Understanding Vess Propellers

     The unique shape, design, and size designations of the Vess Propellers did not come about by accident.  They are the result of many months of computation, prototyping, and testing.  And instead of simply recreating another version of existing designs or following conventional practice, this project began from a “clean sheet of paper” and proceeded in a direction that was guided by formal engineering analysis.  The result is a prop design that truly sets a new standard for performance, efficiency, and noise reduction.

     The introduction of anything unconventional is sure to draw questions since it is not supported by conventional thinking.  It’s the nature of being different.  Vess Propellers certainly fall into this category and thus a little simple education is warranted.  So, by addressing a few common questions, some details of the design philosophy of these props is presented.

Q.  What was done differently during design?

A. An airframe, engine, and propeller combination represents a closed-loop system in which each component continually affects the other two.  So the objectives of this design process were to document this interactive relationship for typical classes of giant scale aircraft (for example, a 100cc engine on a 33-35% airframe) and to understand what the props require to operate efficiently in those


specific applications.  Then computer tools were applied to define props that work well in those “real world” environments.  The resulting designs are then CNC machined to accurately reproduce them.

Q. Why are these props shaped like this?

A. Instead of just picking a shape and using a constant “helical” pitch along the blade, the geometry of Vess Props were computer defined as required by each specific application.  This means that the combination of chord, thickness, blade angle, and airfoil were digitally optimized at several radial stations along each prop blade by applying advanced propeller theory.  In each case, a “mission specific” non-linear twist distribution was defined by the optimization process.  The unique blade sweep was also included for noise considerations.


Q.  Since the pitch is not constant, how do you know what it is?

A.  It is not important to know what the pitch values are.  It is only important to know  how one prop relates to another so that you can select the proper one. The diameter of the prop is chosen to put you into a typical “class” of aircraft/engine.  Remember, our extensive analysis and testing has optimized a blade shape and pitch distribution to work well for that combination.  Conventional pitch descriptions are simply incapable of describing this unique twist, so it is not appropriate to attempt to apply them here.  Instead, we have employed a simple alphabetic designation for pitch.  And we have also created a 3-4 prop “series” for each diameter that will allow you to adjust to your particular requirements.

Q.  So how does this alphabetic pitch designation work?

A.  It’s as easy as A-B-C!  The “baseline” prop that most people will start with in a particular diameter series is denoted as a “B” pitch (simply remember – “B” is for Baseline).  So, if you have a typical 100c powered 33-35% aerobatic airplane, you will start with a “27B” prop. 

27b sizing02

     It will most likely give you the tremendous vertical performance, great acceleration, and low noise that it was designed to deliver.  But all engines, airplanes, and even weather conditions are not alike.  So, there may be a better choice for your particular situation.  If you have an aircraft that is heavier, has more drag, or is larger than a typical 33-35% aerobatic model or has less horsepower (either due to less displacement, higher field elevation, or higher air temperature), you may need to go down to a “27A”, which has less load.  Conversely, if your airplane is lighter, has less drag, or is smaller than a typical 33-35% aerobatic model or has more horsepower (due to more displacement, lower field elevation, or lower air temperature), you may can use a higher loaded “27C” to properly absorb the power and keep the propeller quiet.  Remember, the prop, engine, and airframe directly interact and affect each other so you need to think about that when choosing your prop.  See the prop selection page for a summary of this methodology.

Q. What should my Vess Prop tach on the ground?

A. Don’t waste your time measuring ground RPM unless you are attempting to somehow quantify relative loads on the engine.  Vess Props will usually turn less on the ground and in the air.  It’s part of the design philosophy of properly loading the engine under real flight conditions.  The benefit comes from the thrust that is produced at that lower RPM.  So judge these props against others through performance in the air.  You will most likely be amazed!


Q.  How quiet will my plane be with a Vess Prop?

A.  Noise is driven by the loudest component in a system.  If you have a loud muffler, you will not realize the full potential of using a quieter propeller.  But it will still help!  Vess Props were optimized to absorb the full power of each engine/airframe class at RPM’s below which the tips reach sonic conditions.  In almost every case that we have tested over the past year, the Vess Prop did not unload to the point of producing sonic tip noise.  The in-flight noise was most often dominated by the exhaust sound.

     And recent sound testing by the organizers of the “Don Lowe Masters” competition have shown the true potential of Vess Propellers for controlling noise.  A 43 pound, 42% Hanger 9 Ultimate fitted with a DA150 engine and canister mufflers measured as low as 93db at 25 feet with a Vess 32D prop!  And the in-flight performance of this combination was astonishing.  Also, a 40% Carden Extra 300 with DA150 and Johnson-type mufflers measured 98db with the same Vess Prop and also showed fantastic performance in the air.  You don’t need to fly a loud airplane, even with stock mufflers.

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