Front Risers in Head wind

[morris 0]

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Trying to increase your ground track with double fronts certainly involves the ground, and as such the real wind needs to be considered.

No doubt about it!
I´m not saying that the real wind doesn´t need to be considered, of course it affects your ground track, big time.
I´m only saying that the real wind is not affecting the flight path in relation to the surrounding air.
If the real wind would have no "impact" on your ground track the statement "you´ll always end up shorter applying frontrisers" would be true.
But as the real wind is affecting our true glide there are scenarios where our true glide will be changed to the better by frontrisersinputs - eventhough frontriserputs will always make our relativ glide worse...

[faulknerwn 36]

Having done lots of CRW, I'd definitely say that in a strong headwind you can increase penetration on front risers. The key is how much you pull. If you've ever watched hard-core down the back CRW rotations, those guys are yanking on their front risers hard, and go straight down. Pulling down just a tad on the risers will make you drive forward, and is the option of choice if you get behind the formation.

I use my front risers to shoot accuracy - if I'm going to overshoot, I pull hard on them to make my approach steeper. If I'm coming in a tad short, I just pull a tiny bit and it increase the forward speed and glide.

The above works on "traditionally-trimmed" canopies - one in the middle of the range. On canopies that are extremely steeply trimmed already, you're already past the angle where front risers help.

I remember one big-way CRW event at Zhills a few years back. Only 3 of us made the airport, and every one of us who did were on our front risers. Heck, I was on a CRW jump last weekend and after we broke our 5-stack, I flew my 2-way back to the airport on front-risers because we were downwind. The other 2-stack who was outrunning us during the earlier part of the jump was left in the dust and landed off.

The key is just doing a touch - too much you cause more sinking than drive. Same with rear risers on an upwind spot - the best glide is just the tiniest bit of rear risers on most canopies..

[davelepka 4]

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I´m not saying that the real wind doesn´t need to be considered, of course it affects your ground track, big time.

Unless you're applying double fronts, right? Then it just doesn't need to be considered?

Let's look at kiting your canopy on a windy day. What's the safest thing to do when the wind is pciking up? Get the canopy overhead because it has the least amount of drag, and will simply 'fly' quietly in a higher wind than in any other position. If you let the canopy rock back, the bottom skin begins to catch air, and the drag increases substantaily, maybe pulling you off of your feet.

The basic idea is that any deviation from your canopy being 'level' in terms of pitch angle relative to a horizontal plane will increase drag when flying in winds. More drag equals slower flight, which equals less ground covered flying into the wind. All of these discussions are surrounding landing in high winds, so the increase in drag needs to be considered.

Yes, in high winds your glide angle in full flight is steeper, but your glide angle in double fronts also suffers an equal loss from the higher winds, you just get to the ground faster.

It's a scientific fact that at some trim setting the canopy will have the most favorable lift over drag, just like the best glide speed in an aircraft. That is the trim setting that will net you the greatest distance for a given altitude loss. This is the setting you want to use if distance is your goal when flying into the wind, and it's nowhere near pulling down both front risers, and it's probably not even full lfight.

[DocPop 1]

One thing I have tried to increase penetration into a head wind is to apply then release the front risers a number of times, almost as though you are doing a series of double-front landings.

This seems to me (and it is only my opinion) to build up airspeed which you allow to "surf" you horizontally as the canopy recovers. As the airspeed/groundspeed bleeds off you repeat the procedure. I also try to make myself as small as possible during this to reduce the parasitic drag on the canopy.

Any thoughts on this from the experts?

"The ground does not care who you are. It will always be tougher than the human behind the controls."

~ CanuckInUSA

[linebckr83 3]

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This best glide speed is above the stall speed, which is the slowest speed the aircraft can fly.

The best glide speed is where the lift over drag ratio is the lowest, and it's somewhere a few ticks above the stall speed.

I have witnessed this to be exactly true. In a class called "The Fundamentals of Atmospheric Flight" I took a year or so ago, we had a project to build a glider (obviously with a high aspect ratio) released at 1000 feet with an airspeed of 60mph, and it was a competition to see who could cover the most ground. This was done in X-Plane with no wind. While most groups tried flying their gliders right at stall speed, we found that the best approach was to calculate the airspeed corresponding to the most efficient L/D ratio. This airspeed was, for our setup, about 20mph over the stall speed. The class thought we were crazy when we immediately trimmed nose down to pick up speed instead of holding near the stall speed, but I'll be damned if we didn't win, and win by a considerable margin

"Are you coming to the party?
Oh I'm coming, but I won't be there!"
Flying Hellfish #828
Dudist #52

[linebckr83 3]

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I also try to make myself as small as possible during this to reduce the parasitic drag on the canopy.

Any thoughts on this from the experts?

Not sure about your first point so I'll leave it to someone who knows more, but this is certainly a good idea. There have been a lot of discussions on it, just search ground speed vs. airspeed. Remember that whatever your ground speed is, your canopy is always flying through an air mass that is moving. Reducing your parasitic drag will allow you to fly through that air mass faster. Front risers or not, getting small is a good idea when you need forward penetration.

"Are you coming to the party?
Oh I'm coming, but I won't be there!"
Flying Hellfish #828
Dudist #52

[shropshire 0]

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getting small is a good idea when you need forward penetration.

[smut alert]

Try telling THAT to the Mrs

(.)Y(.)
Chivalry is not dead; it only sleeps for want of work to do. - Jerome K Jerome

[pchapman 261]

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Now when you consdier the effect of the 'real' wind, you have another story. The 'real' wind moves horizontally, and that does not change when you change the angle of attack of your canopy. So when you honk down on the front risers, you 'show' more of your topskin to the 'real' wind, and increase drag.

Most of your posts on dz.com are really good, but I can't agree with this one, not at all. It gets back to all the airspeed / groundspeed fallacies. In a steady air mass it doesn't matter what the wind speed is doing, whether it is a headwind or crosswind or whatever. Your flight through the air will be the same.

If you pull front risers in no wind conditions and get +2 mph forward speed, then if you are flying into a headwind that gives you zero ground speed, pulling front risers will give you the same +2 mph through the air and over the ground.

[shropshire 0]

FWIW - I agree

(.)Y(.)
Chivalry is not dead; it only sleeps for want of work to do. - Jerome K Jerome

[davelepka 4]

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It gets back to all the airspeed / groundspeed fallacies. In a steady air mass it doesn't matter what the wind speed is doing, whether it is a headwind or crosswind or whatever. Your flight through the air will be the same.

Yes, your flight through the air will be the same, however, in the presence of wind from different directions, your flight across the ground will not be the same. The whole point of this thread is your flight across the ground, so we have to consider the winds effect on yoru canopy's progress across the ground.

Take a zero wind day, and do a double fronts approach to the south, and then do one to the north. Same exact reaction from the canopy, and track across the ground.

Now add a 20 mph wind out of the north. Start with your double fronts approach to the south, has anything changed from your no wind landing in the same direction? Indeed, your ground speed is now somewhere up over 50 mph. Big difference.

Why is it that you don't believe that making it a 20mph headwind will have an effect on your canopy's track across the ground? Just like adding a big tailwind made a difference, so does adding a big headwind. The results of a double front appraoch in no winds, and in a 20 mph wind are going to be two very different things.

[adamT 0]

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The 'real' wind moves horizontally, and that does not change when you change the angle of attack of your canopy. So when you honk down on the front risers, you 'show' more of your topskin to the 'real' wind, and increase drag.

I think this is where you lost people, and I think you your self know this to be a false base on other posts of yours I have read. I could just be a matter of wording.  The effect of front riser input on the canopies drag is the same in any wind conditions. The You never show your top skin to any wind, relative or real. If you do manage to achieve wind perpendicular to the top skin you get a collapsing canopy.

The ultimate question is does front riser input increase your lateral speed. Its obvious that it increases your speed down the velocity vector. I would say it depends on what canopy, what loading and how much input. I haven't done any real tests with my canopy using gps, but it doesn't appear that my lateral speed increases with fronts. It seems that Morris does have some quantified data that does show an increase in lateral speed. Which is what you really need to answer this question. So I am inclined to believe him at least for the configurations they have data for.

For what its worth I have always taught that fronts will get you out of the sky faster if you backing up, resulting in less ground lost. But it probably won't allow you penetrate more. Although i have always suspected that some configurations would experience a small increase in lateral speed with a moderate to small amount of front riser input.

[davelepka 4]

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I think this is where you lost people, and I think you your self know this to be a false base on other posts of yours I have read. I could just be a matter of wording.

I think what's happening is that people are so ingrained with the idea, that 'your canopy always flies the same' that they're forgetting that it only applies to in-air references, and when you introduce a ground reference, it's another story.

Fly your canopy due west in no wind. The relative wind is coming from the east, and the canopy track due west. Now do the same with a north wind. The relative wind still comes from the east, but the canopy tracks to the south west due to the effect of the north wind. Yes?

Why then, wouldn't the same apply to flying directly into that wind? With respect to your ground track, the canopy will certainly be effected by adding a headwind, and this applies to all flight configurations. It is a seperate wind component that needs to be considered.

So here you are flying into a horizontal head wind. What is limiting your airspeed is drag, and what is limiting your ground speed is the wind.

Picture yoru canopy in profile, and is relation to the head wind. Add front riser input, and tell me what it does to the profile of your canopy in relation to the head wind? Your tail stays in one place, and nose gets lower. Does this increase or decrease the profile of your canopy with respect to the head wind?

You have to let go of the 'the canopy always flies the same' concept here because with realtion to the ground, it does not. In terms of swooping downwind, or into the wind, your canopy will produce the same dive in either direction, but the realtion of your turn initiation to the gates will be very, very different. Why? Becuase of the effect of the wind on your ground track.

Parachutes are unpowered craft, and as such, every input will have a trade-off in tersm of performance. You cannot go further and go faster without adding thrust, it just doesn't work that way. There is no free lunch.

If you honk down on both front risers, you're going to increase drag. Without the presence of any wind, the increase is minimal because you're also increasing thrust by letting gravity have a little more pull on you. You're sacrificing the glide and reducing your ground track as a trade off.

When you introduce an additional wind component, the same wind that let's you crab sideways, or really burn a good downwinder, the story changes. Just the liek the wind effects you in crosswind and downwind approaches, it also effects you when flying into the wind. It limits your ground speed based on your airspeed, which is drag limited. If you increase that drag, you will reduce your ground speed. If you increase the drag and increase your airpseed, you get nothing.

Just like you canopy experiences the relative wind, and a cross or down wind component at the same time, it also experiences a head wind component, with relation to the ground track, as well.

If you've ever tried to land an airplane in a crosswind, you'll understand what I'm talking about. You need to keep your airspeed up, and maintain airflow over the wings, but you also have to correct for the cross wind component. It's two seperate things that need to be dealt with, and why corsswind landings are tricky to learn (in airplanes).

[adamT 0]

Pulling your front risers results in a reduction of lift and in turn a reduction in drag, hence the increased airspeed(which itself is an increase in drag) and reduction in glide. Your lift vector is less directly opposed to gravity.

You are confusing people by saying that pulling your risers allows your topskin to be exposed to environmental wind. This is 100% incorrect. There is no difference in your canopies aerodynamics weather you pull your fronts facing the wind, cross wind or in a tail wind. Of course your path on the ground will be different but your flight through the air is not affected. When you are on the ground kiting it is a whole different story, you are anchored to the ground so you can pull your canopy far enough in front of you to get wind on the top skin. The result is a frontal, it is not possible to do this in the air with double fronts. If you manage to throw yourself so far above your canopy that you cause slack in the lines then you get to experience wind on your topskin, exciting times.

It i really a very simple question. If in zero wind conditions you can use a specific amount of fronts to increase your horizontal speed slightly then you can use the same configuration to penetrate slightly better at the cost of time aloft. The challenge comes with determining if that front riser input for your given configuration is actually increasing your lateral speed. I can tell you on my canopies that full front riser input seems to decreases horizontal speed. My glide ratio goes to absolute shit so i don't think it matters that im moving down that slope much faster, it appears that im moving slower across the ground. Maybe a small amount of input would result in a speed increase. Again the best way to answer this for sure is with a gps recording unit with a decent number of data points per sec.

[pchapman 261]

Hi Dave:

I agree with what AdamT wrote:

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***when you honk down on the front risers, you 'show' more of your topskin to the 'real' wind, and increase drag.

I think this is where you lost people, and I think you your self know this to be a false base on other posts of yours I have read. I could just be a matter of wording.

For the sake of the thread I don't think I'll get into it too much, but that 'showing the topskin' thing is just wrong. You are decreasing the angle of attack from a positive to a smaller positive value, actually reducing drag until the speed increases to create speed induced drag.

Yes of course when it comes to actual motion over the ground, the wind matters. But the way it is stated in what you wrote, it is easy to confuse the flight through the air vs flight over the ground stuff.

The wind (assuming steady) doesn't affect the way the canopy flies. But I agree one has to add it in when determining what the canopy does over the ground -- and hence - to go back to the origin of the thread -- whether pulling front risers really is of net benefit.

[kallend 1,625]

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I have to say I´m very sorry, but the delta is not a guess.
A whole lot of testjumps has been done in Germany over the last two years likely collecting the most detailed data ever of parachute flight.
(Maybe with the exception of the X-38
http://en.wikipedia.org/wiki/NASA_X-38
but one of the jumpers has been part of the X-38 program).
They are working with a company that is specialized in collecting all kinds of flightdata.
There systems are not only using GPS and airpressuredata but combining those with INS.
http://en.wikipedia.org/wiki/Inertial_navigation_system
In addition they are even monitoring the toggleinputs (how long - inches and time - the input is and what forces are necessary to apply those inputs).

Every canopy design is different, has different trim and different lift/drag characteristics as a function of riser input. Add to that the variation in mass and size (drag) of the jumper and the drag of the lines. You can't claim your one number is universally valid, regardless of the sophistication of the equipment you used to measure it.

The trim speed of most modern canopies is considerably faster than the speed for best L/D, which means in most cases you will reduce your range by applying double fronts, even in a moderate headwind.

...

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

[kallend 1,625]

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It i really a very simple question. If in zero wind conditions you can use a specific amount of fronts to increase your horizontal speed slightly then you can use the same configuration to penetrate slightly better at the cost of time aloft.

It all depends where on the L/D curve you start out. The assumption many seem to be making here is that the canopy is trimmed for best L/D when no control inputs are applied. This is not true for any canopy I have flown (I don't do CRW), every one of which is trimmed to fly hands-off at a faster speed than best L/D speed.

Wendy F - I suspect CRW canopies ARE trimmed somewhere near the middle of their range so you can make these adjustments.

...

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

[davelepka 4]

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The assumption many seem to be making here is that the canopy is trimmed for best L/D when no control inputs are applied.

The trim speed of most modern canopies is considerably faster than the speed for best L/D, which means in most cases you will reduce your range by applying double fronts, even in a moderate headwind.

Which makes perfect sense for a few reasons. The first is that full flight trims are not chosen with L/D in mind, they're selected based on the speed of full flight and how that translates into the flare on a stright-in approach. Another consideration is the turn recovery and ability to hold a dive as steeper trims generally do this better than flatter trims.

Another reason is that if you make full flight 'best glide' the only way to fly faster is with front risers which is not a sustainable input in that as airpseed increases, so does the force required to maintain the riser input.

By making 'best glide' slower than full flight, the pilot can achieve, and maintain that glide with application of toggles or rear risers, neither of which suffer from increasing control forces. If the pilot wants to go faster than 'best glide' they can let the canopy fly in full flight, which of course is sustainable. If they want to go slower, just apply more toggles or rear risers than best glide and hold it.

It's similar to flying in 1/4 brakes in turbulence. One of the advantages is that the pilot has quick and easy access to either more or less airspeed depending on what the situation calls for. If you fly at full flight through the bumps, you have no way to easily increase the speed of your canopy. By using a mid-range point as your starting point, you can adjust in either direction with equal ease.

[morris 0]

We are not talking about moderate but serious headwinds here, or did I misunderstand the first question?
The testing involved (so far) more than a dozen different canopytypes, -sizes and loadings, ranging from a tandem all the way to a Katana 97 (loaded 2.1), resulting in very different numbers, but the "basic message" was always the same...
For canopies of about 150sqft and a loading of about 1.4 the distance over the ground, flying into a headwind, was about equal for fullflight and a certain degree of frontriser input if the headwind was about 8 knots. Flying into a headwind any stronger (10knots or more) resulted in "frontriservictories"...

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The trim speed of most modern canopies is considerably faster than the speed for best L/D

correct/agreed

[kallend 1,625]

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We are not talking about moderate but serious headwinds here, or did I misunderstand the first question?
The testing involved (so far) more than a dozen different canopytypes, -sizes and loadings, ranging from a tandem all the way to a Katana 97 (loaded 2.1), resulting in very different numbers, but the "basic message" was always the same...
For canopies of about 150sqft and a loading of about 1.4 the distance over the ground, flying into a headwind, was about equal for fullflight and a certain degree of frontriser input if the headwind was about 8 knots. Flying into a headwind any stronger (10knots or more) resulted in "frontriservictories"...

I don't agree, since even with the same WL and size, different canopies are trimmed differently. A Stiletto is trimmed quite differently than a Velocity of the same size and WL. Hence the windspeed at which riser input improves gliding distance in a headwind will be different for the two canopies.

Without knowing the L/D polar of the canopy/lines/jumper system you can't possibly calculate the relevant windspeed at which double fronts become advantageous.

I suggest "the accuracy trick" is the way to do it.

...

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

[morris 0]

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I don't agree, since even with the same WL and size, different canopies are trimmed differently. A Stiletto is trimmed quite differently than a Velocity of the same size and WL. Hence the windspeed at which riser input improves gliding distance in a headwind will be different for the two canopies.

No doubt about it, you are absolutely right, I never had the intention to say "things are this way and no other", like somekind of "law" for all canopies, all I wanted to give was a "rule of thumb", not more. And to mention that there are windsituations that make frontriser are reasonable input. How strong that headwind needs to be and how much frontriserinput would be the best choice in those scenarios is differnt for any design, loading and so on... sorry if I didn´t point tht out clearly.

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I suggest "the accuracy trick" is the way to do it.

Always a good idea.