Given the same wing size, heavier pilots go faster, how much faster?
We all know that more weight means more speed but how much? My wing reviews are obviously done with my 150 pound self so I’m unable to see what happens at real high wing loadings since they don’t make wings that small. The Plasma 22 and Pluto 21 were the smallest production wings I’ve tried lately and my Spice 22 is too big for me. To get a high wing loading I have to fly a 17 and nobody makes those in enough quantity to call them production.
So how much faster would a heavier pilot go on a Spice 22? Thankfully, some brainiacs (Dana Hague and Carlos Curti) show us how. The formula is:
SQRT (New Weight / Original Weight) * Original Speed (either airspeed or sink rate).
Lets say a 300 lb pilot+wing+motor wants to know what his speed will be on a wing flown by a 250 pound pilot+wing+motor. He knows the 250 pounder goes 25 mph on that wing.
1. Calculate Weight Ratio: New Weight (300) / Original weight (250) for a weight ratio of 1.095
2. SQRT (Square Root) the ratio (1.095) to get Speed Ratio. That’s 1.2 here.
3. Multiply the Speed Ratio (1.2) by the speed or sink rate to find out the new speed or sink rate.
If the original (250 pounder) goes 25 mph, the 300 pounder will go 27.4 mph. And if the original sink rate was 400 fpm than the new sink rate will be 1.2 * 400 or 480 fpm.
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