Propeller

The standard propeller for this electro  motor is a 30x8 inch plastic propeller. That is a diameter of 80cm. As the effectiveness of a motor depends on the propeller diameter, a larger one would be more apropriate.
For this reason I converted a 30 inch propeller with carbonfiber tubes to a 40 inch propeller, 101cm.
The thrust of the 30" should be about 120 N, increased with the 40" to 150N, nearly 15kg.
The propeller is well balanced and does not produce vibrations at higher RPMs.
Here is the comparative photo:

Next Steps

The first trial with full throttle was successfull. For about 30 seconds I switched on the motor mounted in the Swing Connect Reverse harness. The thrust is about 10kg as expected, an exact measurement will be done later.
But I have to modified the electronic box. Right now the control (an Arduino Uno board) is placed in an experimental plastic case. The wiring has to be more robust to prevent the cables to get loose.
In the next days I expect the new components and switches.
I will also replace the 9V battery as power source for the Arduino board with a BEC connected to one of the main batteries.

Throttle control

The throttle control is a modified comercial throttle. Unless a gasoline powered paraglider, the throttle is not operated with the fingers. The throttle is controled with the thumb which is far more effective and allows to use the throttle grip as brake handle.
The throttle/brake can be mounted parallel to the normal brakes. So in normal flying conditions you use the normal glider brakes and when you change to motor-mode you simply grap the throttle/brake handle and push the throttle with the thumb.

Her some pictures of the throttle before and after attaching it to the brake handles:

Battery pack

The battery pack is stored in a Lipo-Save bag for safety reasons. The bag is attached with velcros on a sports vest. The battery pack weights only about 2kg in the basic configuration.
If a problem with the battery occurs in flight (overheating/fire), it can be easily desconnected with a handle and thrown away (no mini-parachute installed yet).

Physics behind the electrical ascending aid

First of all, what power do I need to keep a paraglider in the air?
From a very simple model, we can estimate the power we need to keep us in the air (without ascending or descending).
If my paraglider has a sink rate of about 1m/s and weights 110kg (weight force: about 1100N), than I need a power P of : P = F x v to keep me in the air.
That means only about 1100W. That is independant of the power source. With an propeller and a efficiency of about 50%, we need 2200W on the propeller to keep us up. Every additional Watt would give me a lift.

Second, what power do I need to get me in the air from ground?
That is far more complicated. The moment with most power consumption is the phase when the paraglider is just behind you at the start. This is the "parachute" moment. The full canopy is open, but not above you, it's behind you and causes a tremendous drag.
The power of the paramotor needs to compensates this drag force and needs to deliver a push force of 500-800N (50-80kg) in a normal condition.
Just for a few seconds, but without this power the canopy will not rise.
As a foot starter you deliver also a lot of power to overcome this drag with your feet. In a trike configuration, the motor has to due all the work and needs even more power.

What is the best canopy?
Normally a reflex canopy is used for paramotors, because it is more stable at higher velocities. But the reflex has a drawback, it has a lower glide ratio as a standard paraglider. The glide ratio defines also the vertical sink speed at a given horizontal speed.
Just an example: the glide ratio of a reflex canopy is half the glide ratio of a normal canopy. That means roughly that the glider has double the sink speed. That means we need to double the power to maintain us in the air.
So the best choice is a standard canopy. We can't fly to fast, but the goal is to reach the next thermic, nothing else.

Picture of prototype

This is the design/prototype of the eHayabusa ascending aid for Swing Connect Reverse harness:

Project description

This a my blog about the project "eHayabusa", a lightweight electric paramotor system ment as ascending aid.

Project philosophy:
The eHayabusa is no "full" electric paramotor for a simple reason: the technology and cost to achieve a full electrical paramotor are not feasible until now.
Nevertheless, an electric ascending aid is possible and economical.
The main difference between an electric paramotor and an ascending aid is the power and the maximum time of power deliverance.
With an ascending aid it is more difficult to make a foot start from even ground, but once in the air, it has nearly the power of an traditional paramotor.
How is it possible that such a low power motor can fly a paraglider? Finally it has only 12kg of thrust. We will come to this point later on.

Project data:

• Weight: basis version only 4kg
• Push force of system: about 120 N 
• Battery capacity: 5 min of full throttle
• Maximum height gain: 150m 
• Assembly time:  < 5min, ready to start
• TOW: <110kg

The design is specially fit to my harness, Swing Connect Reverse, but it's adaptable to nearly all standard harnesses.