How to Choose the Right Paraglider (Weight Ranges & Wing Loading)
Join me in an investigation. Stuff everything into your glider backpack, as you would walk up the hill, with your extra jacket and flying boots. Then stand on the scale! More than you thought, huh?
Your flying equipment and all the extras usually adds 20kg to your naked weight. (Of course this can vary, depending on the weight of your kit and how much other stuff you carry!)
What does it matter? Well they say that by loading a given wing with more weight you will increase all flying speeds, increase stability and get more responsive handling. But is it really true?
EFFECT OF WEIGHT ON SPEED
Top speed is a safety factor, but as we shall see, you cannot change this much with ballast or downsizing, and within a given class, the speeds are very similar.
I tested the effect of adding 20kg to my flying weight on my Icepeak 6.23 (85-105kg), flying directly upwind and downwind and averaging the GPS speeds achieved.
Flying at 85kg: trim speed = 33.3km/h, fullbar = 47.2km/h
Flying at 105kg: trim speed = 36.3km/h, fullbar = 52.8km/h
Speeds vary greatly depending on temperature, pressure, and altitude. I have recorded 39km/h (trim) 59km/h (full bar) on my Niviuk Icepeak many times before; this was a ‘slow’ day (15 degrees, 250m ASL, 1013hPA), but as we are investigating relative changes it doesn’t matter.
So adding 20kg increased trim speed by 3km/h and top speed by 5.6km/h, or +10% speed for +20% weight. 4kg is the practical limit of ballast, more is cumbersome in your harness and upsets your balance. In these conditions, adding a big ballast bag of 4kg would increase trim speed by no more than 0.8km/h and top speed by no more than 1.3km/h or 3%.
(I’ve been generous as it’s not entirely linear: as you add more weight you get less of a benefit in speed as the drag increases at the square of the change in velocity. On earlier tests on a tandem, adding 70kg (a passenger) increased trim speed by only 7km/h, not 10.5km/h).
If you think 1km/h average is going to win you a competition, remember that there is a sink rate penalty for the ballast which will slow you down with more thermaling needed. That might be a strategic advantage, to be slightly behind but faster on glides. Either way, it’s an incredibly marginal benefit.
For most pilots adding ballast is a waste of energy. It will not make a strong-wind day flyable and it makes your carry-up a nightmare.
What about moving down a size onto a smaller wing? This can increase your speed slightly more than 4 kg of ballast. Theoretically, +1.5km/h trim speed, +2.5km/h top speed.
Taking a 95kg pilot off a large Sigma 9.27 (90-115kg) and putting him on a Sigma 9.25 (75-100kg) is the equivalent effect on wingloading of adding 7kg ballast.
It might seem that you are much higher up in the weight range, but wings are often designed with reduced wingloading as they get smaller. Small wings are usually less efficient than larger ones, so the speed change is likely to be lower than expected, and the glide performance might be degraded. I don’t recommend chasing top speed by downsizing. There are more important factors to consider.
WEIGHT AND SAFETY
We’d recommend being well-loaded on your wing to reduce the frequency of collapses, increase control authority and increase flying speeds. A loaded wing becomes slightly more collapse resistant but it will have more energy if it does collapse, so your height loss might be more severe. But if you’re within your quoted weight range, all collapses are roughly within the norms, and you’ll be able to handle them regardless of your weight if you’ve already chosen the right paraglider class. On full speedbar the wing deformation is worse on a loaded wing due to the force of air striking the wing making it pucker – there is a limit to how fast these things can go.
The safety of the wing is determined primarily by the wing design. What you can influence by changing the wing loading (within the certified weight range) will have little effect by comparison to the passive safety of the wing you choose.
WEIGHT AND PERFORMANCE
Optimum performance is found in a broad range: in the morning you need to be light, at peak thermal time you need to be heavy, then in the late afternoon, light again for extended flying in weak conditions. So nobody is ever truly optimised.
There is a broad sweet spot for all wings, which is usually somewhere around 50-75% of the quoted weight range, although this varies depending on the manufacturer.
If you fly in strong conditions (wind, thermals, tricky launches) you’ll get a slight advantage by choosing a wing where you’ll be heavily loaded. If you fly in light conditions (soaring the coast, floating downwind in flatland xc, easy launches) you’ll get a slight advantage by choosing a wing where you’re lightly loaded.
WEIGHT AND HANDLING
An overloaded wing feels ‘hard’ and doesn’t turn well (hard pressure, banks too much, loses height, feels like it is ‘grinding around the turn’). An underloaded wing feels wobbly, collapses more often in a soft, floppy kind of way and doesn’t turn that well either (sluggish handling, difficult to turn back in when thermals push you out).
There is an optimum range for ‘best handling’, often around 50-80% of the certified weight range (however this does vary from model to model, even size to size, and also depends on personal preference, and various other factors). If you’re outside of the weight range, the amount of ballast you’d need to carry before your wing handling changes significantly is impractical and what you mostly feel is the counterbalancing effect of a weight below your body, which stabilises the harness and makes turning less agile.
So you must make an effort to choose a wing where you are well-placed in the weight range in the first place.
If you’re outside the weight range altogether, the wing will still fly. It’s not to say it would not pass certification at this weight: the manufacturer didn’t try to certify it at this weight, because it is not an optimal weight to fly the wing at, and it would probably result in a higher class of certification (EN B now an EN C). At this extreme point of low or high wing loading, you might begin to notice a handling change.
Every wing designer has their own idea of the perfect wing loading, which changes depending on their objective for the wing. If they want their target group of pilots to be impressed with the climb rate, make it larger (Skywalk Chili 3). If they want it to get a reputation as nimble and fast, make it smaller (Swing Mistral 7). As the aspect ratio of the wing increases, so does the ideal wing loading because the wing is more efficient.
This makes it hard to know what your ideal wing loading should be.
Manufacturers usually offer 20kg weight ranges, but each size of wing has to be designed, manufactured, tested, refined and certified, so it’s more economical to make larger weight ranges and smaller overlaps.
In many cases you might like a wing design, but be in an uncomfortable place in the overlap between sizes. As you know already, we don’t recommend ballast. We recommend getting the right wing, which is why we offer many brands.
HOW TO DECIDE
When choosing your next paraglider, narrow it down to those that put you in the right place in the weight range to start with and identify the ones that give you a wing loading that suits your flying environment. If you’re lucky, you can get a trial flight on your size so you can feel the handling at its best.
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