You should be aware that more weight means more speed but how much ?
Wing reviews are obviously done with a set pilot weight, say a light pilot of 70kg (150 Lbs) would be unable to see what happens at real high wing loadings since they don't make wings that small.
The Velocity Recon 18 (65~85kg) is our smalest wing but it would take an 100kg pilot to test. To get a high wing loading a 70kg pilot would have to fly a 16m wing and nobody makes those in enough quantity to call them production.
So how much faster would a heavier pilot go on a Recon 18 ?
The formula is (SQRT (New Weight ÷ Original Weight)) * Original Speed (either airspeed or sink rate).
For example, lets say a 140kg (300 lbs) pilot+wing+motor wants to know what his speed will be on a wing flown by a 115kg (250 lbs) pilot+wing+motor. Calculate the square root of (New Weight - Original weight). So if the original flight test was done at 115kg with a reported speed of 40 kph (25 mph) and the new weight is 140kg you would SQRT (140 ÷ 115) to get 1.1. That is, 140÷115 is 1.21 then SQRT (1.21) is 1.10. Multiply 1.10 by the old speed of 40 kph for a new speed of 44 kph. If the original sink rate was 120 mpm (400 fpm) than the new sink rate will be 1.10 * 132 mpm (438 fpm).
Risk of Small Wings:
Pilots love small wings and it's tempting to keep going smaller and smaller but know the risks and tradeoffs you're getting into. I'll leave overloading wings for Wheeled paragliding as they deal with a higher landing speed easier than trying to run like the Roar Runner!
1. The main reason is what happens after a motor failure. If it quits just after takeoff, you'll be faced with a surge and dive at very high speed. The appropriate response depends on altitude; if you're a foot off the ground, an immediate pull of brakes will do, if you're 10 feet off then a brief pause to allow surging to a mostly level attitude is followed by a pull of brakes to avoid having a big sink rate develop. If you're above 30mt (100 feet) than all is well as you would have enough time to let the wing surge, establish a glide and do a normal flare.
2. You'll be running at break-leg speeds, especially at higher elevations. Any foot dawdle or surface perturbation will have graver consequences and will, generally speaking, suck in quite large doses.
3. Another tradeoff is high fuel flow. Just like with reflex wings trimmed fast, it takes a lot of power to overcome our draggy craft and that means a lot of fuel burn.
4. Handling will be extremely sporty especially for those models that are known for sporty handling to begin with. I can only imagine what the likes of a 16 meter Spice would be like.
5. Lastly, although speed is great, if you do suffer a collapse the recovery will be, pardon the understatement, "dramatic."
So dive into small wings with understanding. Understanding that yes, they're fast, they're easy to inflate and they're easy to carry but they'll bite anyone not giving an appropriate amount of respect.
Glide Ratio And Weight:
Glide ratio can be expressed either as the lift/drag ratio or, more commonly, the distance you'll travel forward for the distance dropped, and its the same at any weight. Every glider has a speed/configuration that gives the best glide ratio and, in that configuration, (usually neutral trim, no speedbar) you'll fly the farthest distance in calm wind. Mind you, the speed at which best glide occurs will be faster at heavier weights but the glide ratio remains the same.
A heavy pilot will fly just as far from 100 feet as a light pilot on the same rig but the heavy pilot will get there faster. Both his sink rate and forward speed will be greater.
Note that power required is based on sink rate and weight so the heavier pilot, not surprisingly, requires more power to stay aloft than the lighter pilot. |
