Angle of attack (or gravity is my only engine)

[SimonM 0]

Hi Guys,

I was doing some jumps with Tonto and Taya over the weekend (S3 & GTi, I was in S3). When they dropped the hammer, they got a lot (and I mean a lot) more forward speed then I could get, however they were also dropping faster. I seemed to have a better glide ratio ie I flew past the point where they opened. However this wasnt much fun as a flocking dive.

It got me thinking about the ideal 'angle of attack' for want of a better word.

Firstly, what angle relative to the horizon will produce the best glide ratio.

Secondly is changing this angle a good way to vary speed/lift ie when trying to stay with very floaty flockers, can you angle upwards and angle downwards when trying to stay with fast flockers. In other words put the gravity engine to use to get more or less speed when needed.

Up to now I have been using my legs & body position to control speed/lift ie bend legs up to stay with slower suits.

Any thoughts appreciated.

Simon

PS it is amazing the more I fly my suit the more I realise it so so much more like flying than skydiving!

[KrisFlyZ 0]

I started playing with angle of attack on the last jump.
From a maxed out position I started to slowly increase the angle of attack. The 20 sec period I have marked on the plot is the part where I was experimenting with angle of attack. I have GPSed a few of my jumps and have flown as fast as 120 mph forward speed but the sensation and visuals of speed I felt during this period was like nothing I have experienced before.

I think that a high angle of attack provides more forward speed because the relative wind is coming at the glide angle, a higher angle of attack provides, lesser resistance to the relative wind and accounts for a higher forward speed. Because the surface provided to the vertical is reduced, fall rate will be more than when flying parallel to the horizon.

The reason you reached farther might have to do with wingloading more than anything else. Want to post height weight for the jumpers involved?

Edited to added: Also check this post by vesa.

Kris.

[verticalflyer 11]

Quote

Because the surface provided to the vertical is reduced, fall rate will be more than when flying parallel to the horizon.

Kris.

Not neccessarily if the angle of attack is at its optimum which is nearly always greater than parrallel, you will be generating greater lift as you fly forwards this coupled with your forward speed should give you a decreased descent rate. This is the whole point of finding the sweet spot, if you look at any basic wing lift diagram you will see what I mean, there are some good interactive models on the NASA website. Your wing profile is entirely dependent on your leading edge arm , body shape and how you fly. So its different for everyone.

This is why when going for longest flights the slowest vertical descent velocities are generally achived on the distance flight. not when trying to maintain a rigid wing parrallel to the horizon.

Hope that helps.

Cheers

Fraser

Dont just talk about it, Do it!

[ph8068 0]

Angle of attack is the relative angle between your body and the approaching airflow.

Angle of pitch is the relative angle between your body and the horizon.

If you are flying almost parallel to the horizon, your angle of pitch is very low and your angle of incidence is very high. This will give you a very slow forward speed.

Now if you lower your pitch angle (i.e. go slightly head-down) then your angle of attack will decrease dramatically, and your forward speed will increase.

Which method gives you the lowest vertical speed is an entirely different debate!

[KrisFlyZ 0]

Quote

Angle of attack is the relative angle between your body and the approaching airflow.

I think when people(and highly experienced people have used the term angle of attack...look at Hans-solos post and videos in the BASE forum, And read Vesa's post(link in my previous post). They specifically said high angle of attack.) I think they meant relative to the horizon. That is why according to them a high angle produces a faster forward speed.

Yeah, I did not know the definition of angle of attack. .

Kris

[verticalflyer 11]

Kris, that was exactly what I meant, Paul Housley is right on terminology but I am not getting into discussion on arm rotation etc which really is the angle of pitch on the arm wing if you represent the human body with wingsuit as an aircraft realtive to the horizon, I could ramble on about all the different dynamics etc and relative airflows but most users of this forum they would probably fall asleep before they got to the bottom. What I have personally found is when flying fairly high "angles of attack" we can achieve the longest flights in distance and time, average speed of 42mph while racing cars on the motorway cant be too bad on a skyflyer.

Most people find this through feel and watching the ground race by with a big grin on there face;)

Anyway for those who would like a little more on basic terminology :http://www.aerospaceweb.org/question/aerodynamics/q0165.shtml

Cheers

Fraser

Dont just talk about it, Do it!

[KrisFlyZ 0]

Thanks for the explanation and the link.
Kris.

[robibird 3]

boys, this will help to those who like to get more....

Ilan Kroo : Applied Aerodynamics-A Digital Textbook (www.desktopaero.com)
John D.Anderson,Jr :Introduction to Flight (www.mhhe.com ,ISBN
0-07-116034-5)

Robert Pecnik
robert@phoenix-fly.com
www.phoenix-fly.com

[j3zz 0]

this is a slightly off topic question but relevant to this thread.

When doing atmonauti you go head low which actually gives you a slower vertical speed than bellly flying which is counter intuitive.

The apparent logic is that somehow your body creates an amount of lift in this configuration.(you can actually feel youself bieng pull up by you rig)

So in a Birdman suit would this hold true and at what angle would you get the maximum lift??

I am not a birdman Yet but in interests me greatly

What is the normal angle relative to the horizontal for Birdman light? head; high, low or neutral

Jezz

"Now I know why the birds fly"
Hinton Skydivers

[SimonM 0]

Quote

If you are flying almost parallel to the horizon, your angle of pitch is very low and your angle of incidence is very high. This will give you a very slow forward speed.

Now if you lower your pitch angle (i.e. go slightly head-down) then your angle of attack will decrease dramatically, and your forward speed will increase.

Thanks for this, together with all the other mails, it has given me another dimension to my flight.

Simon

[LouDiamond 1]

Quote

When doing atmonauti you go head low which actually gives you a slower vertical speed than bellly flying which is counter intuitive

In a BirdMan suit that is known as a dive and won't give you a slower fall rate.

"It's just skydiving..additional drama is not required"
Some people dream about flying, I live my dream
SKYMONKEY PUBLISHING

[TomAiello 26]

Quote

John D.Anderson,Jr :Introduction to Flight (www.mhhe.com ,ISBN
0-07-116034-5)

Is this an updated version of the same text?

Or is it a separate work? Do you know?

Thanks for the references! Much appreciated!

-- Tom Aiello

Tom@SnakeRiverBASE.com
SnakeRiverBASE.com