About the project

Concrete is something not often linked to boat, let alone dragon boat. Traditional concept of concrete based building material is embedded deeply not only in common folks but also in Civil Engineering students.

Concrete, usually Portland cement concrete (for its visual resemblance to Portland stone), is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens over time

Concrete - Wikipedia

Still, concrete is just a material, and material evolves as scientific progress advances. New material such as FRP rebars show even better performance than traditional steel rebars. Moreover, as its Chinese name indicated, concrete is just 'some sort of ash mixed and hardens', expanding its concept to a even higher dimension. Comparing to traditional boat building material, concrete has its own pros and cons.

Pros:

• Stain proof (v.s. steel)
• Flexible shape (v.s. timber)
• Economical (v.s. steel and timber)

Cons:

• Heavier than water and timber
• Brittle
• Low tensile strength

The whole project is aimed at exploiting the advantages of concrete while fixing its problems, expanding our knowledge of concrete through engineering practice.

Prototype 1.x - The First FRP Concrete Dragon Boat

Goal

A new type of boat construction method is proposed firstly by Prof. Yan Xiao. The basic idea is to use a self-hardening FRP cloth material as both concrete model and structural part that provides tensile strength.

Material

FRP Clothes

This is some material recently become popular for its ability of free shaping and fast hardening. Most common scenario of usage is replacement of medical bondage and plaster, or electrical wire joint protection. The mechanism is really simple as it's just piece of FRP soaked into glue. Exposition to air solidify the glue in several minutes, providing the structure with some strength.

Things become interesting when several layers of such kind of material are glued together. As FRP clothes is extremely strong in tensile direction, even glue can sustain the relatively less strong shearing force, guaranteeing high bending and shearing strength.

Plastic Hull

A plastic hull is needed for this model, primarily for the shape control of the self-hardening FRP clothes. To achieve better dynamic performance, hull is modeled to be smooth and continuous - NURBS interposition of key points. Therefore, 3D-printing technology is adopted for precise realization of the model.

Concrete

ECC concrete is a new kind of concrete which includes PVA fiber to increase its tensile strength and crack resistance. Ingredients are listed as below:

Cement	1
Quartz Sand 20-40	1.1
Silica Fume	0.3
Flyash	0.15
Mineral Powder	0.1
Quartz Sand 325	0.1
PVA Fiber
Water	0.18
Water Reduce Agents	0.10%
Early Strength Agents	0.10%

Next Stage

Prototype 1.x focuses itself on boat construction. A boat floating on the water marked success of the first stage. On that occasion, however, path splits for two different prototypes though.

Prototype 2.x stays small and is optimized for wireless remote control. A concrete dragon boat (model) competition is later held based on this. Prototype 3.x is develped with optimization for man-powered sailing in a much larger scale - a real concrete dragon boat.

Prototype 2.x - ICDBC 2019

Goal

Fast, stable, swift steering

To make it fast, the boat has to be speed boat alike, narrow, and light. The concrete layer needs to be as thin as possible. For sure, boat surface still needs to be smooth and continuous.

To make it stable and swift steering, the boat has to be not that narrow in width, motors parallel to each other and as far away as each other as possible.

Power system

Duo RH-380 motors, 1500mAh Li-ion battery

Should gave adopted stronger motors.

Competition

Server

https://www.concretedragon.org/

CentOS7, php7.2, MySQL5.3, Nginx, WordPress Vultr Dallas

See Concrete Dragon Online.

Rule

Should have set limitations on motor power.

Template

Should have provided ai version.

Should have made it clear that theme color can be switched.

Should have designed certificate templates.

Next stage

Should have adopted Arduino.

Prototype 3.x - The Great Dragon Boat

Goal

Strong, stable, light

The large boat is very different from the small boat as construction method can not be inherited directly. It is too slow for the hull to be 3d-printed out. Instead, EPS foam slices cut by CO2 laser are glued (or tied) up to form the basic model of the boat. A FRP clothes layer is then put on the foam, then concrete with FRP bars inside.

To make the boat strong, the boat is modeled even more smooth, to the extent that FRP rebars can be put inside the concrete from head to tail without cut or connect. Such smooth shape without any edge can be regarded as a 2-d arch, making the most of the compressive strength of the concrete. To make the boat stable, the boat should have a lower gravity center.

Next stage

• Should have the whole boat hull made by solid EPS form.
• Should have adopted sprayed concrete technique.
• Should have used more PVA.
• Should have used more FRP fiber clothes.

Credit

Instructor

Yan Xiao 肖岩

Boat Designer, Engineer, Manufacturer, Website Programmer and Designer

Ke Ma 马克

Construction

Ke Ma 马克, Dade Lai 赖大德, Zhiwei He 贺智伟

Also thanks for help by

Anqi Tan 谭安琪, Yiqi Feng 冯亦奇, Kaihang Zhang 张开航, Zhekai Li 李哲楷, Mengjun Wang 王梦君, Guoli Wang 汪郭立, Yang Zhou 周洋, Shangchun Jiang 江上春, Cristoforo Demartino, Zicheng Bao 包梓成

Decoration by

Jiahui Liang 梁嘉惠, Ke Ma 马克, Sicheng Zhou 周思成, Anqi Tan 谭安琪, Qingyun Liu 柳青云

Concrete Recipe

Bo Shan 单波, Dade Lai 赖大德

Logistic Support by

Sicheng Zhou 周思成

Competition Rule Maker

Yan Xiao 肖岩, Ke Ma 马克, Yiqi Feng 冯亦奇, Anqi Tan 谭安琪, Kaihang Zhang 张开航

Activity Organizer

Hang Wu 吴行, Ke Ma 马克, Binbin Li 李宾宾, Yanlong Xie 谢焱龙, Sichen Zhou 周思成, Tao Li 李涛, Jiahui Liang 梁嘉惠, Zhiwei He 贺智伟, Dade Lai 赖大德, Haixiang Zhu 朱海翔, Yi Zhang 张旖, Chenchen Ye 叶晨晨, Qian Yu 余倩, Jinyan Yu 俞静琰, Fengqing Jiang 江凤清 and other volunteers from ZJUI

Special Thanks for

Logistic Support

Jiyao Guo 郭霁瑶, Zhaijin Jia 贾翟菁, Qingbing Xie 谢庆兵

Technical Support

Tianyi Han 韩天屹, Si Li 李斯

Participation

Yue Feng 冯越, Hanyin Shao 邵寒吟

Sponsor

秦山建设，浙江大学创新创业学院