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What are the advantages and disadvantages to going light on your wing loading (i.e. 0.65ish)? Obviously, an advantage is that your descent rate is slower and a disadvantage is that you're carrying a little more weight around, but what else?

You'll know when you hit that rock or find yourself in an unlandable area

shitty inflation and heading performance come to mind.

Personally I don't think 0.65 is a light wingloading in base terms. I'd say 0.5 is light, 0.9 is heavy.

I jump a Troll 285 MDV, weigh about 82kg naked have never felt like I need a smaller canopy. On the contrary, a couple of times I've been very happy about that extra fabric.

edit: IMO, I don't think heading performance correlates much to wingloading. Like that famous basejumper always says, its body position. Body position. :)

Kerkko
BASE1184

I've noticed degradation more below .63... Inconsistent slider up openings, unpredictable snivels, and bad heading performance. Also reduction in flare and tendency to stall more abruptly.

Cool. I'm 180 lbs naked and I've been jumping a Troll 265. I want to get a brand new OSP and I'm thinking of going with a 285 instead of 265. From looking around, it sounds like the OSP 285 is a good call. With Atair's different sizing system, it would put me around 0.65.

Aren't the atair's generally +20 to whats on the label? So a 265 is roughly equivalent to a 285 (which would be appropriate for your body weight)

I've jumped a handful of canopies from 220-315sq/ft, and weigh 177lbs naked. The 220's opened fast and positively while providing a great flare, but too much speed (for me) for tight lz's. The 315 was the most inconsistent performance-wise, and I felt like it was an unnecessary risk

After almost breaking my back on it I sold it and spent some serious coin on a ppro/s7ven 285 combo. Nicest rig I've ever owned

I haven't jumped an OSP, but I believe it's a primarily slider-down designed canopy with a steep trim designed for tight unforgiving LZ's.

Call the manufacturer and ask them..

From: http://www.adrenalinbase.com

Choice of canopy size (Troll, Trango and OSP)
Picking the right canopy size is very important. The recommended weights apply for normal use
only. If you perform jumps with landing areas at high altitude or jumps with difficult landing
areas, we recommend you stay in the lower range, close to the minimum recommended weight.

Weight = jumper with clothes and shoes

• 185 min 55kg max 65kg
• 205 min 60kg max 70kg
• 225 min 67 kg max 77 kg
• 245 min 73 kg max 83 kg
• 265 min 79 kg max 89 kg
• 285 min 86kg max 96kg
• 305 min 92kg max 102 kg

From: http://www.http://baserigs.com

* 205 ft.2 = PIA spec 219
* 225 ft.2 = PIA spec 240
* 245 ft.2 = PIA spec 260
* 265 ft.2 = PIA spec 282
* 285 ft.2 = PIA spec 301
* 305 ft.2 = PIA spec 322

in my experience at lighter wingloadings slider up sub terminal are more prone to off headings

its not digital....the lighter the loading the greater probability of it not being bang on.

at petrnonas one year, Annie H did some surveys of jumper WL just before exit then recorded the heading accuracy...not sure if she published the results or not but would be good to see. I seem to remember it correlated with my experience but thats probably just my cognitive bias kicking in.

that's been my experience as well.

everything's a trade-off

Wrong.

It's been my experience that this is a problem with 300ft + canopies regardless of loading.

Yeah that's alot of fabric up there. Also worth mentioning, you may wish to use one size larger pc with the 300sq/ft+ canopies. If a 42 is appropriate for your buddy jumping his 265, you might consider a 46 for the same jump, due to the increased weight and size of your mega-tarp.

I've been chewing on this a bit, because wing loading certainly has some effect on stall characteristics. So I began thinking along these lines:

When flying a ram-air parachute, it's the suspended load and its acceleration due to gravity that provide the "thrust" in our analysis of flight forces. A heavier suspended load will "increase thrust", so to speak. As such, in full flight with a heavier load, the wing will be flying further above its stall speed than it would with a lighter load.

I understand that speed is not the only factor in a stall, but that angle of attack factors in as well. But if we assume that angle of attack is normalized for both heavy and light wing loadings, can we make the following set of statements about wing loading and stall characteristics???

1. Within certain limits, a heavier loaded canopy will have more available control range than a lightly loaded canopy.

2. A lightly loaded canopy in full flight is closer to its stall speed, and therefore has less available control range separating it from a stall condition.

Or am I missing 11 other factors?

~ Chris

You may. But you may not. I just went from a 260 to a 308 and I use all the same PCs. So far I can't tell a difference in opening speed. My same PC's drag my shlarp out at the same speed as before. Its a weight difference of less than 3 lbs and usually a drag force of more than 20 lbs. This was a huge fear of mine that turned out (so far) to be for nothing. My assumption (taboo on this sight) is that even though it weighs slightly more lifting off your back, it is more area to catch the breeze as you fall, which helps tard it to opening once its exposed anyway. Big canopies rule. Not sure why I fought it for so long.

Well said. Maybe I didn't word it clearly. But the way you said it is better. The flare/ control range is shorter w/ a lightly loaded canopy. And shorter range means shorter flare= more abrupt stall.

And a less pressurized canopy is more prone to collapse from turbulence etc.

but that is not what gives major problems or generally kills a BASE jumpers .
I find the Opposite . the Large BASE canopy gives great flight control in deep break, with precision Flat-Turn control & is easier to ride the wire in steep approach into tight landing area.
Big BASE Canopies Do Rule . Big is badass & big and Slow is your friend when shit goes Bad .
.

when is big too big?

Not trying to be a smart ass, just wanted to bring the info from the article to light.

http://www.basejumper.com/Articles/Gear/BASE_Canopies_681.html
Wing loading (WL) is the ratio of the weight of the jumper plus gear measured in pounds and the square footage of the canopy measured in square feet. Unlike in the skydiving environment, where usually experienced skydivers jump canopies at higher WL than novices, in BASE usually the WL is more consistent across pilots, regardless of the experience level.

BASE canopies can be flown as low as 0.5 to as high as 1.0 WL. Going outside these limits is not recommended. However those are considered extreme limits not to be used on regular jumps. Flying a canopy at very low WL (<0.6) will result in poor inflation, sluggish control responses, and reduced flare power. Flying at high WL (>0.8) is also counterproductive because the canopy might be too twitchy in flight and hard to land due to the added airspeed and higher stall point, among other things.

Also at high WL the canopy might be subjected to additional stress from the openings. It is my opinion that the golden range for the WL of a modern BASE canopy is 0.65–0.75. Deciding which side of the range to choose is a matter of personal preferences. I personally like my BASE canopies at 0.70, other jumpers might prefer a bit lower while other a bit higher. A rule of thumb is to start at 0.70 and see if you need a bit more penetration and responsiveness.

Lately I have seen a trend of going bigger, i.e. lower wing loading. I have taken FJC freshly graduated jumpers on objects and their canopy size was in my opinion borderline unsafe. Bigger is NOT always better. If you do not have the skills to fly and land on a dime a BASE canopy at 0.70 then you should reconsider your participation into the sport altogether. There are many instances where a little performance is desired and too low of a WL will rob this performance away.

I rarely fly in full flight on a BASE jump but it is nice to know I have some extra speed and penetration when needed. If my WL was too low, this speed and penetration would be non-existent and I know for a fact I saved myself from some possible dire consequences a few times because I was able to out-fly obstacles in head winds or to turn quickly and this thanks to my WL.

In the end be very skeptical when someone recommends you anything lower than a 0.65 WL and again if this recommendation is in part due to your canopy skills, reconsider BASE jumping until those skills are adequate.

I disagree... It depends on what type of jumping you intend on doing. I tend to assume that I could be in a shit situation, under canopy on every jump.

I jump at a WL of 0.58-0.6 on a Fox 265.

In Australia as many would know, our landing areas are typically tight, particularly by international standards. We have many sub-terminal slider up jumps on shitty walls with equally shitty landing areas. I have no problems with supposed unreliable opening characteristics or heading performance, compared with jumpers of differing WL. It's a subterminal opening! Of course it's going to be variable. If it was so variable over our shit landing areas, I would reconsider.

The reason I jump at this wingloading is for the better flare from deep braked approaches and more forgiving characteristics. Bad heading performance, reduced/or comprised pressurisation, easier to stall; these are not true in my opinion. If you are stalling, you should work on your general canopy skills on YOUR own canopy.

The main disadvantage with a light WL is jumping in higher winds. You obviously will have less penetration into a given wind speed. If the winds are at that sort of speed, maybe your risk assessment needs tweaking. If clearing obstacles are a concern, then maybe you need to adjust your opening height. I generally do not jump in strong winds anyway and yes, I have walked away from several jumps where my mates have jumped.

Everything Ray said, I generally agree with.

Have fun...
Plummy

I am sure that what you jump works for you, you wouldn't jump it if it didn't. I didn't write that though, that is verbatim from the article on canopies from this site.

No problems, I was aware of that. But I don't agree with what is written and the arguments put forward.

Plummy

Do you have any pics?

My naked weight runs 183 (+/- 5 depending
on the season, injuries, training level) and
my rig, clothes, Protec, Hanwags, knee pads,
phone, stash bag, and 1 GoPro = 24 pounds
hence my exit weight bounces around 207.

207 / 240 = .862
207 / 260 = .796
207 / 280 = .739
207 / 300 = .690
207 / 315 = .657

I have SKY jumped wings 117 to 420 and the
ridiculously Lightly loaded wings open really
slowly even with you pumping the rear risers.

I have BASE jumped wings 240 to 300 and in
my opinion that whole range opened just fine
but landing at high altitudes or in tight areas
I prefer flying a canopy around 280ish.

hey

When you calculate your wingloading you have to add the weight of your rig also or not?

for example if I m 171 pounds shoes clothes. my rig is 15.4 pounds my wingloading is 186/300=0.62 ??

Yes. Wing loading is a quick way of communicating
the amount of weight suspended per each square
foot of canopy, so yes, you do need to add up the
weight of all the things under the wing.

Generalization
Swoopers like 1.5 - 2.2
CRW dogs prefer 1.3
Novices usually fly 1.0
Beginners fly < 1.0
BASE jumpers 0.6 - 0.8

One question i have always had is why do we count the weight of the deployed canopy for wing loading? if the term wingloading is to describe how a jumpers weight effects a given canopy why add the weight of canopy?

Wrong again. Same control range, maybe less noticeable but still the same control range.


Wrong again. Yes a shorter control stroke will make it easier to reach your canopies stall point but it will not make it stall more abruptly. Actually the lighter your wingloading the slower your stall onset will be while the higher the loading the more abrupt it will be. Try stalling a velocity sometime.

+1

because the definition of wing loading is the loaded weight of the [aircraft] divided by the area of the wing.

even the wing [or aircraft] must be calculated to get an accurate figure.

all that said, in parachutes, since different manufacturers measure and cut their wings differently, an exact figure down to the hundredth of a pound is not very helpful.

it is a rule of thumb... no need to count ounces to be sure you buy the "correct" canopy for your weight, i.e. a 260 vs. a 280.

one size up or down, IMO is a minor issue compared to simply being a competent pilot.

Fledgling,

When you say 'wrong' and 'wrong again', can you elaborate a bit? I think this is an interesting topic.

If you're saying the control range is the same regardless of wingloading, I have to disagree, in two ways:

1. The more heavily loaded canopy will obviously have a greater maximum speed, meaning it has more available range of speed control between full flight and the stall.

2. If we take one canopy and let pilots of different weights fly it, the heavier pilots will have greater residual forward speed at any given toggle position than lighter pilots will. Therefore, there's more available toggle stroke at the deep end - within limits.

So while I agree the lightly loaded canopy won't stall more abruptly, I do believe that (within reason) more heavily loaded canopies have more available control range.

We know very heavily loaded canopies (say the Velocity you mentioned), can stall pretty abruptly once that flight condition has been reached. But for big, slow, stable BASE canopies, it seems that within normal loading ranges, the heavier-loaded canopy will enjoy a somewhat expanded available control range.

If this is wrong, can you elaborate?

Thanks!

~ Chris

I am going to say that on a Big Canopy with a lighter wing load . w/ proper deep-brake setting & If you have a 180 . It will have a slower forward-surge speed also .
.

Ok , so I have doing some research and talking to some people.

Every canopy is designed to operate with a certain weight range for the size and the airfoil. Below that weight the pressurization and airflow are reduced and canopy performance decreases. Between canopy sizes, the effect are not linear, so 200 size of one model will not react the same as a 260 of the same model.
for instance, If you jump a 265 fox at .58 and it reacts
great, the same may not be true for the 220 size. And it will be different for the every canopy depending in the airfoil and size.

Comparing a velocity to base canopy? It's like comparing a ferrari to a delivery van.

To a point, I agree. However, I believe that most canopies can be flown at a WL much lower than what even the manufacturer recommends without the pilot noticing an appreciable difference in pressurisation and performance. In fact, I believe the advantages outweigh the disadvantages.

In my opinion, you are far better off erring on the side of a lighter
wingloading than a heavier one. Perhaps that's what the original poster was questioning.

The airfoil design is a much larger factor in control range than the wing loading.

You can load a Rock Dragon at 1:1 and it's still not going to have the control range (or available forward speed) of a Blackjack or Flik loaded at .6.

Also note that control range and control stroke are two different things.

Control range is the difference in speed between the canopy's maximum forward speed and the canopy's stall speed. Control range would be measured in distance per time.

Control stroke is the distance the tail of the canopy must deflect between full flight and stall. We could measure it as the distance the toggles travel between full flight and stall also, but we'll encounter variances caused by flare style there, unless we compensate for the angle of each jumpers personal flare stroke. Adding a 5th upper control line, for example, alters (compresses) the control stroke of the canopy because it pulls down a larger section of the tail.

If you want to adjust the control range, there are much better ways than changing wing loading. Buying a different parachute (with a wider control envelope) will change your control range without having to increase wing loading, allowing you to maintain the lower wing loading for sketchy landing areas while still increasing your control range and available (top) forward speed.


The inflation characteristics of the specific canopy (airfoil, trim and especially presence/absence of bottom skin inlets) are much more important than either the wing loading or the canopy size. The Blackjack 310, for example, has noticeably faster/cleaner pressurization than the Dagger 244.

For what it's worth, I have seen a degradation in pressurization with both larger (300+) size canopies and extremely low (below .5 or so) wingloadings within the same canopy design (so an apple-to-apple comparison).

The amount of degradation in pressurization characteristics varies widely between canopy models, as does the wing loading at which it begins to occur. With fast pressurizing canopies with bottom skin inlets (OSP, for example) the canopies tend to be much larger and the wingloadings much lower before we see them. The opposite is true for canopies with poor pressurization and no bottom skin inlets. The Dagger, for example, appears to suffer major additional pressurization issues in the 300+ size and also when wing loading falls much below .7.

The pressurization issues may effect heading, but I have no data that validates that claim.

With most things in BASE, there are a few ways to safely do something so i usually avoid making absolute statements but the turning quickly part as an advantage to small canopies is bs. I can agree with most of the article but having a big canopy does not mean you have a slow, unmaneuverable boat.

That might be the case once you get in the 300+ range but in my experience, I have seen WAY more issues with canopy performance due to unnecessarily long control lines. A bigger canopy will require higher tail deflection, ie longer control stroke, than a smaller canopy. The longer the control lines, the less turn you will get for a given amount of input. If your canopy doesn't turn well or feels mushy, you should think about checking the control line length.

If you go for toggles in off-headings, this is one of the most important factors in staying off the wall. Every canopy I own or jump is set up so that I can drop the canopy backwards aggressively on just toggle input.

Another point worth mentioning is that short, heavy guys are at a natural disadvantage to skinny, lanky dudes with monkey arms. Longer arms means longer control stroke, shorter arms= shorter control stroke.

In my opinion, this is one the first threads I have seen for a while that has academic merit.

My comments below are all my opinion based on academic knowledge and practical experience of this topic, please take it as such and not as gospel.

While the current discussion is interesting to read, it does contain some contrasting views and statements and there are definite cases of comparing apples with oranges.


There is not a lot of literature available on ram-air airfoil flight characteristics and as such many use rigid wing theory as a starting point.
This seems accurate enough for our purposes until we enter a wingloading(WL) that introduces significant airfoil distortion.
That point seems to be somewhere between 2.0 - 2.1 lbs/sq.ft. for a high Aspect Ratio (AR) elliptical ram air such as the PD Katana.
This is based on my own experiences flying 107, 97 and 89 Katanas at an exit weight of around 190lbs.
PD's recommended and maximum weights for the Katana bear this out, as it shows a 97 to be the smallest Katana I would be inside the max weight for.
I found I liked the 97 better than the 107, as it went faster, but maintained its glide ratio (GR). It had a smaller flight speed envelope (full flight speed - stall speed) and shorter control stroke (toggle movement from the moment you start deflecting the tail to the moment you reach stall). It held with rigid wing theory in that at a higher WL it maintained a constant GR.
I did not care very much for the 89, as it seemed to have a disproportianally small flight speed envelope and high stall speed, in addition to a lower GR. This is not in keeping with rigid wing theory and I believe that can be ascribed to excessive airfoil distortion due the WL exceeding what a standard 9 cell ram air design can support.
To address this issue, manufacturer's developed crossbraced canopies to minimize airfoil distortion and thereby also allowed the use of a thinner airfoil section more suited to higher speed airflow.
This is a major design difference and one of the cases of comparing apples with oranges in this thread.
I found that crossbraced canopies in the same size range as the 89 Katana, would have significantly better GR, flight speed envelopes, control strokes and a lower stall speed. All of these are in contrast to what you would expect from rigid wing theory just looking at WL, but are effects of the design differences. The one flight characteristic that was notably worse on the crossbraced canopies was stability near stall, in stall and during stall recovery. Once again this largely due to the design attributes and therefore it is not really fair to compare the stall behaviour vs WL of a crossbrace to anything else but another crossbrace of very similar design.

Now, I will agree that stability near stall, in stall and during stall recovery does decrease with increasing WL for any given ram air parachute. However, the difference between two low AR ram airs of the same design but different WLs wouldn't be anywhere near as big a difference as between a low AR ram air and high AR crossbrace.



So for the purpose of this discussion it makes sense to limit our comparisons to BASE specific ram airs and the correlation between their flight characteristics vs WL.

People have noted that at low WLs canopies tend to open and pressurize slower. The reasons for this are several:
-Larger size
Mostly a BASEjumper comparing WLs would be doing so by comparing the same model canopies at different sizes. This introduces some other significant variables too. The most important of these would be the ratio of the combined area of the nose cell openings and bottom skin vents (if present) to the internal volume of the canopy. Pressurization time is directly proportional to this ratio. This ratio is not constant for different sizes of the same model of canopy, in fact, in decreases as the canopy size increases. The math behind that is:
Surface Area (canopy size) is a second order (square) function of linear size, i.e. Area = Span x Chord
Volume is a third order (cube) function of linear size, i.e. Volume = Span x Chord x Average Airfoil Thickness
Simply this means that larger canopies have less surface area to inflate their internal volume through and would therefore need more time or a higher airflow to do so.
I have seen two jumpers of very different size but very similar WL jump the same 230ft object with PCA deployments on the same model canopies and the time (and height used) difference was very significantly in favour of the 200 sq.ft canopy vs the 310.
The math for this one:
310/200 = 1.55 (ratios of surface areas)
square root of 1.55 = 1.24 (ratio of averaged linear dimensions)
1.24^3 (cubed) = 1.93 (ratios of volumes)
So the 310 has 1.55 times more surface area (and therefore in proportion 1.55 times more total intake surface area). The 310 also has 1.93 times more internal volume, putting it at a clear disadvantage for filling and pressurization times.

-Smaller difference in drag, weight and inertia between canopy and jumper, for lower WL and same size canopy. The same geometric principle as above regarding surface area to volume ratio applies to the jumper too. In this case surface area of the jumper is directly proportional to their drag and volume to their weight.



Now as for flight characteristics:

Full flight speed:
- increases with increasing WL
- increases with decreasing canopy size for a given WL (ratio of canopy's drag vs jumper's drag changes with size)

Stall speed:
- increases with increasing WL (usually at a higher rate than the full flight speed increases)
- increases with decreasing canopy size for a given WL

Flight Speed Envelope (Full Flight - Stall Speed);
- decreases with increasing WL
- decreases with decreasing canopy size at constant WL

Control Stroke:
- decreases with increasing WL
- increases with increasing canopy size at constant WL

Stability in near stall, stall and stall recovery:
- decreases with increasing WL
- increases with increasing canopy size at constant WL
Note: stall recovery will likely be faster at higher WL and/or smaller canopy sizes, albeit less stable. It may use more height than on a bigger canopy or lower WL but I feel this is an attribute of canopy design and I do not have enough empirical evidence to get a decent understanding of how this relates.

All the above statements apply to the same model of canopy at different sizes or WLs. As Tom A said, differences between models of canopies can have a much larger effect than those of different sizes/WLs of the same canopy.

Somehow this post became much longer than intended, so if you stuck it out, I apologize and congratulate you on your reading stamina!

cya
sam

Best post for a long time now on this forum.
Thanks

So in essence, for a given canopy make and model a WL on the lower end of the "range" will yield:
1. A canopy with a slower forward speed;
2. A canopy with a slower stall speed;
3. A canopy with a longer flight envelope;
4. A canopy with a longer control stroke; and
5. A canopy which is more stable around the stall speed.

That's the description of a near-perfect BASE canopy for me! There are occasions where a faster forward speed may be of benefit, but I have seen many jumpers get into more trouble with a faster forward speed, than benefitting from it. Even though most of those situations can be rectified with better canopy skills.

Plummy