"A lot of time and perseverence and help with manpower." Senku chuckled. "If you mean the drone specifically though, it was from parts of other previously created repurposed. I do that a lot. The few engines we do have tend to be repurposed from stoves we built for winter." Senku hummed. "Although that does mean when winter comes around we have to make the stoves again." He shrugged. "Wasn't a big project."