KrisFlyZ 0 #1 May 27, 2007 Tip Vortex(center parallel to chord) ======== Due to the pressure difference between the upper and lower surface of the wing, a vortex is formed at the tip of all finite wings. The result of the vortex formation is an increase in the drag. This drag is related to the amount of lift produced. The vortices can be visualized in "holy smoke" and "Fly the Line" videos(yellow smoke). Induced drag is proportional to the square of the weight and inversly proportional to square of velocity, square of span and inversely proportional to density. This may explain why BASE flights are better and why people rave about flights in 'clean air'. In the traditional sense L/D = Cl/Cd and this is not effected by density. Weight increases at a faster rate than strength in muscles. Trying to increase strength too much, due to the cost of increased weight is not beneficial to wingsuit performance. Look at how gliders of massive wingspan still have wingtip devices to deal with tip vortices. search for "eta glider" and look at the pictures. If it is significant for then, the relative importance of induced drag for wingsuit flight is more given the short span, the slower speeds and the amount of wing area that is effected by the tip vortex. Can induced drag be reduced for wingsuit flight? We cannot reduce the other forms of drag for a given person and a given wingsuit. a) Drooping tips and Spanwise Camber. There is published research material that shows that wings with spanwise camber and a wingtip at 90 degrees to the flow reduce induced drag. Another effect of drooping wingtips is that they create suction at the leading edge. b) Spanwise twist. This along with a wingtip at a negative(that is correct negative) angle of attack is supposed to create a 'beneficial vortex' (US Patent 5634613...Prof Kallend, your input is much appreciated). Beneficial being in the opposite direction of the tip vortex at the tip in question. We cannot use angle of attack loosely anymore. This is not necessarily constant across the span. Bound Vortex(Center parallel to span) =========== Search inside the book "Nature's Flyers: Birds, Insects and the Biomechanics of Flight " on amazon.com and search for "bound vortex trailing edge" there is a nice explanation on page 23 and 24. Quote Share this post Link to post Share on other sites
riggerrob 558 #2 June 6, 2007 Bound Vortex(Center parallel to span) =========== Search inside the book "Nature's Flyers: Birds, Insects and the Biomechanics of Flight " on amazon.com and search for "bound vortex trailing edge" there is a nice explanation on page 23 and 24. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Similarly, Withold Kasper did a bunch of research about "bound vortices." Kasper built a series of wooden, swept wing sailplanes during the 1950s and 1960s. He demonstrated unique "tumbling" maneuvers at several airshows. During the 1970s, he also built a few powered ultra-lights, also with swept wings. The ultra-lights included extra flaps/spoilers on the top skin to encourage the formation of bound vortices. Kasper reported ridiculously low rates of descent at high angles of attack. Kasper also enjoyed a long engineering career at Boeing designing complex wing flaps for several Boeing airliners. There is a fascinating article about Withold Kapser on the TWITT website. Quote Share this post Link to post Share on other sites
KrisFlyZ 0 #3 June 6, 2007 There are good illistrations of the 'bound vortices' that Kasper Witold researched in patent 3,831,885 that are mentioned in riggerrob's post. The bound vortex that is discussed in that book(original post) is different to the one researched by Kasper Witold. www.twitt.org is an interesting site. Kris. Quote Share this post Link to post Share on other sites
The bound vortex that is discussed in that book(original post) is different to the one researched by Kasper Witold.
www.twitt.org is an interesting site.
Kris.
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