Very interesting. The heavier 7" quad needs more energy to stay airborne, so I think you just proved that disk loading is not the only factor involved here. A 7" quad is typically not flown with the same battery as a 4" quad. If you're aiming for the longest flight time you pick a battery that is optimal for the size of quad you're flying. I put a 6S2P VTC6 pack on my 7" and it flew for 22:40.
i also have 6s2p packs on my 7" but theres no way his motors or frame can handle that weight... a 5s1p or 6s1p would probably be about right for this rig im guessin and just scale the throttle to not overamp the pack
Yes, that's basically what I was testing. Does it make sense to further decrease the disc load or does the extra weight cancel out all the benefits. Of course, I could put a 2P pack on the 7" but then I would end up with basically a normal 7" disc load again
The disc loading is very important. Problem here is that the motors Dave chose are too hungry. The only thing you should not spare weight on an endurance quad is the motors. All my 7" LR setups are based on minimum 2307 motors. Best results for me are using BH 2507 1850kv motors and 4S2P LG MJ1 packs. These motors are far from light but I can cover 25km in 24 minutes of flight without worrying too much about calm weather.
Two things: So on my Sub 250g 7” with the 7038 props, I could get over 9m with a 4s 650mah battery, when I switch to the 7042 props the same battery only gave me around 8m. Sound, your prop area is greater, creating more wind resistance. Don’t match the speed of the two aircraft, match the attack angle and then compare distance and flight time of each aircraft.
was going to comment the exact same thing. Increased speed, from my understanding, is a major factor to going with larger props for long range, so a similar speed test is handicapping the larger prop. Im thinking of how quads will fly for longer when moving forward vs. just hovering. Eitherway thank you loads for these experimentations. MiniLongRange is definitely next on the building block once I get back to quads. I think it was mentioned on your instagram but those 2305 superleggera motors might be a good fit?
So I put an emax 2306 1600kv on an AUW 500g 7” with a 4s 1300mah battery. It flys bobble free and is very efficient, about 12m. I believe GepRC put a similar 2306 motor on their 7” as well, but it’s a much heavier quad. I think each weight increment 250g, 350g, 500g, etc... will have an optimum motor size for a 7” prop.
Yes, I agree. Dave should measure distance travelled to 3.3V and compare those. I always measure the efficiency of my fixed wing aircraft in mAH/km, so perhaps something like that instead.
@@immortalsofar7977 you should measure the efficiency in wh/km since mah only won't give enough info. Obviously 50mah/km on 6s is way different than 50mah/km on 3s
Removing the wobble out of the system is VERY important. As long as there is wobble the motors are constantly speeding up and slowing down to fix the wobble the flight controller is experiencing. This will DRAMATICALY reduce flight time. I would first try tuning, but if not stiffen up the frame. Until you do that you won't get meaningful results. It was fun to watch the attempt though. Good effort. Its cool you're doing this.
As an aero engineer for a rotorcraft company this was both amazing and frustrating to watch! I'm not going to go into all the details but suffice it to say that you're on the right track, keep exploring! Incredible work, and I love my flywoo explorer LR. It's very cool to be able to see how rotorcraft theory is playing out for you in reality with off the shelf parts. Rotorcraft are complex in their design, and playing with different parameters can produce very different results... often due to extremely nuanced reasons. Keep going!
Thanks! Yes indeed reality is always messy. At least for now FPV development is trial an error to a large degree. Probably it will also stay that way since the parts are cheap and quickly pit together compared to running simulations with an acceptable degree of accuracy
@@DaveCFPV but please not from flywoo. Very disappointed by them. And german retailers would be fine, too? Or you order more and sell them to me directly 😂🤪might be possible we are from the same area in Germany
@@nuhbiwan It won't be Flywoo. But honestly not because I don't like Flywoo but because I wanted to start a new brand specifically for LR. Sure, they messed-up the Explorer release big time but probably anybody else would have too. Nobody expected that level of hype and demand.
Also food for thought... I learned years ago that the very ends of the blade is where the most drag not being converted to lift occurs. Its why some of the props now have the little spikes on the trailing edge out at the end. With bigger props this effect is exaggerated because the tips are moving faster all else being the same. Using ducted props is the most effective way to reduce the tip drag turbulence, but has the undesired effect of causing a drone to auto level due to the way ducts work when moving in a direction other then up (in the case of drones). Ducted propellers are the most efficient way to produce lift. Its why all modern jets use ducted engines. I'm thinking maybe a very thin duct just to break up the drag might work? Ducts are a whole rabbit hole. The guy on RCmodel Review explained them pretty well if I remember right. Also Also wind resistance/drag increases exponentially. I don't think the extra wind resistance on the body of the the 7" vs 5' would make much difference at 30mph. Like I said, ... Food for thought.
Ducted fans are theoritically have better efficiency than non-ducted fans, BUT in practice, it's very very hard to make because the low tolerance of the distance between the prop tips and the duct to prevent vortex generation, also the duct's intake and exhaust itself are very hard to design to get the best efficiency. This is why many improperly designed EDFs in the market has lower efficiency than simple open props.
Im researching and planning to build a long range quad as well and from my research, it was found that the overall current/amp draw to hover or light cruising is the best indicator on the overall system efficiency. Because amp hour usage divide by battery capacity will nett us the estimate flight duration. The disc loading is not really the main factor.
Dave_C, great video and set of tests. Disc load and drag, are major factors. I’d like to see more testing on where the battery sweet spot falls. We can fly micro long range 2s, 3s, 4s,5s, even 6s. In each case, there are trade-offs between power delivered by each pack and weight. I typically fly 3s. For motors, we’re looking for the most thrust, able to exceed the total overall weight and provide power to fly in some wind conditions etc. so for motors, there is a sweet spot also of KV, weight & thrust. I have one build I fly with 6 inch, 3S 18650 pack, on Lumenier 1806 2300kv motors. I typically get 9 to over 20 minutes without carrying a GoPro.
Hey Dave, interesting video. Do you think the tune could substantially decrease efficiency on the 7" quad? I have not been able to tune a 7" to perform decently.
Yes the tune can change the efficiency of a 7 inch dramatically on my 7 inch with a more control centered tune from UAV tech it drew almost double the current compared to the defaults
Tuning definitely matters. People literally fry motors and ESCs with too-ambitious tunes. Running at power draws amps, but hard acceleration of the props themselves as demanded by a tight tune draws even more. A tune with high frequency oscillations will be even worse by spending longer in that hard acceleration zone. So an ultra-tight tune will draw more current than a looser, easier tune, and an over-ambitious or troubled tight tune will draw even more.
There's a publication Modeling Flight - NASA that is a 6 MB PDF file on line. Flight efficiency does not scale at a linear rate. A rough estimate based on disc area would be energy consumed versus time. So if you scale up the disc area you would want to see how long it would take to consume the same amount of Watts. Because the discharge rate curve of the batteries are important you would want to use a battery that has proportionally higher weight and amp hours as disc area increases. You're dealing with the issue of cross-sectional surface area goes up by the square as the volume and possibly mass goes up by the cube. I like the smaller quads, they have lower inertia and are less likely to self-destruct if they hit something.
I have 4 of your frames I am working with. My best flying, longest flying is the 4" frame but with 5" arms. I don't have the arm braces installed. The 4" with 4" arms flys great but it gets about 3 minutes less flight time. The 5" I have like the one you are showing with the bicycle connector flys great but does not get the flight time of the 4" with 5" arms even though the weights are within 10 grams of one another. IMHO I think the biggest difference are the props. GemFan Hurricane props fly better and longer with all of mine than similar HP or other props I have tried. I think the center of gravity is enough different on these to have an affect as well as the relationship of the motors in the design.
What five inch arms are you using with the 4-in frame? Is that the 4-in Explorer frame you're talking about? Version one or two? I have version 1 and would like to experiment with 5 inch arms after reading your post. Thanks!
Those MB2204 are pretty neat for builds like this 7”. I’m surprised I had never seen them before. Apparently there was also a 2450kv variant that would be great for a 5” on 3-4S but those are next to impossible to find.
It's obvious, the elephant in the room which you omitted from your calculations was...Drag. Those big 7 inch discs whilst giving bags of lift, also creat a lot of drag and need more power to drive them. Specifically, frontal area with the quad tilted at an angle to achieve 40kph. The bigger disc area = bigger drag...🤔🤔😀🇬🇧🇬🇧🇬🇧🇬🇧🇬🇧
Actually there wouldn’t be an increase in drag for the props. When you think about it, then you’ll see, that the propellers actually don’t create any drag because they spin through the air like a screw...
The drag from the props is reduced with a lower disc loading in fact as the props can spin slower to produce enough lift and because the drag is proportional to the square of the velocity a prop spinning at half the speed gives a quarter of the drag This is just for the actual prop drag not the aerodynamics of the quad itself
@@ferdifant_fpv686 Props do generate drag, but it's cancelled out by the thrust they generate. Thing that actually increases the drag are the longer arms required to fit the props
Thanks Dave for all your hard work to help us all get in the air. One metric it might be interesting to fix is mAh to disk loading? Probably set that from the 4" and scale the appropriate battery for the 7". Having 3000 mAh battery on the 4" then a 5250 mAh on the 7" would be about the mark for the same mAh per cm2. It is a more even point to make your testing from I believe. Thanks again for everything Dave I would be stuffed without you JB and all the others.
"1 year later..." lol Definitely the high pitch of 7"prop induces a lot of drag which ate the expected efficiency from the larger diameter prop. Another thing: ~120g lift per each 7in prop is very low and its rpm is very low as well. Not sure if this is the case but, at very low rpm, the efficiency is horrible (just imagine, e.g. 30 rpm producing 0 g thrust at 1A, efficiency = 0) and increases sharply as rpm increases reaching a peak followed by a gradual decrease at high rpms. It would be cool to see a bench test comparing W/g thrust per each motor in both setups.
A doubt: at 08:30 you said that a 7" have 993 cm2 prop area. Where is this number coming from? It's the prop specification or is there a calculation that you made? Thank you!
I liked when the 7-10" quads were norm with naze32 and afroflight etc for the noise factor. Hopefully people will adopt endurance racing say the FPV version of motorcross and last guy flying wins with laps done. It's that in remote areas or indoor racing only in near future LOL!
...you would also need to fine-tune the drive-train. Check steeper and shallower pitch. Every motor has it's sweet spot of RPM vs torque - you just need to find the right prop to get it there... Keep going, man! :)
I have the 5 and 6 inch rekon quads. It would be very nice if you would also provide a 7inch version of the quad, with a larger battery carrying capability for longer long-range flights.
load up the 7" with enough battery to get similar disc loading of the 4". I think that would be a more "apples to apples" comparison. People that are into long range don't use a larger quad to carry the same small battery - the point of a larger quad for long range is to carry the weight of more battery.
You should look at the efficiency curve of brushless motors, even with the greater weight of a bigger motor, since you'd be at a much lower portion of it's torque potential, you should be able to get a very significant efficiency boost. I'd be curious to see you go in the complete opposite direction and get a 2806ish size motor then test the fight time. Should also significantly help with the feel of the quad.
I agree with a smaller stator the stator gets saturated with energy much sooner than a larger stator, therefore even a larger stator can be more efficient because it does not have to work as hard it's not near its maximum potential which is when the increase in amps causes a decrease in efficiency losses through heat etc.
I think the idea behind the lightweight design of this seven inch is to directly compare the seven inch to a four inch with the same battery as you can get a seven inch to carry a good 600 or so grams of battery which would blow a microlongrange out of the water with flight time Because the 4 inch is at the limit of its carrying capacity with that battery whereas the seven inch would be perfectly capable of double or even triple the battery size And he was mainly testing the efficiency of having a low disc loading But if he where to load up the seven inch to the same disc loading I think we all know that it would win
I am thinking if you could spin a 8" props on 7" frame and reduce its motor kv would give a longer flight time with the same battery capacity or may be a much longer flight time with a higher battery capacity.
Dave those 7inch bi-blade props look very high pitch? I know there are not many out there to choose in 7inch class, you should get Gemfan to make some 7035 bi-blade?
Hi, Nice vid! The main benefit to go larger in propsize is the cruise speed for me. A couple of years ago I build a 3"ultralight with 2s 18650 for long range. I managed to get 25 minutes of flight but the biggest thing I found out that the cruise speed is quite low, and is you go faster then you lose efficiency. My 7" goes for 20+minutes on one 4s lion pack but at a cruise speed of about 70kmh. And got long range I find the speed also very important. What would be interesting to test them at there own cruise speed and look at the distance they flown. And what also would be interesting is to do the same test only then both at 70kmh. Ps, a bad tune also costs a lot of energy.
Yes totally agree. at 70 kmh the 4" will probably start to get way less efficient in comparison. Indeed the PIDs are pretty high to make it stop wobbling like crazy. Pretty sure that costs efficiency. 2204 might be too small after all...
@@DaveCFPV I have the tbs endurance motors on one of my 7" and these are not big, 2306. Dry weight of the quad is also not licht with 451 dry without GoPro. But it's flying super smooth. Also with a big battery. But 2204 is a lot smaller then 2306 of course. I'm curious to see where this project is going!
Glad you are putting yourself out there with your experiments. It is ok to be wrong. You can’t learn from always being right. Like the 7inch design. Maybe 5” props?
You should try the mavic motors and props. With the amount of money dji invests in there drones they are probably very efficient. Banggood has a frame that uses the mavic motors mounting holes.
I saw that there's an 8in frame available on AlieExpress and BG called the "Andy HD8" that uses the motors for the Mavic. I always wondered what could be done with the motors from a mavic mini or a Spark on a light carbon fiber frame.
@@yannickg6904 I think the biggest factor is the way the props are mounted, each blade can lead and lag individually and that helps with efficiency, I have ordered some Mavic Mini / Mini 2 props to experiment.
great video, idea.... motor amp draw at same cruising speed would be higher on the 2204 than the 1404 and at both running 4s. What if you ran the 7" on 5s or 6s, bring disc load closer, and with a higher cell count you can pull fewer amps to get the same cruising speed?
Awesome content Dave!, I really love this deep dive into ultralight LR platforms! Anyway I don't think pure flight time is really a useful data for us. I mean what I care about is "how long (in term of distance, not time!) I can fly". So cruising speed is actually a thing! 18 minutes on the 4'' cruising at about 40 km/h means a12 km trip while 10 minutes on the 7'', cruising (I'm kind of guessing) at 70 km/h means... again roughly 12 km! While I loved my 4'' micro LR, I recently switched to 5'' mini LR because I can simply fly the same distance... but faster!
Thanks! They both cruised at exactly 40 km/h so I guessing that the 7" will do less than 10min at 70 km/h. But sure, picking a pretty low speed might have been an advantage for the 4". If the test was done at 60, 70 or 80 km/h the 4" could start to get much more inefficient since it getting close to its top speed.
Have you ever thought of the concept of having a small airfoil, like the tail of a DC-9, attached to the top of the quad which would generate lift at cruise speeds thereby allowing for much reduced power settings in cruise and longer flight times? The angle of attack of the wing would have to be optimized for a certain speed so as not to create more drag than lift. Anyway just a thought.
I played around with quad / wing hybrids but mostly it was extremely difficult to make them fly well. Seems like the flight controller really has issues handling them
Dave you have 1450kV motors on the 7" and 2750kV motors on the 4", what would happen if the 7" motors were closer in kV to those on the 4"? In the tested setup the 7" has 3x the prop area but at the same current draw it is probably turning at less than half the speed of the 4", with the additional drag of a larger prop to overcome. Do the DJI goggles allow reading the amp draw during flight.
2750kV is very high for a 7" on 4S. Probably too high for the motors and Li-Ion to handle. Yes sure I can read the amp draw in the googles. Although from my experience it's usually very unreliable unless properly calibrated.
Have a question. New to quads. Have a hubsan h501ss don't count that. I do fly long range fixed wing fpv however. Would like to get a long range quad and wondering what to get. All my batteries are 4s lipo and liions so would like to stick with those. Don't care about freestyle or racing or any of that, just long range cruising. What do you think would be a good place to start?
Drag is higher on the bigger quad and there’s the prop+motor efficiency. Most 7” start to wobble because of the aerodynamics, the bigger prop starts to inhibit fixed wing properties and the quad starts to feel the wind like a flying wing does.
Have you thought about stacking the AIO and Vista and mounting the battery behind it? You could ditch the top plate and standoffs to save some weight, and basically get a top mounted unibody.
Hi , In mho regardless of prop loading it costs a given amount of power to lift a given weight . decreasing numerical disc loading does not compensate for the extra power needed to lift a heavier craft. and spin a heavier prop, If you had scaled the battery up so it matched the mah per gram of the 4 inch , then your results would have been closer to what you expected , yes because your actual disc loading on the 7 would still be less than the 4. Lifting heavier things costs more power .
Yes absolutely. I would have expected the decreased disc load to at least compensate for the extra weight but it seems it wasn't even close. Plus other factors like drag and the tune ..
Having a Flywoo explorer and built one of your mini long range frames (both excellent) I think you hit the sweet spot at 5 inch for li-ion and 4 inch for light weight li-po flying. The 7" might be a worthy experiment to test capability but less necessary (plus it's less of a looker!).
by using the same battery the 4" had a much higher ratio of battery power to weight, there seems to be an efficiency curve here where not only is the right ratio of disk load to total mass important but the right ratio of battery weight to total mass.
Here are my thoughts. You concentrated a lot on g/cm², but as you mentioned earlier on, we need to look at g/W too. So I think you're right at the end of the video that you need to further test motor and propeller combinations. A couple of ways you could test this against the 4" quad. 1) The in-situ method. Measure the wattage consumption while hovering until the battery runs down to your cut off voltage. BF black box should be useful here. This is subject to a lot more random errors, but would be more 'real world'. 2) The bench method. Get a table top thrust meter, measure the power to thrust relationship of the 4" prop and motor, then find the best motor and 7" prop combination that matches.
I see Rekon7 coming soon.. real curious on motors. cause i was thinking when i was going to build myself 2303.5 with gemfan new lightweight LR 7035.. arm look so long and skinny.. surprised no braces connecting left and right motors along with front and back
The larger quad will have much more drag maybe more then double. also square/flat surfaces are not your friend, round/curved leg sections would be better. but why not just use the same 4" body/base with long 7" hollow round legs. Or/and try larger dia motors with lower volt/rpm
Fantastic video! Thanks! Next, can you do a range test? For example, if there is a particular mountain I want surf down, how close must I drive my car to be close enough to fly my drone to the top of the mountain? If the 7" has a higher cruising speed than the 4", then perhaps less efficiency won't matter so much if I can fly to the mountain sooner. Much appreciation.
On all of these setups your range should be limited more by the video signal than anything else. The 4" can cover over 20km round trip on those batteries :-)
While the 7 inch has less disc loading, if you give it the same battery you still have more weight to carry. So what if you had the same ratio of battery weight to all up weight?
Hi~ Let me ask you a question. It's a 3 inch cine hoop. In the video, there are videos of making a pack with 4 lithium-ion 18650 batteries and flying it with an FPV long range. With excitement, I ordered batteries and made a pack. LGDBHG21865 3000mA. The problem is... When I hovered, the yaw tick symptom reappeared after it came up, and, after a few seconds, the low-voltage buzzer sounded and the aircraft sank. If I open it again, it opens again,,,,, repeat... So, I changed the low voltage warning in Beta Flight to 2.7V, and when I turned it on, there was no sound. If I take a break for a while, it will float again. But it sinks again... The battery is hot, and the voltage is 3.8V... TT I bought 40 tablets... but I can't use them all? How do people use? Batteries were also made by buying anything. Is my FC the problem? Or is there a special setting for Li-ion? FC is IFlight SucceX Mini F4 V3 Stack, and the manual says 2~6 Lipol. Do I have to use only Lipol? Can I change FC? Why is this happening? It's a waste of money/work time. I'm serious~~ Please advise.~~ TT
What’s currently the pitch of the 7” prop? I guess you should have a very low pitch with a maybe a slightly lower stator but bigger diameter. Maybe you can divide the pitch to disk area and use that factor to divide that with the motor specs and get some factor out of there what you maybe can get some conclusions out of and optimize
Wouldn’t the 7” cover more ground than the 4”? If you were more concerned with a distance I think the 7” would still win if we are actually doing long range. Maybe instead of using a 7” with these motors, I wonder if changing the prop to 5.5”-6.5”? Looking for the efficiency/ distance covered sweet spot.
Hi Dave the TBS pizza box frame will be around 36g cut from Rohacell.com 1mm Carbon skins with polymethacrylimide plastic foam core, would love to see your experiment with this stuff.
Can CNC made easy cut the 7 inch arms? Getting ready to order another 5inch mini LR . Awesome research by the way. Thank you for all the hard work you do.
could be absolutely right. 6" has also been my favourite on more classic setups. I think the next thing I will try is just putting some 6" props on it.
@@DaveCFPV So many new props and motor sizes are coming out, it's hard to keep up. I spotted the SPCmaker G2204, but I'm unsure of the quality. The 4in LR is still a very hard design to beat.
You should try the 7" with a 21700 4S1P with 4100mah Li-Ion pack (Sony | Murata VTC6A 21700 4100mAh). Right now you are decreasing the discload but increasing the AUW with a unchanged capacity of battery, but I think with an increase of AUW you also need to increase the capacity of the battery, so 360gr on 3000mAh or with the 21700 batteries 580gr (I added 100gr for the heavier cells) on 4100mAh. your discload is still considerably less while the 21700 battery also gives you an increase in amp draw. I would also run a test with 18650 packs in 4S2P and 6S1P configuration.
@Dave_C FPV , I was thinking if the bad tune on the 7" would use up the battery... seems logical that if it's wobbly it will have to correct more during each PID loop, thus taking up more unnecessary battery power. But since the results were massively different, other stuff like the props you mentioned is also a good idea. Love this channel, keep it up !. Happy new year !
Think so too. The results were so clear there must be several things (possibly tune, drag, wind, weight, props, more battery sag...) going against the 7" flight time. Thank you! Happy new year!
The 7 inch had additional carbon fibre supports on the arms, while you flew the explorer without them. Air resistance is no joke. If the supports are necessary for the stability of the quad, then maybe the disc load theory simply needs materials science to catch up before it can be used in quads of this size. Perhaps folded aluminium would work
Maybe reducing the discload by using the same prop/motor combo like on the 4inch and choose a hexa/octacopter frame would be more comparable. The "right" motor/prop combo seems to be crucial in terms of amp draw.
I need to do a faster flight, but went 70 min with a lightweight rig based off of the Black Opal 6". Battery pack was a 3S2P 3500mAh Li-Ion. Arducopter was set for ~13kts running a circular do jump pattern. Non-HD rig, super light 215g before the Li-Ion(290g). I think if I increased my speed slightly, it might be more efficient.
Hello Dave quick question have the flywoo exorer but I bought it without caddy Vista and I wanted to build a analog version. Witch I did I added my camera and a vtx but I need help with beta flight and making it fly any help?
My guess is, that the power to weight ratio of the batteries is less efficient on the 7" quad. You should use a way bigger battery and see how that works.
The key to achieve maximum flight times is to decrease dead weight as much as poss and increase the weight of battery in the same way, given that you use a battery with a maximum power density available on the market.
Definitely need to factor in mah per gram of auw and if you want to directly compare efficiency removing this needs to be part of the equation. As the mah per gram of auw should be equivalent to try to directly compare efficiency
You should scale up the size of the battery on the 7inch. Also for the Explorer LR 4inch why didn't you just use a smaller and lighter 3s Li-ion paired with just a little higher kv motors seems like that would have been a more efficient setup and better battery to quad ratio? I know you did the testing on the 3s Li-ion. What about 5s Li-ion for 7inch with low pitch "yet to be created" Gemfan 7035 bi-blade and the correct motor you eventually find , I know you will!
I intentionally used the same pack because I'm interested in what works best with those exact 18650 packs. It wasn't totally obvious that a slightly overloaded 4" is still more efficient than a very light 7" with very low load
LOVE that someone is breaking out the graphs. On the flight testing, should you be using the same battery though? Id expect you'd want that scaled up proportionally to the weight no? Another variable: forward surface area -- the 7" is going to have a much larger silhouette. On a different note, Dave your frame layouts are elegant AF. Like they're aesthetic candy -- nice work dude.
Thanks, this was exactly the video I was looking for. Did you measure the resting voltage afterwards? Since the 7 probably draws a bit more current the LiIon would drop voltage harder. Anyhow - in my case I'd value the total trip distance before flight time, so I'm guessing the 7" would win.
Dave, Can you compare them down to a specific voltage? Because no matter what the 7in is most likely drawing more amperage thus making the battery(especially li-ion) sag slightly more but I really don't know.(I know the cold hand thing my thumbs were gonna fall off the other day as I pitched the nose of the quad forward to get home asap) I've been doing these exact same comparisons between my Explorer LR 4in.(146g analog vtx weight) and my Tomoquads Katana V2 5in. w/fpvcycle 2204 2800kv t-mounts HQ 5030 Bi-Blades(206g analog vtx weight) 4s Li-ion(190g Pack)(18650 Samsung 25r-Green Wrap 2500mah 25amp Cell, best cell for the price at like 3$ each) and even though the katana fly's much much better especially if you add even more weight the amp draw is still slightly higher so flight times are lower on the same pack. I have a second Katana V2 5in. frame I'm going to build out with BrotherHobby 1504.5 2650kv motors I have and see how well it performs swinging a larger 5in prop and if its possible to beat the Explorer LR on the same pack using a 5in prop because the Explorer's efficiency really takes a dive if you add weight with a bigger battery or camera where as the bigger prop/bigger motor combination's efficiency is much less effected. So to get back to your test, the 7in will carry a larger battery and fly longer while of course burning up more mah/min BUT a really cool test would be to see how far each can go at there optimal cruising speed. I have a feeling that the 7in you will find has a much faster optimal cruising speed so where the flight time on the same battery might be less than the 4in, the 7in quad may cover twice the distance even with being in the air less time. Yea distance and finding optimal cruising for the 7in would def be a cool test.
Interesting comparison, taking into account that both quads are limited to use the same energy. But the 7" is heavier and these 7" props weren't designed for efficiency. Props should have low drag, similar to glider plane wings: slim airfoil and low pitch are the way to go. I'm getting the same flighttime of around 28 minutes at similar speed from the same LiIon 4s-pack 3.000mAh VCT6 in no wind conditions: 1) stock 370g AUW EXPLORER LR and 2) 540g AUW Geprc MarkIV 7" frame driven by T-motor MN1806 / 2.300kV and low pitch T-motor CF props 7x.,4. Those props are razor sharp and only fit on the T-motors. Both are nearly impossible to source now. T-motor CF 7x2.4 props are amazing, it would be great to get CF 4" props with same airfoil and actual 5mm T-mount for the EXPLORER LR.
The 4 inch is the sweet spot for 4 X 18650 cells basically....A quad to fit 4 cells of this type....Try fitting 3.5 inch blades, see if it gets better or worse?...🤔🤔
I like the route TBS is going with their Pizza Box frame which is in production right now. The one piece 7” frame, which is SUPER light, as it’s very thin carbon fiber sandwiched around some type of foam. Then has a small canopy that will fit a Vista and and maybe a “Beast AIO”. I think they have their own AIO coming as well. The quad is not very crash worthy, but I think they are onto something.
@@DaveCFPV Not that I know of. They have shown it on the TBS Couch live stream a couple of times, and said that it is finally currently in production. It is a pretty neat design. Like I said it’s one piece (well two thin pieces of carbon with foam sandwiched between), so you don’t have all of the hardware weight, as well as the foam taking the place of the heavy carbon. The only issue they talked about was figuring out how to keep the motor screws from squishing the foam is on the motor mounts. The other is that it probably won’t crash well, but with a long range cruising it should be great. They have been calling it the Pizza Box or they were calling it something else that was mentioned on the stream. Don’t think they have settled on the name. I’ll try to find some information for you. It is super light.
Also, add compass to your units and use inav with waypoints for testing, then all you have to do is tell the quad to run a mission, have a seat and take a nap. And your results will be using the same power (speed) and course for each test of each quad
I also use a full inav setup that way for repeatability, taking out the human factor so you are getting a more consistent flight each time. I make my missions to be at least a km, then it’s easy to calculate the W/h used per kilometer. This will vary day to day based on wind conditions, but the measurements are still valid within the same day where the conditions remain consistent.
Great concepts, good test! Are you sure flying till 3.3v on 2 different packs (that might be in slightly different condition) gain a good comaprison? Have you checked how many MAHs you charged back into both packs after the flight? Could have been quite different MAH consumption / cell behaviour. I say this because I noticed in my last test (regarding LIONs) that temp playes a huge role. The one day (cold, around 0°c) I got horrible flighttimes (and only 2000mah out of a 3500mah pack until the volts dropped down and I had to land, the other day the same pack got me 2900mah and volts were still ~3v/cell only difference: 9°C this time and packs in a plastic bubble wrap... Just got into micro longrange by testing the iFlight Chimera4 and the "great" Shadow Fiend - sorry, both rip-offs of your Explorer - but the Flywoo LR is so hyped it wasnt available really ;) Today just for fun, I flew a few 650mah packs and got ~ 7mins of save flighttime ;) greets from Austria, Mario
Hi Mario, honestly I didn't bother because the result was so clear with roughly +80% of flight time on 4". I noticed the same thing with the temperature and the test was indeed done around only 2°C. With Lipos I always managed to get the battery warm with a few punchouts but on LiIon they come down dead cold.
Doesn't make sense to use the same size battery for both. You wouldn't use the same size gas tank for a sub-compact size car and a full size sedan. The 7" can carry a whole lot more battery than that. In general, larger props are more efficient. So I think if you have an optimized 7" quad, you can get it to fly longer (and definitely farther due to higher speed) than a 4".
It seemed to be pretty windy on that day. Maybe that caused the gap because of the much bigger surface area of the 7"? And how about going for 6S? Btw. Happy new year, Dave!
Happy new year! Yes probably the wind played a role along with many other things. Since the different is so big I assume there is more that one factor that is reducing the effiency of the 7"
Let me simplify this. low rpm propeller = more efficient. But, the weight and momentum and power of 7", it is difficult to fly slow. My typical 7" with 50g Xing2806.5 does NOT get longer flight times. I am gonna give it another try, but even with very light 7" biblade, I advise at least 30g 2306. 7" 9g props are like double 5" prop.
biggest problem is that when you increase pitch. You increase blade drag and it is hard to find probs that have lower than 2.4-2.5 pitch. I have seen one 8020 probs, but i think those are bad.
Has there been any real world implementations of this theory? I read through a few papers but it seemed to be a different way to frame the calculations or a different way to calculate a wings properties. I didn't see anything about it being a game changer in effeciency. I'm not trying to disagree with you or anything, I really just don't know much about it.
@@JustinHunnicutt there aren't many planes built this way, Albion Bowers (NASA chief scientist ret.) Claimed a total gain in efficiency of about 60% . The papers he published, are based on measured data. People who built the prototype confirmed a great gain in efficiency (not 60% tough). Had something to do with the plane not being full size. I don't know why the aero industry seems to ignore it, maybe for the same reasons they mostly ignore canards.
Very interesting. The heavier 7" quad needs more energy to stay airborne, so I think you just proved that disk loading is not the only factor involved here. A 7" quad is typically not flown with the same battery as a 4" quad. If you're aiming for the longest flight time you pick a battery that is optimal for the size of quad you're flying. I put a 6S2P VTC6 pack on my 7" and it flew for 22:40.
i also have 6s2p packs on my 7" but theres no way his motors or frame can handle that weight... a 5s1p or 6s1p would probably be about right for this rig im guessin and just scale the throttle to not overamp the pack
@@badfourlife I suggested 5s1p Li-ion pack
Yea I like that. What if you increase the disk load of the 7" to be more comparable to the 4 inch. Then you might have a better comparison.
Yes, that's basically what I was testing. Does it make sense to further decrease the disc load or does the extra weight cancel out all the benefits. Of course, I could put a 2P pack on the 7" but then I would end up with basically a normal 7" disc load again
The disc loading is very important. Problem here is that the motors Dave chose are too hungry. The only thing you should not spare weight on an endurance quad is the motors. All my 7" LR setups are based on minimum 2307 motors. Best results for me are using BH 2507 1850kv motors and 4S2P LG MJ1 packs. These motors are far from light but I can cover 25km in 24 minutes of flight without worrying too much about calm weather.
Two things: So on my Sub 250g 7” with the 7038 props, I could get over 9m with a 4s 650mah battery, when I switch to the 7042 props the same battery only gave me around 8m. Sound, your prop area is greater, creating more wind resistance. Don’t match the speed of the two aircraft, match the attack angle and then compare distance and flight time of each aircraft.
was going to comment the exact same thing. Increased speed, from my understanding, is a major factor to going with larger props for long range, so a similar speed test is handicapping the larger prop. Im thinking of how quads will fly for longer when moving forward vs. just hovering. Eitherway thank you loads for these experimentations. MiniLongRange is definitely next on the building block once I get back to quads. I think it was mentioned on your instagram but those 2305 superleggera motors might be a good fit?
So I put an emax 2306 1600kv on an AUW 500g 7” with a 4s 1300mah battery. It flys bobble free and is very efficient, about 12m. I believe GepRC put a similar 2306 motor on their 7” as well, but it’s a much heavier quad.
I think each weight increment 250g, 350g, 500g, etc... will have an optimum motor size for a 7” prop.
Yes, I agree. Dave should measure distance travelled to 3.3V and compare those. I always measure the efficiency of my fixed wing aircraft in mAH/km, so perhaps something like that instead.
@@immortalsofar7977 you should measure the efficiency in wh/km since mah only won't give enough info. Obviously 50mah/km on 6s is way different than 50mah/km on 3s
the effect of drag increases as disk loading is lowered
Removing the wobble out of the system is VERY important. As long as there is wobble the motors are constantly speeding up and slowing down to fix the wobble the flight controller is experiencing. This will DRAMATICALY reduce flight time. I would first try tuning, but if not stiffen up the frame. Until you do that you won't get meaningful results. It was fun to watch the attempt though. Good effort. Its cool you're doing this.
Love this episode. Finally a German man talks about metric curves like a real engineer.
As an aero engineer for a rotorcraft company this was both amazing and frustrating to watch! I'm not going to go into all the details but suffice it to say that you're on the right track, keep exploring! Incredible work, and I love my flywoo explorer LR. It's very cool to be able to see how rotorcraft theory is playing out for you in reality with off the shelf parts. Rotorcraft are complex in their design, and playing with different parameters can produce very different results... often due to extremely nuanced reasons. Keep going!
Thanks! Yes indeed reality is always messy. At least for now FPV development is trial an error to a large degree. Probably it will also stay that way since the parts are cheap and quickly pit together compared to running simulations with an acceptable degree of accuracy
Enjoyed this technical outlook on the two variations. Interesting to see which direction you head next. Subscribed
Thank you!
You're becoming a mix of JOSHUA BARDWELL/KABOB with the style of your videos 👍🏻
That's really nice to hear since these are basically my favourite content creators out there! :-)
@@DaveCFPV Well you are spot on 👍🏻. I love that 7in frame, is it for sale?
@@smooth_ops2942 A 5" version of it will be for sale soon. Not sure about a 7" version yet since the testing wasn't super promising
@@DaveCFPV but please not from flywoo. Very disappointed by them. And german retailers would be fine, too? Or you order more and sell them to me directly 😂🤪might be possible we are from the same area in Germany
@@nuhbiwan It won't be Flywoo. But honestly not because I don't like Flywoo but because I wanted to start a new brand specifically for LR. Sure, they messed-up the Explorer release big time but probably anybody else would have too. Nobody expected that level of hype and demand.
Also food for thought... I learned years ago that the very ends of the blade is where the most drag not being converted to lift occurs. Its why some of the props now have the little spikes on the trailing edge out at the end. With bigger props this effect is exaggerated because the tips are moving faster all else being the same. Using ducted props is the most effective way to reduce the tip drag turbulence, but has the undesired effect of causing a drone to auto level due to the way ducts work when moving in a direction other then up (in the case of drones). Ducted propellers are the most efficient way to produce lift. Its why all modern jets use ducted engines. I'm thinking maybe a very thin duct just to break up the drag might work? Ducts are a whole rabbit hole. The guy on RCmodel Review explained them pretty well if I remember right. Also Also wind resistance/drag increases exponentially. I don't think the extra wind resistance on the body of the the 7" vs 5' would make much difference at 30mph. Like I said, ... Food for thought.
Ducted fans are theoritically have better efficiency than non-ducted fans, BUT in practice, it's very very hard to make because the low tolerance of the distance between the prop tips and the duct to prevent vortex generation, also the duct's intake and exhaust itself are very hard to design to get the best efficiency. This is why many improperly designed EDFs in the market has lower efficiency than simple open props.
Im researching and planning to build a long range quad as well and from my research, it was found that the overall current/amp draw to hover or light cruising is the best indicator on the overall system efficiency. Because amp hour usage divide by battery capacity will nett us the estimate flight duration. The disc loading is not really the main factor.
Dave_C, great video and set of tests. Disc load and drag, are major factors. I’d like to see more testing on where the battery sweet spot falls. We can fly micro long range 2s, 3s, 4s,5s, even 6s. In each case, there are trade-offs between power delivered by each pack and weight. I typically fly 3s. For motors, we’re looking for the most thrust, able to exceed the total overall weight and provide power to fly in some wind conditions etc. so for motors, there is a sweet spot also of KV, weight & thrust. I have one build I fly with 6 inch, 3S 18650 pack, on Lumenier 1806 2300kv motors. I typically get 9 to over 20 minutes without carrying a GoPro.
Hey Dave, interesting video. Do you think the tune could substantially decrease efficiency on the 7" quad? I have not been able to tune a 7" to perform decently.
Yes the tune can change the efficiency of a 7 inch dramatically on my 7 inch with a more control centered tune from UAV tech it drew almost double the current compared to the defaults
same, 7inch tuning can be frustrating
Tuning definitely matters.
People literally fry motors and ESCs with too-ambitious tunes.
Running at power draws amps, but hard acceleration of the props themselves as demanded by a tight tune draws even more.
A tune with high frequency oscillations will be even worse by spending longer in that hard acceleration zone.
So an ultra-tight tune will draw more current than a looser, easier tune, and an over-ambitious or troubled tight tune will draw even more.
There's a publication Modeling Flight - NASA that is a 6 MB PDF file on line. Flight efficiency does not scale at a linear rate. A rough estimate based on disc area would be energy consumed versus time. So if you scale up the disc area you would want to see how long it would take to consume the same amount of Watts. Because the discharge rate curve of the batteries are important you would want to use a battery that has proportionally higher weight and amp hours as disc area increases. You're dealing with the issue of cross-sectional surface area goes up by the square as the volume and possibly mass goes up by the cube. I like the smaller quads, they have lower inertia and are less likely to self-destruct if they hit something.
I have 4 of your frames I am working with. My best flying, longest flying is the 4" frame but with 5" arms. I don't have the arm braces installed. The 4" with 4" arms flys great but it gets about 3 minutes less flight time. The 5" I have like the one you are showing with the bicycle connector flys great but does not get the flight time of the 4" with 5" arms even though the weights are within 10 grams of one another. IMHO I think the biggest difference are the props. GemFan Hurricane props fly better and longer with all of mine than similar HP or other props I have tried. I think the center of gravity is enough different on these to have an affect as well as the relationship of the motors in the design.
What five inch arms are you using with the 4-in frame? Is that the 4-in Explorer frame you're talking about? Version one or two? I have version 1 and would like to experiment with 5 inch arms after reading your post. Thanks!
Dave can you do a video on 2-blade props vrs 3-blade props?
Loved the video it would be great to see props better suited to this ultralight 7 inch size factor
Those MB2204 are pretty neat for builds like this 7”. I’m surprised I had never seen them before. Apparently there was also a 2450kv variant that would be great for a 5” on 3-4S but those are next to impossible to find.
It's obvious, the elephant in the room which you omitted from your calculations was...Drag. Those big 7 inch discs whilst giving bags of lift, also creat a lot of drag and need more power to drive them.
Specifically, frontal area with the quad tilted at an angle to achieve 40kph.
The bigger disc area = bigger drag...🤔🤔😀🇬🇧🇬🇧🇬🇧🇬🇧🇬🇧
Actually there wouldn’t be an increase in drag for the props. When you think about it, then you’ll see, that the propellers actually don’t create any drag because they spin through the air like a screw...
@@ferdifant_fpv686 Lol....that was funny...Don't give up your day job...🤔😀🇬🇧
The drag from the props is reduced with a lower disc loading in fact as the props can spin slower to produce enough lift and because the drag is proportional to the square of the velocity a prop spinning at half the speed gives a quarter of the drag
This is just for the actual prop drag not the aerodynamics of the quad itself
@@H.J.B More utter rubbish....🙄🙄
@@ferdifant_fpv686 Props do generate drag, but it's cancelled out by the thrust they generate. Thing that actually increases the drag are the longer arms required to fit the props
Thanks Dave for all your hard work to help us all get in the air.
One metric it might be interesting to fix is mAh to disk loading? Probably set that from the 4" and scale the appropriate battery for the 7".
Having 3000 mAh battery on the 4" then a 5250 mAh on the 7" would be about the mark for the same mAh per cm2. It is a more even point to make your testing from I believe.
Thanks again for everything Dave I would be stuffed without you JB and all the others.
"1 year later..." lol Definitely the high pitch of 7"prop induces a lot of drag which ate the expected efficiency from the larger diameter prop. Another thing: ~120g lift per each 7in prop is very low and its rpm is very low as well. Not sure if this is the case but, at very low rpm, the efficiency is horrible (just imagine, e.g. 30 rpm producing 0 g thrust at 1A, efficiency = 0) and increases sharply as rpm increases reaching a peak followed by a gradual decrease at high rpms. It would be cool to see a bench test comparing W/g thrust per each motor in both setups.
A doubt: at 08:30 you said that a 7" have 993 cm2 prop area. Where is this number coming from? It's the prop specification or is there a calculation that you made? Thank you!
I liked when the 7-10" quads were norm with naze32 and afroflight etc for the noise factor. Hopefully people will adopt endurance racing say the FPV version of motorcross and last guy flying wins with laps done. It's that in remote areas or indoor racing only in near future LOL!
you've just drawn the lift off logo 0:56 🤣
...you would also need to fine-tune the drive-train. Check steeper and shallower pitch. Every motor has it's sweet spot of RPM vs torque - you just need to find the right prop to get it there...
Keep going, man! :)
I have the 5 and 6 inch rekon quads. It would be very nice if you would also provide a 7inch version of the quad, with a larger battery carrying capability for longer long-range flights.
load up the 7" with enough battery to get similar disc loading of the 4". I think that would be a more "apples to apples" comparison. People that are into long range don't use a larger quad to carry the same small battery - the point of a larger quad for long range is to carry the weight of more battery.
With the same disc load, the 7" would have to bring about 900g battery, so almost 4x of the pack. That seems unfeasible in that small frame.
You should look at the efficiency curve of brushless motors, even with the greater weight of a bigger motor, since you'd be at a much lower portion of it's torque potential, you should be able to get a very significant efficiency boost. I'd be curious to see you go in the complete opposite direction and get a 2806ish size motor then test the fight time. Should also significantly help with the feel of the quad.
I agree with a smaller stator the stator gets saturated with energy much sooner than a larger stator, therefore even a larger stator can be more efficient because it does not have to work as hard it's not near its maximum potential which is when the increase in amps causes a decrease in efficiency losses through heat etc.
I think the idea behind the lightweight design of this seven inch is to directly compare the seven inch to a four inch with the same battery as you can get a seven inch to carry a good 600 or so grams of battery which would blow a microlongrange out of the water with flight time
Because the 4 inch is at the limit of its carrying capacity with that battery whereas the seven inch would be perfectly capable of double or even triple the battery size
And he was mainly testing the efficiency of having a low disc loading
But if he where to load up the seven inch to the same disc loading I think we all know that it would win
I am thinking if you could spin a 8" props on 7" frame and reduce its motor kv would give a longer flight time with the same battery capacity or may be a much longer flight time with a higher battery capacity.
Dave those 7inch bi-blade props look very high pitch? I know there are not many out there to choose in 7inch class, you should get Gemfan to make some 7035 bi-blade?
Hi, Nice vid! The main benefit to go larger in propsize is the cruise speed for me. A couple of years ago I build a 3"ultralight with 2s 18650 for long range. I managed to get 25 minutes of flight but the biggest thing I found out that the cruise speed is quite low, and is you go faster then you lose efficiency. My 7" goes for 20+minutes on one 4s lion pack but at a cruise speed of about 70kmh. And got long range I find the speed also very important. What would be interesting to test them at there own cruise speed and look at the distance they flown. And what also would be interesting is to do the same test only then both at 70kmh. Ps, a bad tune also costs a lot of energy.
bad tune uses a lot of extra power.
and yes, i agree, the more interesting test would be a real world flight of each to 2.5v.
Yes totally agree. at 70 kmh the 4" will probably start to get way less efficient in comparison. Indeed the PIDs are pretty high to make it stop wobbling like crazy. Pretty sure that costs efficiency. 2204 might be too small after all...
@@DaveCFPV I have the tbs endurance motors on one of my 7" and these are not big, 2306. Dry weight of the quad is also not licht with 451 dry without GoPro. But it's flying super smooth. Also with a big battery. But 2204 is a lot smaller then 2306 of course. I'm curious to see where this project is going!
Glad you are putting yourself out there with your experiments. It is ok to be wrong. You can’t learn from always being right. Like the 7inch design. Maybe 5” props?
You should try the mavic motors and props. With the amount of money dji invests in there drones they are probably very efficient. Banggood has a frame that uses the mavic motors mounting holes.
I saw that there's an 8in frame available on AlieExpress and BG called the "Andy HD8" that uses the motors for the Mavic. I always wondered what could be done with the motors from a mavic mini or a Spark on a light carbon fiber frame.
@@yannickg6904 I think the biggest factor is the way the props are mounted, each blade can lead and lag individually and that helps with efficiency, I have ordered some Mavic Mini / Mini 2 props to experiment.
I'm thinking you should be looking into the props as far as being properly matched to the motor - to produce 'enough' lift for the weight of the quad
great video, idea.... motor amp draw at same cruising speed would be higher on the 2204 than the 1404 and at both running 4s. What if you ran the 7" on 5s or 6s, bring disc load closer, and with a higher cell count you can pull fewer amps to get the same cruising speed?
Awesome content Dave!, I really love this deep dive into ultralight LR platforms! Anyway I don't think pure flight time is really a useful data for us. I mean what I care about is "how long (in term of distance, not time!) I can fly". So cruising speed is actually a thing! 18 minutes on the 4'' cruising at about 40 km/h means a12 km trip while 10 minutes on the 7'', cruising (I'm kind of guessing) at 70 km/h means... again roughly 12 km! While I loved my 4'' micro LR, I recently switched to 5'' mini LR because I can simply fly the same distance... but faster!
Thanks! They both cruised at exactly 40 km/h so I guessing that the 7" will do less than 10min at 70 km/h. But sure, picking a pretty low speed might have been an advantage for the 4". If the test was done at 60, 70 or 80 km/h the 4" could start to get much more inefficient since it getting close to its top speed.
Very interesting test and results. Maybe you could try another test where the battery mass fraction is the same for both quads....
Have you ever thought of the concept of having a small airfoil, like the tail of a DC-9, attached to the top of the quad which would generate lift at cruise speeds thereby allowing for much reduced power settings in cruise and longer flight times? The angle of attack of the wing would have to be optimized for a certain speed so as not to create more drag than lift. Anyway just a thought.
I played around with quad / wing hybrids but mostly it was extremely difficult to make them fly well. Seems like the flight controller really has issues handling them
Disc loading doesnt really account for the extra power needed to swing the larger props on the bigger motors, does it?
Dave you have 1450kV motors on the 7" and 2750kV motors on the 4", what would happen if the 7" motors were closer in kV to those on the 4"? In the tested setup the 7" has 3x the prop area but at the same current draw it is probably turning at less than half the speed of the 4", with the additional drag of a larger prop to overcome. Do the DJI goggles allow reading the amp draw during flight.
2750kV is very high for a 7" on 4S. Probably too high for the motors and Li-Ion to handle. Yes sure I can read the amp draw in the googles. Although from my experience it's usually very unreliable unless properly calibrated.
@@DaveCFPV I realize its very high but this is a bit different than normal using the LiIon 4s, I know you often think outside the box. Just a thought
Have a question. New to quads. Have a hubsan h501ss don't count that. I do fly long range fixed wing fpv however. Would like to get a long range quad and wondering what to get. All my batteries are 4s lipo and liions so would like to stick with those. Don't care about freestyle or racing or any of that, just long range cruising. What do you think would be a good place to start?
your 7 frame from rekon6? or what
Drag is higher on the bigger quad and there’s the prop+motor efficiency. Most 7” start to wobble because of the aerodynamics, the bigger prop starts to inhibit fixed wing properties and the quad starts to feel the wind like a flying wing does.
Have you thought about stacking the AIO and Vista and mounting the battery behind it? You could ditch the top plate and standoffs to save some weight, and basically get a top mounted unibody.
Great video! I've found that the tune helps a bit with regard to efficiency.
what did you alter in your tune that affected efficiency the most?
Hi , In mho regardless of prop loading it costs a given amount of power to lift a given weight . decreasing numerical disc loading does not compensate for the extra power needed to lift a heavier craft. and spin a heavier prop, If you had scaled the battery up so it matched the mah per gram of the 4 inch , then your results would have been closer to what you expected , yes because your actual disc loading on the 7 would still be less than the 4. Lifting heavier things costs more power .
Yes absolutely. I would have expected the decreased disc load to at least compensate for the extra weight but it seems it wasn't even close. Plus other factors like drag and the tune ..
Thanks for the info!
Having a Flywoo explorer and built one of your mini long range frames (both excellent) I think you hit the sweet spot at 5 inch for li-ion and 4 inch for light weight li-po flying. The 7" might be a worthy experiment to test capability but less necessary (plus it's less of a looker!).
by using the same battery the 4" had a much higher ratio of battery power to weight, there seems to be an efficiency curve here where not only is the right ratio of disk load to total mass important but the right ratio of battery weight to total mass.
What was the difference in speed during the flights?
I think flight speeds might impact flight times
Here are my thoughts. You concentrated a lot on g/cm², but as you mentioned earlier on, we need to look at g/W too. So I think you're right at the end of the video that you need to further test motor and propeller combinations.
A couple of ways you could test this against the 4" quad.
1) The in-situ method. Measure the wattage consumption while hovering until the battery runs down to your cut off voltage. BF black box should be useful here. This is subject to a lot more random errors, but would be more 'real world'.
2) The bench method. Get a table top thrust meter, measure the power to thrust relationship of the 4" prop and motor, then find the best motor and 7" prop combination that matches.
I see Rekon7 coming soon.. real curious on motors. cause i was thinking when i was going to build myself 2303.5 with gemfan new lightweight LR 7035.. arm look so long and skinny.. surprised no braces connecting left and right motors along with front and back
I have an dji pfantom 2 copy with 2212 920kv motors 9450 props. Do you think will work 3s sony li-ion battery.?
Thank you for show the experiments.
The larger quad will have much more drag maybe more then double. also square/flat surfaces are not your friend, round/curved leg sections would be better. but why not just use the same 4" body/base with long 7" hollow round legs. Or/and try larger dia motors with lower volt/rpm
скажите, как называются пропеллеры на 7 дюймовом квадрокоптере
You always put the GPS in the wrong place! Above the GoPro is by far the best place I've found. Thanks for the video!
Fantastic video! Thanks! Next, can you do a range test? For example, if there is a particular mountain I want surf down, how close must I drive my car to be close enough to fly my drone to the top of the mountain? If the 7" has a higher cruising speed than the 4", then perhaps less efficiency won't matter so much if I can fly to the mountain sooner. Much appreciation.
On all of these setups your range should be limited more by the video signal than anything else. The 4" can cover over 20km round trip on those batteries :-)
While the 7 inch has less disc loading, if you give it the same battery you still have more weight to carry. So what if you had the same ratio of battery weight to all up weight?
Hi~
Let me ask you a question.
It's a 3 inch cine hoop.
In the video, there are videos of making a pack with 4 lithium-ion 18650 batteries and flying it with an FPV long range.
With excitement, I ordered batteries and made a pack.
LGDBHG21865 3000mA.
The problem is... When I hovered, the yaw tick symptom reappeared after it came up, and, after a few seconds, the low-voltage buzzer sounded and the aircraft sank.
If I open it again, it opens again,,,,, repeat...
So, I changed the low voltage warning in Beta Flight to 2.7V, and when I turned it on, there was no sound.
If I take a break for a while, it will float again. But it sinks again... The battery is hot, and the voltage is 3.8V... TT
I bought 40 tablets... but I can't use them all?
How do people use? Batteries were also made by buying anything.
Is my FC the problem? Or is there a special setting for Li-ion?
FC is IFlight SucceX Mini F4 V3 Stack, and the manual says 2~6 Lipol. Do I have to use only Lipol? Can I change FC?
Why is this happening?
It's a waste of money/work time.
I'm serious~~ Please advise.~~ TT
What’s currently the pitch of the 7” prop? I guess you should have a very low pitch with a maybe a slightly lower stator but bigger diameter.
Maybe you can divide the pitch to disk area and use that factor to divide that with the motor specs and get some factor out of there what you maybe can get some conclusions out of and optimize
Wouldn’t the 7” cover more ground than the 4”? If you were more concerned with a distance I think the 7” would still win if we are actually doing long range.
Maybe instead of using a 7” with these motors, I wonder if changing the prop to 5.5”-6.5”? Looking for the efficiency/ distance covered sweet spot.
Hi Dave the TBS pizza box frame will be around 36g cut from Rohacell.com 1mm Carbon skins with polymethacrylimide plastic foam core, would love to see your experiment with this stuff.
Hi,I decided for your frame but I'm having a lot of yello.
Have you some solution to suggest me?
Thanks a lot
Can CNC made easy cut the 7 inch arms?
Getting ready to order another 5inch mini LR .
Awesome research by the way. Thank you for all the hard work you do.
I like the happy compromise that a 6in prop brings. Your 5in frame adapted to 6in props, with t-mount 2204s and HQ T6x2.5x3 would be a nice combo.
could be absolutely right. 6" has also been my favourite on more classic setups. I think the next thing I will try is just putting some 6" props on it.
@@DaveCFPV So many new props and motor sizes are coming out, it's hard to keep up. I spotted the SPCmaker G2204, but I'm unsure of the quality. The 4in LR is still a very hard design to beat.
Great test Dave!! Just an idea...make this frame little bigger to use DJI phantom motors with DJI low noise 9"props😊
You should try the 7" with a 21700 4S1P with 4100mah Li-Ion pack (Sony | Murata VTC6A 21700 4100mAh). Right now you are decreasing the discload but increasing the AUW with a unchanged capacity of battery, but I think with an increase of AUW you also need to increase the capacity of the battery, so 360gr on 3000mAh or with the 21700 batteries 580gr (I added 100gr for the heavier cells) on 4100mAh. your discload is still considerably less while the 21700 battery also gives you an increase in amp draw. I would also run a test with 18650 packs in 4S2P and 6S1P configuration.
@Dave_C FPV , I was thinking if the bad tune on the 7" would use up the battery... seems logical that if it's wobbly it will have to correct more during each PID loop, thus taking up more unnecessary battery power. But since the results were massively different, other stuff like the props you mentioned is also a good idea. Love this channel, keep it up !. Happy new year !
Think so too. The results were so clear there must be several things (possibly tune, drag, wind, weight, props, more battery sag...) going against the 7" flight time. Thank you! Happy new year!
The 7 inch had additional carbon fibre supports on the arms, while you flew the explorer without them. Air resistance is no joke. If the supports are necessary for the stability of the quad, then maybe the disc load theory simply needs materials science to catch up before it can be used in quads of this size. Perhaps folded aluminium would work
Where i can get the Arms for the 7 inch buidt?
Maybe reducing the discload by using the same prop/motor combo like on the 4inch and choose a hexa/octacopter frame would be more comparable. The "right" motor/prop combo seems to be crucial in terms of amp draw.
where we can collect the drawings to test the arms
Interesting video, thanks Dave.
Are you going to release the dxf for the 7inch frame?
I need to do a faster flight, but went 70 min with a lightweight rig based off of the Black Opal 6". Battery pack was a 3S2P 3500mAh Li-Ion. Arducopter was set for ~13kts running a circular do jump pattern. Non-HD rig, super light 215g before the Li-Ion(290g). I think if I increased my speed slightly, it might be more efficient.
Hi,what is the name of the 7 inch frame on the video?
Hello Dave quick question have the flywoo exorer but I bought it without caddy Vista and I wanted to build a analog version. Witch I did I added my camera and a vtx but I need help with beta flight and making it fly any help?
Check out Oscar Liang's Blog and Bardwell they cover all you need to know
My guess is, that the power to weight ratio of the batteries is less efficient on the 7" quad. You should use a way bigger battery and see how that works.
The key to achieve maximum flight times is to decrease dead weight as much as poss and increase the weight of battery in the same way, given that you use a battery with a maximum power density available on the market.
Definitely need to factor in mah per gram of auw and if you want to directly compare efficiency removing this needs to be part of the equation. As the mah per gram of auw should be equivalent to try to directly compare efficiency
Do you factor into overall frontal area drag of the discs into the equation?
You should scale up the size of the battery on the 7inch.
Also for the Explorer LR 4inch why didn't you just use a smaller and lighter 3s Li-ion paired with just a little higher kv motors seems like that would have been a more efficient setup and better battery to quad ratio? I know you did the testing on the 3s Li-ion.
What about 5s Li-ion for 7inch with low pitch "yet to be created" Gemfan 7035 bi-blade and the correct motor you eventually find , I know you will!
I intentionally used the same pack because I'm interested in what works best with those exact 18650 packs. It wasn't totally obvious that a slightly overloaded 4" is still more efficient than a very light 7" with very low load
LOVE that someone is breaking out the graphs.
On the flight testing, should you be using the same battery though?
Id expect you'd want that scaled up proportionally to the weight no?
Another variable: forward surface area -- the 7" is going to have a much larger silhouette.
On a different note, Dave your frame layouts are elegant AF. Like they're aesthetic candy -- nice work dude.
Thanks, this was exactly the video I was looking for. Did you measure the resting voltage afterwards? Since the 7 probably draws a bit more current the LiIon would drop voltage harder.
Anyhow - in my case I'd value the total trip distance before flight time, so I'm guessing the 7" would win.
Dave, Can you compare them down to a specific voltage? Because no matter what the 7in is most likely drawing more amperage thus making the battery(especially li-ion) sag slightly more but I really don't know.(I know the cold hand thing my thumbs were gonna fall off the other day as I pitched the nose of the quad forward to get home asap) I've been doing these exact same comparisons between my Explorer LR 4in.(146g analog vtx weight) and my Tomoquads Katana V2 5in. w/fpvcycle 2204 2800kv t-mounts HQ 5030 Bi-Blades(206g analog vtx weight) 4s Li-ion(190g Pack)(18650 Samsung 25r-Green Wrap 2500mah 25amp Cell, best cell for the price at like 3$ each) and even though the katana fly's much much better especially if you add even more weight the amp draw is still slightly higher so flight times are lower on the same pack. I have a second Katana V2 5in. frame I'm going to build out with BrotherHobby 1504.5 2650kv motors I have and see how well it performs swinging a larger 5in prop and if its possible to beat the Explorer LR on the same pack using a 5in prop because the Explorer's efficiency really takes a dive if you add weight with a bigger battery or camera where as the bigger prop/bigger motor combination's efficiency is much less effected. So to get back to your test, the 7in will carry a larger battery and fly longer while of course burning up more mah/min BUT a really cool test would be to see how far each can go at there optimal cruising speed. I have a feeling that the 7in you will find has a much faster optimal cruising speed so where the flight time on the same battery might be less than the 4in, the 7in quad may cover twice the distance even with being in the air less time. Yea distance and finding optimal cruising for the 7in would def be a cool test.
That 7" looks epic
Omg can't wait to see tmount 7" motors and props.
Now wondering if the new t-mount design from iflight 2005 might be a design testing for this.
I think you should do the same thing again but switch the batterys because even though the batteries are the same the resistance might be different
Interesting comparison, taking into account that both quads are limited to use the same energy. But the 7" is heavier and these 7" props weren't designed for efficiency.
Props should have low drag, similar to glider plane wings: slim airfoil and low pitch are the way to go.
I'm getting the same flighttime of around 28 minutes at similar speed from the same LiIon 4s-pack 3.000mAh VCT6 in no wind conditions:
1) stock 370g AUW EXPLORER LR and
2) 540g AUW Geprc MarkIV 7" frame driven by T-motor MN1806 / 2.300kV and low pitch T-motor CF props 7x.,4. Those props are razor sharp and only fit on the T-motors. Both are nearly impossible to source now.
T-motor CF 7x2.4 props are amazing, it would be great to get CF 4" props with same airfoil and actual 5mm T-mount for the EXPLORER LR.
The 4 inch is the sweet spot for 4 X 18650 cells basically....A quad to fit 4 cells of this type....Try fitting 3.5 inch blades, see if it gets better or worse?...🤔🤔
Exactly what i was looking for, thank you :)
I like the route TBS is going with their Pizza Box frame which is in production right now. The one piece 7” frame, which is SUPER light, as it’s very thin carbon fiber sandwiched around some type of foam. Then has a small canopy that will fit a Vista and and maybe a “Beast AIO”. I think they have their own AIO coming as well. The quad is not very crash worthy, but I think they are onto something.
Oh wow I wasn't even aware of that one. Are there any infos online already?
@@DaveCFPV Not that I know of. They have shown it on the TBS Couch live stream a couple of times, and said that it is finally currently in production. It is a pretty neat design. Like I said it’s one piece (well two thin pieces of carbon with foam sandwiched between), so you don’t have all of the hardware weight, as well as the foam taking the place of the heavy carbon. The only issue they talked about was figuring out how to keep the motor screws from squishing the foam is on the motor mounts. The other is that it probably won’t crash well, but with a long range cruising it should be great. They have been calling it the Pizza Box or they were calling it something else that was mentioned on the stream. Don’t think they have settled on the name. I’ll try to find some information for you. It is super light.
@@DaveCFPV Search “TBS Couch - Squarce Maiden” I think that’ll get you a look at it
4" platform reasonable only in under 250g format. And your solution not optimal for flight time, but has advantage in field of dynamic.
Also, add compass to your units and use inav with waypoints for testing, then all you have to do is tell the quad to run a mission, have a seat and take a nap. And your results will be using the same power (speed) and course for each test of each quad
I also use a full inav setup that way for repeatability, taking out the human factor so you are getting a more consistent flight each time. I make my missions to be at least a km, then it’s easy to calculate the W/h used per kilometer. This will vary day to day based on wind conditions, but the measurements are still valid within the same day where the conditions remain consistent.
@@kelleysislander exactly!!!!
Great concepts, good test! Are you sure flying till 3.3v on 2 different packs (that might be in slightly different condition) gain a good comaprison? Have you checked how many MAHs you charged back into both packs after the flight? Could have been quite different MAH consumption / cell behaviour.
I say this because I noticed in my last test (regarding LIONs) that temp playes a huge role. The one day (cold, around 0°c) I got horrible flighttimes (and only 2000mah out of a 3500mah pack until the volts dropped down and I had to land, the other day the same pack got me 2900mah and volts were still ~3v/cell only difference: 9°C this time and packs in a plastic bubble wrap...
Just got into micro longrange by testing the iFlight Chimera4 and the "great" Shadow Fiend - sorry, both rip-offs of your Explorer - but the Flywoo LR is so hyped it wasnt available really ;)
Today just for fun, I flew a few 650mah packs and got ~ 7mins of save flighttime ;) greets from Austria, Mario
Hi Mario, honestly I didn't bother because the result was so clear with roughly +80% of flight time on 4". I noticed the same thing with the temperature and the test was indeed done around only 2°C. With Lipos I always managed to get the battery warm with a few punchouts but on LiIon they come down dead cold.
Doesn't make sense to use the same size battery for both. You wouldn't use the same size gas tank for a sub-compact size car and a full size sedan. The 7" can carry a whole lot more battery than that. In general, larger props are more efficient. So I think if you have an optimized 7" quad, you can get it to fly longer (and definitely farther due to higher speed) than a 4".
It seemed to be pretty windy on that day. Maybe that caused the gap because of the much bigger surface area of the 7"? And how about going for 6S? Btw. Happy new year, Dave!
Happy new year! Yes probably the wind played a role along with many other things. Since the different is so big I assume there is more that one factor that is reducing the effiency of the 7"
Let me simplify this. low rpm propeller = more efficient.
But, the weight and momentum and power of 7", it is difficult to fly slow.
My typical 7" with 50g Xing2806.5 does NOT get longer flight times.
I am gonna give it another try, but even with very light 7" biblade, I advise at least 30g 2306. 7" 9g props are like double 5" prop.
I read an article about Vertically Offset Overlapped Propulsion System (VOOPS), improves efficiency could you give it a try?
I think the new DJI FPV drone may be using a similar vertical offset but no overlap, same with other folding drones.
Very interesting video as always! Well I think I'll have to try out Liion too... Where do you order your VTC6 cells? I'm from Germany too :)
I order them from the netherlands :-) nkon.nl
@@DaveCFPV thanks :)
biggest problem is that when you increase pitch. You increase blade drag and it is hard to find probs that have lower than 2.4-2.5 pitch. I have seen one 8020 probs, but i think those are bad.
I wonder if prob arms would be shaped like airfoil, and wires would be inside how much would it help for flight times.
I think 2104 kv1800 would do too.
a lower pitched 7 inch prop would be nice. implementing Prandtl lifting line theory in propellors could also give an enormous boost in flight time.
Has there been any real world implementations of this theory? I read through a few papers but it seemed to be a different way to frame the calculations or a different way to calculate a wings properties. I didn't see anything about it being a game changer in effeciency. I'm not trying to disagree with you or anything, I really just don't know much about it.
@@JustinHunnicutt there aren't many planes built this way, Albion Bowers (NASA chief scientist ret.) Claimed a total gain in efficiency of about 60% . The papers he published, are based on measured data. People who built the prototype confirmed a great gain in efficiency (not 60% tough). Had something to do with the plane not being full size. I don't know why the aero industry seems to ignore it, maybe for the same reasons they mostly ignore canards.