Research is difficult, Zhang says, because historical Chinese ships are "very rare." Many ship-building skills were not passed along on paper.

Exactness is vital for a model ship. In China, the same type of ship may vary in different regions.

"For example, a pulley shaped as a pagoda for the boat rope is different in the south from that in the north of China. In the southern part, the pulley is more delicate, and you can see different layers of design like stories of a pagoda on it, while in northern areas, it's a simple shape," he says.

After doing the research, it usually takes Zhang a month to finish a historic model ship in a proportion of 1:25.

Sometimes, a model is almost finished when he gets some new information about the original and he has to start over.

Among all historic ships, Zhang is most fond of the large Chinese junk - it goes back 1,400 years in the city and is virtually synonymous with Shanghai's past, so much so that the city emblem shows a magnolia flower, a large junk and a propeller.

"The difference between a large junk and other ships is that the junk evolved from the river boat. Because the bottom of the ship is flat, with a shallow draft, it's lined with ballast so it can sail in strong winds. It is a reflection of the wisdom of ship-building technology in China," he says.

Zhang went four times to the Taihu Lake, crossing Jiangsu and Zhejiang provinces, doing research before building his favorite junk.

"I hope that Chinese people will pay more attention to our legacies," he says. During his visit, many objects he sought out were not well preserved, showing a disregard for the culture and civilization.

Zhang next plans to do a series of models on wooden ships used in the area of the Yangtze River. He hopes in the future he can establish a museum to showcase his works.

His daughter and nephew, Zhang Zhenying and Xia Xia, are now his apprentices. Together they have created an online forum and website (www.zgchuan.com) for Chinese ancient ship model lovers.

"I have to do some other plastic assemblies or ship models to make a living but I will never give up on ancient ship modeling. Fewer and fewer people participate in this kind of ship modeling, thus if no one insists on doing it, this culture might vanish," he says.