Here's several interesting links on confederate semi submersible torpedo boats and the Winans cigar boats.
This one is about an archaeological find of a David torpedo boat, possibly THE original David found underground in Charleston S.C.
by ground penetrating radar.
This one is a good site about the David semi submersible torpedo boats. http://www.charlestonillustrated.com/hunley/david.htm
This last one is about the Winans cigar boats that the David torpedo boats designer's used the Winans hull design of.
The hull design and early model circular amidships propeller (that was discontinued) is very unusual and interesting. The final model of the Winans cigar
ocean going ship has multiple blade propellers both fore and aft and looks very futureistic for its time.