Basejumper.com - archive

I'm heading to TF this weekend and one of the things on my "may do" list is what I've been calling the cat flip. I've seen this done many times before, and it seems like a good starting point for exits other than "flat and stable".

The idea, in case it isn't perfectly obvious, would be to exit more or less on my back, then roll onto my front and pitch. I've been thinking about this for a year or so now, and I think I've got the mechanics worked out. But I want to take this opportunity to confer with the rest of you who may have tried this before...

For the exit, I'm thinking it's important to launch into the back-to-earth position, rather than rotating into it. I've seen a friend try to rotate backward off the bridge, and naturally it turned into an aweful mess. I've never done this kind of exit before, but it doesn't really seem like the sort of thing one can try before doing a cat flip (otherwise, what are you going to do about pulling?). On my face-to-earth exits lately, I've been toying with exiting fairly flat--not by rotating there, but just by placing my body on the air that way. This seems to work fine, and I assume the theory would carry across to a backward exit.

Once I'm in the air, as I understand it what I want to do is to cross my right arm over my chest with sort of a "pushing through" motion instead of swinging around a wide arc. Similarly, I want to cross my right leg over top of my left. To do the flip, I imagine using my crossed right arm and leg as kind of an inertial "anchor" while I bring the left half of my body underneath so that I am face-to-earth.

There are a couple of safety points I've thought about. I'm thinking of doing this slider-down in order to minimize the risk of severe line twists on opening, but I am also aware that this puts time constraints on the manoeuvre. Also, I'm obviously thinking of rolling onto my left side, so that if the thing goes only partway I am at least chucking the pilot chute into clean air.

What I'd like to hear is any advice on performing the flip. If you think this is a great/terrible idea as a first advanced exit, I'd like to hear that. If you have tried this and have some tips to share, I'd like to hear that. Also, I'd like to hear any recommendations on the gear configuration, things I should watch out for, etc.

Of course, if you have something to share that doesn't fit neatly into the above categories, I am positively not interested in hearing it. I'm kidding. Any advice at all is welcome. Thanks, everyone!

Michael

P.S. Edited because I meant to say that slider-down should result in less chance of severe line twists.

Huh? That sounds contradictory to what I've been taught. Please elaborate.

Anyway, you probably already thought of this, but diving-board training would be great for this.

Edited to add: I assume you've seen the Higgly Wiggly in the "Portland Crew In Perrine" video (the one with the backseat packjob)? Not entirely the same, but related...

This was the very first aerial I ever did. It seemed to me then (and still does) to be a good safety skill before trying other things (so that I could get off my back if I stalled there).

I've found that bringing both hands and both feet in simultaneously helps me start the rotation (you do have to use body english to establish the direction of rotation). I've also found that bringing them (hands and feet) back out helps to stop the rotation once you are belly to earth.

You can actually practice this in relative safety in your living room by just jumping up in the air and trying to spin once you're off the ground. You can also do it into a swimming pool (or similar training aid), but you have to be careful of the belly flop potential.

My bad. I meant to say "slider-down" would result in less chance of extreme line twist.

Michael

 

This is very good advice.

Rounds work well, too.

I was told this was called a" NESTE Plunge".I first saw Jason Bell do it on one of my first bandit jumps off a bridge many moons ago.Looks like fun.I saw something even cooler.I have a guy doing a cork screw(Barrel Roll) off a cliff.It was awesome.Way to go DUDE.

Hmmmmm.....this one's giving me visions of Michel G's first aerial attempt

Quote:"....and now for something a little different!"

(Tree knows what I'm talking about!) Want video!!

My only advice is exit head high...the rotation effort may send you head low on deployment.

Slider up and a boat highly recommended!

If you have access to a trampoline, try to bounce on your back several times then rotate over all the way back to your back. Doing this will teach you how to do it without taking you off axis.It is surprising how little input you need to do this.

 

Definately agree with slider up. My first arial was a front flip. Needless to say, I overrotated and opened up head down slider off. Worst pain I ever felt in jumping. Luckily nothing is broken, however my back is still sore, a month later. I thought about trying the Cat flip too but was gun shy after the painful opening.

Good luck. Let us know how it goes.

The phrase, "Let's try something a little different," as well as the ensuing flail-fest is burned into my mind. This is one of the reasons I'm not so sure about the back-to-earth exit. I believe the key would be to launch into it, rather than rotate off the exit point.

I haven't heard from Michel in forever, but I heard he's back in town, so perhaps that will change.

Michael

It was the first thing (aerial) I tried. I did it on Italian TW, slider up. It took me ~4 sec to do a comfortable exit (back-to-earth), comfortable freefall and flip. Last time I did it in ~2 or a bit longer sec.
It's easy to go headdown (same as in standart face-to-earth freefall). But you will go headdown only if you make an input to it during the exit movement. If you're able to go flat'n'stable faced to earth, try to apply it to this jump. Same flat'n'stable thing, but faced to the sky.
It's also very easy to do a flip if you really want to open in a regular position. I've been training it in gymnasium for a couple of hours. Not on trampoline or to the foam-pool. Just from 3-6 feet platform to the thick matrasses. Look on figure skating athletes or on dancers -- they are doing twists using their arms/legs movements. Same thing.

But even if you'll do it with "running" legs in headdown, it'll be ok, you have to roll anyways if you want to pull the PC faced to the ground.

Just my experience suitable for 4+ delays
Some pics of the very first one are here: exit -- http://maxf.net/...4/pages/IMG_0347.htm and two next pics -- freefall. I went slightly headdown as you can see.

And the main thing -- SMILE!

edited to add pics

If you are doing it off a terminal object, I think it's easier to learn by doing a standard flat and stable exit, then flipping onto your back, then flipping again onto your front. Once you have this down, it's easy to do it in 3 or 4 seconds. As an added bonus, you don't carry any rotation.

That's what the other jumpers said to me then. But the "backward" exit scared me much harder and terminal object made me relaxed. Plus my intention to film my friends here jumping on the back from ~1200 ft exit.

You could also use an aircraft and a basic skydive as training grounds for any terminal aerials, the 'hill' is a great place to learn from a slower jump run aircraft. But maybe I am just stating the obvious.

nic

I thought the law of conservation of angular momentum would prevent the body from doing 180 in dead air, unless you have a tail, which you can rotate to make your body rotate in opposite direction, like cats do.

When air is not so dead after a couple of seconds, you can flip, but that's not a true cat flip.

Saying this not to teach you, but just in case, so you don't find yourself in dead air thinking, "Jeez, physics does work!"

That's not the case.

Since your angular momentum is conserved, you can twist your body and flip by essentially pushing the momentum around.

Hee, hee... Let ME tell you about that! I'm waiting for the x-rays then I'll show ya what that did to me.

Hi veter_,


as Tom says, a twist in dead air is indeed possible (luckily for crwper ).

What is not possible of course is to create a continuous twisting motion if you start with zero total angular momentum. But a 180 degree (which then stops) twist is done via varying the relative moments of inertia of your body parts (with the arms etc.).

It is a little bit weird to follow all the moments of inertia, change of angular momentum etc., but it is essentially what cats do if you have let them drop back to earth: they have zero (total) angular momentum, no torque is applied, and still they manage to twist 180 degrees in order to land on their feet.

Do a search in the net e.g. for "physics cat twists". Physics at work...


All the best.

http://www.usa-gymnastics.org/...1997/2/twisting.html

http://www.coachesinfo.com/category/gymnastics/68/

This is just a list of what is being done in ski freestyle aerials:

http://www.tommy.com/skiteam/glossary.jsp

With the help of inertia of the skis they can do up to
four flips with three twists and land right side up on a steep slope. They flail hands like crazy to rotate and twist. The body is supposed to stay straight for good style.

This is a little bit off topic (related to physics, but not BASE), but a friend and I were arguing the other day about whether or not there's a linear analog to this. Do you think, if you were floating around in zero g, you could get from point a to point b by small linear "scoots", the same way you can spin around while sitting on a barstool by several "flail" type motions that each rotate you a little ways?

base515 sez:
"Aerials are soooo 90's."

I don't think so. You can actually generate a continuous rotation of your body if your swing your arms. Imagine that you are floating in the middle of space. Then begin windmilling your arms. This introduces angular momentum to your arms, which must be countered by an opposing momentum in your body, i.e. your body will rotate in the opposite direction. The reason this can work is because angular motions can eventually return to the starting point without changing the direction of motion, so you can do it indefinitely. With a linear motion, the only way to move forward would be to shoot something backward. But you can't get back to the "starting point" without reversing your hard work.

Michael

For the physics-inclined... Imagine you're looking down on someone's head. They have just launched on their back and are now in freefall, but not yet with any appreciable windspeed. They are going to roll over onto their left side.

First, they cross the right arm and right leg over the left, and possibly also the left arm and leg under the right, but keeping them close to the axis of the body. This generates a small amount of angular momentum in the counter-clockwise direction (mass of arms and legs, but with a very small radius of motion). The body will respond by moving very slightly in a clockwise direction. Thus, total angular momentum is zero.

Next, the arms and legs are brought back to the starting position but around a wide arc. This means arms and legs as far as possible from the body. This is the same mass as the first motion, but over a much larger radius. Thus, more angular momentum in a clockwise direction. The body responds with a significant movement in the counter-clockwise direction.

When you have completed the cycle, you have at no point created anguular momentum (the total was zero all the time), but the net effect is that your body has rotated in a clockwise direction.

As I said in another post, part of the reason this seems wierd is because it's possible to carry out a rotational motion and wind up back where you started. The classic linear momentum experiment, where you throw a ball away from you in freefall, would look a little different if you could throw the ball away from you, then catch it again without ever actually reversing the momentum of the ball.

Michael