catalystmachine
New member
This is just too damn cool. I am so happy you reached out to us Cyber. We have never seen your thread or your design until now. We began really thinking about ways to improve the aero of these racers back in October last year. I had the idea to flip the plates 90 degrees one day. I presented the idea to my team pilots and they all saw the advantages I was describing, so as a team we decided to move forward with the project. Back in the early design phase I did a bunch of searching online but I guess Dr. Google failed me! I wish I had found your thread before now. It would have really been nice to pick your brain and discuss the subject with you seeing as you had put the theories to reality a year before we thought of it. When we first started our project I knew someone had to have tried it at some point. I was right! And you are right in that our main goal with this design is to increase TCE (is this your coined phrase?). In the beginning I wanted to go with a design where the arms are suspended out in free space all by themselves, only attached at the center hub (no outer bracing). But, as you know with these racers that just wasn't practical due to the constant abuse they see. With the outer brace the forces from an impact are distributed to all 4 arms, through the braces. This distributes the loading, instead of placing all the stress at the inner portion of one (or two depending on the crash) arm where it attaches to the center hub. Also, the outer braces deflect a strike with overhanging limbs or a race gate top. The Stigg tends to just bounce off during a strike like this instead of getting caught up like an "H" or "X" frame will with no outer braces. So while I agree with you that the TCE would be higher without those outer braces there is simply no way around them. Unless of course we look into military grade CF which can handle the high stresses, but that is too expensive and not realistic for this application. So our goal was to keep the outer braces as thin as possible while still providing enough cross section to resist damage from most typical crashes.
Our goal with this design was not to simply make something different for the sake of being different. Not at all. Like you, we want to push the envelope. Lets be honest. There are only so many ways to draw an "H" frame. That has pretty much been flushed out. With regard to performance you can step up the aero and move into a 'flat plate' (my coined phrase lol) "X" frame with arms perpendicular to the thrust vector and you will have improved performance over an H frame, but we wanted to take the "X" frame a step farther and improve aero performance even more. And that is what we have done. This machine flies like its on rails. And that isn't just some regurgitation of descriptive words that people love to use to describe anything geared for performance. No, its freaking true. The Stigg tracks through the air like nothing myself or any of my 6 team pilots have experienced before. And between us we have flown MANY different machines. It also turns like nothing we have experiences before. Its unreal. Ryan has handed over his prototype to some of the guys he flies with and they were all stunned. We are excited to get this bird out to the public so people can get to experience it.
On the subject of the arms (2.5mm thick) and the outer braces (3mm thick) adding up to nearly the same total area under the props we actually are quite a bit thinner. 8.5mm compared to about 20mm on most properly designed frames. But, there has to be more going on here than just how much surface area is sitting under the props because we are seeing a noticeable increase in flight performance for an admittedly small change in total reduction in area under the props. Now its just a theory OK?! My team pilot Ryan (aka Rotorious) has the most experience flying the Stigg, even more so than myself. He specialized in fluid dynamics in grad school and wrote up his theory to explain why you have to consider more than just how much overall material is behind the props. The predictability of the turns was actually something we were not expecting at all. The focus was on efficiency and improving net thrust. This was an unplanned, but very awesome side effect.
From Rotorious:
"When a fluid (air) impinges on a broad plate, or that plate moves through fluid, there is a big region of low pressure behind it. It is not turbulent air that causes the low pressure zone, the same thing happens when laminar air hits the plate, but the low pressure zone can cause air around it to become extremely turbulent. Behind the arm you have high pressure air flowing at high speed past a region of low pressure at low relative speed. That causes strong vortices (swirling air) and extreme turbulence. Those are basically the same conditions required to start a tornado. With vertical arms, the low pressure zone is much much smaller and causes smaller vortices to form. Even if the total width of the arms and braces matched the width of a single wide arm, the flow would be smoother because the size and strength of the vortices scale with the size of the low pressure pocket. When we fly through "dirty" air on a sharp turn, we are interacting with turbulence. The smaller the size and strength of the vortices (pockets of swirling air) in turbulent air, the less It disrupts our quads as we turn sharply through it."
Anyways.. I look forward to discussing this subject more with all of you. Its fun to push the limits of design. We don't move forward without that.
PS: Here is my first post on this forum where I was advertising one of my early H frame designs. Boy I got railed on here lol. Tough crowd back then. I wonder if you all have eased up any? To be honest all that constructive criticism really fueled me to go back to CAD and come up with something better. So please be critical, it makes us better.
http://forum.flitetest.com/showthre...figurable-FPV-racing-frame&highlight=fearless
Our goal with this design was not to simply make something different for the sake of being different. Not at all. Like you, we want to push the envelope. Lets be honest. There are only so many ways to draw an "H" frame. That has pretty much been flushed out. With regard to performance you can step up the aero and move into a 'flat plate' (my coined phrase lol) "X" frame with arms perpendicular to the thrust vector and you will have improved performance over an H frame, but we wanted to take the "X" frame a step farther and improve aero performance even more. And that is what we have done. This machine flies like its on rails. And that isn't just some regurgitation of descriptive words that people love to use to describe anything geared for performance. No, its freaking true. The Stigg tracks through the air like nothing myself or any of my 6 team pilots have experienced before. And between us we have flown MANY different machines. It also turns like nothing we have experiences before. Its unreal. Ryan has handed over his prototype to some of the guys he flies with and they were all stunned. We are excited to get this bird out to the public so people can get to experience it.
On the subject of the arms (2.5mm thick) and the outer braces (3mm thick) adding up to nearly the same total area under the props we actually are quite a bit thinner. 8.5mm compared to about 20mm on most properly designed frames. But, there has to be more going on here than just how much surface area is sitting under the props because we are seeing a noticeable increase in flight performance for an admittedly small change in total reduction in area under the props. Now its just a theory OK?! My team pilot Ryan (aka Rotorious) has the most experience flying the Stigg, even more so than myself. He specialized in fluid dynamics in grad school and wrote up his theory to explain why you have to consider more than just how much overall material is behind the props. The predictability of the turns was actually something we were not expecting at all. The focus was on efficiency and improving net thrust. This was an unplanned, but very awesome side effect.
From Rotorious:
"When a fluid (air) impinges on a broad plate, or that plate moves through fluid, there is a big region of low pressure behind it. It is not turbulent air that causes the low pressure zone, the same thing happens when laminar air hits the plate, but the low pressure zone can cause air around it to become extremely turbulent. Behind the arm you have high pressure air flowing at high speed past a region of low pressure at low relative speed. That causes strong vortices (swirling air) and extreme turbulence. Those are basically the same conditions required to start a tornado. With vertical arms, the low pressure zone is much much smaller and causes smaller vortices to form. Even if the total width of the arms and braces matched the width of a single wide arm, the flow would be smoother because the size and strength of the vortices scale with the size of the low pressure pocket. When we fly through "dirty" air on a sharp turn, we are interacting with turbulence. The smaller the size and strength of the vortices (pockets of swirling air) in turbulent air, the less It disrupts our quads as we turn sharply through it."
Anyways.. I look forward to discussing this subject more with all of you. Its fun to push the limits of design. We don't move forward without that.
PS: Here is my first post on this forum where I was advertising one of my early H frame designs. Boy I got railed on here lol. Tough crowd back then. I wonder if you all have eased up any? To be honest all that constructive criticism really fueled me to go back to CAD and come up with something better. So please be critical, it makes us better.
http://forum.flitetest.com/showthre...figurable-FPV-racing-frame&highlight=fearless
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weather must be getting nicer on the east and they are flying.. im in the desert so about to hide for a month or two behind the A/C flying my nano qx. 
