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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 0
Quote>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 1,819
Quote
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.
The only sure way to survive a canopy collision is not to have one.
kallend 1,819
Why are toggle pressures so different on different canopies, if my suspended weight never changes? Are there some additonal factors we're overlooking?Quote[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.
Load distribution between front and rear.
The only sure way to survive a canopy collision is not to have one.
billvon 2,691
>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.)
JohnMitchell 16
So, for the same suspended weight, should some canopies be easier to front riser than others? Would the difference be significant?Quote
Load distribution between front and rear.
BTW, I've never even tried to front riser a tandem canopy. Just didn't see the point. Hope I'm still qualified to do tandems.
hackish 8
-Michael
d123 1
QuoteLoad 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.
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.
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