Forums: Skydiving: Safety and Training:
180 degree front riser requirement for "A"

 

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Andrewwhyte  (C 1988)

Sep 19, 2007, 10:16 AM
Post #26 of 99 (1013 views)
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Re: [hackish] 180 degree front riser requirement for "A" [In reply to] Can't Post

Getting back to the OP. I have never heard a novice complain that they were unable to complete the riser spiral for the A CoP.
Your post said that you believed you had done it, but because of something somebody said you now know you didn't. When observations don't fit the theory I suggest you re-examine the theory. If you still have doubts go for a skydive and repeat the experiment; go try another 360 front riser spiral.
You talk about being on a 1:1 wing-loading, but then about being on student gear; are you in the 250lb range?
You asked if some people working on their A are jumping smaller, faster canopies. The answer is yes they are. Most dZs have some smaller transition canopies that people start to use around the time they get their SOLO certificates. If however you do weigh 250 lbs, I suspect you will be staying on the 280s for a while.


(This post was edited by Andrewwhyte on Sep 19, 2007, 2:34 PM)


hackish  (No License)

Sep 19, 2007, 10:44 AM
Post #27 of 99 (1006 views)
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Re: [Andrewwhyte] 180 degree front riser requirement for "A" [In reply to] Can't Post

Well I just honked on the front riser and it turned around. I sometimes do this if there is a tandem coming down after me so I've landed and am well clear of that.

However, someone with a respectable amount of experience pointed out that the physics of pulling a front riser on a larger canopy make it impossible. For that reason I'm exploring the possibility. He also pointed out that a body builder friend wasn't strong enough. If he isn't then I am probably not!

I'm flying a sabre 210 as I got my solo license about 10 jumps ago. Body weight is 180 so my exit weight should put me around 1:1.

-Michael


mnskydiver688  (D 30125)

Sep 19, 2007, 10:55 AM
Post #28 of 99 (1002 views)
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Re: [rehmwa] 180 degree front riser requirement for "A" [In reply to] Can't Post

Agreed!


riggerrob  (D 14840)

Sep 19, 2007, 11:08 AM
Post #29 of 99 (995 views)
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Re: [hackish] 180 degree front riser requirement for "A" [In reply to] Can't Post

I am not sure who is feeing you that foolish theory.

Any canopy can be turned with front risers.

However, big student canopies tend to turn very slowly - with front risers.
That is why I usually wait until students transition down to 230 or 190 square foot canopies to teach them front riser turns.

There is also the issue of grip strength. Front riser turns require a lot of grip strength, more than some students have, ergo we wait until they down-size to 190s (with front riser dive loops) before teaching front riser maneuvers.

In conclusion, you need to skydive more and listen to less theory.


rehmwa  (D 12816)

Sep 19, 2007, 11:12 AM
Post #30 of 99 (994 views)
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Re: [] 180 degree front riser requirement for "A" [In reply to] Can't Post

Not trying to flip here, but I think the point is, no one is 'pulling the canopy down', they are actually just pulling their body weight up.

So, since people keep talking about the 'physics' here:

I don't think it matters what size the canopy is, the most force one can apply to the start of a turn is their body weight almost on one riser. (And no, I don't think this is a simplification in any way)

In fact, for those that can do a pullup (and gripping and pulling isn't always easy on a smooth riser - understood) centrifugal force being the point that limits the pilot, it is likely harder to stay on a front riser with a small 'fast turning' canopy, than a big boat that turns slow. As the spec will load up in the turn much quicker. On the big boat - the issue is you have to hold on Longer, but the force is likely less - so stamina in holding on the extra few seconds matters.

So if a student can't do a front riser turn, then they really should work on two things, their grip strength, and pull ups. The canopy size is not the issue.

IMHO.


(This post was edited by rehmwa on Sep 19, 2007, 11:14 AM)


rehmwa  (D 12816)

Sep 19, 2007, 11:14 AM
Post #31 of 99 (990 views)
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Re: [riggerrob] 180 degree front riser requirement for "A" [In reply to] Can't Post

Once again, riggerrob says is better and more briefly than I could.


Chris-Ottawa  (A License)

Sep 19, 2007, 11:23 AM
Post #32 of 99 (983 views)
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Re: [riggerrob] 180 degree front riser requirement for "A" [In reply to] Can't Post

Ok, for clarification.

I still stand by my post. Everyone should be able to lift at least their own weight to "bend" the canopy and get it to turn. I load my Spectre 135 at 1:1 and after a 360, it is pulling damn hard, but I can still hold it. After a 720, it is pretty near impossible for me. Now, introduce a second hand and....sprials away...

However.....

I had not considered the dive loops. Every canopy I've jumped, other than Mantas have had dive loops. On the Mantas, I was able to grab the top of the riser and thread my fingers through the lines then pull down.

Sorry about that, but I wouldn't consider that the inability to do a front riser spiral, but the inability to get a good grip on the riser.


hackish  (No License)

Sep 19, 2007, 11:24 AM
Post #33 of 99 (981 views)
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Re: [rehmwa] 180 degree front riser requirement for "A" [In reply to] Can't Post

I always like to hear more than one opinion. Now I'm anxiously awaiting the theory books I ordered from Paragear and the weekend so I can try this stuff out again. Since my instructor is more than willing to sign me off he's obviously satisfied that the tasks were complete but I'm considering this a learning exercise.

-Michael


Premier skybytch  (D License)

Sep 19, 2007, 11:35 AM
Post #34 of 99 (972 views)
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Re: [Chris-Ottawa] 180 degree front riser requirement for "A" [In reply to] Can't Post

In reply to:
I still stand by my post. Everyone should be able to lift at least their own weight to "bend" the canopy and get it to turn.

Why?


rehmwa  (D 12816)

Sep 19, 2007, 11:57 AM
Post #35 of 99 (964 views)
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Re: [skybytch] 180 degree front riser requirement for "A" [In reply to] Can't Post

In reply to:
In reply to:
I still stand by my post. Everyone should be able to lift at least their own weight to "bend" the canopy and get it to turn.

Why?

I think in terms of 'strength' in skydiving it's less important to be able to do 'that' pullup (though being strong enough to fully use your canopy inputs is a "good thing") than the following safety issues:

1 - Being strong enough to be able to close your container vs having a loose closing loop because you can't...

2 - Being strong enough to be able to push on the air enough in freefall to establish control (some people just aren't strong enough to fly well, surprising but true. I know one woman who just isn't strong enough to push down during dearching to slow down, the freefall pretty well puts her into one body position and that's it. She will be very less effective in the event of a total and that slowness may affect her safety.)

3 - Strong enough to be able to run it out and not collapse on landing. I've seen people with problems in this area too. injuries could result.

Being strong enough to effectively use all the inputs for canopy piloting? I think that it is rare that the inability to confidently do front riser pulls results in a safety issue. But it's possible. Just not likely. I'd rather see someone with a good tight closing pin. (I'd rather see both, but if I had to choose....)

{{{I think in most cases, the whole pullup strength isn't needed for riser turns anyway}}}}

skydiving doesn't require much strength, but it's essential to be able to do certain things well. But it only 'really' matters like in the above in terms of safety

so, "everyone SHOULD be able to to lift...." I agree with Chris, but -too bad- not everyone CAN - and they'll still be able to skydive fine, they just won't have all the tools they could.. Let's hope it doesn't result in them colliding with someone someday because they couldn't take the proper evasive actions due to being strong enough to use toggles only.


Edit: The bigger issue isn't if someone can't do 1 of those things above. It's that most that can't do 1 of them can't also do ANY of them. We watch over those people carefully.


(This post was edited by rehmwa on Sep 19, 2007, 11:59 AM)


Premier billvon  (D 16479)
Moderator
Sep 19, 2007, 1:45 PM
Post #36 of 99 (947 views)
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Re: [hackish] 180 degree front riser requirement for "A" [In reply to] Can't Post

>However, someone with a respectable amount of experience pointed
> out that the physics of pulling a front riser on a larger canopy make it
>impossible.

Experience in skydiving does not indicate competence in physics.

If I jump a 300 square foot canopy, the load on the lines is my weight plus my harness/reserve - about 190 pounds. I will have to deflect a percentage of that (usually around 1/4 to 1/3, depending on design) to pull down a front riser to start a front riser turn.

If I jump my 108 Nitro, the load on the lines will be . . . 190 pounds. Jumping a large canopy does not change the load on the lines, and no canopy out there is rigid enough to present much opposition to deflection (compared to the load on the lines that is.)

There is no difference (other than canopy design and front/rear loading breakdowns) in starting a front riser turn with a big or a small canopy. However, it's harder to HOLD a turn with a small canopy because your speed increases rapidly.


riggerrob  (D 14840)

Sep 19, 2007, 2:28 PM
Post #37 of 99 (933 views)
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Re: [billvon] 180 degree front riser requirement for "A" [In reply to] Can't Post

IOW, the lighter the wing-loading, the less muscle required to do riser turns.
For example, if I take a 100 pound girl and a 250 pound guy for tandem jumps - with the same 400 square foot canopy - I can easily do rear riser turns and rear riser flares with the light girl, but those same maneuvers are a struggle with the heavy male student.


hackish  (No License)

Sep 19, 2007, 2:43 PM
Post #38 of 99 (927 views)
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Re: [billvon] 180 degree front riser requirement for "A" [In reply to] Can't Post

It is the physics I was trying to decode. RiggerRob and others suggested some books covering rigging and canopy flight so maybe those will be able to fill in some of the technical details. My concern in this thread dealt with whether I had "done it right" especially if the physics (which I do not yet fully understand) say otherwise.

-Michael


Premier DSE  (D 29060)

Sep 19, 2007, 3:00 PM
Post #39 of 99 (923 views)
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Re: [hackish] 180 degree front riser requirement for "A" [In reply to] Can't Post

Rightfully or wrongfully, at least you're thinking about it, and IMO, that's the most important aspect.
Putting it into practice may be an entirely different matter, however.Smile


JohnMitchell  (D 6462)

Sep 19, 2007, 3:18 PM
Post #40 of 99 (910 views)
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Re: [billvon] 180 degree front riser requirement for "A" [In reply to] Can't Post

[replyThere is no difference (other than canopy design and front/rear loading breakdowns) in starting a front riser turn with a big or a small canopy. However, it's harder to HOLD a turn with a small canopy because your speed increases rapidly.Why are toggle pressures so different on different canopies, if my suspended weight never changes? Are there some additonal factors we're overlooking?


kelpdiver  (B 7)

Sep 19, 2007, 3:23 PM
Post #41 of 99 (908 views)
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Re: [Chris-Ottawa] 180 degree front riser requirement for "A" [In reply to] Can't Post

In reply to:
I still stand by my post. Everyone should be able to lift at least their own weight to "bend" the canopy and get it to turn. I load my Spectre 135 at 1:1 and after a 360, it is pulling damn hard, but I can still hold it.

well, it's a lot easier to turn a 135 then it is a 200+, even at the same wing load. That's why the warnings apply to 150s and under.

With a dive loop, I can force the triathlon 210 to turn, but it doesn't do it in any hurry. I think the distinction of doing a pullup rather than trying to pull down the riser is helpful.


kelpdiver  (B 7)

Sep 19, 2007, 3:26 PM
Post #42 of 99 (907 views)
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Re: [bob.dino] 180 degree front riser requirement for "A" [In reply to] Can't Post

In reply to:
In reply to:
but begs the question, what was the point then?

So the jumper can see & feel how a canopy reacts to front riser input?

Many swoopers start from brakes.

ah, good to know. If I put into deep brakes I can then do a double front riser dive, though it doesn't take very long before the riser pressure wins again.


kschilk

Sep 19, 2007, 4:14 PM
Post #43 of 99 (895 views)
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Re: [billvon] 180 degree front riser requirement for "A" [In reply to] Can't Post

In reply to:
>but can't get enough of a grip on a front riser to move it more than
>an inch or two. But thats me.

Oh, OK! That's a different problem. One way to solve it is to grab the riser at the link where there's more "stuff" to hang onto. If you can't reach that, dive loops or dive blocks can help, and are fairly easy to add.

A redneck jumper'd just use comealongs.


kallend  (D 23151)

Sep 19, 2007, 4:31 PM
Post #44 of 99 (891 views)
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Re: [hackish] 180 degree front riser requirement for "A" [In reply to] Can't Post

In reply to:

However, someone with a respectable amount of experience pointed out that the physics of pulling a front riser on a larger canopy make it impossible.

Maybe you should talk to a REAL physicist.


kallend  (D 23151)

Sep 19, 2007, 4:37 PM
Post #45 of 99 (888 views)
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Re: [JohnMitchell] 180 degree front riser requirement for "A" [In reply to] Can't Post

In reply to:
[replyThere is no difference (other than canopy design and front/rear loading breakdowns) in starting a front riser turn with a big or a small canopy. However, it's harder to HOLD a turn with a small canopy because your speed increases rapidly.
Why are toggle pressures so different on different canopies, if my suspended weight never changes? Are there some additonal factors we're overlooking?
Load distribution between front and rear.


Premier billvon  (D 16479)
Moderator
Sep 19, 2007, 5:51 PM
Post #46 of 99 (869 views)
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Re: [JohnMitchell] 180 degree front riser requirement for "A" [In reply to] Can't Post

>Why are toggle pressures so different on different canopies,
>if my suspended weight never changes?

Canopy design.

A Strong tandem main is a good example. There are "turn" toggles and "flare" toggles. The pressure on the 'turn' toggles is fairly light (well, for a tandem anyway) and it's how you steer the canopy. When you flare you bring all four toggles down. The toggle pressure then becomes much heavier, because you're deflecting more of the canopy.

Think about the rear of the canopy and where the brake lines are attached. If you deflect a small part of the canopy, you're changing the line loading very slightly, and thus there's not too much pressure. If you deflect a lot of the tail, then you're changing line loading more significantly, and there is more pressure.

Likewise, many steeply-trimmed canopies have heavy front riser pressure because the canopy has more area suspended from the A-B lines as opposed to the C-D-brake lines, and more of the lift is happening over those lines. Heck, on Katanas (and many other elliptical canopies) they omit some D lines because they're just not needed! The result can be heavier front riser pressure.

However, in all cases, no matter what the design or loading, 100% of your weight is suspended from the risers - no more and no less. (Unless you're turning of course.)


mnskydiver688  (D 30125)

Sep 19, 2007, 7:03 PM
Post #47 of 99 (850 views)
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Re: [kallend] 180 degree front riser requirement for "A" [In reply to] Can't Post

Now I am not a physicist so I am merely thinking out loud. If the canopy already has a fairly steep angle of attack wouldn't that make front riser input easier because you are not changing the angle of attack as much as you would on a canopy with a flatter angle of attack in full glide? On a canopy with a flatter angle of attack you are having to deflect more of the canopy in order to get that increased angle of attack. Also if more weight is distributed to the nose wouldn't that also make front riser input easier because you are not having to shift that much weight to the front risers? I could be and probably am way off, but I like this thinking out loud stuff.


JohnMitchell  (D 6462)

Sep 19, 2007, 7:31 PM
Post #48 of 99 (843 views)
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Re: [kallend] 180 degree front riser requirement for "A" [In reply to] Can't Post

In reply to:

Load distribution between front and rear.
So, for the same suspended weight, should some canopies be easier to front riser than others? Would the difference be significant?

BTW, I've never even tried to front riser a tandem canopy.CrazyLaugh Just didn't see the point. Hope I'm still qualified to do tandems.Smile


hackish  (No License)

Sep 19, 2007, 7:55 PM
Post #49 of 99 (831 views)
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Re: [JohnMitchell] 180 degree front riser requirement for "A" [In reply to] Can't Post

During the turn you are effectively increasing your weight through the centripetal force you are applying on the lines. The real trick is figuring out what affects the amount of force being applied to a single front riser at different amounts of deflection.

-Michael


d123  (B 6134)

Sep 19, 2007, 8:48 PM
Post #50 of 99 (817 views)
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Re: [kallend] 180 degree front riser requirement for "A" [In reply to] Can't Post

In reply to:
Load distribution between front and rear.
Hi Kallend,

I have a small theory about why the front riser pressure is high on some wings and maybe you can take a look over it and let me know what you think about it. I'll try to explain it as clear as I can but I doubt it that I'll do a good job since English is not my first language. I'm guessing that the weight distribution between AB and CD lines is controlled by the parafoil profile and not by trimming (RiggerAngleOfIncidence). Off course that I might be wrong also but anyway here goes:

If front riser pressure is high this means that the AB lines sustains most of your weight and CD lines just a small fraction of your weight. In that case, I believe that most of the lift is generated near the nose of the canopy where the AB lines are connected to the wing (but on the upper skin). Probably somewhere in the CD area the flow gets detached and that's why there's only litle lift created in the CD area. Also somewhere between the AB lines the wing camber has the biggest thickness and from that "bump" on we have the "down wash" of the attached flow that "creates" the lift.

By changing the trimming (Rigger Angle Of Incidence) I don't know if you can change the place where the main lift is generated on the wing and I'm still expecting to have strong front riser pressure.

If we move the area where the wing camber has the biggest thickness (that "bump") somewhere closer to the center of the wing this might change the place where the main lift is generated and change the weight distribution between AB and CD lines = lower the front riser pressure and increase the back riser pressure.

I know 2 other things that might suggest that the main lift is generated in the front of the wing if I'm interpreting them right.

1. Some wings have ZP only on the 1st half of the upper skin. I've seen one like that somewhere but I forget where exactly.

2.In paragliding only on "some" wings you have something called B Lines stall. ABCD lines are not cascaded. By pulling on the B lines you can lower your glide ratio BIG time. I'm thinking that you actually mess around with the area where the main lift is generated and that's close to the B lines for those wings.

If I'm right and most of the lift is generated in the AB area for the wings that have high AB presure then maybe by pulling on left AB is similar with pulling on left ABCD. So when you pull on left AB you basically change the weight distribution between the left and right just like in a harness turn. The difference might come from drag because the wing is changing shape when you put most of your weight on left AB.

Let me know if this could make sense.

Just to politically correct:
Apparently "B lines stall" is a DANGEROUS thing to do and it doesn't work on all the wings. I never try it and I heard from my instructors that recovery from B lines stall gift wrapped few people.


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