Of course, Gao Yuan and Yang Keshi had long been looking forward to attacking Xianghe, which was the first step set by Zhou Nan to defeat the Xi army, cut off the passage between Xiao Gan and Agu Zhe, and then destroy Agu Zhe, weakening Xiao Gan's forces step by step, and finally Xiao Gan would be insignificant.

It's just that the two of them have been in Sanhe for some time, and the people sent to deliver letters to Zhou Nan have been dialing one after another, but they have never received a reply from Zhou Nan. Gao Yuan and Yang Keshi had no choice but to wait for Zhou Nan while boringly patrolling between the two cities of Guoyin and Sanhe.

If they returned to Gu'an City, Gao Yuan and Yang Keshi would know that the current Zhou Nan had no time to reply to them.

Now the pro-army in Zhou Nan rarely sees Zhou Nan.

In the past few days, Zhou Nan actually felt that it was troublesome to go to the craftsman's yard next door to walk back and forth, so he simply moved into the craftsman's yard. In this way, although it was in the courtyards of those craftsmen, and those pro-soldiers were guarding outside the courtyard, they couldn't see Zhou Nan anymore.

Since the day before yesterday, the craftsmen reported that everything they had ordered to prepare had been done, and Zhou Nan asked the craftsmen to fetch the things he had told them to prepare. In a short time, the cobbler was holding a dozen sheets of first cowhide, the stalker was holding a frame made of wicker, the blacksmith was bringing a small box of charcoal, and the carpenter was bringing a jar of fish maw gum.

Zhou Nan walked up to everyone, picked up these things one by one, and looked through them carefully. These craftsmen are all good at this, and they do it with their hearts, and the things they do are naturally very authentic. Especially the first layer of cowhide, soft as satin and as thin as paper, not at all like the thick and clumsy appearance of cowhide in Zhou Nan's impression.

Zhou Nan nodded in satisfaction, turned back to his seat, and picked up a wooden board from the table, and the craftsmen all looked at the wooden board curiously.

Seeing a large piece of white paper nailed to the wooden board, Zhou Nan picked up a carbon rod and said to the craftsmen: "I want to thank you first, and you are not allowed to accompany your wife and children at home during the Spring Festival, and work here." Seeing that Zhou Nan was so polite, the craftsmen said: "The little people do some work, where is it worth thanking the horses?" It's just that I don't know these things, but the horse is still satisfied? ”

Zhou Nan said with a smile: "You are very satisfied with the construction site. But this is not the work that you are expected to do. ”

When the craftsmen heard that these were not the work they were asked to do, they didn't know what Zhou Nan meant mysteriously for a while, and they all looked at Zhou Nan suspiciously.

Zhou Nan didn't say what he wanted these people to do, but he said first: "What I want you to do is a confidential matter, and I ask you not to talk about it to anyone outside here, even if it is your dear parents, wife and children, you can't talk about it." If there is a violation, it will be severely punished according to the law of the country! ”

All people who are skilled have more or less secret skills in the industry, which are passed down from master to apprentice. Because this is related to his own job, when Zhou Nan said that he wanted everyone to keep this matter strictly confidential, all the craftsmen said in unison: "The villains swear never to leak the things that the horse commands, and if they leak, they are willing to be punished." ”

Zhou Nan saw that everyone agreed, so he comforted again: "You can rest assured, this matter is done, and the government can order you to accept you as official craftsmen, and the government will give you silver and rice every month, so that your family will have no worries about food and clothing in this life." ”

When the craftsmen heard it, they were all overjoyed, Da Liao and the Great Song Dynasty were different, if the craftsmen of the Great Song Dynasty were selected to work in the general prison, it would almost be selling coolies, and it would be good for the family to have something to eat. However, there are few official craftsmen in Daliao, but if they can be selected as official craftsmen, the treatment is far better than that of their peers.

Zhou Nan actually originally wanted these craftsmen to prepare materials for themselves, and then find someone else to assemble them. However, in this way, some details are not as good as having these craftsmen participate in the work from beginning to end. So Zhou Nan finally decided not to find another person to assemble it, but to have these people participate in it.

Seeing that these craftsmen swore an oath to come down, Zhou Nan didn't say much, picked up the carbon rod, first drew a circle on the white paper, then drew a square under the circle, connected the circle with the square with a few lines, drew a gap in the lower part of the circle, and drew a flame in the gap.

- Hot air balloons!

Zhou Nan thought about using a hot air balloon to solve Xiao Gan's soldiers and horses from the beginning.

Zhou Nan pointed to the picture he drew and explained one by one: "The above circle must be spliced together with the first layer of cowhide to make a balloon, the lower part of the balloon has a mouth like a cloth bag, but the spliced cowhide cannot be sewn with needles and threads, and can only be glued together." ”

Speaking of this, Zhou Nan looked at the cobbler and the carpenter, and the two craftsmen said: "Please rest assured, what we have done will definitely satisfy the horse." ”

Zhou Nan nodded, and said: "At the opening of the balloon, there should be a tendon rope to hang the frame below, and the frame should be made of pure wicker. The craftsman nodded hurriedly, signaling that he understood.

Zhou Nan finally said to the blacksmith: "You must make a small charcoal stove, a slender and tall iron furnace, and the weight should be light, the lighter the better." ”

The blacksmith said, "It's not difficult, but I don't know how big a stove the colt should be?" ”

The cobbler also asked, "Yes, how big do I want to make this balloon?" ”

"How big is the frame?" The craftsman also asked.

Zhou Nan did not calculate how big it was. It is indeed a difficult problem for a liberal arts student to remember and be able to calculate the density difference between air and hot gas, so as to calculate how much volume of hot air balloon is needed to lift each hundred pounds of weight. Fortunately, when Zhou Nan was in school, he often used a test algorithm for questions that he couldn't do. Although I don't remember the density of the air, I can use experimental methods to adjust step by step, and finally I can always find the right size of the hot air balloon.

Zhou Nan said: "First make a five-foot square balloon, the mouth of the balloon should be made to the size of one foot, the mouth of the small iron furnace should be able to extend into the mouth of the balloon, and the frame should be able to place the small iron furnace." Let's do it. ”

A day later, the craftsmen came to Zhou Nan to see if the things they had made were made by horses.

Zhou Nan walked to the courtyard where the craftsmen were working, and between them was a round, dark red balloon spread on the open space of the courtyard, crumpled and spread on the ground; There is a willow frame next to the balloon, and there is a small iron stove with a thick waist and a thin neck in the willow frame, but this willow frame can just fit into this small iron stove, and it seems that the size of the willow frame needs to be adjusted in the future - someone has to stand somebody, right? Sure enough, there are still a few tendons on the willow frame that are connected to the opening of the balloon, but these few tendon cords, Zhou Nan is very worried about whether they will fall halfway.

Looking at the style and shape, it was similar to the hot air balloon he painted, so Zhou Nan hurriedly asked the blacksmith to find some charcoal and put it in the iron furnace to light it. Then the craftsmen found a few wooden sticks, carefully inserted them through the opening of the balloon, and propped the balloon into the air. Finally, the small iron furnace with a thin neck was also stretched out into the opening of the bag, and Zhou Nan patiently watched the changes in the cowhide balloon.