Mathematics for Today's Modeler Modeling these days seems to be getting more technical, even though the techniques used to build the models offered here are exactly the same as they were over 50 years ago when the true art of modeling was in full swing. For that reason, many are confused about how to figure out the "why's and where-for's" involved. So what I'll do is list a few of the simple equations I use all the time to set up my models and to estimate the kind of performance the model will deliver. All you have to do to make them work on your specific model is plug in the numbers. So, grab your calculator and let's get started: 1- Watts: watts = volts X amps2- Power Loading: watts divided by flying weight (in lb.) = watts per lb. To convert the flying weight of your model in ounces to pounds, simply divide the weight (in ounces) by 16 3- Wing Area: wing span (in inches) X wing chord (in inches) = wing area (in sq. in.) divided by 144 = wing area (in sq. ft.)4- Wing Loading: flying weight (in oz.) divided bywing area (in sq. ft.) = wing loading (in oz. / sq. ft.) 5- Stall Speed: wing loading divided by 4 X 3.47 = stall speed This is just a rule of thumb, but it will get you in the ball park as to knowing how fast your model will land: 6- Propeller Pitch Speed: rpm X pitch (in inches) divided by 1056 = flying speed (in MPH) This will give you a ball park idea of how fast your model will fly at full throttle with a given prop and battery combination. 7- Scale: full scale wing span (in inches) divided by the model's wing span (in inches) = scaleThe basic formulas listed here should be helpful in getting you heading in the right direction. The speed related items are just a rule of thumb, but being precise really isn't necessary since we can't know the exact speeds we're flying anyway. And finally, to properly set up a model's power system for best all around performance for a Light-Weight Park-Flyer type scale model, a good rule of thumb for powering your model is that the calculated top speed using formula #6 should be roughly 4 times the stall speed obtained using formula #5. |