Wind Penetration and Turbolence

[Signo 0]

Hi everybody,

I have two questions about wind penetration and turbolence for different canopy models given the same wing loading.

1) among the models below, which one have better wind penetration given the same wing loading (1.7) when properly flown in a upwuind situation?

2) among the models below, which one is less likely to collaps on a straight in landing during turbolance?

Here are the different models and sizes I am considering:
Sabre1 135 (my current canopies)
Crossfire2 139
Stiletto 135
Katana 135

Thanks,
Riccardo

[billvon 2,384]

>which one have better wind penetration . . .

In general the Katana will, since it has a slightly steeper trim than the rest of them.

>which one is less likely to collaps on a straight in landing during turbolance?

In my experience, the Sabre 1. (To be more accurate, it is the least likely to collapse/deform in such a way that you are injured.)

[AggieDave 6]

Turbulence is simply something that should be tried to be avoided. People work themselves into a false sense of security with a canopy choice or belief, but any canopy can fold when subjected to turbulence.

Understanding what causes turbulence and avoiding it is really the smarter choice then trying to buy a canopy to "allow" you to fly in it.

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

[Signo 0]

Thank you billvon for answering my questions and adressing my concerns.

I could not agree with you more AggieDave, knoledge and prevention are the best way and they are my way. At the same time I'd like to be under a canopy that increases my chances to walk away from situations in which I experiance turbolence when I was not expecting it.

Thanks,
Riccardo

[danielcroft 2]

Samurai?

Not that it's a solution to turbulence, may just increase your chances of a safe landing in unexpected turbulence.

[AggieDave 6]

Quote

Samurai?

Not that it's a solution to turbulence, may just increase your chances of a safe landing in unexpected turbulence.

I would argue that airlocked canopies are one of the worst "offenders" in terms of a false sense of security. Sure, they are rigid as Sister Mary but they can and will fold in turbulence, just as any canopy will. The longer you're in the sport I promise you'll hear "its was ok since I jump an airlock" in terms of jumping in very hazardous conditions.

At the end of the day you'll find that most modern design canopies (from the last 10 years or so) perform well in most conditions; however, most people who refuse to stand down find out that their canopy performs poorly in their condition as their canopy folds.

Just two weeks ago I traveled to a boogie and completed only two jumps. On the first jump I flew through a rotor during my Velo's dive and then had another "speed bump" while planed out. This is at speeds that would end in an expensive ticket in a car on the freeway. I stood down for about 4 hours then did a jump with a demo PD Storm. The conditions were still extremely turbulent even in the large main landing area. So I stood down for the rest of the day.

Why? I jump a very rigid wing. I'm traveling at speeds that typically keep me from even feeling all but extreme turbulence. Why? Well, I don't want to find out which condition causes my canopy to fold. I take a deep personal satisfaction in keeping my name out of the incidents forum.

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

[danielcroft 2]

You've echoed what a lot of people have told me and it certainly rings true. I'm thinking about getting a Lotus, not so I can jump in turbulence, that's just silly but so, in the event of unexpected turbulence close to the ground I'm giving myself every chance of making it out the other side.

Given the original question, do you think that the Samurai or Vengeance for that matter would be more likely to resist turbulence? Again, nothing is impervious, just airlocks are *meant* to improve your chances.

[obadz 0]

Quote

>which one have better wind penetration . . .

In general the Katana will, since it has a slightly steeper trim than the rest of them.

I guess the answer would be dependent on what gives you best glide in those winds. If you find that hanging on the double fronts gets you further, then the Katana will probably have the best penetration. But in many cases depending on loading / wind speed, a bit of rears extend the glide. In those instances, you'd probably be better off with a canopy that has a flatter trim.. no?

Anyhow, to me the more interesting question is: does the Katana's steep trim make it more prone to collapsing in turbulence? I've been wondering about this for a while now and have not found an answer that satisfies me.

The consensus used to be "add a bit of brakes in turbulence". Now the consensus seems to be, "fly through turbulence in full flight". I think most would agree double fronts in turbulence isn't a good idea. So my follow up question to all this: if the Katana has a steeper trim built-in (i.e. a "permanent double fronts" without the distortion), does that make it more vulnerable in turbulence?

[phoenixlpr 0]

Quote

The consensus used to be "add a bit of brakes in turbulence". Now the consensus seems to be, "fly through turbulence in full flight". I think most would agree double fronts in turbulence isn't a good idea. So my follow up question to all this: if the Katana has a steeper trim built-in (i.e. a "permanent double fronts" without the distortion), does that make it more vulnerable in turbulence?

What do you think? What makes your canopy stable and flying? Air pressure in cells and tension in lines. Keep maintaining those! Speed keeps your canopy pressurized and line tension keeps it in shape and you in control. If you feel that your lines getting loose because some bump you'd rather apply some breaks to pull it back.

[Signo 0]

This conversation is being interesting.

On the turbulence, my understanding is that, given a wind loading, steep trim results in greater airspeed which keeps the canopy pressurized also allowing to fly through bumpy air more rapidly. Concurrently though, a more "elliptical" or "tapered" design is more catastrophic in the case of one side of the canopy collapsing before the other side since this would result in a quicker dive toward the ground. Is this reasoning correct?

On the wind penetration case, given a wind loading, in order to cover more ground while flying upwind, the lift to drag ratio has to be maximized. So far as, I understand then the decree of the forum is that Katanas, given a wind loading, present the max L/D ratio (over the other non cross braced models) when flown correctly (either with rr or fr input). Is this right?

Thanks for your input,
Riccardo

[phoenixlpr 0]

Quote

Concurrently though, a more "elliptical" or "tapered" design is more catastrophic in the case of one side of the canopy collapsing before the other side since this would result in a quicker dive toward the ground. Is this reasoning correct?

Based on what? You can fold any airfoil. Its getting academic.

Quote

I understand then the decree of the forum is that Katanas, given a wind loading, present the max L/D ratio (over the other non cross braced models) when flown correctly (either with rr or fr input). Is this right?

See? Thats not the arrow, thats the indian.

[Signo 0]

I guess the best line of action for now, is to keep my Sabre 135, which I love. It will save me money and I will probably re-think the argument next year

One of these days I will demo a Katana though...

Cheers,
Riccardo

[phoenixlpr 0]

Quote

I guess the best line of action for now, is to keep my Sabre 135, which I love. It will save me money and I will probably re-think the argument next year
One of these days I will demo a Katana though...

Ask yourself: what do you want from your next canopy.

[yoink 321]

Quote

>which one is less likely to collaps on a straight in landing during turbolance?

In my experience, the Sabre 1. (To be more accurate, it is the least likely to collapse/deform in such a way that you are injured.)

I've used my Sabre1 135 for ground launching for a while in some fairly windy and turbulent conditions. It's generally OK at full drive, but once you start adding even small amounts of brake input it starts tucking very easily and breathes a great deal. It stops being fun at that point...

Keep your speed up with the Sabre 1 in turbulence.

[phoenixlpr 0]

Quote

I've used my Sabre1 135 for ground launching for a while in some fairly windy and turbulent conditions. It's generally OK at full drive, but once you start adding even small amounts of brake input it starts tucking very easily and breathes a great deal. It stops being fun at that point...

Have you ever seen a Sabre oscillating like an accordion?

[obadz 0]

Quote

Quote

The consensus used to be "add a bit of brakes in turbulence". Now the consensus seems to be, "fly through turbulence in full flight". I think most would agree double fronts in turbulence isn't a good idea. So my follow up question to all this: if the Katana has a steeper trim built-in (i.e. a "permanent double fronts" without the distortion), does that make it more vulnerable in turbulence?

What do you think? What makes your canopy stable and flying? Air pressure in cells and tension in lines. Keep maintaining those! Speed keeps your canopy pressurized and line tension keeps it in shape and you in control. If you feel that your lines getting loose because some bump you'd rather apply some breaks to pull it back.

Agreed, but you do realize my question was about the Katana's relative behavior in turbulence, not about what a pilot should do.

I'll clarify my question further: with the front riser pressure being so light, the line tension on As & Bs must be relatively low, it would stand to reason than the nose is then that much easier to pull down and fold under. Am I missing something? Are there other design parameters that people can think of that would offset (or worsen) this tendency? Has anyone had first hand experience with Katana collapses?

[yoink 321]

Quote

Quote

I've used my Sabre1 135 for ground launching for a while in some fairly windy and turbulent conditions. It's generally OK at full drive, but once you start adding even small amounts of brake input it starts tucking very easily and breathes a great deal. It stops being fun at that point...

Have you ever seen a Sabre oscillating like an accordion?

Yup. It's nasty, but tucks are worse!

Best to be on the ground.

[dharma1976 0]

Quote

Quote

Quote

The consensus used to be "add a bit of brakes in turbulence". Now the consensus seems to be, "fly through turbulence in full flight". I think most would agree double fronts in turbulence isn't a good idea. So my follow up question to all this: if the Katana has a steeper trim built-in (i.e. a "permanent double fronts" without the distortion), does that make it more vulnerable in turbulence?

What do you think? What makes your canopy stable and flying? Air pressure in cells and tension in lines. Keep maintaining those! Speed keeps your canopy pressurized and line tension keeps it in shape and you in control. If you feel that your lines getting loose because some bump you'd rather apply some breaks to pull it back.

Agreed, but you do realize my question was about the Katana's relative behavior in turbulence, not about what a pilot should do.

I'll clarify my question further: with the front riser pressure being so light, the line tension on As & Bs must be relatively low, it would stand to reason than the nose is then that much easier to pull down and fold under. Am I missing something? Are there other design parameters that people can think of that would offset (or worsen) this tendency? Has anyone had first hand experience with Katana collapses?

I have seen velos fold under in turbulance as well...I know a certain amera person who breaks out his stilletto when it gets dodgy out and so do you

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.

[ianmdrennan 2]

Quote

I know a certain amera person who breaks out his stilletto when it gets dodgy out and so do you

Not directed at you:

Any canopy is susceptable to collapse in turbulence.

If you have to 'change canopies because it's too turbulent' you may want to SERIOUSLY re-evaluation your jumping criteria.

Blues,
Ian

Performance Designs Factory Team

[Reginald 0]

Quote

I'll clarify my question further: with the front riser pressure being so light, the line tension on As & Bs must be relatively low, it would stand to reason than the nose is then that much easier to pull down and fold under.

Interesting question. I'm not sure that your assumption about A&B line tension being low is the reason the front riser pressure is so light though. Hmm, interesting question...

"We've been looking for the enemy for some time now. We've finally found him. We're surrounded. That simplifies things." CP

[billvon 2,384]

>I guess the answer would be dependent on what gives you best glide in those winds.

Definitely. But if you are flying into winds, the faster canopy is going to have the advantage.

>If you find that hanging on the double fronts gets you further, then
>the Katana will probably have the best penetration.

In my experience, double fronts gives you a very, very small increase in forward speed, but a large increase in downward speed. That's why your landing point gets closer to you when you use double fronts while facing into the wind. In other words, you will generally not make it as far if you try to use double fronts to penetrate wind.

The exception to that is if you're backing up. Double fronts will get you on the ground much faster, and thus reduce the amount you back up.

[obadz 0]

Quote

Quote

I'll clarify my question further: with the front riser pressure being so light, the line tension on As & Bs must be relatively low, it would stand to reason than the nose is then that much easier to pull down and fold under.

Interesting question. I'm not sure that your assumption about A&B line tension being low is the reason the front riser pressure is so light though. Hmm, interesting question...

It is an interesting question, isn't it? Might deserve a thread of its own..

[DrewEckhardt 0]

Quote

Thank you billvon for answering my questions and adressing my concerns.

I could not agree with you more AggieDave, knoledge and prevention are the best way and they are my way. At the same time I'd like to be under a canopy that increases my chances to walk away from situations in which I experiance turbolence when I was not expecting it.

Something in the 320 square foot range will work nicely. It won't have much forward speed when you get slammed into the ground and will have a lot of drag so that even if it's not flying it will set you down softer.

At contemporary skydiving wingloadings the right answer is to just avoid turbulence.

A square canopy may be less likely to spin you into the ground, but it can't stop as well as a more modern tapered design so you'll be more likely to break something landing out on an uneven surface where you can't run or slide as well.

[Signo 0]

Quote

A square canopy may be less likely to spin you into the ground, but it can't stop as well as a more modern tapered design so you'll be more likely to break something landing out on an uneven surface where you can't run or slide as well.

You have an interesting point. Actually, on a no wind day I cannot come close to a horizontal stop under my Sabre 135 and when I touch down I have to run. I have heard before that more tapered canopies, given the same wind loading, on a no wind day can "stop better". Could you please explain to me why that is? Is this true for elliptical canopies like Katana, Stiletto, and Crossfire as well?

Thanks,
Riccardo

Let me know if you sell your 320. I might be interested

[billvon 2,384]

>I have heard before that more tapered canopies, given the same
>wind loading, on a no wind day can "stop better".

They have a bit more flare.

Every modern canopy out there can get you to zero downward speed when you flare it correctly. However, a well-designed canopy (of any taper) will give you a stronger flare i.e. more lift for a given amount of energy. With this extra lift you can:

-pop up higher
-plane out longer
-get your canopy to a lower speed before it stops flying.

_Typically_ the more elliptical canopies have more flare.