For the longest time, one of the most difficult thing to do for a new boater was to select a suitable power system for their RC boat. This is no longer the case. Radio Control Info now has a boat calculator tool called the RCI FE Boat Calculator that will assist in this process. This page is here to help explain a few items about the boat calculator to ensure its proper use.
RC FE Boat Calculator Terms
Voltage – Voltage measured at the battery
Nominal Voltage – Nominal Voltage of the LiPo pack
Total Energy – The total measured energy of the LiPo pack calculated from voltage and mAh.
Load – Measured in a C rating to represent the stress of the LiPo.
LiPo C rating – The manufacture provided C rating of a LiPo pack. Similar to a load capacity of the LiPo.
Load Capacity – The ratio of the Load vs load capacity. A Key indicator of the stress level of the LiPo pack.
Total Capacity – Measured in mAh representing the storage capacity of the LiPo pack.
Used Capacity – The used capacity based on 80 percent maximum discharge level of a LiPo pack.
Min. Run Time – The minimum run time based on 100% throttle for the entire duration of 80% LiPo pack capacity.
Mixed Run Time – An average amount of run time a sport boater may see.
Voltage – Voltage measured at the motor.
RPM – The Rotational speed of the motor in revolutions per minute.
Current – The current the motor is consuming
Wattage – The power consumption of the motor measured in watts.
Diameter – The physical diameter of the motor.
Can Length – The physical length of the motor can.
Efficiency – The efficiency of the motor.
Kv – RPM per volt of the motor.
Rm – Resistance of the motor winding at standard temperature.
Io – The current measure at no load at the specified voltage.
Est. Temp – The estimated motor temperature using adequate liquid cooling.
Overall Efficiency – Overall efficiency of the entire power system including mechanical efficiency.
Speed – Measured in km/h and mph.
Horsepower output – The total amount of horse power output by the power system. Mechanical Power.
Diameter – The diameter of the propeller.
Pitch – The pitch of the propeller.
Prop Bore – The prop shaft bore of the propeller.
Max Current – The maximum amount of Continuous current.
Cell Count – The range of LiPo cells that the ESC can handle.
Why use the RC Boat Calculator?
You may want to use this boat calculator for a few different reasons. We will look at the top two:
1) Check a specific power system
2) Assist in a Build Plan / Power system Selection
Check a specific power system
To check a specific power system there are 2 super easy and very quick steps. One would simply select using the drop down menus on the RCI FE Boat calculator page all the components used in the build. If you happen to miss a selection or input the hull length with an unrealistic value, you will receive an error with an action message to correct before resubmitting. Once you have your inputs selected, simply submit the page.
Once you have the results, which appear directly beneath the input drop down menus, you must make comparisons with the maximums of the components you have selected. Your primary concern is to compare the battery performance, motor performance and lastly ESC performance. The ESC and battery parameters to not exceed are listed in the results. Pay attention to the Load Capacity in terms of a percentage. An ideal situation is below 70%. For the ESC, be certain that the current and the voltage is within the range that the ESC can handle. As for the motor, make certain that the maximum continuous current of the motor is at least 20% higher than the calculated current.
Be certain to check that the motor estimated temperatures are within the range of the motor specification.
Additional comments will be listed below the results chart highlighting any additional concerns that may be over looked.
Assist in a Build Plan / Power system Selection
To help assist in the power system selection process, it is best to choose a LiPo cell count, ESC and motor based on the parameters and information available on the site. Visit the FE Boat page here.
Once you have correctly selected the above components the last component remaining to be selected is the prop. Typically the prop is sized accordingly from experience. The advantage of the calculator is that you may try out many propellers that you think can work in order to determine if your goals are met and that they are met without over stressing the components in your power system. The procedure is the exact same as described above with the difference being many more iterations to review all the possible combinations you may use.
The Challenge in RC Boat Calculators
It is very difficult with RC boats to predict the overall power consumption of any particular power system setup. This mainly comes down to two significant reason. (There are many more) The fact that an RC boat is heavenly dependent on the drag that the hull produces when traveling through the water and its affect on the load of the motor. The second major reason is that the propeller on a RC Boat does not simply travel through one medium. The propeller is traveling through both air and water. Depending on your complete setup, the ratio difference between mediums can very greatly and completely change the loading on the motor. This contributes to quite a few factors increasing the uncertainty of the calculator. For this reason it is important to confirm the results through alternate resources such as experienced people in either a forum or at the local RC Boat club. Does this mean that you can not trust the calculator? Actually, No, this does not mean you can not trust the calculator. This calculator has been designed to help assist new boaters in choosing a power system that is on the near extreme side of failure. It stops one from choosing a particular RC boat setup that is far out of the ranges of safe as spoken about on this site.