Thank you, I try to take feel out of the equation a little bit because 1. I'm not a pro pilot 2. It's very subjective and can sometimes lead you down the wrong path for the right reasons or the right path for the wrong reasons!
Bardwell sent me over to check your channel out, really glad that he did. Being an ex aircraft and helicopter mechanic, I guess that from my technical education required to get my license, a lot of the principles that you explain seem to be common knowledge, but that is only because of my own education. You did a great job of explaining a uncommon topic! Ain’t no perfect prop for all conditions, you have to choose the one that fits your flying parameters.
If my algebra teacher would talk in the same interesting way, I would graduate from high school with A+ Just found why need to decrease kv, going to 6" and higher diameter props. I knew before that I had to do this, but now I know why :) I didn't even think about the speed of the propeller tip before. Thank a lot! You doing great job!!
This is insanely good content. Learned more about props from this video than an entire course in aerodynamics at uni! Your explanations are great, thanks for taking your time to make these videos!
How much do I like your videos? I watch them twice. They are so full of great technical analysis that I pick up details I missed the first time through. Keep it up!
At last, I understand prop wash, your videos are soooo good. Thank you so much. Having the equations and their explanations to understand the physical phenomenons is absolutely marvelous.
I've been here from day #1, and I don't regret it. I love how it's nothing but straight information. Keep up the the explanations coming, it's always interesting
So much insight! Thank you. I have always thought that props with more pitch should be more efficient. Many youtubers told otherwise and it really confused me.
It depends a lot on how you fly but if you fly reasonably fast and are gentle with the throttle you can really benefit from a steeper pitch prop! Thank you for your comment 😁
Part of the reason for the confusion is that most pilots don't mean the same thing when they say "efficiency", as Chris does. When testing motors, efficiency means grams of thrust per watt of power. But when pilots talk about efficiency, they usually mean longer flight time. A lower pitch prop will usually give longer flight times all else being equal, because it makes less thrust and so it draws less power. Lower pitch props also load the motor less. This is especially true when talking about a high kv motor, which will need to draw more current to generate the torque to try to spin the higher-pitch prop at higher rpms. I think the effect of the prop loading down the motor is not taken into account when it's said that lower pitch props are more efficient. Rather, the motor is assumed to have infinite torque reserve, and so the motor's performance doesn't change as the prop changes. But real motors don't have infinite torque reserve. Take a 6S battery and a 1900kv motor and spin a Ethix S2 prop and a Gemfan 51499 on it. I think you'll find that the 51499 is less efficient in terms of grams per watt due to it heavily loading down the motor, and because at higher rpm you enter the stall condition that Chris discussed. But even if that turns out to be false, I'm 100% sure that you'll get longer flights on the S2, simply because it's making less thrust. And that's what lay-people usually mean when they say a prop is "more efficient".
@@JoshuaBardwell Totally agree. Most pilots mean flight time, when they say "efficient". I also think that manufacturers are partly to blame. Such as every motor is advertised as efficient, light, powerful, and easy to control.
Thank you very much for this video and your scientific analyses. I have been waiting for discussions like this in FPV. I look forward to all of your future content.
Very excited to watch as your channel inevitably grows tremendously. You combine some of my favorite aspects of the likes of Joshua Bardwell and KababFPV. Please keep up the good work because I definitely learned a lot and enjoyed every second of this video. Also, I literally checked to see if you had a review of the Glide frame and what a coincidence that it's your next video
both your disk loading and prop tip speed lessons helped me 1) verify that someone's 3.5" digital toothpick actually matches kabab's analog 3" toothpick characteristics, and 2) how to calculate the ideal and maximum motor output % to make my over-kv motors match that same config. you are a legend for bringing sanity and safety to this hobby
Congrats on 10k subs today! I was one of the latest 😎👍 I only comment here because this is the video I was watching when I noticed the change from "9.99k" to "10k." Your almost purely scientific approach lifts the fog of uncertainty in several aspects of quad build considerations. I fully agree with the rest of these comments saying it was great to find you and learn so much more than expected! Keep it coming!
Your channel has given me a while new excitement for drones, I'm now extremely interested in the building and perfecting of the quad to squeeze performance. Before I couldn't digest it all, but giving us an understanding in more understandable terms will allow me to further delve in
@@ChrisRosser one of my group friends keep asking me if placement of VTX above Power Cables will affect the components from the VTX. I just simply says yes for micro magnetic field. Might be a good theme to cover, maybe?
This content is awesome kabab fpv had a video on the babyhawk 2 hd and had talked about how it’s frame resonance was really good then bardwell talked about it now I can’t stop thinking about this is awesome stuff you are doing !!
Now this is CONTENT!!!!💯👍 My only mistake is that I didn't find out about Chris until recently!!!! When the Yoda of fpv had his quad filter set by Chris and absolutely loved it I was like ok.....I need to find this Chris guy 🤣 I subbed immediately after watching the first vid I saw....just great information all around man✌....PS.....YODA IS JB 😁
this was a very useful 18+ minutes of my life, thank you! now choosing a new props would be much less of intuition/reviewers influence and much more of understanding of physical processes which make quadcopter fly. subscribed!
I would really love a video about cinewhoops. The trends are covering the actual data. The Shendrones Squirt is supposed to benefit from a "duct effect" (and I feel like it flies really bad). Everyone is jumping on the "Slammed Squirt" trend and getting rid of the ducts. Who is right ? Meanwhile, HQprop is making a 6-blade and now 8-blade 3" prop. What's the science behind these choices ? I'm using 6-blade and it feels alright, but it's supposed to be quite inefficient for a quad that already has a big disadvantage in weight to power ratio.
Ducts are on my radar as another topic to apply some science to, I think you are right people need some more information on when and how to best use ducts to get the most from them and when to go with just prop guards.
Perfect! 😀Having both options on the Squirt and on a 3D printed frame, it will be easier to compare them with a bit more knowledge on the physics behind it.
Is the slammed squirt trend actually getting rid of the ducts? still looks like a duct to me, just a bit shorter... Anyhow Rosser has since made the duct video and I have just ordered a slammed squirt, I'm a little concerned that maybe I won't get the actual beneficial effect he described in the video from the slammed version, and maybe I should ask for a regular non slammed version. The slammed version looks nicer though 😅😅
@@definingslawek4731 It is actually different because it doesn't benefit from the "turbine" effect. Chris made a video about it if you want all the details : th-cam.com/video/7f2DZIC8a1k/w-d-xo.html
@@LenordeFPV I'm told the slammed squirt still has ducts, and there's a video showing an increase in thrust with the duct versus without. Anyhow I ordered a slammed one and I hope that it wasn't the wrong choice vs the non slammed version. In OP's video on cine whoops he says the most interesting part of the ducts is not the extra thrust but how it makes it more stable and thus comfortable for flying slow proximity and Indoors and stuff
Once again you have put out some very useful information that will help us all build and design better flying quads. Your points are clear and concise and understandable for even people like me with no engineering background. You more or less answered this in the video but how does weight factor in to prop selection for 5" freestyle quads? I have some that are in the mid 600g and others close to 725g AUW. Would the weight difference lead to choosing different props all else being equal? Higher pitch on heavier quads? Thank you Chris!
As you increase AUW your inflow velocity in a hover is going to increase and so you might pick a steeper prop for more efficiency. If you do a lot of reverse flow moves that could affect propwash handling so another solution is to go up to a 5.1" or 5.5" if you can and keep a lower pitch.
@@ChrisRosser Thanks for taking the time to answer my question and that makes a lot of sense. I would like to see some more prop manufacturers make 5.5" props especially low pitch ones. I haven't seen any freestyle 5.5" props yet but would love to try some out for my heavier quad that can actually accommodate the 5.5 props (marmotte lol).
@@chibikaiju922 Actually have bought some 5.5" props (also for a Marmotte frame) but only had time to do arround 5 packs or so. I really like how stable they make my heavy quad (717g) and also they just made my marmotte the fastest quad I have, but my batteries hate them. My motors are so much more capable of pulling Amps (before max arrond 96A, now all the battery has to offer, arround 130A). That went that far, that I accidently had a sag (if you can call it like that) to 8.8V on my 4s-Lipo. I hadn't pulled to many mAh at that point, but just the gigantic, onholding load killed it. Just did a dive/half loop over a big tree and hat to catch it, and then the volage began to sag out, so I had to throttle even more, but that only resulted in more amps and so on, untill I hitted the ground (at 8.8V XD ). Okay, now back to the prop: It is definetly a little quieter at hover and also I can hover now at arround 7A, before it was arround 11A which i guess is pretty amazing, and also the normal flying takes a little less Amps, but as I said, when u punch, the motors just can work hader and pull more Amps. So there is just a benefit for me in that area. I had some problems with some pretty significant bounce-backs after fast flips and rolls, guess that will be mostly an issue of retuning the PIDs, but havent had time to look into it. All in all, I really would reccomend everyone that has a quad with 700g+ to just try a set of 5.5" props, I have bought these: HQProp Durable 5535. Also I bought some 5" props with 4 blades, havent had any time to test these, but I hoped to just get more surface area and maybe also a better flying quad when its rather in the heavy part for normal 5" 3baldes, but as I said that is just my hope and will be tested as soon as the weather here gets better. Hope I could help you, have fun ;^D
Thanks for the insights. I though do not exacly buy into your concrete prop spec recommendation. I guess that also heavily depends on the prop manufacturer and how they form the tip ends. So as relative recommendations in the line of one manufacturer, I do buy into this. For freestyle imho the compromise is that you need "punch" and you have to deal with all this adverse flow conditions. Most freestyle videos are so appealing because there is smoothness and flow interrupted by phases of hard punchs. But certainly going for the most high-pitch prop is not the right thing to do.
So where my physics teacher ears are burning. Because I am set here like WHY DID I NOT LISTEN IN CLASS!!!!. Good info really putting this with your motor video I have a better feeling about the props I am picking for my rigs. Instead of just well so and so use this let's see.
i have a big box with 30 packs of differents new props (for test only) and when i have a new quad, i take the box to test and know for the quad i have buid what props are the best. thank you for this video ;)
I’ve had a couple of questions regarding props. 1. How much of an adjustment should we consider for different altitudes? I’m in the Rocky Mountain region, which is about 4000ft above sea level. 2. How can we tell if a prop is killing battery performance? Is there more to consider than a drop in flight times? I guess I’m looking for some general rules to apply to a 5” 6s low-kv freestyle setup. I’ll give it some thought, revisit, and try the math. Thanks for the info. I’ve been curious about the subject.
Have you checked out my video on Motors? It should give you some pointers on battery considerations. As for altitude consider more blades, slightly higher KV and as a last resort a steeper pitch.
@@ChrisRosser gotcha. I think I need to shift my perspective. I’m coming into this from a mindset of choosing the “best” prop for an existing setup in my circumstances. Perhaps I should consider whether that existing setup is appropriate to begin with.
Hi Chris- love the scientific approach- would be really great to see how theory stood up to practice by setting up a double blind trial with some experienced pilots - suspect it would be difficult to get sufficient numbers for a significant result though
Hi Chris, what is the effect of pitch and efficency vs number of blades? I guess a lower pitch creates less turbulences which affect the next propblade and probably decrease less the effiency compared to a prop with higher pitch blade. I expect not a dramatic effect, but I think the question is interessting, if low pitch props are loosing less effiency with more propbaldes over high pitch props with more propblades. Also your recommendations of Longrange props brings up a question: on 4"LR you see mosten low pitch props like 4024. The Reason is the amound of amps, LI-Ions can`t provide much amps, so there is also an electrical tradeoff of pitch vs amount of amps which can be delivered from a Li.Ion pack. So where is the sweetspot of pitch vs. amps?
Pitch and number of blades should be relatively independent of each other if that helps. For LR cruising a higher pitch prop will give more efficiency but you need to use a throttle limit to control your peak amp draw. If you don't use a throttle limit you need to run low pitch to control amp draw (but you suffer with lower efficiency overall)
Another great presentation. I've been thinking about pitch vs inflow speed with airplane variable-pitch propellers in mind. Everything makes sense except the efficiency up to 8 degrees (or 16?) and how that applies to 5" long range propellers with pitches as low as 25. Should we be trying something around 30-35, or even higher? I have ran across people getting surprising efficiency out of very high pitched props. Can't wait for the Glide analysis, and hoping You can get a Fouride in at some point.
The best efficiency should occur at the best lift to drag ratio of the prop which will depend on shape but is typically around 8 degrees (this is for a hover). Obviously inflow velocity affects the angle of attack so can get a little complicated. Once you start flying the drag of the quad and the inflow velocity due to your forward speed starts to matter. At high forward speeds a steeper pitch prop is probably going to give you more efficiency in g/W.
I was thinking about this more, do you know if the prop flex has any effect? These fpv props are quite flexible, I presume at a certain disk load the majority of the flex will have occurred and have little impact. I wonder if there is excessive flex at a certain low load threshold.
Hi Chris, this is reallly good. There is only question regarding AOA. The first diagram showed maximum efficiency at typically 4 degrees and stall at 16 degrees. However later you mentioned that efficiency will be improved all the way up to 16 degrees . Probably I missed something there.
Nearly every time I try a new prop I think what a wonderful prop. Everything from a 3" pitch to a 4.9" pitch. I even like the 5.2" pitch but I don't use those because I get about half the flight time. I don't think I'm good enough yet to tell much difference between props.
Hi, I asked myself all the time how to think about this on my Cinewhoop. I just finished watching your new video about ducts, and I have a squirt V2 at home. Also I am just designing my own "megas-quirt", that can handle 3.5" (89mm) props, as my Squirt is barely holding itself in the air with a Hero 8 and a 1300mAh 4s lipo. Now to my question: How do you think that multiple blades change the therory. By that I mean the 6- or 8-bladed HQ props, or the much steeper Gemfan D76 or sth like this. My testing tells me, that two props that both are called to have a pitch of 3 aren't really comparable, doesnt matter whitch size (3", 5", ...). In the cinewhoop-part also the diffrent blade-count makes everything even more uncompareable. I really have problems to compare a Gemfan D90 (3 bladed prop, pitch "3") to a HQ 89mmX8 (also pitch of "3") but they clearly are diffrent in their steppness-angle and will poth have very diffrent thrust. toothpick-class: Gemfan for example has a 3018-2 prop (biblade) and a 3016-3 (triblade), I also cant tell in this case which prop I could expect to have more thrust. The issue is, that we often dont have real numbers to calculate with or alternatively have simulation-values or static-bench test from the manufacture himself (1st hand). Sometimes I have the feeling, the manufacuters dont use the pitch-value to tell us how steep the balde is, rather to tell how much thrust they think the prop makes compared to their other props on the market. By adjusting the pitch value they use for marketing so they can put their props in somewhat of an order they make comparison for us pretty rough, and practically impossible to compare to other companies. Did/Do you think/feel the same as I do, or do you understand my problem? If so, do you have any idea how we could interpret these values we get from the manufactures, or do anything about it other than just buying a ton of props just to find out that 99% arent the ones we where looking for? Thank you so much for your videos, it is great to understand such topics in greater detail, love it, keep it up!
Comparing props is difficult because they are not fully specified by the manufacturers. Their performance is also very dependent on your AUW and flight style. I would suggest trying a prop and then asking yourself what you want more of: thrust? smoothness? efficiency in hover? efficiency in fast forward flight. Then use the info in the props video to move you in the right direction. E.g. more thrust = more blades or steeper pitch (but steeper pitch may be less smooth). more smoothness = shallower pitch It is not really possible in my view to pick the perfect prop just by looking on the web. But it is also not necessary to just buy every prop and try them all. You can take a more focused approach. I hope this helps.
This explains why I wasn't getting the top end performance for the Ethix peanut butter jelly props. I thought it was the weight, but it's likely my lower KV motors for 4S?
I guess the only thing I still feel curious about; is props based around air density... I.E. how would a high pitch props performance be affected by flying at a mountaintop where air is thin? Also another incredible video mate. Doing the FPV God's work!
At higher altitude the air is thinner so you will get less thrust. I think the best way to combat that without affecting any other parameters would be to use a prop with a longer chord or additional blades. If you change pitch you will affect the stall performance but additional pitch could be another way to get back some of the thrust you're losing due to the thinner air.
I would really appreciate a video relating to altitude. I fly freestyle and long range between 8,000 and 13,000' above sea level. I've enjoyed experimenting, but I also enjoy your videos, science, and experience
How might the number of blades on a prop affect the overall vibration characteristics of a multicopter? The presence of load changes on the arms from the downwash of each prop blade makes me think that a certain number of blades might perform better or worse for a given frame design.
I can only imagine a prop hitting 1.0 Mach and hearing a bang as a trail of fire burning on a road is all that is left as the drone travels back to the future.
What if you had a 5” quad running 2806.5 motors but usied 5” 6 blade propellers? Would you get the trust performance of a 7” quad with tri-blades? Because the surface are of prop should actually be greater on the 5” hex blade. So would you be able to go with a bigger motor on a smaller quad and get similar performance? Better? Worse?
Small propellers are less efficient than big propellers. So you get less thrust for the same power = shorter flight times. But if you don't care about efficiency then you can get more thrust with more blades and a bigger motor.
Hey Chris - I know this might be semantic but I think it is an important distinction when talking about the dynamics of our kwads. I thought that the prop generates lift and the portion of that lift that provides forward motion is thrust? So wouldn't the specific airfoil and angle of incidence change the how much thrust is generated? I thought, Angle of attack is generally in reference to the prop where angle of incidence is relative to the craft's attitude of a specific axis. Additionally, I think the use of certain generalizations is a slippery slope. Also I have a question regarding the V(inflow), I don't think it always has to be axially aligned - but the angle should be a known value for calculation.
Hi Zach, in the video thrust just means the force generated by the prop in the axial direction. The lift generated by each prop blade creates this thrust. There are certainly some simplifications in the analysis to allow general conclusions to be drawn. I think that it is important to make content that is easy to understand so that everyone can benefit from it. You are right that it is important to distinguish between AOA of the blade and AOI of the incoming air stream. In flight the incoming air will rarely be axially aligned to the prop (more on that in my upcoming video on ducts) but I think it is a valid simplification for the analysis in the video which primarily considers hovering where the the flow will be close to axial. Thanks for your comment I hope this answer was useful 😁
give us a cinewhoop already!! for a batteryless gopro >D ... also check the astrorc carbon fly 25 frame ,, diagonal frame.. keep the videos coming!!! and what controller should we use for maximum wall concrete penetration and dont failsafe and available >D
Great video. Question: regarding heavy-lift applications, would I want to increase or decrease the AoA of my props? My intuition is that I would need a lower pitch prop, like a lower gear in my car for pulling a heavy load. Is that right and if not, what am I missing?
Another interesting thing to consider would be if "Floppy proppies" have an advantage in response time compared to their fixed counterparts. And if so is it quantifiable?
I have a question about prop tip speed. So I used a calculator, and I saw someone had 5 inch props spinning at 65,000 RPM (max power) so I wondered what would be the tip speed and got 966.8 mph which is supersonic yet the quad was just flying normally even at full power, although it had a very loud “buzzsaw” kinda sound. I feel like there wouldn’t be supersonic airflow that would cause lots of drag on these kinds of props as planes with supersonic propellers like the XF-84 have straight trapezoidal blades, which still wasn’t so efficient. These drone props look like they’d totally handle supersonic airflow with little drag bc of how they curve towards the tip. Just wonder if what I calculated is true, as I would love to find out if/how it is possible to make a race quad with supersonic props as well…I want lots of noise and (maybe) speed lmfao. More noise for sure
In terms of emptying the reservoir of vibration in the frame it seems like the battery pad would have the largest influence considering its holding an isolated mass that's about 1/3 the total quad weight. In my case the under mounted battery has a sticky pad connected directly to a carbon surface that also mounts to the flight controller. I wonder if rubberized pads have a high Spring rate that could create harmonic frequencies... Versus gel or soft foam.
This question puzzled me for quite a while as well. But if you review some of my frame resonance analysis videos you can see that the relative movement of the battery compared to the frame is very little for these high frequency vibrations. I think that's why it doesn't do as much as the grease on the arms. The arms really do the vast majority of the moving for the high frequency modes of vibration.
I agree with you, the arm displacement is the highest and dampening that movement is hard to accomplish in a rigid body. Some viscous movement is helpful to reduce vibration. How was your battery mass coupled to the frame in the simulation? Is it a soft spring boundary? I'd like to understand the result of decoupling the battery mass from the frame with the commonly used rubber layer. Could the lithium polymer dampen the vibration better if it is pressed hard up against the carbon without a soft layer?
@@nateteator3901 The battery is sitting on top of a rubber battery pad 2mm thick in the simulation. So there is definitely flexibility and movement but not as much as I expected. I don't know whether a battery pad helps or hurts damping. I would imagine a thinner pad would have less damping but I'm not certain.
Would you consider, the 5inch vs 5.1inch props, the extra .1 inch diameter is being done to increase the lift/efficiency that is lost by the lower pitch in a freestyle setting? Also, would you consider a $1 slot on your patreon?
The extra .1 inch diameter provides a bit of extra thrust without increasing the risk of stalling the blade. They help a lot for carrying the extra weight of the newer non-session go pros. IMO I think the new hero 8 and 9 probably warrant 5.5in or 6in props!
Just bought some Gemfan 5051 tri blades for my freestyle drone. They were on sale, I'm new, and I crash a lot 🙃 4s 2450kv 500g quad. I guess I'll set a throttle limit and see how they do!
Okay I'm late to the game but everyone says you're the man to go to for facts. And I can't really find any good factual information on whether if the stock props or the prop adapters and a different type of aftermarket prop is better on the DJI fpv.?? It just seems like to me if you add the adapters and a lighter smaller prop than it really is being counterproductive and adding a smaller pop to spin off faster... Any advice would be greatly helpful
This is very very interesting and confirms and extends much of my own investigations. I have a question: how does the inflow velocity calculation change for fixed wing? Obviously the vin from the airspeed but do you need any additional factor to account for the inwash from the prop of can I just plug in airspeed in m/s?
I think you should be able to calculate inflow velocity using a momentum balance taking into account that the initial airspeed is not 0 as it is for a quad in hover.
Hello, thank you for the great video! My Question is: What about tiny whoops (e.g. Moblite 7 HDZero 1S). Is there a way to make it more efficient by changing the Gemfan 1610 2-Blatt Propeller?
awesome video. I just recently went from a 5135 that came with my nazgul 5 and went to a 5043 and I was noticing I was having trouble getting it to float over things while trying to split s over them andbai could hear it grabbing more in the maneuver this video really helped me understand why it's doing that. What do you think of the really low pitch prop that it came with. When I look them up it says the pitch is 3.5
I have a scenario for you. You have a 7" kwad that weights in at around 1kg AUW with 2806.5 1300kv RUNNING A 2200MAH 6S battery. You want to do aggressive long-range flying. Your going to be flying up a mountain that starts at 7500' elevation and tops at around 11k'. What size prop would you recommend to give good quick thrust but also efficiency for distances like 6 mile round trip. I have tried a few different types and settled on one that I really love but curios if there is one you might recommend that I haven't tried yet.
I like light pitch props for good propwash handling. I would also choose a prop with a relatively long chord to maximise thrust at high altitude. If you aren't going to ever get into a propwash situation a steeper pitch prop might give more efficiency at speed but you'd want to use a throttle limit to prevent sucking down your battery!
@@ChrisRosser I started out using biblades but didnt like how much throttle I needed to give it while try to pull out of a long dive. So I went to 7x3.5x3 then 7x4x3 and have ultimately landed on 7056 triblades. The 7056 seem to help give more low end thrust to compensate for the low kv and thin air. The big motors turn them really good as well. I tuned out the propwash issues early on while using the 7x3.5x3 props and havent needed to change that since so I dont think the props stall at all. Honestly this build would probably make you start twitching as it doesnt follow any of your advise I have seen in any of your videos so far. Thanks for your thoughts.
Great content! It got me thinking though, what if one would (theoretically) construct a prop that utilizes centrifugal force to alter the pitch slightly? Think of how a CVT system works with weights and ramps/rollers.. Would it be possible? Would there be benefits to reap from doing this? And yeah, it would likely not be suitable for a 5" prop for rigidity and durability reasons.. Maybe this is already a thing, I haven't read anything on the subject, but this video just had me thinking about how it could be done.
This series of videos is amazing. I have some questions, do these same pitch recommendations apply to all propeller diameters?, for example 3-4 in; and what would be the best propeller for a cinewhoop to get the maximum flight time?
I've put the slides from my last few videos here: drive.google.com/drive/folders/1md9Vc2l-PnY5jVDQSH7HXB_FSh5z8dr_?usp=sharing If you download them you can watch the embedded videos as well!
I have a question about relationship between prop pitch and oscilations. I was using ethix s3(5031) with lots of oscilations. tried to manage it by tuning the PID but failed. One day I had a chance to use ethix s5(5040), all of the oscilations were removed and feel like propwash was even better. Everything was in same condition. BTW I’m flying my quad with these specs. 6s, 1750kv, rpm filter, lowest filter slide, default PID on BF.
@@ChrisRosser thanks! well….after this happen, I thought s3 might be too flexy on 6s quads. oscilation is always big issue to me, so I am always serching for a best prop.
Nice! I graduated as a lawyer, am building my first 4inch semi longrange sub 250gr. 4s quad, and after checking motor load charts, making some calculations I've diside to get 1507 2680kv motors with biblades 4024 on a throttle limited around 20% for LR, and 4023 triblades for freestyle.. (haven't seen less pitch im a triblades 4 inch props yet). Hope I'll get parts of it soon to complete, film, test and finaly have enough footage to start my channel. Ty for your sience, I'll be waiting for your frame, and hope we'll get a affordable shipping cost for it (Russian Pilot in the house 😉)
I think some useful oversimplification would be possible just in comparing chord profile, and what the relative pitch across that profile is going form the hub to tip. It's impressive that all of the most recent props have converged on roughly the same chord profile (with varying amounts of leading edge sweep) as a trade between durability and in-air performance, and the 'best' of the latest units all share reduced chord that helps lower rotational moment without results in a frail edge of the prop, and I think that's why the propwash response is so good (compared to back in the day when we were flying bullnose props).
@Chris Rosser - the rule of thumb I've been using to calculate maximum tip tolerable RPM has been 38k RPM, in nominal cases, for 5". Thanks for that WarpDriveProps calculator tool, since I feel like doing the more simplistic calculations lose accuracy by the time I'm at 7", as I keep finding myself just over the limit on builds I have calculated to be marginal but within bounds (the good news being that throttle limits are easy to adjust downward).
I would add to this that I think manufacturers are designing props that don't require throttle expo or throttle limits because no-one is using these (except to run 2400KV motors on 6S). They are realising they need to reduce thrust to give pilots more control. If everyone tuned their feel using throttle expo I think we would see more props that are designed to get the most from our motors.
I'm working with Bob on the video so it'll be the FPV cycle glide. Because of the similarities in geometry the results should be applicable to both frames? They certainly look very similar.
@@ChrisRosser They were up until about 8 months ago when Kabab upgraded the bottom arm brace and the bottom main plate to a much more solid design with fewer cutouts, the fpvcycle glide is now much beefier structural wise. As far as I know the hyperlite glide still uses the old design, though they still look very similar at the first glance.
@@shtumpa1 Ok, I'll make it clear that the analysis is for the FPVCycle Glide but that the Hyperlite Glide is similar. I would like people who search for the Hyperlite Glide to find the video because it will still be relevant for them.
The fact that you incorporate actual science instead of "Oh, I flew this one, then that one, and then I liked this one better." Well done mate.
Thank you, I try to take feel out of the equation a little bit because 1. I'm not a pro pilot 2. It's very subjective and can sometimes lead you down the wrong path for the right reasons or the right path for the wrong reasons!
Bardwell sent me over to check your channel out, really glad that he did. Being an ex aircraft and helicopter mechanic, I guess that from my technical education required to get my license, a lot of the principles that you explain seem to be common knowledge, but that is only because of my own education. You did a great job of explaining a uncommon topic! Ain’t no perfect prop for all conditions, you have to choose the one that fits your flying parameters.
I’d love to see an updated take on this with the new wave of all these 5.1 props like 51433, 51466, 51477, etc.
I finally understand why all the top pilots use low pitch props for freestyle and what I've been doing wrong with my own prop choices. Thank you!
If my algebra teacher would talk in the same interesting way, I would graduate from high school with A+
Just found why need to decrease kv, going to 6" and higher diameter props. I knew before that I had to do this, but now I know why :) I didn't even think about the speed of the propeller tip before.
Thank a lot! You doing great job!!
Thank you! I have an advantage over your algebra teacher: FPV is more awesome than calculus 😎
@@ChrisRosser i was gonna say the same thing: you have interest in the subject. Changes everything haha
I feel like this is a very expensive lesson for free. Amazing level of detail here in a science I don't know jack about
Thanks so much! I hope you found it useful and enjoy the other videos 🤠
This is insanely good content. Learned more about props from this video than an entire course in aerodynamics at uni! Your explanations are great, thanks for taking your time to make these videos!
Glad it was helpful!
How much do I like your videos? I watch them twice. They are so full of great technical analysis that I pick up details I missed the first time through. Keep it up!
Wow, thank you! I appreciate your positive support.
At last, I understand prop wash, your videos are soooo good. Thank you so much. Having the equations and their explanations to understand the physical phenomenons is absolutely marvelous.
You are so welcome!
Best FPV video I have ever seen, beats even JB in my opninion. Do more please!!
Thank you for your wonderful comment. I'm not sure I'm quite at JBs level but I love that you are finding my videos valuable.
even Paweł Spychalski, if nothing else Chris does not say "basic-A-lly" (I pick on Paweł only because I have the same outrageous accent)
I've been here from day #1, and I don't regret it. I love how it's nothing but straight information. Keep up the the explanations coming, it's always interesting
Thanks Vitroid! I really appreciate your support
your videos pushed me to the other side of peak on dunning-kruger curve. thank you.
You're welcome, we're all on the climb up the next slope now!
So much insight! Thank you. I have always thought that props with more pitch should be more efficient. Many youtubers told otherwise and it really confused me.
It depends a lot on how you fly but if you fly reasonably fast and are gentle with the throttle you can really benefit from a steeper pitch prop! Thank you for your comment 😁
Part of the reason for the confusion is that most pilots don't mean the same thing when they say "efficiency", as Chris does. When testing motors, efficiency means grams of thrust per watt of power. But when pilots talk about efficiency, they usually mean longer flight time. A lower pitch prop will usually give longer flight times all else being equal, because it makes less thrust and so it draws less power.
Lower pitch props also load the motor less. This is especially true when talking about a high kv motor, which will need to draw more current to generate the torque to try to spin the higher-pitch prop at higher rpms. I think the effect of the prop loading down the motor is not taken into account when it's said that lower pitch props are more efficient. Rather, the motor is assumed to have infinite torque reserve, and so the motor's performance doesn't change as the prop changes. But real motors don't have infinite torque reserve.
Take a 6S battery and a 1900kv motor and spin a Ethix S2 prop and a Gemfan 51499 on it. I think you'll find that the 51499 is less efficient in terms of grams per watt due to it heavily loading down the motor, and because at higher rpm you enter the stall condition that Chris discussed. But even if that turns out to be false, I'm 100% sure that you'll get longer flights on the S2, simply because it's making less thrust. And that's what lay-people usually mean when they say a prop is "more efficient".
@@JoshuaBardwell Totally agree. Most pilots mean flight time, when they say "efficient". I also think that manufacturers are partly to blame. Such as every motor is advertised as efficient, light, powerful, and easy to control.
Thank you very much for this video and your scientific analyses. I have been waiting for discussions like this in FPV. I look forward to all of your future content.
Glad you enjoyed it!
Very excited to watch as your channel inevitably grows tremendously. You combine some of my favorite aspects of the likes of Joshua Bardwell and KababFPV. Please keep up the good work because I definitely learned a lot and enjoyed every second of this video. Also, I literally checked to see if you had a review of the Glide frame and what a coincidence that it's your next video
I really appreciate the positive comment and can't wait to hear what you think of the analysis of the FPVCycle Glide Frame.
Damn. You posted this just after I passed my canadian rpas exam. Stall mechanics was one of the questions!
both your disk loading and prop tip speed lessons helped me 1) verify that someone's 3.5" digital toothpick actually matches kabab's analog 3" toothpick characteristics, and 2) how to calculate the ideal and maximum motor output % to make my over-kv motors match that same config. you are a legend for bringing sanity and safety to this hobby
Congrats on 10k subs today! I was one of the latest 😎👍 I only comment here because this is the video I was watching when I noticed the change from "9.99k" to "10k."
Your almost purely scientific approach lifts the fog of uncertainty in several aspects of quad build considerations. I fully agree with the rest of these comments saying it was great to find you and learn so much more than expected! Keep it coming!
Thank you! Very excited to keep producing the videos 😁
Your channel has given me a while new excitement for drones, I'm now extremely interested in the building and perfecting of the quad to squeeze performance. Before I couldn't digest it all, but giving us an understanding in more understandable terms will allow me to further delve in
As a scientist and also a pilot... FOUR THUMBS UP for you my man
Thanks for the support! 😁
@@ChrisRosser one of my group friends keep asking me if placement of VTX above Power Cables will affect the components from the VTX. I just simply says yes for micro magnetic field. Might be a good theme to cover, maybe?
This content is awesome kabab fpv had a video on the babyhawk 2 hd and had talked about how it’s frame resonance was really good then bardwell talked about it now I can’t stop thinking about this is awesome stuff you are doing !!
Some great content dude
Thanks! I appreciate your support.
It is!!
G'WeekenD Mr. Thanks 4 everything U do 4 this great community. I really enjoy your content, takeCare mate
Now this is CONTENT!!!!💯👍 My only mistake is that I didn't find out about Chris until recently!!!! When the Yoda of fpv had his quad filter set by Chris and absolutely loved it I was like ok.....I need to find this Chris guy 🤣 I subbed immediately after watching the first vid I saw....just great information all around man✌....PS.....YODA IS JB 😁
this was a very useful 18+ minutes of my life, thank you! now choosing a new props would be much less of intuition/reviewers influence and much more of understanding of physical processes which make quadcopter fly. subscribed!
Glad it was helpful! Hope this helps you to find your perfect props.
@@ChrisRosser it will for sure!
Very useful info, also for larger quads of course. Much appreciated.
The man Chris does it once more...outstanding vid bruh
dude you are my new favorite person, thank you!
Happy to help!
0:00 Intro
0:39 Prop Thrust
1:46 Prop Efficiency
2:18 Disc Loading
3:01 Angle of Attack (AoA)
3:53 Stall
5:20 Prop AoA Calculation
7:41 Inflow Velocity
8:48 Estimating AoA Adjustment
9:44 Adverse Inflow Conditions (aka when flying)
11:10 Max Tip Speed
12:48 PROP SELECTION - Freestyle
14:24 PROP SELECTION - Technical Racing
15:39 PROP SELECTION - Long range Racing
17:10 Conclusions
*Chris Rosser* 💯 🏆 🥇
Щиро дякую за просвітницьку 🧑🔧🔬🧠✨ діяльність, дуже корисно!
I was scouring the internet for equations to solve for the right props, and I have FINALLY FOUND IT. also I'm so glad I took AP physics
Brilliant! I really like the academic approach! Well done!
This video was fantastic. Thank you for doing this.
I would really love a video about cinewhoops. The trends are covering the actual data. The Shendrones Squirt is supposed to benefit from a "duct effect" (and I feel like it flies really bad). Everyone is jumping on the "Slammed Squirt" trend and getting rid of the ducts. Who is right ?
Meanwhile, HQprop is making a 6-blade and now 8-blade 3" prop. What's the science behind these choices ? I'm using 6-blade and it feels alright, but it's supposed to be quite inefficient for a quad that already has a big disadvantage in weight to power ratio.
Ducts are on my radar as another topic to apply some science to, I think you are right people need some more information on when and how to best use ducts to get the most from them and when to go with just prop guards.
Perfect! 😀Having both options on the Squirt and on a 3D printed frame, it will be easier to compare them with a bit more knowledge on the physics behind it.
Is the slammed squirt trend actually getting rid of the ducts? still looks like a duct to me, just a bit shorter... Anyhow Rosser has since made the duct video and I have just ordered a slammed squirt, I'm a little concerned that maybe I won't get the actual beneficial effect he described in the video from the slammed version, and maybe I should ask for a regular non slammed version. The slammed version looks nicer though 😅😅
@@definingslawek4731 It is actually different because it doesn't benefit from the "turbine" effect. Chris made a video about it if you want all the details : th-cam.com/video/7f2DZIC8a1k/w-d-xo.html
@@LenordeFPV I'm told the slammed squirt still has ducts, and there's a video showing an increase in thrust with the duct versus without.
Anyhow I ordered a slammed one and I hope that it wasn't the wrong choice vs the non slammed version. In OP's video on cine whoops he says the most interesting part of the ducts is not the extra thrust but how it makes it more stable and thus comfortable for flying slow proximity and Indoors and stuff
Good video. Appreciate your hard work in making such quality content.
Once again you have put out some very useful information that will help us all build and design better flying quads. Your points are clear and concise and understandable for even people like me with no engineering background. You more or less answered this in the video but how does weight factor in to prop selection for 5" freestyle quads? I have some that are in the mid 600g and others close to 725g AUW. Would the weight difference lead to choosing different props all else being equal? Higher pitch on heavier quads? Thank you Chris!
As you increase AUW your inflow velocity in a hover is going to increase and so you might pick a steeper prop for more efficiency. If you do a lot of reverse flow moves that could affect propwash handling so another solution is to go up to a 5.1" or 5.5" if you can and keep a lower pitch.
@@ChrisRosser Thanks for taking the time to answer my question and that makes a lot of sense. I would like to see some more prop manufacturers make 5.5" props especially low pitch ones. I haven't seen any freestyle 5.5" props yet but would love to try some out for my heavier quad that can actually accommodate the 5.5 props (marmotte lol).
@@chibikaiju922 Actually have bought some 5.5" props (also for a Marmotte frame) but only had time to do arround 5 packs or so. I really like how stable they make my heavy quad (717g) and also they just made my marmotte the fastest quad I have, but my batteries hate them. My motors are so much more capable of pulling Amps (before max arrond 96A, now all the battery has to offer, arround 130A). That went that far, that I accidently had a sag (if you can call it like that) to 8.8V on my 4s-Lipo. I hadn't pulled to many mAh at that point, but just the gigantic, onholding load killed it. Just did a dive/half loop over a big tree and hat to catch it, and then the volage began to sag out, so I had to throttle even more, but that only resulted in more amps and so on, untill I hitted the ground (at 8.8V XD ).
Okay, now back to the prop:
It is definetly a little quieter at hover and also I can hover now at arround 7A, before it was arround 11A which i guess is pretty amazing, and also the normal flying takes a little less Amps, but as I said, when u punch, the motors just can work hader and pull more Amps. So there is just a benefit for me in that area.
I had some problems with some pretty significant bounce-backs after fast flips and rolls, guess that will be mostly an issue of retuning the PIDs, but havent had time to look into it.
All in all, I really would reccomend everyone that has a quad with 700g+ to just try a set of 5.5" props, I have bought these: HQProp Durable 5535.
Also I bought some 5" props with 4 blades, havent had any time to test these, but I hoped to just get more surface area and maybe also a better flying quad when its rather in the heavy part for normal 5" 3baldes, but as I said that is just my hope and will be tested as soon as the weather here gets better.
Hope I could help you, have fun ;^D
I learned something today! Great video, thanks for uploading!
Thank you for sharing so useful information! Keep on going!
Thank you! Will do!
Thanks for the insights. I though do not exacly buy into your concrete prop spec recommendation. I guess that also heavily depends on the prop manufacturer and how they form the tip ends. So as relative recommendations in the line of one manufacturer, I do buy into this.
For freestyle imho the compromise is that you need "punch" and you have to deal with all this adverse flow conditions. Most freestyle videos are so appealing because there is smoothness and flow interrupted by phases of hard punchs. But certainly going for the most high-pitch prop is not the right thing to do.
You are correct, this can only be a guide, to try and help people know what type of prop might be right for them. Thanks for your comment!
Love this, Looking forward to the next load of knowledge you can share with us. Keep it up !!
I seen you briefly touched on the density of air. I am interested to see what your thoughts are on elevation and prop and pitch adjustments.
Typically the best way to combat elevation is to increase the chord length of the prop blade. Steeper pitch can hurt propwash handling.
This justifies my findings in my prop reviews.
I love it when theory aligns with experience!
So where my physics teacher ears are burning. Because I am set here like WHY DID I NOT LISTEN IN CLASS!!!!. Good info really putting this with your motor video I have a better feeling about the props I am picking for my rigs. Instead of just well so and so use this let's see.
I'm glad to hear that, hopefully you'll find the perfect props for you more quickly now you know what to look for.
thanks the video clarified what prop should I use thanks a lot
Glad I could help! Thanks for your support.
Great content for some one luke me who wants to understand everything thanks Chris !
i have a big box with 30 packs of differents new props (for test only) and when i have a new quad, i take the box to test and know for the quad i have buid what props are the best. thank you for this video ;)
Scientific approach which i like.
I like your positive comment. Thank you!
I’ve had a couple of questions regarding props.
1. How much of an adjustment should we consider for different altitudes? I’m in the Rocky Mountain region, which is about 4000ft above sea level.
2. How can we tell if a prop is killing battery performance? Is there more to consider than a drop in flight times?
I guess I’m looking for some general rules to apply to a 5” 6s low-kv freestyle setup. I’ll give it some thought, revisit, and try the math.
Thanks for the info. I’ve been curious about the subject.
Have you checked out my video on Motors? It should give you some pointers on battery considerations. As for altitude consider more blades, slightly higher KV and as a last resort a steeper pitch.
@@ChrisRosser gotcha. I think I need to shift my perspective. I’m coming into this from a mindset of choosing the “best” prop for an existing setup in my circumstances. Perhaps I should consider whether that existing setup is appropriate to begin with.
Hi Chris- love the scientific approach- would be really great to see how theory stood up to practice by setting up a double blind trial with some experienced pilots - suspect it would be difficult to get sufficient numbers for a significant result though
Great content.
Thank you this helps tremendously!! Your'e video's are very educational I appreciate the knowledge!
So detailed and complete, I love it!
I was freestyling at 2700 kv 4s with 5042 props already though :p.
Hi Chris, what is the effect of pitch and efficency vs number of blades? I guess a lower pitch creates less turbulences which affect the next propblade and probably decrease less the effiency compared to a prop with higher pitch blade. I expect not a dramatic effect, but I think the question is interessting, if low pitch props are loosing less effiency with more propbaldes over high pitch props with more propblades.
Also your recommendations of Longrange props brings up a question: on 4"LR you see mosten low pitch props like 4024. The Reason is the amound of amps, LI-Ions can`t provide much amps, so there is also an electrical tradeoff of pitch vs amount of amps which can be delivered from a Li.Ion pack. So where is the sweetspot of pitch vs. amps?
Pitch and number of blades should be relatively independent of each other if that helps.
For LR cruising a higher pitch prop will give more efficiency but you need to use a throttle limit to control your peak amp draw. If you don't use a throttle limit you need to run low pitch to control amp draw (but you suffer with lower efficiency overall)
@@ChrisRosser Understood, but with high pitch I expect to be already close to the limits if LiIon packs.
Excellent work. Very informative video. Keep it up
Thanks, will do! It's really nice of you to leave a positive comment 😁
Another great presentation. I've been thinking about pitch vs inflow speed with airplane variable-pitch propellers in mind. Everything makes sense except the efficiency up to 8 degrees (or 16?) and how that applies to 5" long range propellers with pitches as low as 25. Should we be trying something around 30-35, or even higher? I have ran across people getting surprising efficiency out of very high pitched props.
Can't wait for the Glide analysis, and hoping You can get a Fouride in at some point.
The best efficiency should occur at the best lift to drag ratio of the prop which will depend on shape but is typically around 8 degrees (this is for a hover). Obviously inflow velocity affects the angle of attack so can get a little complicated. Once you start flying the drag of the quad and the inflow velocity due to your forward speed starts to matter. At high forward speeds a steeper pitch prop is probably going to give you more efficiency in g/W.
I was thinking about this more, do you know if the prop flex has any effect? These fpv props are quite flexible, I presume at a certain disk load the majority of the flex will have occurred and have little impact. I wonder if there is excessive flex at a certain low load threshold.
Hi Chris, this is reallly good.
There is only question regarding AOA. The first diagram showed maximum efficiency at typically 4 degrees and stall at 16 degrees. However later you mentioned that efficiency will be improved all the way up to 16 degrees . Probably I missed something there.
Nearly every time I try a new prop I think what a wonderful prop. Everything from a 3" pitch to a 4.9" pitch. I even like the 5.2" pitch but I don't use those because I get about half the flight time. I don't think I'm good enough yet to tell much difference between props.
Hopefully this video has helped you decide what prop to pick for how you like to fly! 😁
Again a really good video!
Hi,
I asked myself all the time how to think about this on my Cinewhoop. I just finished watching your new video about ducts, and I have a squirt V2 at home. Also I am just designing my own "megas-quirt", that can handle 3.5" (89mm) props, as my Squirt is barely holding itself in the air with a Hero 8 and a 1300mAh 4s lipo.
Now to my question:
How do you think that multiple blades change the therory. By that I mean the 6- or 8-bladed HQ props, or the much steeper Gemfan D76 or sth like this. My testing tells me, that two props that both are called to have a pitch of 3 aren't really comparable, doesnt matter whitch size (3", 5", ...).
In the cinewhoop-part also the diffrent blade-count makes everything even more uncompareable. I really have problems to compare a Gemfan D90 (3 bladed prop, pitch "3") to a HQ 89mmX8 (also pitch of "3") but they clearly are diffrent in their steppness-angle and will poth have very diffrent thrust.
toothpick-class: Gemfan for example has a 3018-2 prop (biblade) and a 3016-3 (triblade), I also cant tell in this case which prop I could expect to have more thrust. The issue is, that we often dont have real numbers to calculate with or alternatively have simulation-values or static-bench test from the manufacture himself (1st hand).
Sometimes I have the feeling, the manufacuters dont use the pitch-value to tell us how steep the balde is, rather to tell how much thrust they think the prop makes compared to their other props on the market. By adjusting the pitch value they use for marketing so they can put their props in somewhat of an order they make comparison for us pretty rough, and practically impossible to compare to other companies.
Did/Do you think/feel the same as I do, or do you understand my problem? If so, do you have any idea how we could interpret these values we get from the manufactures, or do anything about it other than just buying a ton of props just to find out that 99% arent the ones we where looking for?
Thank you so much for your videos, it is great to understand such topics in greater detail, love it, keep it up!
Comparing props is difficult because they are not fully specified by the manufacturers. Their performance is also very dependent on your AUW and flight style.
I would suggest trying a prop and then asking yourself what you want more of: thrust? smoothness? efficiency in hover? efficiency in fast forward flight.
Then use the info in the props video to move you in the right direction. E.g. more thrust = more blades or steeper pitch (but steeper pitch may be less smooth).
more smoothness = shallower pitch
It is not really possible in my view to pick the perfect prop just by looking on the web. But it is also not necessary to just buy every prop and try them all. You can take a more focused approach. I hope this helps.
This explains why I wasn't getting the top end performance for the Ethix peanut butter jelly props. I thought it was the weight, but it's likely my lower KV motors for 4S?
The moral of the story is that 5043 props are all that you ever need as it seems to strike the ideal balance.
I guess the only thing I still feel curious about; is props based around air density... I.E. how would a high pitch props performance be affected by flying at a mountaintop where air is thin? Also another incredible video mate. Doing the FPV God's work!
At higher altitude the air is thinner so you will get less thrust. I think the best way to combat that without affecting any other parameters would be to use a prop with a longer chord or additional blades. If you change pitch you will affect the stall performance but additional pitch could be another way to get back some of the thrust you're losing due to the thinner air.
I would really appreciate a video relating to altitude. I fly freestyle and long range between 8,000 and 13,000' above sea level. I've enjoyed experimenting, but I also enjoy your videos, science, and experience
thanks Chris, very informative content
The high pitch for lr was a big ah ha momemnt for me. Thanks man.
No worries, don't forget that throttle limit otherwise you might be tempted to use all that performance and kill your flight times.
Very useful, thanks!
You're welcome!
Awesome information Sir
How might the number of blades on a prop affect the overall vibration characteristics of a multicopter? The presence of load changes on the arms from the downwash of each prop blade makes me think that a certain number of blades might perform better or worse for a given frame design.
I can only imagine a prop hitting 1.0 Mach and hearing a bang as a trail of fire burning on a road is all that is left as the drone travels back to the future.
What if you had a 5” quad running 2806.5 motors but usied 5” 6 blade propellers? Would you get the trust performance of a 7” quad with tri-blades? Because the surface are of prop should actually be greater on the 5” hex blade. So would you be able to go with a bigger motor on a smaller quad and get similar performance? Better? Worse?
Small propellers are less efficient than big propellers. So you get less thrust for the same power = shorter flight times. But if you don't care about efficiency then you can get more thrust with more blades and a bigger motor.
Hey Chris - I know this might be semantic but I think it is an important distinction when talking about the dynamics of our kwads. I thought that the prop generates lift and the portion of that lift that provides forward motion is thrust? So wouldn't the specific airfoil and angle of incidence change the how much thrust is generated? I thought, Angle of attack is generally in reference to the prop where angle of incidence is relative to the craft's attitude of a specific axis. Additionally, I think the use of certain generalizations is a slippery slope. Also I have a question regarding the V(inflow), I don't think it always has to be axially aligned - but the angle should be a known value for calculation.
Hi Zach, in the video thrust just means the force generated by the prop in the axial direction. The lift generated by each prop blade creates this thrust.
There are certainly some simplifications in the analysis to allow general conclusions to be drawn. I think that it is important to make content that is easy to understand so that everyone can benefit from it.
You are right that it is important to distinguish between AOA of the blade and AOI of the incoming air stream. In flight the incoming air will rarely be axially aligned to the prop (more on that in my upcoming video on ducts) but I think it is a valid simplification for the analysis in the video which primarily considers hovering where the the flow will be close to axial.
Thanks for your comment I hope this answer was useful 😁
(I really wish the x and y axis where labeled in the 'prop tip speed efficiency' graph😬) Great content Chris! Thank you for the educational material.
give us a cinewhoop already!! for a batteryless gopro >D ... also check the astrorc carbon fly 25 frame ,, diagonal frame.. keep the videos coming!!! and what controller should we use for maximum wall concrete penetration and dont failsafe and available >D
Great video. Question: regarding heavy-lift applications, would I want to increase or decrease the AoA of my props? My intuition is that I would need a lower pitch prop, like a lower gear in my car for pulling a heavy load. Is that right and if not, what am I missing?
Another interesting thing to consider would be if "Floppy proppies" have an advantage in response time compared to their fixed counterparts. And if so is it quantifiable?
I have a question about prop tip speed. So I used a calculator, and I saw someone had 5 inch props spinning at 65,000 RPM (max power) so I wondered what would be the tip speed and got 966.8 mph which is supersonic yet the quad was just flying normally even at full power, although it had a very loud “buzzsaw” kinda sound. I feel like there wouldn’t be supersonic airflow that would cause lots of drag on these kinds of props as planes with supersonic propellers like the XF-84 have straight trapezoidal blades, which still wasn’t so efficient. These drone props look like they’d totally handle supersonic airflow with little drag bc of how they curve towards the tip. Just wonder if what I calculated is true, as I would love to find out if/how it is possible to make a race quad with supersonic props as well…I want lots of noise and (maybe) speed lmfao. More noise for sure
In terms of emptying the reservoir of vibration in the frame it seems like the battery pad would have the largest influence considering its holding an isolated mass that's about 1/3 the total quad weight. In my case the under mounted battery has a sticky pad connected directly to a carbon surface that also mounts to the flight controller. I wonder if rubberized pads have a high Spring rate that could create harmonic frequencies... Versus gel or soft foam.
This question puzzled me for quite a while as well. But if you review some of my frame resonance analysis videos you can see that the relative movement of the battery compared to the frame is very little for these high frequency vibrations. I think that's why it doesn't do as much as the grease on the arms. The arms really do the vast majority of the moving for the high frequency modes of vibration.
I agree with you, the arm displacement is the highest and dampening that movement is hard to accomplish in a rigid body. Some viscous movement is helpful to reduce vibration. How was your battery mass coupled to the frame in the simulation? Is it a soft spring boundary? I'd like to understand the result of decoupling the battery mass from the frame with the commonly used rubber layer. Could the lithium polymer dampen the vibration better if it is pressed hard up against the carbon without a soft layer?
@@nateteator3901 The battery is sitting on top of a rubber battery pad 2mm thick in the simulation. So there is definitely flexibility and movement but not as much as I expected. I don't know whether a battery pad helps or hurts damping. I would imagine a thinner pad would have less damping but I'm not certain.
Very informative videos.
Glad you think so, thanks for your comment!
Would you consider, the 5inch vs 5.1inch props, the extra .1 inch diameter is being done to increase the lift/efficiency that is lost by the lower pitch in a freestyle setting? Also, would you consider a $1 slot on your patreon?
The extra .1 inch diameter provides a bit of extra thrust without increasing the risk of stalling the blade. They help a lot for carrying the extra weight of the newer non-session go pros. IMO I think the new hero 8 and 9 probably warrant 5.5in or 6in props!
@@ChrisRosser Thanks for all the great content and insight. Really enjoying learning the science behind all what we do.
very well done video. i like the maths and thinking.... bravo!!!!
Thank you! Cheers!
Just bought some Gemfan 5051 tri blades for my freestyle drone. They were on sale, I'm new, and I crash a lot 🙃 4s 2450kv 500g quad. I guess I'll set a throttle limit and see how they do!
Hey @chris. Can you give an insight about number of blades. Should i go for 4 blade or 3 blade for long range
Okay I'm late to the game but everyone says you're the man to go to for facts. And I can't really find any good factual information on whether if the stock props or the prop adapters and a different type of aftermarket prop is better on the DJI fpv.?? It just seems like to me if you add the adapters and a lighter smaller prop than it really is being counterproductive and adding a smaller pop to spin off faster... Any advice would be greatly helpful
I have a cinebot 30 any suggestions for different props mostly recreational flying and I love the science behind what you do koodos to you
This is very very interesting and confirms and extends much of my own investigations. I have a question: how does the inflow velocity calculation change for fixed wing? Obviously the vin from the airspeed but do you need any additional factor to account for the inwash from the prop of can I just plug in airspeed in m/s?
I think you should be able to calculate inflow velocity using a momentum balance taking into account that the initial airspeed is not 0 as it is for a quad in hover.
Hello, thank you for the great video! My Question is: What about tiny whoops (e.g. Moblite 7 HDZero 1S). Is there a way to make it more efficient by changing the Gemfan 1610 2-Blatt Propeller?
Its really helping
awesome video. I just recently went from a 5135 that came with my nazgul 5 and went to a 5043 and I was noticing I was having trouble getting it to float over things while trying to split s over them andbai could hear it grabbing more in the maneuver this video really helped me understand why it's doing that. What do you think of the really low pitch prop that it came with. When I look them up it says the pitch is 3.5
I have a scenario for you. You have a 7" kwad that weights in at around 1kg AUW with 2806.5 1300kv RUNNING A 2200MAH 6S battery. You want to do aggressive long-range flying. Your going to be flying up a mountain that starts at 7500' elevation and tops at around 11k'. What size prop would you recommend to give good quick thrust but also efficiency for distances like 6 mile round trip. I have tried a few different types and settled on one that I really love but curios if there is one you might recommend that I haven't tried yet.
I like light pitch props for good propwash handling. I would also choose a prop with a relatively long chord to maximise thrust at high altitude. If you aren't going to ever get into a propwash situation a steeper pitch prop might give more efficiency at speed but you'd want to use a throttle limit to prevent sucking down your battery!
@@ChrisRosser I started out using biblades but didnt like how much throttle I needed to give it while try to pull out of a long dive. So I went to 7x3.5x3 then 7x4x3 and have ultimately landed on 7056 triblades. The 7056 seem to help give more low end thrust to compensate for the low kv and thin air. The big motors turn them really good as well. I tuned out the propwash issues early on while using the 7x3.5x3 props and havent needed to change that since so I dont think the props stall at all. Honestly this build would probably make you start twitching as it doesnt follow any of your advise I have seen in any of your videos so far. Thanks for your thoughts.
Great info. Thank you!
Great content! It got me thinking though, what if one would (theoretically) construct a prop that utilizes centrifugal force to alter the pitch slightly? Think of how a CVT system works with weights and ramps/rollers.. Would it be possible? Would there be benefits to reap from doing this? And yeah, it would likely not be suitable for a 5" prop for rigidity and durability reasons.. Maybe this is already a thing, I haven't read anything on the subject, but this video just had me thinking about how it could be done.
This series of videos is amazing. I have some questions, do these same pitch recommendations apply to all propeller diameters?, for example 3-4 in; and what would be the best propeller for a cinewhoop to get the maximum flight time?
whats ideal to optimize in-ground effect hover and out-of-ground effect hover?
Chris, these slides are available somewhere so we could quickly refer to your graphs when needed?
A blog or server perhaps?
I've put the slides from my last few videos here: drive.google.com/drive/folders/1md9Vc2l-PnY5jVDQSH7HXB_FSh5z8dr_?usp=sharing
If you download them you can watch the embedded videos as well!
I have a question about relationship between prop pitch and oscilations.
I was using ethix s3(5031) with lots of oscilations. tried to manage it by tuning the PID but failed.
One day I had a chance to use ethix s5(5040), all of the oscilations were removed and feel like propwash was even better.
Everything was in same condition.
BTW I’m flying my quad with these specs.
6s, 1750kv, rpm filter, lowest filter slide, default PID on BF.
You may have had an unfortunate case of prop resonant frequency matching frame resonant frequency.
@@ChrisRosser thanks! well….after this happen, I thought s3 might be too flexy on 6s quads. oscilation is always big issue to me, so I am always serching for a best prop.
Nice! I graduated as a lawyer, am building my first 4inch semi longrange sub 250gr. 4s quad, and after checking motor load charts, making some calculations I've diside to get 1507 2680kv motors with biblades 4024 on a throttle limited around 20% for LR, and 4023 triblades for freestyle.. (haven't seen less pitch im a triblades 4 inch props yet). Hope I'll get parts of it soon to complete, film, test and finaly have enough footage to start my channel.
Ty for your sience, I'll be waiting for your frame, and hope we'll get a affordable shipping cost for it (Russian Pilot in the house 😉)
I'm hopeful that my frame will be globally available at a reasonable price! Good luck with your channel.
I think some useful oversimplification would be possible just in comparing chord profile, and what the relative pitch across that profile is going form the hub to tip. It's impressive that all of the most recent props have converged on roughly the same chord profile (with varying amounts of leading edge sweep) as a trade between durability and in-air performance, and the 'best' of the latest units all share reduced chord that helps lower rotational moment without results in a frail edge of the prop, and I think that's why the propwash response is so good (compared to back in the day when we were flying bullnose props).
@Chris Rosser - the rule of thumb I've been using to calculate maximum tip tolerable RPM has been 38k RPM, in nominal cases, for 5". Thanks for that WarpDriveProps calculator tool, since I feel like doing the more simplistic calculations lose accuracy by the time I'm at 7", as I keep finding myself just over the limit on builds I have calculated to be marginal but within bounds (the good news being that throttle limits are easy to adjust downward).
I would add to this that I think manufacturers are designing props that don't require throttle expo or throttle limits because no-one is using these (except to run 2400KV motors on 6S). They are realising they need to reduce thrust to give pilots more control. If everyone tuned their feel using throttle expo I think we would see more props that are designed to get the most from our motors.
Would be great o see real life examples with known props and quads during a test? Great video.
Thanks for the support and the great suggestion. 😁
@@ChrisRosser
Thank you for the content! Next tuning a 7”? :-)
Why drones with x8 motors have props obtained in a different direction each arm?
The hyperlight is not bobs frame so I hope your doing the fpvcycle glide
I'm working with Bob on the video so it'll be the FPV cycle glide. Because of the similarities in geometry the results should be applicable to both frames? They certainly look very similar.
@@ChrisRosser They were up until about 8 months ago when Kabab upgraded the bottom arm brace and the bottom main plate to a much more solid design with fewer cutouts, the fpvcycle glide is now much beefier structural wise. As far as I know the hyperlite glide still uses the old design, though they still look very similar at the first glance.
@@shtumpa1 Ok, I'll make it clear that the analysis is for the FPVCycle Glide but that the Hyperlite Glide is similar. I would like people who search for the Hyperlite Glide to find the video because it will still be relevant for them.