During the dinner at the February IMAA Meeting, hosted by the 49th Jumbo Squadron, the discussion at our table got around to the weight limits of our giant scale aircraft. Most everyone knows it is not so much the weight of an object but the speed of that weight that constitutes a danger to anything impacted. This discussion was still roaming around ir: my mind when I got home so, I decided to do a comparison of model sizes.

Kinetic Energy is that energy stored in an object or mass due to motion of that object or mass. Kinetic Energy is defined in units called foot-pounds. One foot-pound is that energy required to raise one pound one foot. The formula for calculating Kinetic Energy is:

	E kt 	= 1/2 mV2 or WV2/Zg 
	Where: 
	E kt 	= Kinetic Energy 
	V 	= Velocity of C.G. of Body in Ft./Sec. 
	W 	= Weight of Body in lbs. 
	M 	= Mass of Body of W/g 
	g 	= Acceleration due to gravity or 32.16 Ft./Sec./Sec. 
	Ft. lb. = Energy to lift 1 lb. 1 ft.

We can see from the formula that the weight of the body is a linear function (W). Velocity, on the other hand, is a squared function (V2) thus, Kinetic Energy will increase at a more rapid rate per unit of velocity than per unit of weight.

I happened to recall an ad for a ducted fan model which stated a top speed of 175 mph. No weight was given so I assumed 9 lbs. as being average for a ducted fan model. Plugging in the numbers or the ducted fan model we find:

	175 mph x 5280 ft. 	
    V = ------------------  = 256.66 Ft./Sec. 
	60 min. x 60 sec. 

	9 lbs. x 256.66 (sq) Ft./Sec. 
  Ekt = -----------------------------
	2 x 32.16 Ft./Sec./Sec. 

  Ekt = 9218 Ft. Lbs. 

The equivalent weight of a giant scale model, flying at 75 mph, to produce this amount of energy is 49 lbs. Do you realize the energy stored in the above examples is enough to lift a 4,000 lb. Van 2.3 feet in the air?

Granted, this will not happen, if you decide to try it, due to the dissipation of energy as the aircraft structure collapses and is destroyed; much like the energy absorbing steering columns in automobiles. But, it is obviously enough to do great damage to human tissue. It is also interesting to note that a 120 grain bullet fired from a high powered rifle at a muzzle velocity of 2244 ft./sec. produces only 1625 ft. lbs. of Kinetic Energy.

The point of all this is not to defend large models but to graphically illustrate the extreme importance of safety and keeping one eye on aircraft in the air. We all have - or inevitably will - gained great respect for that 18 to 24 inch disc which will ONLY cut off our fingers. We should have even greater respect for that airborne aircraft. The rules we have set for ourselves as a club and as an international organization are for our protection and that of the spectators watching us fly. Let's all blow the dust off those rules, study them, and most of all, abide by them!