Forward Speed: Opening v. Available

[TomAiello 25]

I noticed this in another thread:

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This canopy had excessive forward speed (IMHO) during flight and I would not want this if I was facing a wall.

This statement appears to be based on a mis-conception about canopy forward speed. Please forgive a short lecture.
There is an important difference between a canopy's available forward speed, and a canopy's forward speed on opening.
Forward speed on opening is the relative forward motion of the canopy during and after the opening sequence, prior to releasing the control lines from the deployment brakes. In other words, it's how fast the canopy is flying before you pop the toggles.
Forward speed on opening is primarily governed by the brake setting used for the jump. A canopy with brakes set deeper will open with less forward speed. Of course, overly deep brake settings can result in a deployment stall. It is for this reason that it is absolutely essential that BASE jumpers customize their own deep brake setting, dependent on their own personal weight and canopy type. It is forward speed on opening that is undesirable in the event of an off heading opening facing an object. It is important to note that forward speed on opening is almost completely within the control of the canopy owner, and, for the most part, is independent of canopy design.
Available forward speed is the canopy's maximum speed, with no brake pressure applied (more strictly, with hard front riser input, as well, but that's not really relevant for this discussion). In other words, it's how fast the canopy can fly in full drive.
Available forward speed is largely determined by two factors, canopy type and wingloading. Assuming equal wing loadings, the available (maximum) forward speed of a canopy will depend on the canopy's design. Assuming good canopy control skills, having more available forward speed can never be a bad thing--you can just fly the canopy in brakes to reduce forward speed.
A canopy with a wider performance envelope (i.e. higher maximum speed and lower minimum speed) is (again, assuming good canopy skills) always superior to a canopy with a narrower control range. This is because the canopy with a wider envelope can always be flown within the control range of the other canopy. The canopy with less performance envelope can, of course, not be flown in those parts of the wider envelope that exceed it's own.
The bottom line is that a canopy that can fly faster need not always fly faster. A canopy that can fly both faster and slower, is (in terms of flight) almost invariably superior.

-- Tom Aiello

[email protected]
SnakeRiverBASE.com

[Dd0g 0]

I typed up a long, insightful, brilliant response to this today. Just before posting, my laptop decided to take a siesta. I lost the post, and I've lost the last 18 hours teaching that laptop a lesson it'll never forget!

If, by some miracle, I can reconstruct the thoughts and motivation behind the post, I'll do it all over again. Suffice it to say that I disagree with Tom on one relatively substantial point.

Gotta run right now - I have a laptop that still needs more punishment to understand it's proper place in pack heirarchy. Grrrr. . . .

Peace,

D-d0g

+~+~+~+~
But this, surely, was the glory that no spirits, canine or human, had ever clearly seen, the light that never was on land or sea, and yet is glimpsed by the quickened mind everywhere.

[mac266 0]

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Forward speed on opening

Would you say that a canopy is more responsive with some forward speed as apposed to no forward speed? – If so would you prefer a more responsive canopy should you be facing the object? Thus should some forward speed on opening be a good thing?

Just some thoughts I have!

Michael

[TomAiello 25]

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Would you say that a canopy is more responsive with some forward speed as apposed to no forward speed?

This is a tricky question. The short answer is "yes", but in this case I believe the short answer is insufficient.
A canopy in flight with more forward speed will respond in a shorter time to control inputs. It will not necessarily respond in a shorter distance. In avoiding object strike, the most important measurement is the horizontal distance travelled toward the object. This distance can usually be minimized by minimizing forward speed on opening.
In general, a canopy with zero forward speed will be stalled, so a canopy must open with some (minimal) forward speed. However, a canopy with secondary (bottom skin) inlets will be able to maintain inflation with far less forward speed. So, if you are likely to be facing a solid object with less distance than a toggle turn can be initiated in, you are, in my opinion, best off with a canopy that has secondary inlets. The secondary inlets, combined with well customized deep brake settings and riser input, will likely be the optimum combination for minimizing forward (i.e. toward the object) travel prior to and during the turn.

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If so would you prefer a more responsive canopy should you be facing the object?

Again, the short answer would appear to be "yes." In fact, I'd always prefer a more responsive canopy.
A more complete answer, though, would be: the best canopy to avoid object strike is the one that will use the minimum distance (both horizontal and vertical) to turn away from the object.
Secondary inlets will greatly enhance the responsiveness of a canopy with minimal forward speed on opening. Thus, if you are planning a jump in which you will open close enough to the object to require riser correction to avoid striking, you are best off with a vented (or valved) canopy.
Obviously, the optimum setup depends on the object you are jumping. Equally obviously, even the most gear-headed rigging freak isn't going to be able to precisely adjust forward speed or turn response on every jump.

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Thus should some forward speed on opening be a good thing?

There is only one situation in which I could argue that more forward speed on opening could be positive. This is a jump from a big wall (hence, lots of horizontal separation), with a relatively low pull (hence, little vertical separation), and/or a strong headwind (blowing you into the wall).
A 180 in these circumstances could result in an object strike from wind (you'd get blown into the wall) [or altitude loss (you sink into the object during your turn)]. Even if your canopy sits perfectly still in both the horizontal and vertical components, relative to the air around it, you will still strike the wall in a fixed time. In this situation, you need to make your turn in the shortest possible time, as opposed to the shortest possible distance. In this case, forward speed on opening might work to your advantage. However, since this combination of circumstances is likely to arise on less than 1% of your jumps, you are probably better off to keep your gear dialed in for more "normal" deployments.
In this (unusual) case, I'd recommend correcting the off-heading on toggles, rather than risers, to make the correction in the minimum time (so the wind has less time to blow you into the object), and with minimum altitude loss (so you don't strike the ground (or underhung portion of the object) during the turn.
Truthfully, the vast majority of off-headings on beginner, or even intermediate, jumps can easily be corrected on toggles. If you don't have enough distance to correct on toggles, then things become more interesting. But for all the standard objects in my (and most--cue D-Dog here with a comment about how in his neck of the woods they pitch 5 jump beginners off underhung cliffs) area, any timely off heading correction can easily be made on toggles. And any time that you have enough distance to correct on toggles, your forward speed on opening is more or less irrelevant. This is one of the reasons that so many jumpers are running around with wildly shallow break settings (and setting themselves up for trouble the first time that they experience a serious off heading on an advanced object).
This has all definitely come out garbled and unclear. I guess what I'm trying to say is this: Forward speed can give you a turn in less time, and less vertical distance. In general, these two components are far less important than horizontal distance. To minimize horizontal distance, you must (in 99% of cases) minimize forward speed on opening.

-- Tom Aiello

[email protected]
SnakeRiverBASE.com

[narcimund 0]

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cue D-Dog here with a comment about how in his neck of the woods they pitch 5 jump beginners off underhung cliffs.

It's only underhung for the first 2 seconds then overhung.

First Class Citizen Twice Over

[mac266 0]

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I'd recommend correcting the off-heading on toggles, rather than risers, to make the correction in the minimum time (so the wind has less time to blow you into the object), and with minimum altitude loss (so you don't strike the ground (or underhung portion of the object) during the turn.

my general feeling is that correction on risers is quicker than toggles - (straight on risers - no time taken popping off the toggles - no forward surge - initiate the turn in a shorter time) - i think more altitude can be lost on rear risers but the time taken to act i believe is quicker - can you please explain your feelings on risers v toggles for correction of off headings.

again some other thoughts going around my head!!!!

thanks

Michael

[TomAiello 25]

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my general feeling is that correction on risers is quicker than toggles

Definitely true in 99% of cases. In the above case, I was discussing a possible exception to the rule--where the decrease in turning time can actually decrease the forward travel during the turn, due to a relatively high wind, which would push the canopy toward the cliff during the (longer duration--that's time) riser turn.
Perhaps I'm misunderstanding your question. Can you explain where the confusion was?
Thanks,

-- Tom Aiello

[email protected]
SnakeRiverBASE.com

[mac266 0]

the confusion was in me consuming red wine before reading your post!

having now re-read - i get what you were saying!!

this phuqking weather and wind is doing my alcohol consumption the world of good!!

Be safe.....dont be getting mingingly pissed and trying to read!!

[manship 0]

I tend to agree on "Risers first" in most cases. Another thing to be aware of when tuning your canopy for brake settings comes to mind. I recently took another approach to adjusting brake settings, requiring no sewing. I just started to lose weight. At a point I thought I had the forward speed in DBS just about perfect, very little forward and no stall on opening. Then I went and flung myself off a relatively low cliff. 90 degree right opening towards a
reasonably far off wall section - no real problem, just riser around and pop toggles. Pulled Left riser, and got RIGHT turn towards wall NOW, problem. I decided to pop toggles and get the hell out of there which I did. So, realize in really slow flight, reverse turns can occur. I now am jumping in the shallow brake setting all the time. Seems to work better.

[andrewstewart 0]

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I tend to agree on "Risers first" in most cases. Another thing to be aware of when tuning your canopy for brake settings comes to mind. I recently took another approach to adjusting brake settings, requiring no sewing. I just started to lose weight. At a point I thought I had the forward speed in DBS just about perfect, very little forward and no stall on opening. Then I went and flung myself off a relatively low cliff. 90 degree right opening towards a
reasonably far off wall section - no real problem, just riser around and pop toggles. Pulled Left riser, and got RIGHT turn towards wall NOW, problem. I decided to pop toggles and get the hell out of there which I did. So, realize in really slow flight, reverse turns can occur. I now am jumping in the shallow brake setting all the time. Seems to work better.

Okay, I'm confused ;-|

Can someone explain to me why a left rear riser correction would result in a turn to the right?

[Treejumps 0]

Yo Tom,

How many 150 to 180's have you had on slider down solid objects? Just wondering with your jump numbers and objects what your experience has been. I pretty much always go toggles, unless I think I'm about to die or be seriously injured, in which case fear and risers seem to go hand in hand. I still think in critical situations I would be better off on toggles, but the response just seems programed.

Cya.

[Skydawg 0]

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I tend to agree on "Risers first" in most cases. Another thing to be aware of when tuning your canopy for brake settings comes to mind. I recently took another approach to adjusting brake settings, requiring no sewing. I just started to lose weight. At a point I thought I had the forward speed in DBS just about perfect, very little forward and no stall on opening. Then I went and flung myself off a relatively low cliff. 90 degree right opening towards a
reasonably far off wall section - no real problem, just riser around and pop toggles. Pulled Left riser, and got RIGHT turn towards wall NOW, problem. I decided to pop toggles and get the hell out of there which I did. So, realize in really slow flight, reverse turns can occur. I now am jumping in the shallow brake setting all the time. Seems to work better.

Okay, I'm confused ;-|

Can someone explain to me why a left rear riser correction would result in a turn to the right?

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Deep brakes, lighter mass than previously, short delay and nil forward speed.
The input on the left rear riser caused the canopy to slide/fly backwards and induced drag on the left hand side. This caused the canopy to turn to the right rear.

[TomAiello 25]

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How many 150 to 180's have you had on slider down solid objects?

I'd have to crunch through log books (most of which are in California, so I probably won't see them until sometime in the spring) to know for sure. But I'd guess around 50 "object strike imminent" openings, with about 10 of them corrected on risers, and the balance (40) on toggles.

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I still think in critical situations I would be better off on toggles, but the response just seems programmed.

I tend to use the Dwain strategy: if your body is tensing for impact, grab the risers (both of them). Otherwise pop the toggles and turn around.

I still think the fastest way to stop your canopy from flying into an object is to pull on both rear risers, then let one up and switch the hand to the opposite front riser. I also think that 4 times in 5, toggles are just fine (and cost you less altitude--if you are close enough to the wall to need risers, stalling into the ground is probably the lesser of two evils).

-- Tom Aiello

[email protected]
SnakeRiverBASE.com