Why can't I pull my front risers?

[kallend 2,115]

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Actually, a Sabre is a rectangular square and a Pilot is a tapered square. Essentially, yes, it's a design decision; you'll simply have to try.

Just to clarify, the Sabre is square, while the Sabre 2 is tapered.

The Sabre is rectangular, not square.

...

The only sure way to survive a canopy collision is not to have one.

[BUBLHED 0]

Ellipticals have less drag on the sides of the canopy. This in turn will make them faster and more responsive in turns.

Any canopy that is built to be very stable will have more lift at the front of the canopy. Which is wear your a and b lines are therefore making front riser pressure higher. When this canopy increases speed more lift equals more pressure. This trait is determined by the trim more than anything else.

A less stable canopy will have the lift positioned further back thereby relieving some of the front riser pressure and making it easier to sustain a dive longer.

Doing the partial flare then going straight to front risers will help. As the canopy surges forwrd after the partial flare the riser pressure will be reduced. This will only be for a few seconds but may give you enough time to get it into a carving turn with even greater speed than a front riser dive.

At least that's the way i understand it. I could be totally wrong however. probebly am. not a canopy designer. not a expert pilot. Matter of fact you might want to ignore everything I've said. Maybie Brian G. will give us his thoughts.

ATTACK LIFE ! IT'S GOING TO KILL YOU ANYWAY!!!!

[riggerpaul 1]

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Any canopy that is built to be very stable will have more lift at the front of the canopy. Which is wear your a and b lines are therefore making front riser pressure higher. When this canopy increases speed more lift equals more pressure. This trait is determined by the trim more than anything else.

Something's still not quite right.

I have no problem with the center of lift being forward on a more stable canopy.

I have no problem with that meaning the proportion of the weight being supported by the A and B lines is higher, and that this will mean greater strength required to pull the front risers.

But you said "When this canopy increases speed more lift equals more pressure" and I'm having some trouble with that.

If this is true, then pulling the front risers would make you go UP? (Pull riser = more speed. More speed = more lift. More lift = flatter glide, or, apparently going UP?)

No, pulling front riser will decrease the angle of attack, making the canopy dive more. That's not increasing the lift. Yes, your speed increases, but your lift decreases. When you release the risers, you will be above the trim speed, and the canopy will glide flatter for a while, but that's not what you're talking about, is it?

If you do a front riser turn, the riser pressure will go up due to higher G forces in the turn. As your turn tightens, the force to hold the riser goes up.

But simply pulling down both fronts doesn't result in a force that builds.

At least that's not what I feel on my Spectre when holding fronts while doing CF. Sure, given enough time, my arms get tired. But I can hold it for a while before that happens, and the forces don't seem to be building.

When it comes down to it, if you cannot do chin-ups, you'll have some trouble with front risers.

[BUBLHED 0]

"But you said "When this canopy increases speed more lift equals more pressure" and I'm having some trouble with that.

If this is true, then pulling the front risers would make you go UP? (Pull riser = more speed. More speed = more lift. More lift = flatter glide, or, apparently going UP?) "


As I said I could be wrong But, As the front risers are pulled down you are effectively changing the trim of the canopy. As the canopy accelerates it will have an increase in the amount of lift. It will not go up as it is now trimed downward. The front riser pressure will increase with faster speed on very stable canopies. I suspect that a Crw type canopy is set from the factory to be more neutral as to allow as light a riser pressure as possible.

Rember as an airplane flys through the air at say 80 knots you will need to trim the nose up more than the same plane at 140 knots. This is because of the differance in the amount of lift at differant airspeeds. When we front riser we change the trim and only by the speed increase do we change the amount of lift.

edit to add: When we apply brakes and slow the canopy, we increase our sink rate. Why? Because at the slower airspeed we have a significant decrease in lift. Yes as we change the shape of our wing with tail input we will have an increase in lift do to the more curved shape of our wing, but that quickly dissipates as we approach the stall point. If we could simply slow the canopies airspeed without increasing our pitch angle our lift drop off would be much more dramatic

ATTACK LIFE ! IT'S GOING TO KILL YOU ANYWAY!!!!

[riggerpaul 1]

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"But you said "When this canopy increases speed more lift equals more pressure" and I'm having some trouble with that.

If this is true, then pulling the front risers would make you go UP? (Pull riser = more speed. More speed = more lift. More lift = flatter glide, or, apparently going UP?) "


As I said I could be wrong But, As the front risers are pulled down you are effectively changing the trim of the canopy. As the canopy accelerates it will have an increase in the amount of lift. It will not go up as it is now trimed downward. The front riser pressure will increase with faster speed on very stable canopies. I suspect that a Crw type canopy is set from the factory to be more neutral as to allow as light a riser pressure as possible.

Rember as an airplane flys through the air at say 80 knots you will need to trim the nose up more than the same plane at 140 knots. This is because of the differance in the amount of lift at differant airspeeds. When we front riser we change the trim and only by the speed increase do we change the amount of lift.

edit to add: When we apply brakes and slow the canopy, we increase our sink rate. Why? Because at the slower airspeed we have a significant decrease in lift. Yes as we change the shape of our wing with tail input we will have an increase in lift do to the more curved shape of our wing, but that quickly dissipates as we approach the stall point. If we could simply slow the canopies airspeed without increasing our pitch angle our lift drop off would be much more dramatic

I was trying to be gentle. That didn't work. Some of what you say is just wrong.

When you pull down on the front risers, you do not increase your lift.

Pulling on front risers makes you come down faster, right?
Pulling on front risers increases your rate of descent, right?

If, as you say, descending faster means more lift, where is that extra lift going?

When you pull down the front risers, you decrease the angle of attack.
Decreasing the angle of attack reduces the lift, so you come down faster.

The canopy is moving faster, but the reduced angle of attack means less lift is being produced.

If you pull evenly on both front risers and hold it steady, you will find that the force does not continue to increase. The only change in force is because you have transferred a bit of your weight off the rear risers and onto the fronts. Hold that steady and the force will not change any further.

Go out and try it.

Riser turns are a different matter because turning is an acceleration. When you are turning, your risers are experiencing a load greater than your weight.

But when you are flying straight in a steady state, there is no acceleration, and the only weight there is to support is your body and gear. Some of the weight is supported by the front risers, and some is supported by the rears. When you pull the fronts together, and let it get to a steady state (which only takes a second), the only increase in force on the fronts is the weight you took off the rears. It will not change after that.

Go out and try it.

[BUBLHED 0]

Yes when you have reached a steady state the force will go unchanged. during the time of Getting to a faster airspeed the force (lift) will increase. This is why alot of people can't hold there fronts down for very long not because the get tired. the angle of attack does determine which way the canopy will fly. You can however be producing more or less lift at any angle of attack. Remember you can stall (less lift) at ANY angle of attack.


As I said I am not an expert in aerodynamics but this is how I see it. Maybie there is an aeronautical engineer on here who can give us the benefit of there wisdom.

ATTACK LIFE ! IT'S GOING TO KILL YOU ANYWAY!!!!

[riggerpaul 1]

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Yes when you have reached a steady state the force will go unchanged. during the time of Getting to a faster airspeed the force (lift) will increase. This is why alot of people can't hold there fronts down for very long not because the get tired. the angle of attack does determine which way the canopy will fly. You can however be producing more or less lift at any angle of attack. Remember you can stall (less lift) at ANY angle of attack.


As I said I am not an expert in aerodynamics but this is how I see it. Maybie there is an aeronautical engineer on here who can give us the benefit of there wisdom.

Better go check your aerodynamics texts.

You cannot stall "at any angle of attack".

From my pilot texts, "You can stall in any attitude at any airspeed if the angle of attack exceeds the critical angle as determined by the airfoil".

A stall is all about angle of attack, and nothing else. A stall is defined as having the angle of attack exceed a critical angle. So you cannot stall "at any angle of attack". You can only stall if the angle of attack goes past the critical angle.

If you are in unaccelerated flight, the force of lift is exactly balancing the weight of the craft. If this were not true, you would be accelerating.

What is unaccelerated flight? Unaccelerated flight is steady state flight. It will be straight, not turning, and it can be at any angle of climb or descent, as long as the rate of climb or descent is a constant. If the path of the canopy is a straight line, it is unaccelerated flight. Since our parachutes are not powered, you will not be able to see steady state climbing, but you can absolutely see steady state descents.

The weight of the craft is you and your gear.

For that docile, stable canopy, the following will be true.

When you pull the front risers, initially the riser pressure will be the amount of your weight that is supported by the front risers. As you decrease the angle of attack of the wing, the pressure will actually go down for a moment as the lift is reduced. The canopy will accelerate due to the reduced lift. During the acceleration, the force on the riser will increase as the lift builds to balance the new airspeed. This will take only a second, give or take. At that point, the force will stabilize to be exactly that portion of your weight that is now supported by the front risers. No more.

If, at that point, you find you cannot hold it after a time, it is because your arms got tired.

I don't fly extreme high perf canopies, so the explanation above will be a bit different for them. The important difference is how long it will take to reach the new trim speed. All else will be the same. Once the new trim speed is reached, the riser pressure will stay stable.

You can test all this yourself. Get one of those digital altimeters that will report rate of descent. See how long it takes to get to a stable descent when you change the trim with risers. Once you reach the new trim speed, the force of lift is again in balance with your weight, and there will be no change in the force, or the rate of descent.

If you cannot hold the riser steady, find someone who has a set of 2-fers on their front risers. These are leverage devices that allow lower riser forces at the cost of limiting how far the riser can be pulled. You can only pull the riser half as far with a 2-fer, but that will be plenty. With the extra leverage, even a weaker person can easily experiment with riser work.

[dragon2 2]

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The Hurricane is frankly DANGEROUS on front risers, seen a few of those fold under, not pretty.

Interesting... the hurricane is very popular around here. Much much more popular than the sabre2 for example. Never seen any issues like that. Very scary.

Dave

Actually I starting doubting a bit so I asked around to be sure and turns out I made a mistake in recalling the problem canopy's name: heatwave not hurricane.

ciel bleu,
Saskia

[billvon 3,088]

> during the time of Getting to a faster airspeed the force (lift) will increase.

That's incorrect. To descend on an airplane, you push the yoke forward. That tilts the wing down and _decreases_ lift. You start to descend. Your airspeed then increases (because you are descending) and thus your lift increases until you are at a new equilibrium.

When you pull back on the yoke, the opposite happens. You increase lift which accelerates you upward (thus slowing your descent) until you slow down to your previous speed.

Parachutes are in many ways different from airplanes, but at the most basic level (i.e. decrease in lift causes you to descend faster) they are similar.

[BUBLHED 0]

"You can stall in any attitude at any airspeed if the angle of attack exceeds the critical angle as determined by the airfoil".

Yes I mistated on that one what you say here is what I meant to say. Too early this am.


"During the acceleration, the force on the riser will increase as the lift builds to balance the new airspeed. This will take only a second, give or take. At that point, the force will stabilize to be exactly that portion of your weight that is now supported by the front risers. No more. "


Although I may not have said it clearly enough this is what I am saying. As the speed increases so does the lift. Now alot of people cannot support there weight pulling the risers so as this happens the pressure build is to much for them. I can get the risers down quite far and it is surely more than a second of acceleration and the building of riser pressure. I can hold this for a few hundred feet max. I don't have any kind of way to track this acceleration but in my perception when doing this it seems to take 3 to 5 seconds before reaching a new equlibrium.


I think we are on the same page just not effectively communicating it to each other. That's why I really hate typing and text messages. To hard for effective communication, at least for me. I always try to learn however that's why I'm here.

Blue Skies

ATTACK LIFE ! IT'S GOING TO KILL YOU ANYWAY!!!!

[riggerpaul 1]

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"You can stall in any attitude at any airspeed if the angle of attack exceeds the critical angle as determined by the airfoil".

Yes I mistated on that one what you say here is what I meant to say. Too early this am.


"During the acceleration, the force on the riser will increase as the lift builds to balance the new airspeed. This will take only a second, give or take. At that point, the force will stabilize to be exactly that portion of your weight that is now supported by the front risers. No more. "


Although I may not have said it clearly enough this is what I am saying. As the speed increases so does the lift. Now alot of people cannot support there weight pulling the risers so as this happens the pressure build is to much for them. I can get the risers down quite far and it is surely more than a second of acceleration and the building of riser pressure. I can hold this for a few hundred feet max. I don't have any kind of way to track this acceleration but in my perception when doing this it seems to take 3 to 5 seconds before reaching a new equlibrium.


I think we are on the same page just not effectively communicating it to each other. That's why I really hate typing and text messages. To hard for effective communication, at least for me. I always try to learn however that's why I'm here.

Blue Skies

What I am saying now is not to contradict anything you said above, but to further clarify.

You say that you have held double front risers for a few hundred feet. That is much longer than the 3 to 5 seconds for the acceleration to complete. After those 5 seconds, the speed stabilized, and the force of lift again equaled the suspended weight. You held it for maybe another 10 or 15 seconds. At that point, it was arm strength that failed you. It was not a continuing increase in lift.

As I said, different parachutes will take a different amount of time to complete that speed change. This is mostly about the drag of the parachute. Small, high performance, elliptical (including cross-braced) canopies have lower overall drag than my big 7 cell Spectre. They have a higher top speed, and take longer to complete the acceleration. But once the acceleration is complete, the forces balance, and the lift matches the suspended weight.

In summary -

The only thing that "powers" our parachutes is the suspended weight. When you increase wing loading by increasing the suspended weight, the parachute will fly faster, but it flies on the exact same line as it did with the lower weight. That line represents the L/D ratio of the wing, and is independent of the suspended weight. While flying on that line, the lift exactly matches the suspended weight. The suspended weight determines the speed at which you fly down that line, but it does not change the angle of the line.

The only time the force of lift can exceed the suspended weight is during accelerated flight, like in turns or during the pull out from a dive. ( BTW - A landing flare is just a particular case of pulling out of a dive.)

The amount of weight supported by the front risers versus the rear risers is a function of the design and trim of the wing and lineset. Some parachutes carry more of the load on the rear risers than others. These parachutes will have a lower front riser pressure, but the sum of the two will equal the suspended weight, except during accelerated flight.

If you can do some chin-ups on a bar, you can pull your front risers.
If you cannot do chin-ups on a bar, you will have trouble pulling front risers.

[dharma1976 0]

if it is set up stock you might need to adjust your brake lines...talk to a rigger about it..

D

http://www.skyjunky.com

CSpenceFLY - I can't believe the number of people willing to bet their life on someone else doing the right thing.

[JohnMitchell 16]

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I had a Nova 150 that had very light front riser pressure.

Did you ever have those lightly loaded risers go slack? I never jumped a Nova, but I heard enough 1st hand stories from people on crutches . . .

[mdrejhon 8]

The risers on my Sabre 170 loaded at 1.1 is very high. You are slightly more heavily loaded than I. I can only barely pull it down, but I am now doing double-front straight-in swoops that more than double my normal surf-the-turf distance.

But practice at full altitude, of course. Get appropriate dropzone help for bringing double-fronts all the way to near the ground.

Go to half brakes. Go to full glide quickly (i.e let go of brakes, raise the toggles quick). As the canopy surges forward, grab front risers and pull both down immediately. You'll get much lighter front riser pressure for the first 3 to 4 seconds after suddenly letting go of brakes. Enough time for double-front approaches. Beyond that, I have to do a chin-up on the risers essentially to continue to hold them down beyond that.

Try to see if you're able to at least practice double fronts before you downsize. Also experiment with how easy it is to steer using the front risers to keep yourself balanced and flying straight (usually easy at these wingloadings), and experiment with letting go of the front risers suddenly (which is generally safe to do so on most canopies)

Practicing chin-up exercises can help, too. But if you can do 0 chinups, you'll have trouble.

[Blink 1]

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...let go of brakes, raise the toggles quick...

A better way describe the process is, go from half-braked to full flight quickly, and pull down on your front risers. Do NOT let go of your toggles.