Leaning back while coming in fast

[vortexr1 0]

Just curious if someone can help me out.So as im coming down from my 180 s or 90 s i tend to lean back while traveling across ground.Getting lots of speed but just cant figure out how to lean forward and the pros and cons of that.Thanks.

[AggieDave 6]

Ever do heavy barbell squats in the gym? Big chest and head up.

That is what it feels like to me as you roll out of the dive, big chest forward and head up.

You'll probably get more out of your roll out technique if you focus on being still in the harness. Moving around promotes movement in the canopy. Most find this happening side to side in the harness as they roll out of the dive. So to keep in the course through the swoop people end up making really small side to side rocking motions, which eats efficiency, speed and distance.

--"When I die, may I be surrounded by scattered chrome and burning gasoline."

[vortexr1 0]

Hey thanks. That makes alot of sence.

[polarbear 1]

I had a conversation with Nick Batsch about this a year ago. He told me that his experience with forward/backward lean started with ground launching, where they found that leaning forward caused the canopy to fly flatter while leaning backwards caused the canopy to fly steeper. Translating over to swooping, this means leaning back keeps the canopy in a dive, leaning forward causes the canopy to start recovering.

This seems counter-intuitive to me; I would expect the opposite. But that's what the man said, and Nick is probably the best at forward/backward weight shift I have ever seen.

I also think there is an aertodynamic benefit...leaning forward in the harness aggressively presents your body to the wind in a more aerodynamic shape, sort of like flying head down vs. belly flying.

Personally I agree with Dave that being smooth in the harness is probably more important then forward/backward lean. I also find that forward and backward lean is pretty difficult. I've only seen a few who are really good at it, but they sure get good results.

"Holy s*** that was f***in' cold!"

[DaVinciflies 0]

Can anyone expand on why this might be?

I too thought, originally, that leaning back would cause loading of both rear risers and a resultant planing out of the canopy.

However, in reality, the weight shift between the fronts and rears is likely to be negligible since we are effectively hung beneath a pivot where the risers meet the harness.

So, how does leaning forward/back actually affect the glide of the canopy? One theory I have is that is relates purely to the drag of the jumper.

Lean back - more drag - canopy moves forward relative to jumper - more dive.

Lean fwd - less drag - jumper moves forward relative to canopy - flatter glide.

[Calvin19 0]

The only effects a hanging harness body position can have on any canopy is:

-variable parasite drag.
-lateral riser spacing.
-accessibility to riser inputs
- feelings of brake and riser inputs.

Any claim that "leaning forward" in a harness affects canopy flight is most likely true, but it uses one of the above to do so.

[yoink 321]

what about suspended centre of mass?

We're not suspended from our C of G, although while vertical it all tends to be in the same place regardless of our harness shift. I don't think it's unbelievable to think that a human who leans forward and tucks their legs up shifts their centre of mass forward under the wing - not by much, but maybe it's enough.

As far as I'm aware, a for a human that centre of mass is just in front of the second sacral vertebrae. If someone is wearing a weight vest, leaning forward will move a larger portion of that suspended mass forward than is counter balanced by the legs.


WHY this would affect a wing in the way it does, I've no idea. I've never understood it. I may well be wrong. My point is that I do think it's overly simplistic to state that the 4 reasons that you've listed are definitively the only possible reasons for a change in performance unless you can prove it mathematically.

[Calvin19 0]

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what about suspended centre of mass?

We're not suspended from our C of G, although while vertical it all tends to be in the same place regardless of our harness shift. I don't think it's unbelievable to think that a human who leans forward and tucks their legs up shifts their centre of mass forward under the wing - not by much, but maybe it's enough.

As far as I'm aware, a for a human that centre of mass is just in front of the second sacral vertebrae. If someone is wearing a weight vest, leaning forward will move a larger portion of that suspended mass forward than is counter balanced by the legs.


WHY this would affect a wing in the way it does, I've no idea. I've never understood it. I may well be wrong. My point is that I do think it's overly simplistic to state that the 4 reasons that you've listed are definitively the only possible reasons for a change in performance unless you can prove it mathematically.

I'm open to a mathematician telling me I am wrong, but the way I understand physics and aerodynamics, Newton and Bernoulli usually win.

There are two different "CGs" we can talk about.
There is the overall pilot/canopy aircraft CG that is located, depending on the kind of canopy, about at the pilots upper chest or higher. (we could also go into inertial mass CG because our airfoils are filled with a neutrally boyant fluid, but lets draw the line at the first example)

The center of mass (CG) is going to be directly underneath the hang point, this is entire principal of a suspended load.

No matter how you change your body position, the center of mass/CG will be suspended directly below the center of lift of the wing. If you have no riser or brake pressure this will be directly underneath the harness hang points. (Of course, air drag will come into effect, but at trim speed this would be negligible, let's keep it simple)

One thing I did not mention was we could change the distance between the COL and the CG. If you lean forward or backward, the center of mass of the pilot/canopy will be shortened.

Batsch mentioned "flatter" glide while leaning forward while ground launching. The basic PG/ground launching idea for launching is leaning as far forward as possible and charging head-low to power the glider into the air with maximum speed. This "torpedo" position allows the pilot to get ahead of the lifting force of the glider to allow them to use the remaining tread friction they have from the remaining weight on their feet. A pilot runs until the lift of the wing equals the force of gravity and there is no available weight left to power the pilot forward. The opposite of this is the "half assed" launch where the pilot hesitates on the launch run, possibly getting off the ground in a more vertical or even leaned back position. Obviously the initial glide on this flight would be of significantly steeper angle.

-SPACE-

[morris 0]

At the moment I don´t have the time to write a detailed answer. So I´ll give you just some thoughts to think about...
Let´s say you´re under canopy and apply a frontriser input. This will - as we know - bring the nose down. Now lets give the very same input once again, but in addition lets lift your legs up in front of your body. What will happen?
Lifting your legs will move the masscenter of your body forward.
It will now not be any longer "somewhere in your stomach"/hips/inside your body - instead, it will be inbetween your body and your legs, "somewhere in front of your stomach"/body/hips.
Agreed so far? Got it so far?
Someone already mentioned that the masscenter will always be (or always wants to be) in a neutral position under the wing. (Inputs can of course move it away from that position, but that´s not what I´m talking about here.)
Now that you moved the masscenter to the front of your upperbody, your upperbody will move backwards(!) to place the masscenter back into that neutral position under the wing.
What does that cause?
As your upperbody is connected by the risers to the wing, any backward movement of your upperbody is also a backward movement of your risers.
Any backward movement of your risers will bring the nose of your canopy even more/steeper down.
If you havn´t done so far, give it a try, compare a frontriser input while being neutral under the wing with a frontriserinput with the legs in front of your body. The difference in the steepness of your dive (straight on, no turn) will be very noticable...
Now lets talk about flaring and swooping (I´m talking about the horizontal (or even climbing) part of swooping here, the traveling across the round, not the turn or recovery or whatever).
If it comes to those, things are a bit different.
I guess you know the difference between braking and flaring? Just once again: If you go slowly(!) from full flight to deep brakes, your body will stay in the neutral position under the wing at any time. (Neutral position for full flight and deep brakes might be a different one, but that´s once again not what I´m talking about here). To make the input be called flaring instead of braking, you need to apply the input faster. From a certain speed on, it´s a dynamic "thing" that will make your masscenter move out to the front - bringing the nose up. The more you are able to move to the front, the more you´ll bring the nose up (in addition to the nose-up-movement caused by toggle- or rearinput). For that reason leaning forward while flaring will result in better outcomes, and the same goes for swooping. During a swoop your body wants to place itself in front of the wing anyways as the wing has more drag (and less mass) than your body. The higher the airspeed the more noticable is that effect. During a swoop you are kind of pulling your wing along (behind yourself).
The more you are able to place yourself in front of the neutral position, the more you´ll bring the nose up.
If you are going for the extreme by being horizontal in the harness, timing (and speed) is critical.
Why is that? Lets say you are waiting till most of your airspeed is gone before you move to that bodyposition. Now bringing the masscenter out front while flying at a slow airspeed, will cause the opposite! We are now not in that dynamic high airspeed flaring kind of mode anymore. So moving the masscenter out to the front will now be causing the same it did while giving a frontriser input out of a neutral position under the wing - it will cause you to move back and bring the nose down...

[davelepka 4]

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The only effects a hanging harness body position can have on any canopy is:

-variable parasite drag.
-lateral riser spacing.
-accessibility to riser inputs
- feelings of brake and riser inputs.

Any claim that "leaning forward" in a harness affects canopy flight is most likely true, but it uses one of the above to do so.

Without going into an extended explanation, I'm with you on this one. It's been discussed ad nauseum here, but the simple fact is that we're hanging from a single point, the pilot's weight will always center itself under the attachment point. It's called gravity.

In order for weight shift to effect the pitch of the canopy, you need a second attachment point which you can lever yourself against to hold your weight in that alternate position. Hang gliders are the model for this control input, as that is their entire basis for control input, hence the classification of 'weight shift gliders'.

In terms of the drag reduction, and it's potential as a side effect of pilot position, reduction in frontal area will always casue a reduction in drag, however, let's remember that drag increases with the square of speed, which means the inverse is true, so the effects of drag (and any advantage pilot position may afford) will decrease sharply as your airspeed decays toward the end of your swoop.

[Guinness_fr 0]

Man I love those discussions, especially when non-swooping skydivers look down on us as some front-risers pulling monkeys
If only they knew how much care is given to scrape every further inch out of our swoops

Keep it coming guys !

[AdD 1]

I would love to know the answer to this one, from a speedfly point of view there is a lot of benefit to leading forward on launch but there is not enough speed for drag difference to really be a factor.

Life is ez
On the dz
Every jumper's dream
3 rigs and an airstream

[davelepka 4]

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there is a lot of benefit to leading forward on launch

Every try to run leaning backwards? I'm think a big part of it is biomechanics, not aerodynamics. You cannot be accelerating and putting one foot in front of the other unless you're leaning forward.

Try running 50ft and see which direction you lean. For fun, try stopping as quickly as possible, and see which way you lean then.

Additionally, think about your launches. Do you lean more forward when there is less wind? When there is substantial wind, don't you somtimes just take one or two easy steps, or maybe even just hop up and apply input create some lift? In those cases, the forward lean isn't needed because you're not running anywhere. The wing will launch just the same because the airspeed is provided by the wind, not the pilot.

From a pitch perspective, you're just a piece of meat hanging from a hook. Case in point, look at paragliders, and which direction they lean for their entire flight.

[Calvin19 0]

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I would love to know the answer to this one, from a speedfly point of view there is a lot of benefit to leading forward on launch but there is not enough speed for drag difference to really be a factor.

Like I said earlier:

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Batsch mentioned "flatter" glide while leaning forward while ground launching. The basic PG/ground launching idea for launching is leaning as far forward as possible and charging head-low to power the glider into the air with maximum speed. This "torpedo" position allows the pilot to get ahead of the lifting force of the glider to allow them to use the remaining tread friction they have from the remaining weight on their feet. A pilot runs until the lift of the wing equals the force of gravity and there is no available weight left to power the pilot forward. The opposite of this is the "half assed" launch where the pilot hesitates on the launch run, possibly getting off the ground in a more vertical or even leaned back position. Obviously the initial glide on this flight would be of significantly steeper angle.

Really not that complicated.

In acro/XC paragliding (like high end competitive swooping) these tiny things like .1% drag degrease that are discussed at length on dorkzone actually come into play. In paragliding, we use glide ratio and sink rate benefit factors religiously.
SO: If it were a benefit to the flight characteristics of a canopy/pilot machine, paraglider engineers and competitors would be doing it.
AND: the best paraglider and "ground launch" pilots in the world "lean forward" to launch, lay WAY back in a custom aerodynamic harness to fly long distances (or WAY forward like a pro swooper does). the reason for this in paragliding is a significant decrease in parasite drag/form drag. For acro we sit upright giving the most nimble harness inputs and acceleration ("G force") rigidity.

-SPACE-

[Calvin19 0]

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At the moment I don´t have the time to write a detailed answer. So I´ll give you just some thoughts to think about...
Let´s say you´re under canopy and apply a frontriser input. This will - as we know - bring the nose down. Now lets give the very same input once again, but in addition lets lift your legs up in front of your body. What will happen?
Lifting your legs will move the masscenter of your body forward.
It will now not be any longer "somewhere in your stomach"/hips/inside your body - instead, it will be inbetween your body and your legs, "somewhere in front of your stomach"/body/hips.
Agreed so far? Got it so far?
Someone already mentioned that the masscenter will always be (or always wants to be) in a neutral position under the wing. (Inputs can of course move it away from that position, but that´s not what I´m talking about here.)
Now that you moved the masscenter to the front of your upperbody, your upperbody will move backwards(!) to place the masscenter back into that neutral position under the wing.
What does that cause?
As your upperbody is connected by the risers to the wing, any backward movement of your upperbody is also a backward movement of your risers.
Any backward movement of your risers will bring the nose of your canopy even more/steeper down.
If you havn´t done so far, give it a try, compare a frontriser input while being neutral under the wing with a frontriserinput with the legs in front of your body. The difference in the steepness of your dive (straight on, no turn) will be very noticable...
Now lets talk about flaring and swooping (I´m talking about the horizontal (or even climbing) part of swooping here, the traveling across the round, not the turn or recovery or whatever).
If it comes to those, things are a bit different.
I guess you know the difference between braking and flaring? Just once again: If you go slowly(!) from full flight to deep brakes, your body will stay in the neutral position under the wing at any time. (Neutral position for full flight and deep brakes might be a different one, but that´s once again not what I´m talking about here). To make the input be called flaring instead of braking, you need to apply the input faster. From a certain speed on, it´s a dynamic "thing" that will make your masscenter move out to the front - bringing the nose up. The more you are able to move to the front, the more you´ll bring the nose up (in addition to the nose-up-movement caused by toggle- or rearinput). For that reason leaning forward while flaring will result in better outcomes, and the same goes for swooping. During a swoop your body wants to place itself in front of the wing anyways as the wing has more drag (and less mass) than your body. The higher the airspeed the more noticable is that effect. During a swoop you are kind of pulling your wing along (behind yourself).
The more you are able to place yourself in front of the neutral position, the more you´ll bring the nose up.
If you are going for the extreme by being horizontal in the harness, timing (and speed) is critical.
Why is that? Lets say you are waiting till most of your airspeed is gone before you move to that bodyposition. Now bringing the masscenter out front while flying at a slow airspeed, will cause the opposite! We are now not in that dynamic high airspeed flaring kind of mode anymore. So moving the masscenter out to the front will now be causing the same it did while giving a frontriser input out of a neutral position under the wing - it will cause you to move back and bring the nose down...

Awesome info. morris goes into the more complicated inertial energy retention of a glider, and I did not mention any of that. Also, my posts are mostly discussing un-accelerated flight. Obviously, one can change the center of lift and center of mass of there canopy/pilot machine by manipulating risers (front riser diving turn). This would move both the center of lift and the center of mass forward. (The center of mass would still be directly below the center of lift, not accounting for form and induced drag). In un-accelerated flight, the COL is ahead of the CG in a balance between form drag, induced drag, and lift. in accelerated flight these vectors will all change, but still be in the same orientation. "leaning forward" without manipulating the airfoil (pulling on front risers) will only change the form drag of the pilot. Pulling on the front risers, pulling legs to chest and leaning to one side is in part leaning forward, but all you really are doing is changing the AOA of the wing by pulling down the nose. If you could lean back while pulling down the front risers it would do the same thing.

-SPACE-

[gaz511 0]

practice leaning forward whilst doing your turn and plaining out at altitude, you'll soon get used to it, you can lean much further forward once you've let go of the riser onto brakes as your sholder joint has it's limits. Get used to leaning on your chest strap too, you soon learn to trust it especially if it's loose and you don't feel it until you think your about to fall out. Soon you'll be leaning so far foward you'll want a longer strap or doing shit like this where trusting your chest strap is pretty much a must


http://www.youtube.com/watch?v=yl-XsUF0C44

[kuai43 7]

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practice leaning forward whilst doing your turn and plaining out at altitude, you'll soon get used to it, you can lean much further forward once you've let go of the riser onto brakes as your sholder joint has it's limits. Get used to leaning on your chest strap too, you soon learn to trust it especially if it's loose and you don't feel it until you think your about to fall out. Soon you'll be leaning so far foward you'll want a longer strap or doing shit like this where trusting your chest strap is pretty much a must


http://www.youtube.com/watch?v=yl-XsUF0C44

Did I miss the part where he trusted his rears?

Every fight is a food fight if you're a cannibal

Goodness is something to be chosen. When a man cannot choose, he ceases to be a man. - Anthony Burgess

[matt002 0]

You can also flare on rears by twisting the rears rather than pulling them, basically leaning forward and twisting your arms so you elbow face upwards with a straight locked out arm.
This allows you to lean forward aggressively while still using the rears. Takes some practice to get smooth imput this way though.

[gainer 0]

Here is my solution. Sorry if my explanation is confusing

Think of vector calculus. If we have a force that goes straight down and two forces at an equal angle then it stands to reason that the forces at angles will be equal, assuming you are in a neutral position. If I move forward, the angle on the rear will be less and the angle on the front riser will be more. What this means is that the rear risers gets more “force” but crucially the front riser get less “force” pitching the nose up.

It works the same if you lean back, more pressure on the front riser, less pressure on the rear hence the nose pitches down.

My 2c

[DaVinciflies 0]

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Here is my solution. Sorry if my explanation is confusing

Think of vector calculus. If we have a force that goes straight down and two forces at an equal angle then it stands to reason that the forces at angles will be equal, assuming you are in a neutral position. If I move forward, the angle on the rear will be less and the angle on the front riser will be more. What this means is that the rear risers gets more “force” but crucially the front riser get less “force” pitching the nose up.

It works the same if you lean back, more pressure on the front riser, less pressure on the rear hence the nose pitches down.

My 2c

I can't get my head around this. Do you not just pivot around the 3-ring?

[phoenixlpr 0]

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Just curious if someone can help me out.So as im coming down from my 180 s or 90 s i tend to lean back while traveling across ground.Getting lots of speed but just cant figure out how to lean forward and the pros and cons of that.Thanks.

How can you lean forward if you are suspended on 2 points only ?

[gs8613 0]

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At the moment I don´t have the time to write a detailed answer. So I´ll give you just some thoughts to think about...
Let´s say you´re under canopy and apply a frontriser input. This will - as we know - bring the nose down. Now lets give the very same input once again, but in addition lets lift your legs up in front of your body. What will happen?
Lifting your legs will move the masscenter of your body forward.
It will now not be any longer "somewhere in your stomach"/hips/inside your body - instead, it will be inbetween your body and your legs, "somewhere in front of your stomach"/body/hips.
Agreed so far? Got it so far?
Someone already mentioned that the masscenter will always be (or always wants to be) in a neutral position under the wing. (Inputs can of course move it away from that position, but that´s not what I´m talking about here.)
Now that you moved the masscenter to the front of your upperbody, your upperbody will move backwards(!) to place the masscenter back into that neutral position under the wing.
What does that cause?
As your upperbody is connected by the risers to the wing, any backward movement of your upperbody is also a backward movement of your risers.
Any backward movement of your risers will bring the nose of your canopy even more/steeper down.
If you havn´t done so far, give it a try, compare a frontriser input while being neutral under the wing with a frontriserinput with the legs in front of your body. The difference in the steepness of your dive (straight on, no turn) will be very noticable...
Now lets talk about flaring and swooping (I´m talking about the horizontal (or even climbing) part of swooping here, the traveling across the round, not the turn or recovery or whatever).
If it comes to those, things are a bit different.
I guess you know the difference between braking and flaring? Just once again: If you go slowly(!) from full flight to deep brakes, your body will stay in the neutral position under the wing at any time. (Neutral position for full flight and deep brakes might be a different one, but that´s once again not what I´m talking about here). To make the input be called flaring instead of braking, you need to apply the input faster. From a certain speed on, it´s a dynamic "thing" that will make your masscenter move out to the front - bringing the nose up. The more you are able to move to the front, the more you´ll bring the nose up (in addition to the nose-up-movement caused by toggle- or rearinput). For that reason leaning forward while flaring will result in better outcomes, and the same goes for swooping. During a swoop your body wants to place itself in front of the wing anyways as the wing has more drag (and less mass) than your body. The higher the airspeed the more noticable is that effect. During a swoop you are kind of pulling your wing along (behind yourself).
The more you are able to place yourself in front of the neutral position, the more you´ll bring the nose up.
If you are going for the extreme by being horizontal in the harness, timing (and speed) is critical.
Why is that? Lets say you are waiting till most of your airspeed is gone before you move to that bodyposition. Now bringing the masscenter out front while flying at a slow airspeed, will cause the opposite! We are now not in that dynamic high airspeed flaring kind of mode anymore. So moving the masscenter out to the front will now be causing the same it did while giving a frontriser input out of a neutral position under the wing - it will cause you to move back and bring the nose down...

I agree until you say:

Quote

As your upperbody is connected by the risers to the wing, any backward movement of your upperbody is also a backward movement of your risers.

Are you saying it creates a moment about the 3-ring or is just a conservation of momentum? Either way I don't really see how that could happen.

As far as I can tell, leaning forward in the harness can only reduce drag and bring your COM up.

Obviously reducing drag increases speed, and lift along with it.

Think of it this way.
In normal flight, you are hanging slightly behind your canopy due to the drag you create, this pitches your canopy slightly forward and steepens your glide. If you decrease your drag, you will hang further forward below the canopy. This will pitch the canopy up slightly and flatten the glide, increase your speed (reduced drag) and put the canopy into a more efficient flying configuration.

Think of hanging a coin from the ceiling then blowing on it. It'll swing backwards. The ceiling in this case represents the canopy and is flying in a stable configuration so you can think of it as being "fixed". Difficult to explain exactly why.

Camera flyers - try suddenly opening your wings under canopy. You'll swing behind it, then go into a dive.

I think the canopy will also fly more efficiently as the AoA to the relative air will be more suitable. But I don't know that for sure....

[davelepka 4]

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Do you not just pivot around the 3-ring?

You do. From a fore/aft perspective, you're just a side of beef hanging from a meat hook. If you hook a side of beef in the center, it hangs level from the hook. If you hook it to one side, the 'bigger' end on one side of the hook will droop, while the 'little' end will raise. If you look at it from the side, and imagine a plumb line exending down from the hook, you'll see equal mass on either side of the line.

Same thing under canopy. You're always going to hang straight down under the canopy/3-ring, it's just how it works. Even if you could find some way to sustain an off-center position, the confluence wrap on the bottom of the riser will cancel out any forces you might be imparting. The risers don't become 'front' and 'rear' until above the confluence wrap, so any input intended to be specific to one riser or the other needs to be made above the confluence wrap. As it sits, the confluence wrap is above the pivot of the 3-ring, so you those two factors inbetween you as a hanging mass, and any discreet input to the front or rear risers.

The benefit to the forward lean is aerodynamic. It's very slight, and reduces exponentally with the decrease in speed, but that's the benefit. More important than that is flying a clean approach, and maintaining correct control inputs during the swoop. I would venture to say that spending time learning to lay forward in the harness without perfecting the rest is probably a waste. Chances are that you're going to give up some distance jacking around your body position, so you're giving up one thing to gain another.

Truth is, I wonder if laying back like a PG is the better way to go. As it sits, at the end of a distance run the pilot makes a huge move in the harness to pivot back and land on their ass. Some might argue that the swining motion might create a temporary pitch-up, but I would suggest that by the time the pilots are making that move, the canopies have 'given up the ghost' and are not going to be going any further. So if pilots could adopt a laying back position, they could remain still in the harness and maintain that position all the way to touchdown.

That's limited to competition distance runs. For normal swooping, you do want to be leaning forward to get your weight out in front of your feet, and facilitate running out a landing.

[daleskydive 0]

HI Morris,I only have just over400 jumps and

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I have just completed an intermediate canopy swoop course with Matt Harris. I want to make sure I have this right. So when I pitch roll and yaw its best to have my weight back a bit more to the rear of the canopy even when Im rolling out of the dive. Correct? And while I have plenty of airspeed move my weight forward until my airspeed starts to diminish? And when my airspeed diminishes?

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[daleskydive 0]

Sorry I got the last bit keep my weight forward to start running.