Originally Posted by
megan
You are not interested in airspeed because measurements are being taken from ground impact references (prop slash marks) which relate to GS.
The last data point gives a GS of 108 knots, which equals,
108*6080/60 ft/min = 10944
Four bladed prop - distance over five (one RPM) consecutive blade strikes I measure at 6.9 feet ie one complete prop rotation
Prop RPM then equals 10944/6.9 = 1,586 RPM
I used a mixture of Google Earth and the dimensions between ridges of the roof cladding to work numbers.
Connedrod, quite correct that you have no idea of the power being produced, though touchdown was with yaw about 25° and a 6° descent (rough figures).
Megan,
Hats off to you on your practical maths but can I ask what dimensions did you use for the roof cladding?
The ridges/corrugations in the cladding should be 30 cm apart. By my measurements the first five prop strikes occur over a distance of 1.82 metres or 5.97 feet. That yields an average prop rotation of 1833 rpm. As you'd expect the last five prop strikes occur over a slightly greater distance; about 1.89metres or about 6.21 feet by my measurements, yielding 1762 rpm.
I make the yaw to achieve the left and nose wheel gear marks nearly aligning as they do to be around 30°.
Last edited by MickG0105; 1st Apr 2017 at 08:51.
Reason: Correct missing spacing.