?" Seth asked.


    "I was not able to find out," Quinn said. "I have not seen Maxius since he left for the palace. Maybe Kiera or Claire would know, but I am fairly certain that they have quit the club permanently."


    "I have not seen them on campus," Bjorn said. "Either way, I think it''s safe to assume that we are not going to get any help from them in any reasonable timeframe. We need to work with the resources we have. So have you made any progress on a design starting from first principles?"


    "In theory," Quinn began, "if you use ethermancy to create heat, then you can boil water and then use the steam to push a piston or spin a turbine. Once the steam has done its work, it needs to be cooled using ethermancy so it can be reclaimed. For closed-circuit engines, the fireman needs to alternate between two weaves, one fire-aspect and the other water-aspect. I did some experiments with glass tubes and flasks, however I don''t think we can avoid simple trial-and-error using metal components."Stolen novel; please report.


    "That''s fine," Seth said. "But that wasn''t what I was asking."


    Quinn offered a bundle of papers with a few of his working designs. Seth scratched his head, uncomprehending, but Bjorn gave a low whistle.


    "You are insane," Bjorn said.


    "What am I looking at?" Seth asked.


    "My current design uses eight pistons. A single boiler is used to heat the water in eight isolated closed-circuit steam engines arranged radially around a central gearbox. All eight circuits pass through a heat exchanger. Therefore, all sixteen components can be heated or cooled by just two weaves, just like a train engine. The eight pistons will be carefully offset so that the power from one decompressing piston is used to re-compress the piston on the exact opposite side."


    "I might be able to come up with an equation to describe the offsets and the timing," Bjorn said.


    "Is there anything else?" Vince asked. "Because if not, I have made a lot of progress on the propeller design."


    "By all means," Seth said.


    The man pulled a detailed painting out of his folio and passed it to Quinn. It looked a bit like a ship''s propeller, but it was much longer and much narrower, with a funny twist in the middle. The diagram was very detailed, with arrows demarking various forces acting on the blades. The coloring of the wood was very skillful, in Quinn''s estimation, because it gave the image a vivid sense of depth.


    "This design is inspired by hiking," Vince announced.


    "Hiking?" Quinn asked.


    "Yes, hiking. I spend a lot of time hiking in order to reach the best birdwatching locations. So I''ve had a lot of time to think about it. Imagine that you know exactly where your destination is, however, there are two paths to reach it. One of the paths is straight and steep, the other is winding and gentle. Two hikers leave at the same time, and they both arrive at the same time. What can you say about the hikers?"


    "They must be traveling at different speeds," Bjorn said. "The hiker on the gentle slope is likely moving much faster than the fellow who is scrambling straight up the steep slope."


    "Exactly so," Vince agreed. "Imagine this propeller attached to the front of your flying machine. The flying machine travels one mile through the sky in some period of time. The propeller travels with the craft, from beginning to end. Note that the propeller is spinning very fast, which means that the tip of each propeller blade is moving much faster than the root of the same blade. However, like the two hikers traveling at different speeds, the tip and the root need to arrive at the destination at exactly the same time."


    "I am not seeing the connection," Quinn said.


    "The angle of the propeller blade relative to the air must follow exactly the same principle as the angle of the trails that the hikers are climbing. The slower hiker has a higher angle to overcome, while the faster hiker has a more gentle angle to overcome. The root of the propeller therefore must have a steep angle relative to the air, which gradually decreases as you get closer to the tip."


    "If that was not the case," Bjorn said, "then either the tips and the roots reach the destination at different times, which would imply that the propeller broke apart, or there would be an intense strain on the tips that cause them to bend, potentially reducing the power the propeller provides."


    "I understand now," Quinn said. "However, I think the weave required to craft this particular shape will be rather complex."


    "Which is why your work is so important," Seth said. "I am happy with this design Vince. Good job."


    "Boys?" Irene said from the doorway. "I went looking for some bells around campus, and when I came back... Well, perhaps you should see it for yourself."


    The four men shuffled out of the workshop to find the new prototype where they had left it. However, it was coated with a very thin layer of frost. Small icicles had begun to accumulate on the leading edges of the wings.


    "Do you think it will harm the boat?" Irene asked.


    "I will need to come up with a model," Bjorn said. "I do not know exactly how much all this moisture weighs, so I cannot give you an accurate estimate of the additional stress on the wing spars. However, those icicles will absolutely change the way air flows under the wings."


    "I agree," Vince said. "I can''t say I''ve ever seen a bird flying with icicles on the wings."


    "If the boat is not safe," Irene said, "then you will need to add this issue to your safety traditions. The ones you promised. Do you remember?"


    "I''ll add this to the checklist," Quinn promised. "No flying when it is cold and wet."