jimboflying
MEMBER
Anyone have a good way to measure takeoff distances while on floats?
Take off, turn around & look @ your tracks.
What I was looking for was a way to see how the present flap setup works and compare it to the same plane with double slotted flaps. I would want multiple records taking into account density altitude for each measurement.
You can use a bit of easy math.
1. Calculate your acceleration using the equation: Velocity at rotation divided by time in seconds for takeoff run. (v/t = a)
2. Next you can calculate the distance using the equation: distance = .5*a*t^2 where time is squared (t^2)
This equation should allow you to compare configurations. All you need is the time and velocity in ft/s at rotation. You will likely need to convert the latter from knots.
jimbo,What I was looking for was a way to see how the present flap setup works and compare it to the same plane with double slotted flaps. I would want multiple records taking into account density altitude for each measurement.
Assuming constant acceleration, of course. That works pretty well on wheels, but for floats, the part before you get on step is a lower rate of acceleration than once on step. At least it is for boats unless you have a lot of power to jump out of the hole quickly.
Something to consider is the angle of attack of the wings during acceleration. There are many shown in videos who appear to like to carry the tail in a very high attitude during the take off run. When in this attitude the drag of the wheels on the ground increases as the speed increases due to the increased downward pressure from the wings. If the tail was carried with the tail wheel just clear of the ground, the drag of the main wheels would be decreasing as the speed increased due to the wings taking more of the weight of the plane. There is less drag in the air than there is when rolling contact with the ground is happening.Good point and I agree with the other comment that even on wheels acceleration wouldn't be constant as drag increases. I'm not sure how far off the constant acceleration assumption would be on wheels but it would be neat experiment using known distances.