What keeps the canopy in a dive?

[yurbai 0]

Hi guys!!! My question is why Xbrassed canopys stay in a dive longer/recover slower? Is it possible, let's say take a Stileto and make its recovery ark longer. How is it done. What do constructors do to make a canopy's recovery arc longer???

Thanks to all.

[johnny1488 1]

I'm grabbing at straws here, but I would guess line trim, line length and wing loading. I am sure there are plenty of construction techniques that make it happen, but I think I got 3.

Johnny
--"This ain't no book club, we're all gonna die!"
Mike Rome

[alan 1]

I woud also add in the specific airfoil used. The nose design.

alan

[SkymonkeyONE 3]

Longer risers make for a longer recovery arc as well.

[MathmatiC 0]

Hey Skymonkey,

Do you know the specifics on about how much longer the canopy will dive with longer risers compared to shorter risers? Or is it slightly noticeable?

[johnny1488 1]

Not sure about specifics, but longer risers, like longer lines, will add to the recovery arc. I takes the pilot longer to swing back under the canopy once he or she is out from under it.

Johnny
--"This ain't no book club, we're all gonna die!"
Mike Rome

[SkymonkeyONE 3]

specifics? No. I am not sure who, if anyone, keeps information that specific, but I would bet that Chris Hayes, Rixter Powell, and the other PD test jumpers would be the people in the best position to have correlated such info.

[MathmatiC 0]

Cool.
What the hell I thought you guys knew everything. What a rip off!

[BrianSGermain 1]

There are several variables that control the recovery arc. In general, the dive of a canopy is determined by the amount of drag it produces in relation to the amount of body drag exhibited by the suspended load. If the wing produces a great deal of drag, due to its shape, trim or angle of attack, it will forcibly strive to remain above the jumper. This creates a short recovery arc.

Line length also contributes to the frequency of the pitch axis oscillations, including deliberate reduction in the pitch angle. In other words, the further the suspended load is from the wing, the longer it will take for the system to recover to static glide ratio.
This does not mean that all short lined canopies have short recovery arcs and vice-versa, however, as confounding variables such as wing loading have a significant impact on the issue.

Cross-braced canopies are designed to have very little drag, are trimmed fairly steep, and typically have long lines.

It is important to note that the way in which you perform your diving turn has a very siginificant effect on the amount of altitude lost. A canopy with a "short" recovery arc can be made to dive for a long time by maintaining the ROLL angle on approach. Most of us have experienced a high plane-out when in double front risers, because the canopy's lift overcomes our physical strength. If however, we delay our arrival at the final approach heading, and keep our roll angle until the correct altitude, and "lifty" canopy will dive all the way to the ground. This dies not mean that you must start lower, it just means that you have to turn slower by adding the other front riser as well. This keeps the "lift" vector from lining up in opposition to "weight" vector, and thus prevents a spike of the "G's" in the system. The parachute will keep diving because the lift is tilted.

The pilot will always be the most important variable of the system.

Instructional Videos:www.AdventureWisdom.com
Keynote Speaking:www.TranscendingFEAR.com
Canopies and Courses:www.BIGAIRSPORTZ.com

[rmsmith 1]

The center of lift along the top surface plays a huge roll in the canopy's recovery to natural glide.

Canopies like the Spectre have the center of lift forward near the nose, which gives it a short radius recovery arc and also makes it very stable in windy turbulent conditions.

One the other hand, canopies like the Crossfire have the center of lift moved back away from the nose, which tends to increase the radius of the recovery arc and give the canopy a flatter glide. However, the trade off is poor handling in turbulence.

Several photos have been posted here of x-braced canopies folded under or folded in half due to turbulence. The swoop toyz might be fun, but they are not good all-around canopies for the general fun jumpers among us.

[BrianSGermain 1]

The interesting thing is, the airfoils on most canopies out there today have the "center of lift" in the same position, slightly forward of the midpoint between the "A" and "B" lines. I agree that the center of lift can be a major factor in the recovery arc, but this is not a variable that is commonly manipulated in today's canopies.

Just thought you'd like to know...
+

Instructional Videos:www.AdventureWisdom.com
Keynote Speaking:www.TranscendingFEAR.com
Canopies and Courses:www.BIGAIRSPORTZ.com

[superstu 0]

hey brian can you explain your thing on roll angle a little more i'm confused. is it better, in your opinion, to do a slower turn? why or why not?

Slip Stream Air Sports
Do not go softly, do not go quietly, never back down

[BrianSGermain 1]

You bet.

Roll angle is the driving force that creates high descent rate. This is due to the fact that your lift vector is angled with respect to the horizon. In other words, your lift is less effective against gravity, but it still exists in full force. By keeping the high roll angle, we can keep the canopy in a dive. As soon as the roll angle is zeroed, the lifting force begins to make the canopy struggle back to level flight.

The way to apply this is the following technique:
1) Initiate the roll with the front riser up high
2) Allow the canopy to turn for at least 90-180 degrees to attain more airspeed, and allow the centrifugal forces create a balance that keeps you in the spiral.
3) Slow the turn rate between 45 and 90 degree of the final approach heading by applying the opposite front riser during the turn. You are now in "off-set double fronts".
4) Dive the canopy in the bank until the approproate altitude and then ease yourself onto final heading.

The goal is the get the dive going up high, and slow the rate of turn as you get to final approach heading. The "fastest" part of the turn is up high, the initiation phase. The slowest part is just prior to level off, as you ease into your final heading. You can, however, slow the turn rate in this manner at any point during the turn. You are flying the approach, rather than blindly "whipping" it around.

This method allows you to dive a canopy longer, even if it has a fairly strong recovery tendency. The opposite technique is the whip the turn around aggressively and then pull your other front riser when you get to final heading, regardless of altitude. the problem of this method comes when you reach final heading too high. The "G's" spike, and the lift pulls the front risers out of your hands.

In other words, do not reach final heading until the altitude is right.

Instructional Videos:www.AdventureWisdom.com
Keynote Speaking:www.TranscendingFEAR.com
Canopies and Courses:www.BIGAIRSPORTZ.com

[superstu 0]

thanks, so it sounds like what i'm doing is correct and ithis way is probibly better for getting greater speed and distance

Slip Stream Air Sports
Do not go softly, do not go quietly, never back down