Paramotor Geometry Part 6: Speed bar behavior.

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Pushing the speed bar sometimes leads to surprising results. And the suspension system is crucial.

This is part 6 in our classroom. Miroslav Svec, designer of SCOUT paramotors shares his knowledge about paramotor construction, the theory and reasoning behind. At the end of the roughly 30 videos in the series you will be able to make a qualified judgment what is the ultimate best paramotor for you.

Pushing the speedbar has two direct and immediate effects:
1. your upper back applies pressure on the paramotor frame backwards
2. your center of gravity changes especially when pushing the speedbar forward not downwards.

While pushing the speedbar with your legs your body seeks for support and leans against the paramotor frame with your upper back. This cause some trouble with the low suspension with moving bars. Consider the bar as the fixed part of the paramotor and the frame rotates around the hinge. As the pressure on the frame is above the bar hinge, the frame will lean backwards. Now the thrust line is pointing upwards thus some part of the engine power gives you lift = decreasing the wing loading. With lower wing loading the speed is lower than it could be.
To minimize this behavior it is recommended to push the speedbar straight down on such paramotors so you need to seek less support with your upper back. This increases wing drag and is sub-optimal as well.

A better solution are the goosenecks bar where the hinge is behind pilot’s upper back thus the you lean directly into the pivot point and the frame remains neutral.
When pushing the speed bar straight forward, the pilot’s center of gravity moves forward and pilot and paramotor leans forward too. This will point the thrust line slightly down and part of the engine power increases the wing loading. With higher wingloading the speed increases.

On high hook-in paramotors the the straps go all around the body and are highly tensioned = the harness does not flex and remains neutral.

Summary:
1. high suspension paramotors remain neutral when speedbar is applied
2. low suspension with fixed bars remains neutral
3.. low suspension with moving bar will lean backwards which is an unwanted behavior
4. Medium suspension with gooseneck bars remains neutral or even slightly pitch-positive.

Should you have questions, pleasse leave a comment.
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