:::: What to be cleaned? Here are some suggestions: 
 ::::*The introduction is too much about speed records.  
 ::::*The drawings are nice but have a too large font size and the arrow indicator on the wind vectors are pointing the wrong direction.  
 ::::*The headings "Sailing on a broad reach" and "Sailing perpendicular to the wind" should use the same terminology (angle -vs- reach/broad reach).  
 ::::*"Normal cruising boats yachts can sail at a about 45 degrees off the apparent wind (50 to 60 degrees off the true wind)." is (still) not representative for a modern yacht (40-50 degrees off true wind is more the case).  
 ::::*The tables should use a more standard layout (i.e. without border).  
 ::::*"Further Reading" should be cleaned up.  
 ::::*The language should be clarified/shortened in general.