Paramotor Geometry

Miroslav Svec, designer of SCOUT paramotors shares his knowledge about paramotor construction.

We will cover every aspect of paramotor construction, the theory and reasoning behind. At the moment we have around 30 videos on the list. At the end of this, you will be able to make a qualified judgment what is the ultimate best paramotor for you.

If someone’s first question about a paramotor is, “How much does it weigh?”, I immediately know that this person is not an experienced pilot. Its geometry is much more important than kilograms and horsepower.   –Miro

Welcome to “Insights into Paramotor Geometry”.  This is the first part of a complete series where we will cover every aspect of paramotor construction and design. By the end of this, you will be able to make your own judgment and decision:  What is the best paramotor you?

In “Top Gear”, the famous TV show where they test fancy sports cars, they don’t solely judge vehicles based on their horsepower, acceleration, and quarter-mile times.  What is more important is how these cars truly feel when you drive. It’s the same with paramotors. It’s not about weight and horsepower, but how they feel.  So in fact, it’s about their geometry.  Geometry is what influences how it feels in the air, how it turns, how it ground handles, how easy it is to get in and out of the seat, how well it handles turbulence, and how much fun you’re going to have when you flip it around. Many don’t realize that a paramotor’s geometry can also influence its speed in flight.  Even with the same glider, the same engine, and the same pilot, one paramotor can fly faster than another.  Luckily, we can predict how a paramotor is going to act and feel in the air just by looking at it.  Its geometry defines this.

There are over 40 parts to this series where we will cover every aspect of paramotor construction. By the end, you will be able to decide which is the best paramotor for you is.  You will learn that there is no such thing as the “best paramotor” which is perfect for everyone.  Each pilot has their own needs and priorities, the first of which is flying style.

In this series we will refer to these flying styles:

  • Local cross-country flying (probably most pilots)
  • Adventure cross-country flying and bivouacking
  • Freestyle and slalom
  • Acrobatics
  • Thermalling with paramotors

In each part, we will identify the advantages and disadvantages of specific paramotor designs based on these categories. We will try not to be biased and will show that a SCOUT with a Vittorazi Moster Plus is not necessarily the ideal paramotor for all pilots.

Let’s start with the most important aspect of paramotor design, and that’s its suspension.

Click to watch video

Suspension is where you find the largest differences between paramotors, and in my opinion, it is the most important characteristic of a paramotor. It defines handling and the fun you have in the air.  It also defines comfort, both in the air and on the ground.  It has safety implications, as well. –Miro

There are a few decisions that a paramotor designer needs to make regarding suspension. The first is the position of the carabiners relative to the pilot’s body.  On high-suspension paramotors, the carabiners are up around the pilot’s ears.  On low-suspension paramotors, they are down towards the pilot’s waist.  On mid-suspension paramotors, they are closer to the pilot’s armpits.   Also, the suspension bars can either be fixed or moving.   Between these two aspects, there can be several solutions, and each of these has benefits and disadvantages that we will examine in depth throughout this series.

 

Beyond this, there are a few more decisions that a paramotor designer needs to make regarding its suspension:

  • The shape of the suspension bars
  • Where to place the thrust line relative to the carabiners
  • If using moving bars, where to place their pivot points

 

[SLIDE: Design vs. effect]

 

Let’s look at each design choice and the effect it has on a paramotor.

 

  1. The positioning of the carabiners relative to the pilot’s body defines the in-flight comfort, how much weight-shift authority there will, be and how it handles turbulence
  2. Using fixed vs. moving bars influences weight-shift authority and ground handling
  3. The shape of the bars helps in-flight comfort
  4. The thrust line relative to the carabiners controls the pitch stability under power and ground handling
  5. The location of the pivot point for moving bars helps the speed bar behavior

 

As you can see, suspension is a complex issue that we will dive into in the ensuing parts of the series.

 

Let’s start with weight-shift authority which is the most influential.  First, we’ll explain why we need weight-shift, and then we will go on to compare the various suspension systems and how they correlate with weight-shift authority.

 

After we cover the other aspects of suspension systems and their effects, we will show a full comparison to give you the complete picture.

 

Click to watch video

I must warn you that I am biased. I’m a big advocate of weight-shift steering in paramotors. I know many pilots who have switched to weight-shift paramotors and they will never go back. Yet, there are many pilots who have never tried it, so give me a chance to convince you. –Miro

 

“Look, Lean, Pull!”

This is what paragliding instructors will tell you.   This is how they core thermals.   It means to look towards the side you want to turn, lean to that side, and then gradually pull the brake.  With paramotors, it’s pretty much the same.  You can do it with a little bit of leg work and by leaning over the bar.  Leg work is just raising one leg and pressing the other one down.   Leaning over the bar is just moving your body over the bar and shifting your center of gravity closer to one side.

Many of today’s pilots are flying smaller gliders with 2-D steering that are quite agile, and they can skip the weight-shift and just pull the brake.  But turning with weight-shift is much more efficient than turning without.  In effect, with weight-shift, you have more turning authority.  You’re using two steering inputs instead of one.   So, you could use half of the brake input to achieve the same turn or get a much tighter turn with the same brake input.

[SLIDE: Benefits vs. Disadvantages of weight-shift]

Here is a summary of benefits and disadvantages of weight-shift steering.  Regarding benefits, primarily, turns are more efficient.   When you pull less brake, you are turning with less drag.  Your glider is closer to the ideal profile and flies closer to its most efficient way.  Secondly, turns are more fun. This is a bit tricky to explain…you just need to try it.  When you lean to the side and you feel the pressure in your body, it feels much more engaging.  It’s like leaning into a turn on a motorcycle.   It’s also safer.  The less brake you pull, the further away the glider is from stalling or spinning.  Finally, you get more feedback from the glider.  You feel more of the turbulence and what’s happening to your glider.  This gives you a chance to react and compensate earlier.

Some pilots believe that flying a weight-shift paramotor exposes them to more turbulence, but it’s not true.  If you fly into turbulence, it’s there regardless of what paramotor you are flying.  The only difference is that, with a weight-shift paramotor, you feel more feedback from the glider and the paramotor doesn’t hide it from you.   The turbulence will make the glider feel twitchy and bumpy which may make the pilot feel more nervous.  Having said that, it’s a personal preference and we like the “sporty” feeling where you can feel what the air is doing.

There are arguments that weight-shift paramotors are more difficult to learn for beginners.  We disagree on this point as well, because having more feedback from the glider during takeoff or in-flight will make it easier for the for the pilot to understand and feel the glider.  In the end, we believe the student will learn more quickly.

It’s true that weight-shift paramotors are heavier. The bars need to be made of solid and strong material because the pilot, engine, and fuel tank is hooked onto them.  So, the added strength of these bars adds some weight.

[SLIDE: Do you need weight-shift steering?]

So, here’s the big question: Do you need weight-shift steering for your flying?

You absolutely need it if you are an acro pilot, fly freestyle or slalom, or do thermalling because you just need the feedback from the glider…you need to feel the glider perfectly.  For cross-country pilots, it’s not as necessary.  You could be happy flying a high hang-point paramotor for cross-country flights, but it still doesn’t hurt to have weight-shift ability.

So, if your flying styles overlap such that you do mostly cross-country but sometimes you do some freestyle flying with tight turns and have some fun, then you surely want to add weight-shift steering as well.   Beyond this, we believe it is more comfortable, which we will cover in the ensuing chapters.

For the next chapter, we will be a bit more technical.  We will compare all the suspension systems and explain how much weight-shift authority you get and why.

Click to watch video

Hi guys!  The last time we talked about why you want or need weight-shift on your paramator. Today, now let’s how much weight-shift authority you actually get. –Miro

 

[SLIDE: Designer’s Decisions]

Here is a slide from an earlier part that itemizes the suspension decisions that a paramotor designer must make.   Let’s go through them all and see how they affect weight-shift.

[SLIDE: Carabiner position]

The first decision is where to place the carabiner relative to the pilot’s body, high, medium, or low.

[SLIDE: High-suspension options]

We have four high-suspension options, two with fixed bars and two with moving bars.  The one on the left is a fairly “old school” solution.   It’s a solid bar of metal that rises from the back up and over your shoulder.  It’s similar to a coat hanger that keeps the harness in shape.  Without that bar, the harness would just flop down.   This design is not really used much anymore.

The second solution is more common.  It’s a high-hook-in system where the carabiner is connected to a strap that goes up and over your shoulder.  There is a fixed spreader bar under your shoulder that keeps the strap in position.

Then, there are variations of each of these, but with moving bars.  They are attached to the frames at a pivot point, indicated by the red dot, that allows rotation and some flex in the harness.

[SLIDE: Medium-suspension options]

For medium-suspension designs, there is effectively only one solution on the market.  This is referred to as a “gooseneck bar” that goes underneath your arm before curving up close to your chest where the carabiner is positioned.  Then, it has a pivot point at the red dot where the bar can rotate for easy takeoff and maneuvering.  This is the most common suspension used with paramotors, and later we’ll discuss why.

[SLIDE: Low-suspension options]

For low-suspension systems, there are primarily two options: fixed bar and moving bar.   The fixed bar is a solid construction that’s attached directly to the frame, and the moving bar has a pivot point that can rotate around the red dot.  In truth, there is a third option that is more complicated and not common.  Consider this a teaser, and we’ll cover it in a separate part.

[SLIDE: Weight-shift vs. suspension options]

Let’s go through the full comparison of all suspension systems and how they affect weight-shift.  Remember that you can impart weight-shift in two ways.  The first is leg work or hip work, and the second is leaning over.  If your suspension system has a fixed bar, there is no flexibility in the frame to allow leg work to alter the carabiner positions relative to each other.  So, there is not much weight-shift you can do with just leg work.  This is true with any fixed-bar system, high or low. 

There is a lot more weight-shift authority with moving-bar systems when using leg work.  As you press one leg down and raise the other, you effectively lower one carabiner and raise the other and shift the loading on the glider.

The other way to perform weight-shift is by leaning over.   With high-suspension systems, bars and/or straps are up around your shoulder and head level and don’t leave you much room to lean over.   So, the lower the carabiner is, the more weight-shift authority is possible.  This is why the four paramotors on the left have no lean-over weight-shift authority and the three on the right have significant lean-over weight-shift authority.

The other aspect that influences your weight-shift authority on a paramotor is the pendulum auto-balance effect.   Put simply, the further that an object is suspended above a point, the stronger its intention to move back to the center position.   It effectively requires more weight-shift to achieve the same tilt angle of the pendulum.   So, if you are suspended higher and closer to the pivot point of the pendulum, the same amount of weight-shift will cause a lot more tilt in the pendulum.  Put simply on our chart, high-suspension systems have the most pendulum auto-balance fighting weight-shift, and low-suspension systems have the least.

Let’s now look at the summary of total weight-shift authority for each design.   You get limited weight-shift authority with high-suspension systems, but bit better with moving bars.  You get fairly good weight-shift authority with medium-suspension systems with moving gooseneck bars.  And, you get the best with the low-suspension systems with moving bars.

Because we discussed how weight-shift is an advantageous tool for paramotor pilots, this leads us to the conclusion that low-suspension systems with moving bars are the best option.    However, there are other considerations that we will discuss in the next few parts.  Also, there is a mistake in at least two of these pictures.  Continue with the series to learn more.

Click to watch video

When we did the big comparison of various suspension systems regarding weight-shift authority, we said there are at least two pictures with a mistake.  Let’s add a bit of power and find out.  –Miro

[SLIDE: Weight-shift summary, which pictures are wrong?]

At least two pictures are wrong in this lineup. To find out, we will discuss the fourth decision that a paramotor designer needs to make when designing paramotor suspensions: Where to place the thrust-line relative to the carabiners?

[SLIDE: Designer’s decision #4]

The ideal position of the thrust-line is directly in line with the carabiners, where the paramotor will pivot relative to the glider.   If we apply thrust above this pivot point, the paramotor will pitch forward.  If we apply below, it will pitch backward.   But, if we apply thrust in line with the carabiners, the paramotor won’t pitch either direction.

[SLIDE: 4th decision: Where to place the thrust line?]

Let’s see how it works with these paramotors. 

With the high-suspension system, where the carabiners are higher than the thrust line, the pilot will be pitched backwards under full power.   With the medium-suspension system, where the thrust line is in line with the carabiners, the pilot won’t be pitched backwards or forwards under full power and will just start to climb in an efficient manner.  With the low suspension system, where the carabiners are below the thrust line, the pilot will be pitched forwards under full power.   Having said this, due to gravity, the weight of the pilot will resist the pitching force caused by the imbalance to a degree.

[SLIDE: We need to move the engine higher/lower]

Is it possible to fix this unwanted behavior?   For the low-suspension system, the solution is to move the engine, propeller, and cage down to be in line with the carabiner position.  We will also get a beautiful crumple zone beneath the pilot.   For the medium-suspension system, there is no need to make any adjustment.  For the high-suspension system, we could raise the engine, propeller, and cage up to the carabiner position.   This would be great for flying, but horrible for taking off.  Imagine what it would feel like to have 80kg of thrust at your neck.   It would just push your head into the ground, and another pilot bites the dust.

[SLIDE: The correct thrust line position]

Let’s return to our line-up of suspension systems from Part 2.  We have now placed the engine, propeller, and cage lower for the low-suspension systems.   On the high-suspension systems, we have placed them a bit higher, though not all the way.  This means that the thrust line is in an ideal position for medium and low-suspension systems.  But, it is less than ideal for the high-suspension systems.  Thankfully, the pendulum auto-balance effect helps to mitigate the issue in those four designs.

In summary, medium and low-suspension systems have ideal pitch stability, but it’s acceptable on high-suspension systems.   Don’t jump to any conclusions just yet.  Yes, it looks like a winner for the low-suspension system with moving bars, but there is a fifth decision that a paramotor designer needs to make.  We now need to discuss where to place the pivot point for the bars.  To determine the ideal position, we need to add some speed by pushing the speed bar.

 

Click to watch video