Vladimir Milosavljevic's mistakes on his 'Body Pilot in Command' video

[sundevil777 94]

He claims that the relative position of the center of pressure and the center of gravity has an effect on how fast/easy it is to turn (yaw axis).

This is not true. In the video, he claims that the mantix position with the lower center of pressure makes turning faster. The mantis position makes turning faster because of the relative effectiveness (force) of the surface presented to the wind, and the distance from the CG, not at all because of the CP/CG relative position. This relative position has an effect on pitch stability, and roll stability (therefore also effects your ability to slide in any direction), but does not at all effect yaw stability.

Vladimir talks like he has had some formal engineering education. He should be embarrassed.

People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am

[FrogNog 1]

You may be completely right about his being wrong, and perhaps about his background vis-a-vis his apparent claim to background, as well.

But recall that even professionals in their fields make mistakes and can't remember details - sometimes critical details that explain why something works.

And in those situations, it's good for someone to pipe up and suggest corrections.

If I recall with a chuckle, there still isn't aviation engineering agreement on whether airplanes fly because they generate lift on top of the wings or because they just shove enough air down.

-=-=-=-=-
Pull.

[upndownshop 0]

Vladimir talks like he has had some formal engineering education. He should be embarrassed.

[sundevil777 94]

Quote

If I recall with a chuckle, there still isn't aviation engineering agreement on whether airplanes fly because they generate lift on top of the wings or because they just shove enough air down.

There is no disagreement, it can just be done either way. A normal wing doesn't shove air down, in fact the air has to take a longer path on top of the wing, the bottom of a wing can be horizontal (not shoving any air down).

People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am

[sundevil777 94]

Unfortunately, Tamara doesn't know any better either.

Vlad says that a style jumper can turn faster because of their CP/CG position. WRONG! They can turn faster because the high speed gives more force on a 'control surface' and because of the tuck position having a lower rotational moment of inertia.

The CP/CG relative position does allow faster flips, that is the pitch axis.

I just find this very irritating when people talk technical, but are wrong.

People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am

[Kris 0]

Quote

You may be completely right about his being wrong, and perhaps about his background vis-a-vis his apparent claim to background, as well.

But recall that even professionals in their fields make mistakes and can't remember details - sometimes critical details that explain why something works.

Exactly. I was at a seminar with Orly King a couple of years ago. During his talk he remarked how important separation between groups is (and I agree, it is), then he went on to tell that using the "45-degree" rule is the best method for ensuring proper separation. As I was just a 200-jump chump at the time, I didn't speak up to correct him.

Orly King is a hell of a freeflyer, but I'll get out of the plane after him if that's how he's doing his spotting, thank you very much.

Point is, Vlad is a great jumper as well, and even the best can't have knowledge over all areas, or may have heard an explanation that seemed to fit and used it without checking into it further.

Sky, Muff Bro, Rodriguez Bro, and
Bastion of Purity and Innocence!™

[winsor 189]

Quote

Unfortunately, Tamara doesn't know any better either.

Vlad says that a style jumper can turn faster because of their CP/CG position. WRONG! They can turn faster because the high speed gives more force on a 'control surface' and because of the tuck position having a lower rotational moment of inertia.

The CP/CG relative position does allow faster flips, that is the pitch axis.

I just find this very irritating when people talk technical, but are wrong.

Vladimir gave me a copy, which I watched and returned. I consider it a waste of tape, and it was a waste of time watching it. I feel badly that Tammy's name was associated with the effort.

Any Sophomore in a related filed could tell you the truisim that instability is the handmaiden of maneuverability. By Grad school you should be able to evaluate this concept by means of a variety of analytical tools.

He does have a degree from an Engineering school in Belgrade, but does not work in the field. In the time I spent with him it was very apparent that he is weak in the fundamentals, and the tape simply demonstrates that fact.

Vladimir had maybe 350 jumps when he hung it up (he may have returned to the sport, but I doubt it), so you should bear in mind that you are viewing the product of a low time jumper with a rudimentary technical education who set out to make some money.

Since you have a copy of the tape to watch, it seems his goal was met - he made some money on the deal.

The Vladiball is also a money-making venture. A crude solution to a niche problem, it is cheap to make and ensures a good profit margin. Whether it works or not, he makes money.

Don't worry about the content of the video, it isn't worth discussion.


Blue skies,

Winsor

[winsor 189]

Quote

Quote

You may be completely right about his being wrong, and perhaps about his background vis-a-vis his apparent claim to background, as well.

But recall that even professionals in their fields make mistakes and can't remember details - sometimes critical details that explain why something works.

Exactly. I was at a seminar with Orly King a couple of years ago. During his talk he remarked how important separation between groups is (and I agree, it is), then he went on to tell that using the "45-degree" rule is the best method for ensuring proper separation. As I was just a 200-jump chump at the time, I didn't speak up to correct him.

Orly King is a hell of a freeflyer, but I'll get out of the plane after him if that's how he's doing his spotting, thank you very much.

Point is, Vlad is a great jumper as well, and even the best can't have knowledge over all areas, or may have heard an explanation that seemed to fit and used it without checking into it further.

Uh, I know Orly and I know Vladimir, and they are in no way comparable.

Orly is World Class, coming and going. An Engineer he is not, and, even if he says "45 degrees," in practice he is using a Mark 1 eyeball to be assured that the preceding group is well clear. When gauging separation he is WAY safe.

Vladimir was a mediocre Intermediate skydiver when he gave it up (look at the body position in the video - he doesn't even know enough to be embarrassed).

The video was not about passing on knowledge - he has nothing of significance to pass on. It's about a source of income for Vladimir.


Blue skies,

Winsor

[SurfFlite 0]

Wow, for a minute there I thought I was at .rec

I think Vladimir may have got lost in translation in that video. I really think his heart was in the right place. The bottom line is that as stability increases, maneuverability decreases and vis-versa. He's got that right and that's really the only point of the video.

As for the Vladiball. It works. There are ~400 Vladiballs out there right now and those who take the time to dial one in and can fly, like it. There are belly flyers using the ball with students and swear it is one of the best teaching tools to come along in quite a while.

Ever been paid Serbian wages Winsor? $120/month salary is considered middle class. So what's wrong with what he is doing? Vladiballs and Body Pilot In Command are both totally refundable if not satisfied and they are selling.I can't speak for the video but I have never had to refund money for a Vladiball. I have replaced 7 for either loosing the ball on the 1st jump or a broken hinge after not catching the ball on the 1st jump but that's it.


BTW, Cheryl Sterns had a great deal of input in the video. She likes it, but what does she know right?

At least, Vladimir has helped a few people understand the stability/maneuverability issues during a skydive.
At most, he invented a simple device that contributes to the safety of our sport. Cut the guy some slack.

Kerry

[billvon 2,464]

>A normal wing doesn't shove air down . . .

Every heavier than air flying machine shoves air downward to maintain level flight. In fact, they exert exactly the same amount of force on the air as their weight. You can see this 'shoving' explicitly under a hovering helicopter. In an airplane, the wing rapidly leaves behind the air it shoves down, and afterwards air from above rushes in to fill the space left behind. This results in wingtip vortices, where the air towards the center of the wing is moving down and the air outside the wing is moving up to "fill the void."

To see an animation of this check out http://www.aeromarineresearch.com/foilsim/foil.html Note that the only time that the streamline directly behind the wing is flat (i.e. no 'shoving' going on) is when lift is zero.

>in fact the air has to take a longer path on top of the wing, the bottom of
>a wing can be horizontal (not shoving any air down).

If you look at a wind tunnel streamline plot of that wing (or check out the above simulation) you will note that the air leaves the edge of the wing with a slight downward motion. The shape of the wing causes the air to exit with that slight direction change. That is where the lift comes from. It's an extension of Newton's second law.

[winsor 189]

In any language, Body Pilot in Command is execrable.

As far as the Vladiball goes, I'm underwhelmed.

I know more about things Serbian than you might imagine, and I take that into account in my assessment of these products. Even with the benefit of the doubt, I'm still unimpressed.

I cut slack where slack is due. I'm being generally benevolent here.


Blue skies,

Winsor

[sundevil777 94]

The chord line will be inclined to the horizontal, but just aft of the curved leading edge, a wing can be flat on the bottom and generate lift. The airfoil from your link looks to be symmetric, but it doesn't have to be.

Quote

The shape of the wing causes the air to exit with that slight direction change. That is where the lift comes from. It's an extension of Newton's second law.

Doesn't the lift comes from the difference in pressure, and the downward flow aft of the wing is a effect of that pressure difference?

Anyway, I was trying to distinguish between a flat plate and the more efficient airfoil section.

People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am