T-Hawk ARTF Parkflyer Propeller Info

by Chuck

Left-Hand vs Right-hand Propellers (or Airscrews) for the T-Hawk RC Airplane

Left-handed (aka pushers) props are rare in comparison to standard props which are right-handed (aka tractors). Without first defining the normal running direction of rotation of the prop shaft it is hard to argue which is a left or right-hand prop and it really depends on the normal operating direction of rotation of the engine or motor. Most are powered in a clockwise (CW) direction as you face the propeller from the spinner or nosecone side, and that is the convention used in this conversation thread. Pushers are considered left-hand props which means that they spin in a counter-clockwise direction. Compare photos of props listed as pushers and you will see that the leading and trailing edges are exactly opposite from a standard RH prop. What does "pusher" mean in relation to this? Technically, by definition it's a propeller located on the trailing edge of an aircraft wing. When facing the airflow if the top of the propeller moves to the right (CW), it is designated "Right Hand" and if the top moves to the left (CCW) it is "Left Hand". On a T-Hawk, the propeller is behind the wing (and motor) and so "pushes" the plane forward and can be considered a pusher, but it does NOT use a pusher (left-hand) prop as some people have mistakenly commented. The T-hawk uses a standard RH-prop that you push-on! Push-on props normally have a 2.3mm electric motor shaft. Most common is 380/400.

BTW, you can NOT just flip props over and expect to get good results. Remember that the rotation of the motor stays the same, and the angle appears to stay the same, but by flipping the prop over the leading and trailing edges change places. Just like any airfoil, the leading edge is slightly thicker and one side is slightly convex while the other is slightly concave.


Finding Replacement T-Hawk Propellers - Size and Pitch:

The stock propeller on a T-Hawk is a 5-3/4" (length) with a 4" (pitch), press-on, standard right-hand prop listed as either 5 3/4 x 4 or 5.75 x 4. Theoretically, a pitch of "4" means that for every single revolution of the propeller, the plane will move ahead in a forward direction of 4 inches. The shaft diameter on all 380 (aka 400) and 480 (aka 500) size electric motors is 2.3mm. When ordering replacement props, ask yourself these questions and look at other similar planes - is it a "pusher" configuration with the prop mounted behind the wing? Look at the size of the motor that comes with the plane - is a size 380/400? Does the prop just push-on to mount itself to the motor shaft. If so, as long as you order a replacement prop that fits a size-380 or 400 motor with the proper length and pitch it will work just fine. Very slight length variations are ok, but try to stick with the same length and pitch if possible. Note: You can not use a 6" press-on prop on a T-Hawk without the prop hitting the tail boom unless you first convert it to use a prop shaft adapter. Because the tail boom tapers away just below the propeller, adding a nice 2.3mm adapter moves the prop back toward the tail just enough to clear the boom. If you use an adapter you can use a 6 x 4 2.3mm prop with the propeller bore of your choice.


Propeller Load Formula: Length and Pitch

Propeller load and engine rpm are inversely related: as load increases rpm decreases and vice-versa. Load is represented by the propeller; change the propeller size, and the load is changed. By using the “Propeller Load Factor” (PLF) formula, Load = D2(P), incremental propeller load changes can be determined and applied to your engine/model combination.


Propeller Load Factor” (PLF) formula: Load = D2(P)

where:

• D = diameter
• P = pitch

So for the T-Hawk D = 5.75, P=4 so the PLF is: 5.75 x 5.75 x 4 = 132.25 (the stock propeller)

Other example PLF's:
5 x 5 x 4.5 = 112.5 (too low)
5 x 5 x 5 = 125 (slightly low)
5.75 x 5.75 x 4 = 132.25 (stock T-Hawk propeller)
5.5 x 5.5 x 4.5 = 136.125 (OK)
5.25 x 5.25 x 4.75 = 131 (OK)
6 x 6 x4 = 144 (slightly high, but OK)
6 x 6 x 5 = 180 (too high)

Straying form these recommendations can cause premature death of your motor or speed controller. Also be sure props are balanced.