I believe that you are describing 'luffing'; to flap while losing wind.
I don't think there is another name other than blade.
They are referred to as four-cornered sails.
They were referred to as "four-cornered" sails.
Sails are attached to the mast.
A Submariner
In Italian, it ,eans "rhythmic slapping sounds"
"Four-cornered".
a mast
The nickname of Auckland is the "City of Sails".
There are some stores that offers various sails for use on the water. Walmart, Kmart, Dollar Store are some of the stores to name a few. They have vairous sails.
Trusting your instincts. That and slapping Jessica Simpson's name on everything from sunglasses to catfood.
The Hispaniola is the name of the fictional vessel featured in Robert Louis Stevenson's classic adventure novel, Treasure Island, which Jim Hawkins sails aboard.