The planes database (PLANES.EDB) characterizes planes and includes the cell,
motor/gearbox, and prop database selections.
PLANE is a description of the selected aircraft (up to 20 characters).
Wing is the total wing area in square inches. Wing area is normally considered to
include the area over/under the fuselage. The area of a wing with non-parallel
leading & trailing edges can be figured by taking the width at the center plus
the width at the tip and multiplying by the length (perpendicular to fuselage)
from the center to the tip.
WGT is the total aircraft weight in ounces. Don't forget to adjust the weight if
you change motors. This weight should be appropriate for the number and type
of cells you have entered, since the program adjusts the weight with cell
changes. ElectriCalc is not ambitious enough to keep up with the weight of hundreds
of motor/gearbox combinations (or the weight of different props for that
matter!). A good rule of thumb for aerobatic sport planes is that the weight of
batteries and motor should be about half the total weight.
DRAG COEF. is an aerodynamic constant used in calculating the thrust required to move
the plane through the air at a given speed. This number can be entered here or a
reasonably good estimate can be quickly made by selecting C drag from the menubar. Wing struts and wires add a lot of drag. A good
aerodynamics text is "Model Airplane Design and Performance for the Modeler" by Howard
Chevalier. Reduction of drag in electric models is quite important. Biplanes in
particular give disappointing flight times. Thick airfoils, fat fuselages, struts
and wires should be avoided or minimized wherever possible. Remember that wing
loading also contributes to drag.
PROP DIA. is the propeller diameter expressed in inches.
PROP PITCH is the propeller pitch expressed in inches. The number represents the number
of inches the prop would advance if it were a screw in an inelastic medium.
Pitch is normally measured at 75% of the distance from the center to the tip. The
best pitch for most electric applications is between half the diameter
(P/D=0.5) and the diameter (P/D=1.0). This assumption is used in some of the tools.
Tip: try modeling a 6-10 pitch as an 8.5 or 9.0.
CELLS is the number of cells in your battery pack. The most popular values are 7
and 10 cells. It is common to hook packs in series to make larger sizes. If you
need to model two packs in parallel, create a new cell type with half the Cell
mohm and twice the MAH and name it something like "2xRC2000".
ESC is the equivalent resistance of the ESC (Electronic Speed Control) plus all
the wiring and the connectors, fuse(s), and switch(es). The resistance of ESCs
is a function of design and number and type of FETs. Also, brushless
controllers have inherently higher resistance because they must switch both sides of the
winding and this requires p-channel FETs with higher resistance. High
performance brushless controllers have a bunch of FETs.
MTR CFG is an alphanumeric representation of the motor configuration. Information
cannot be entered directly here, but can be selected by clicking the raised panel
or the Multi menubar selection. Two motors in parallel have same Kv, half Rm, and twice
Io. Two in series have half Kv, twice Rm, and same Io. Etc, etc.
-pointers- are 3-character alphanumeric constants assigned by the program to identify
respectively the Cells, Motors, and Props database selections. These constants are generated by the actual text of
the database line. Their purpose is primarily to allow all of the plane setup
data to fit in an 80-column line. Not pretty, but it made things a whole lot
easier to program. There is a small chance that two entries will have the same
pointer and thus "confuse" the program into selecting the wrong one. This can
generally be fixed by making a slight change in the description.