(A second flair for biology and a picture would help, but oh well)
The membrane in a bat’s wing bends inwards, but it does so closer to the outer digit, what effects could this have on airflow and do these act as winglets?
(A second flair for biology and a picture would help, but oh well)
The membrane in a bat’s wing bends inwards, but it does so closer to the outer digit, what effects could this have on airflow and do these act as winglets?
Comments
Not an expert of any kind, but I do have some adjacent knowledge here, anyway.
I’m inclined to think that no, it’s not something resembling a winglet. In fact, I wouldn’t be surprised to learn that thinking of a bat’s wing in terms of an airfoil or conventional wing wouldn’t be a poor model.
Tangentially, I wouldn’t be surprised to learn that winglets were much less viable at low Reynolds numbers in general 🤔. Unsure here.
Bats don’t really cruise or glide much. My guess is you’d be better served thinking of them in terms of ‘swimming’ in air, and that their wings could be thought of as ‘air scoops’, hence the shape.
Bats have super long fingers, and the skin stretches between them to form the wing. But the bend helps with flight control. It’s like a built-in steering system. The membrane is flexible, so that curve acts almost like a mini airbrake or flap. Helps them turn quick, slow down, or even hover a bit. Also, it gives the wing more surface area when they need it. Think of it like spreading out a hoodie, you get more coverage without changing the shape of your arms. That curve helps reduce stress on the skin. If it was stretched out flat all the time, it’d wear out fast. So the bend gives it a bit of slack, like a hammock instead of a tight rope.
It doesn’t have anything to do with aerodynamics. The trailing edges of a bat wing is a catenary because the membrane of the wing only has strength in tension and the catenary shape is the most structurally efficient (strongest for least material and strength required). The anchor points on the digits are basically the same as the towers of a suspension bridge and the membrane is basically the cables. So if you search for why suspension bridges have the inverted arch shape (catenary), it will be your mathematical answer for why the trailing edge of bat wings are like that.