Last time we talked about RC Boat Propeller Pitch for RC boats so today we’re going to take a look at blade cupping and diameter and how they work on a rc boat propeller.  We are still assuming you’re into using a remote controlled boat as a racing boat.  Although, you can still make these modifications on a boat that is not used in racing, especially if you just want your RC boat to go very fast.

How Blade Cupping Effects Your RC Boat Propeller

Blade cupping is not hard to understand because it just the little curved tip at the end of a rc boat propeller.  When you change the cupping, it helps hold the water on high turns.  It also gives you more speed, especially on racing RC boats.

NOTE: Don’t change the concave face of the propeller – you risk reprofiling the propeller and changing the pitch or cupping.

Cupping level, if designed properly, lends a hand to performance and the effectiveness of a rc boat propeller.  Much in the same manner propeller pitch does.  As the water hits the rc boat propeller the cup allows the water to be pushed from under the boat.  Now, how cool is that?  Cupping actually spins the water away from the propeller.  Setting the cupping at the right angle will make your racing boat much faster (adjusting it happens when you sharpen a propeller). 

How the Diameter Affects Your Racing RC Boat Propeller

 According to some experts on propellers, the “diameter is the distance across the circle made by the blade tips…”  It’s the difference between  the RPM and the amount of power to the propeller.  The Propeller Handbook (see below for link) is an easy and very comprehensive book about propellers.  Even though it’s for big, regular boats, propellers act the same with the smaller RC Boats.  I found it to be very informative without being too technical to understand.

There is an imaginary circle a propeller makes when it’s running and you can calculate the diameter by measuring across the center of the hub to the end or tip of the blade and multiply by 2.  That will give you the diameter of your propeller.  Of course, each brand and manufacture will have difference diameters for their propellers.  It’s not the small variances that affect the performance of your RC Boat but the big variances.  So, check with your boats model to see if you have the correct propeller for your boat.

A Trick to See What Part Of Your RC Boat Propeller Is Doing All the Work

All propellers have a cup of some degree.  Think about how you swim with a cupped hand.  You go faster when you cup your hand to pull yourself through the water when swimming.  The cup on a propeller works the same way.  Here’s a way to check to see how your propeller is performing. 

Take a machinists bluing marker and mark your propeller.  Then put it in the water and run it and it will show you what part of the prop is working properly and which part is not.  You can tell because the blue that is washed off is the part that’s doing all the work.

Hope all this helps you with your rc boat propeller.  Next time we’ll talk about how vents rake, and balancing work on a propeller. 

Do you have any suggestions for those who want to change the cupping on their propeller? 

Leave a comment below so you can help those who are still learning about a RC boats.  As always, you can also go to our Best RC Boats   and ask any question you might have about rc boat propeller.  See ya next time.  Enjoy!