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Project Sink Rate



Sink Rate is a measurement of how fast an aircraft is descending.  For gliders, sink rate determines the duration of the flight, absent any thermal or other updraft.  Although low sink rate can be associated with higher performance, a glider need not have a great glide ratio to have a low sink rate.  The Tumbling Wing has no glide ratio at all, since it technically doesn’t glide.  It falls forward at about a 1 to 1 slope, which would be a very poor glide ratio; even by paper airplane standards.  However, the plane descends so slowly, the sink rate is easily counteracted with an updraft.  Even at normal walking speed, a piece of cardboard, held nearly vertical, can create enough upward moving air to counter the sink rate. 



What’s the best predictor of sink rate; glide ratio or wing loading?



Wing loading is a better predictor of sink rate than glide ratio.



A video camera will be used to accurately assess time and measure vertical position.  A grid will be created or coopted from surroundings (tile, bricks, or other repeating pattern).  At least five aircraft will be created, first from graph paper and then from varying paper weights: 9lb, 20lb, 24lb, and 26lb.  Specific wing loading for each aircraft will be calculated.  A total of twenty aircraft (five designs in four paper weights) will be tested for glide ratio and sink rate using video analysis. 


A method for measuring distance flown, amount of descent, and time of descent will be specified.  (methods have been described in Glide Ratio and Wing Loading projects)


Measurements will be recorded and correlated to compare the effects of wing loading on sink rate.  Glide ratios will be compared and correlated to determine if better glide ratios coincide with lower sink rates.  Conclusions will be drawn from the results of the trials and correlations.



 Find your plane's sink rate

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