Rear risers and glide ratio?

[hackish 8]

I read that most canopies, especially student gear is "detuned" to a more agressive slope to make them more difficult to stall. I've also read that flying with 1/4 brakes can also improve your glide distance.

I'm wondering if pulling slightly on the rear risers would allow a more efficient glide than using brakes as in theory it should allow a more shallow glide without adding the wind resistance of the brakes. Or do the brakes make the airfoil slightly "fatter" for a more lift efficient wing? What would be more efficient?

-Michael

[Peej 0]

This has been discussed quite a bit and the results vary from canopy to canopy. You should try a search using the terms glide ratio and rear risers and see what comes up.

Generally if i am downwind i will use the rears to get back from a long spot and if i am upwind i will climb onto deep brakes.

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[diablopilot 2]

When people say student gear is "detuned" it usually means that the brake lines have been intentionally lengthened by a few inches, this making a stall harder to archive.

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You're not as good as you think you are. Seriously.

[darkwing 4]

Rather than say "detuned" you should look any canopy as the result of some design parameters, just like airplanes and cars. A hot canopy isn't detuned to be a student canopy, but rather a good student canopy is designed to be a good student canopy. There are different desirable characteristics for each, and designers keep them in mind during R&D.

For almost any reasonably modern canopy though, the glide angle flattens out with brakes.

-- Jeff
My Skydiving History

[seal_S49 0]

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if i am downwind i will use the rears to get back from a long spot

WTF?

[Peej 0]

I've always been taught that the rears flatten the canopy and achieve a longer glide ratio. And that flying into wind hanging on the brakes adds more drag. Am i wrong? I realise that if the wind is so strong that you're going backwards the fronts probably are the best option.

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[seal_S49 0]

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I've always been taught that the rears flatten the canopy and achieve a longer glide ratio. And that flying into wind hanging on the brakes adds more drag. Am i wrong? I realise that if the wind is so strong that you're going backwards the fronts probably are the best option.

Your wing load and canopy performance are way more than the OP (student), so we can't expect the techniques that work for you (under some conditions) to have the desired effect on a docile to moderate canopy at light to moderate wing load. I won't contradict your own experience, but even as you mentioned, the rear riser technique will have a diminishing benefit as headwind increases. With a more docile canopy there will be no benefit at all in a headwind--in fact it's counterproductive. In my own experience at wing loads up to 1.5 (way above the OP/student), I still get the best penetration into a moderate headwind by letting the canopy fly. As the wind increases, I may need to use front risers.

While it's true that rear input (toggles or risers) "flattens the canopy," this may not actually flatten the glide. Although you are slowing your rate of descent, you're also creating more drag and slowing your airspeed. With enough tailwind, these disadvantages are overcome to increase your travel accross the ground. With enough headwind, they are amplified to reduce that travel. The trade-off point will depend on a canopy's performance envelope.

[Peej 0]

Fair enough

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[hackish 8]

With 285' of canopy and probably a 220lb exit weight (I'm flying a 9 cell student rig) I sort of expected that the results would be somewhat equipment specific.

If my instructor has no canopy tasks for me this weekend I'll ask him if I can try playing with the rear risers a little. Those of you with lots of canopy experience do you think a beginner would even notice the difference between pulling the rears and using the brakes? I mean is it just a very subtle difference?

-Michael

[seal_S49 0]

Rear risers will take more muscle to pull down, and a shorter stroke will have a more dramatic effect on forward speed & turns. You may get tired of pulling both simultaneously for an extended time.

Toggles are easier to pull and have a longer stroke to equal the same input—the advantage being more sensitive, precise control. With a docile canopy, these will probably give you all the control input you need, even when running downwind coming back from a long spot.

The advantage of using rear risers to turn is that this can be accomplished immediately after opening before you release your brakes. Later on when you’re a bad-ass skydiver in heavy traffic at break-off, you can use this technique to avoid collisions with other opening canopies. It’s a practice that will serve you well later.

As always, your instructor is the #1 person to guide you through the learning process. Your curiosity and interest in learning are a big advantage in progressing with all these skills.

[hackish 8]

Thanks for the extra info. After reading an article on canopy control I'm chomping at the bit to try the flat turns and such while I'm still at altitude.

Something I don't quite get is all these people going on about how hard tandem toggles are and how hard this and that will be on your muscles. I'm not in perfect shape by any means but I have yet to find these hard to move toggles or difficult to manipulate parts. Perhaps it's the equipment?

-Michael

[jurgencamps 0]

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Something I don't quite get is all these people going on about how hard tandem toggles are and how hard this and that will be on your muscles. I'm not in perfect shape by any means but I have yet to find these hard to move toggles or difficult to manipulate parts. Perhaps it's the equipment?

-Michael

Try the toggles on a EASY 384 tandemcanopy.

Jurgen

[hackish 8]

I flew an eclipse all the way down and it wasn't hard. How do they compare with required toggle pressure? I'll see how the risers go this weekend if the instructor says yes.

-Michael

[kallend 1,651]

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I've always been taught that the rears flatten the canopy and achieve a longer glide ratio. And that flying into wind hanging on the brakes adds more drag. Am i wrong? I realise that if the wind is so strong that you're going backwards the fronts probably are the best option.

Your wing load and canopy performance are way more than the OP (student), so we can't expect the techniques that work for you (under some conditions) to have the desired effect on a docile to moderate canopy at light to moderate wing load. I won't contradict your own experience, but even as you mentioned, the rear riser technique will have a diminishing benefit as headwind increases. With a more docile canopy there will be no benefit at all in a headwind--in fact it's counterproductive. In my own experience at wing loads up to 1.5 (way above the OP/student), I still get the best penetration into a moderate headwind by letting the canopy fly. As the wind increases, I may need to use front risers.

While it's true that rear input (toggles or risers) "flattens the canopy," this may not actually flatten the glide. Although you are slowing your rate of descent, you're also creating more drag and slowing your airspeed. With enough tailwind, these disadvantages are overcome to increase your travel accross the ground. With enough headwind, they are amplified to reduce that travel. The trade-off point will depend on a canopy's performance envelope.

According to its designer, the Stiletto acheives a better glide ratio by using brakes than by using rear risers, and that has been my experience too.

How to flatten the glide depends on the relation between the canopy's trim speed and its best glide speed (best L/D). In almost all modern canopies the trim speed is significantly higher than the best L/D speed, so slowing down with risers or brakes will flatten the glide relative to the airmass. When the airmass is itself moving (wind) it gets trickier

There was a thread many years ago in the swooping and canopy forum where this topic was analysed in great detail, with numbers crunched for the technically minded. The consensus was that the headwind has to be pretty strong indeed before front risers will increase your glide distance, on account of the typical trim of a modern canopy. In a light to moderate headwind rear risers may be still be best.

Check out these threads:

www.dropzone.com/cgi-bin/forum/gforum.cgi?post=788037#788037


www.dropzone.com/cgi-bin/forum/gforum.cgi?post=119183#119183

www.dropzone.com/cgi-bin/forum/gforum.cgi?post=119653#119653

www.dropzone.com/cgi-bin/forum/gforum.cgi?post=120238#120238

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

[Broke 0]

It is not necessarly improving glide ratio.

When you use rear risers you change the trim of your wing and thus flattening the glide ration.

However when you are in brakes just before your stall point is a flight mode called minimum sink. In other words you aren't going there fast, but you aren't coming down as fast as you would normally. In other words in minumum sink you can use the wind on your back to push you back to the DZ given a long spot. You won't get there quickly but you'll get there. As long as you are on a down wind run. If you are heading upwind this might not help you out

Divot your source for all things Hillbilly.
Anvil Brother 84
SCR 14192

[seal_S49 0]

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In almost all modern canopies the trim speed is significantly higher than the best L/D speed

I haven't been able to find any credible, canopy-specific information published on that topic. It would be of great help if you would share that.

My canopy-control methods are based almost solely on my limited experience. I have, however, noticed that over the last decade, mfrs are responding to customer demand by trimming newer canopies to glide at a steeper angle, more ground-hungry. As we see this flight characteristic becoming more popular, pilots are finding more benefit from rear riser input than from toggles alone. In fact, this dogma is all I hear anymore. A decade ago when the average jumper focused more on brake input, I don't necessarily think that it was from a lack of understanding about glide characteristics. We were just responding to the products we used. Some of us still jump old-school (Stiletto), flat-gliding canopies. To put my post back into it's original context, this is why I don't think it's advisable to teach a student to "always user rear risers," when they're usually flying a lightly loaded canopy with a relatively flat glide, even without input.

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According to its designer, the Stiletto acheives a better glide ratio by using brakes than by using rear risers, and that has been my experience too.

And mine as well, but I'd never say that out loud around the "always use rear risers" crowd. Again to get back into context, I'm not convinced that either type of rear input is necessarily desirable when downwind from the LZ and trying to penetrate upwind. It is certainly more likely to bring the desired result in a light wind using a more heavily loaded canopy that has a naturally steeper glide.

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In a light to moderate headwind rear risers may be still be best.

OK, maybe--depending on trim, WL, etc. But when I see a lightweight student under a big canopy downwind from the LZ, and he's barely penetrating or coming straight down, the last thing I'd tell him to do would be "brakes" or "rear risers."

[Broke 0]

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OK, maybe--depending on trim, WL, etc. But when I see a lightweight student under a big canopy downwind from the LZ, and he's barely penetrating or coming straight down, the last thing I'd tell him to do would be "brakes" or "rear risers."

Well with that kind of wind how did the student get up there to begin with. Also I believe that front risers would give you better penetration into the wind because it changes the angle of attack of your wing.

Divot your source for all things Hillbilly.
Anvil Brother 84
SCR 14192

[seal_S49 0]

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Well with that kind of wind how did the student get up there to begin with.

Probably in an airplane, but one thing is for sure--no amount of rhetorical questions would get him down safely.

BTW, do you suppose that it's possible for the winds aloft to be stronger than those on the ground?

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Also I believe that front risers would give you better penetration into the wind because it changes the angle of attack of your wing.

Congratulations.

[Broke 0]

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BTW, do you suppose that it's possible for the winds aloft to be stronger than those on the ground?

Typically Winds aloft are which is why it is manditory to learn how to read the aviation forecats to get you USPA A liscence

Divot your source for all things Hillbilly.
Anvil Brother 84
SCR 14192

[seal_S49 0]

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it is manditory to learn how to read the aviation forecats to get you USPA A liscence

That would be a great topic for a new thread.

[Broke 0]

Also lets not forget about the selections of outs in high winds. Ie if the wind is pushing you away from the DZ look where you are going to be pushed to, maybe there will be a place for you to land behind you

Divot your source for all things Hillbilly.
Anvil Brother 84
SCR 14192

[kallend 1,651]

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OK, maybe--depending on trim, WL, etc. But when I see a lightweight student under a big canopy downwind from the LZ, and he's barely penetrating or coming straight down, the last thing I'd tell him to do would be "brakes" or "rear risers."

Well with that kind of wind how did the student get up there to begin with. Also I believe that front risers would give you better penetration into the wind because it changes the angle of attack of your wing.

You didn't read the threads I linked, did you?

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