The Stock MK IV performance has been characterized and has provided a value for the equivalent flat plate drag in this configuration. It now becomes appropriate to add the impact of the infinity retractable undercarriage to the performance calculations. Many builders who have installed the Infinity Retractable Undercarriage insist that the performance gains range from 16 mph to 22 mph. To be conservative I have assumed a performance gain of only 14 mph when operating with a gross weight of 1500 lbs. Don Bates' model is again used to determine the flat plate drag area for this configuration but using the same propeller as that which is used to achieve the 216 mph that Nat Puffer claims for the stock MK IV in the POH. The same propeller is used in the model since it is believed that most builders do not change the propeller after installing the RG and that the performance gains are for that configuration. The tables below are the input and output tables for the Bates model using the same propeller as the stock MK IV but RG has been added resulting in an improved cruise velocity to 230 mph.

Output data, from the program is given below. The equivalent flat plate drag has reduced from the nominal 2 ft2 to a value of 1.681 ft2. This is a substantial improvement over the stock Cozy MK IV.

To reiterate, the drag has been reduced to a value of 1.681 ft2.

Last Updated:    Thursday August 31, 2006