Chapter 3 Two external engines

 The speed is not enough and the power is sufficient. This is applicable to any means of transportation. For example, there is a saying on aircraft: As long as the engine is powerful, bricks can fly into the sky!

Therefore, for Qin Tao, a reborn person with decades of experience in ship design, it is definitely quite simple to increase the speed of this speedboat with a displacement of about ten tons.

The target customer is customs inspection, and they require faster speed, so what else can I say? Just blame the engine!

Especially the speedboats in front of us use external engines, which makes it even simpler. If one is not enough, just hang two. If two are not enough, just hang three. It is simple and easy.

 The ones that took this layout to the extreme were, of course, the smuggling ships at sea. Not to mention three ships, Qin Tao had seen them all with six external engines.

There are two ways to arrange the engines of ships. For large ships, they are arranged inside the hull and drive the propeller at the tail through the transmission shaft. If the power of one engine is not enough, two or even four engines may be used. It can drive different propellers or be connected together to work together.

For small ships, you don’t have to go to such trouble. Just put the engine, drive shaft, and propeller together and put them at the stern. When needed, flip the device down to provide power. When you get to the dock, flip the device back. Avoid damage caused by long-term immersion in water.

 In the past, Mingzhou Shipyard produced fishing boats, at least with a displacement of hundreds of tons, so the engine was inside the hull. What we are building now is a speedboat, using blueprints purchased from the island country and a plan for an external engine.

 For the workers at Mingzhou Shipyard, this is the first time they have been exposed to this kind of power output method. It is okay to just copy everything, but it is impossible for them to innovate.

However, in the eyes of Qin Tao, a time traveler, this is a piece of cake.

"Power? Change to a high-power engine? Our factory does not have the funds to purchase new engines. If we had used domestically produced engines, we would have saved a lot of money. However, Director Song insisted on purchasing engines from island countries. , What a waste of money!" Zhao Changshui sighed again.

At this time, Qin Tao pointed to the Yamaha F100 external engine at the tail of the speedboat and said, "How many such engines have we imported in total?"

"I bought ten units in total, five of them are used on the ship, and five more are kept in the warehouse. When I bought them, the wholesale price for ten units was 95,000 yuan each. Just these engines cost nearly 100,000 yuan. Wan!"

"That's right, the factory ran out of money at that time. The scammer Song mortgaged the factory's assets to the bank and took out a loan from the bank. Now, the customs doesn't want these ships. Seeing that the repayment date is coming, the bank wants to seize us. assets, if Big Liar Song doesn’t run away, you must beat him up to vent your anger!”

 Everyone was angry again.

Qin Tao nodded: "Well, that's easy to say. Take out the engine from the warehouse and hang two engines on the back of this speedboat!"

What? Everyone was stunned.

“For a ship with a displacement of ten tons, two 100-horsepower engines are driven together, which is 200 horsepower. Now, are you afraid that the customs will be dissatisfied?” Qin Tao said

Qin Baoshan frowned: "Isn't this inappropriate?"

"Why is it inappropriate? Modifying the engine mount is not difficult at all." Qin Tao was a little curious.

“One engine weighs at least more than 100 kilograms, and two engines weigh more than 200 kilograms. In this way, the center of gravity of the ship will change, the bow will rise, and high-speed navigation will be unstable.”

 When Qin Baoshan heard his father say this, he almost gave him a thumbs up.

Although my father had a high school education, his teaching level was really not very good in the 1950s and 1960s. How much knowledge can be learned in five years of primary school, two years of junior high school, and two years of high school? Not to mention that my dad only went to high school for a freshman year and entered the shipyard in his sophomore year.

At that time, schools were run in accordance with the spirit of the "May 7th" directive: when schools were opened, students not only had to study literature, but also study engineering, agriculture, and military... Therefore, even if high school education was universalized, the cultural level...

Dad is a special case. He loves to learn and use his brain. Otherwise, he would not have made a name for himself after entering the shipyard. He worked hard for decades and became the director of the factory.

Now, Qin Tao said that he would install two external engines, and his father immediately raised the risk of such external engines.

"Yes, of course the bow of the ship will rise. In fact, we just want to make the bow of the ship rise so that we can speed up." Qin Tao said, "According to specific calculations, a 100-horsepower engine can drive less than ten A ton ship should be able to run up to 30 knots, but the current test of speedboats is very unoptimistic. Why is this?"

 “Is there a lot of resistance?” Qin Baoshan’s eyes flashed.

Changing from aluminum to steel increases the weight of the boat. Therefore, the Yamaha marine engine placed at the rear of the original design could lift the bow of the boat three times, but now it cannot lift it even once. The contact area between the boat and the water surface is large, so it will not work properly. The resistance will become greater. This is why current speedboats cannot reach their design speed.

If a ship wants to speed up, it faces a very complex fluid mechanics problem. To put it simply, when the speed is low, the resistance is proportional to the speed. After the speed exceeds twenty knots, the resistance is proportional to the square of the speed. Proportional, at thirty knots, the resistance will be proportional to the cube of the speed. Therefore, the power required will also increase in geometric proportion.

If no other changes are made, a 100-horsepower engine can drive the speedboat to a speed of thirty knots. A two-hundred-horsepower engine can only drive the boat to a speed of forty knots at most. Now we want to reach To design indicators, other changes must be made.

 The weight of the two engines pry up the bow of the ship. In this way, the area in contact with the water surface is reduced, which greatly reduces the resistance, allowing the ship to increase to the predetermined speed.

“Will the ship be unstable?” Qin Baoshan was full of worry again.

"Unstable? How is it possible? The aluminum is replaced with steel. The weight of the hull increases, so the stability should be better. If converted according to proportion, the three engines at the back have just reached the inclination of the aluminum hull." Qin Tao said: "So, don't worry, it's absolutely safe."

As he was talking, someone was already pushing the engine out on a cart.

Qin Tao directed several workers to work quickly, dismantling the original engine, changing the position of the bracket, welding the second bracket, and installing the engine. The work was completed in an hour.

“There is no champagne for a grand launching ceremony.” Qin Tao said: “Let’s try it like this!”

The slipway is very simple. There are two rails under the speedboat. Everyone can push the speedboat directly into the water.

There was a pop and water splashed. Qin Tao couldn't wait to jump into the cockpit: "I'll try it!"

 (End of this chapter)