I am very new to multirotordrones and I decide to learn how to build one myself. Technically I am thinking to build two drones, one 7” quadcopter and one 10” quadcopter.
So far I only did research on FC, ESC, Motor, battery and prop size, I haven’t dug into other parts, such as receiver, GPS, or analog cam, yet. For now, I just want to make sure I am heading to the right direction and getting the right parts for the drone I am going to build.
First, for the 7’’ quadcopter. I am aiming for a long range, high efficiency cinematic FPV.
FC: F7 I saw many demo videos and budget build videos on YouTube, and I decide to go with a F7 stack flight controller for this model. It is an easier start for me and less wiring and soldering I need to do. I haven’t decide on any brand yet (There are so many brands like holybro kakute, iFlight, etc.) I can choose from and there are review videos, so I am not so concerned about the brand, and I know F7 will give me some headroom for future firmware update.
ESC: come with the FC stack
Motor:1300KV-1700KV I know the efficiency is decided by the combination motor(amp draw), prop size, battery (size and voltage) and the weight of the quad. I won’t do a lot of freestyle or racing, because I am just not that skilled, so is this right KV range for a 7” quad?
Propeller:7x4.2 2-blade I want to use a 2-blade on the 7” instead of 3-blade. What is difference between a 2 blades and a 3 blades on quadcopter. I see 3 blades on 7” quad very often, but I don’t understand why.
Battery:6S li-ion Li-ion battery can increase the flight time comparing to li-po battery, right?
That’s what I have decided for the 7” quadcopter so far, if there is something doesn’t look right, please let me know. I am not ask anyone to do the work for me, I just want to know if everything above sounds like a good start, and from there I can narrow the selection down.
For the second quadcopter I want to build, I have a lot uncertainties.
This 10” quad will be used for aerial filming, and I want to be able to stay in the air for about an hour (when it is not carrying any heavy equipment). With a low KV motor(900KV-1100KV), a 1045 propeller, and a 12S battery pack should be able to achieve this, right? Then, because the voltage is too high for most of the F7 FC, I think it is best to follow the same build-up of a X-class/Beast quad, right?
This is a general idea I have for this 10” quad. Does it sound practical? If it sounds alright, then I can choose the parts for this drone based on the X-class build up I see on YouTube. Unless some changes can be made here, or what I am think here is no right and I need a different design.
I very appreciate all the help, any comment, any suggestion, a video or a picture of similar build up will be helpful to me. I am new to FPV drone, the more feedback I get, the more I learn.
Welcome to the hobby/forum. Great explanation of what you're trying to achieve and what you know so far. Everything you said sounds reasonable from someone who has been building and flying for a few years so I think you're on the right track, will call out a couple things you asked about and other things you mentioned.
Just to set you off in the right direction Oscar Liang's site is often one I just end up on finding solutions to random problems I have with quads or just technical questions about how things work or affect performance and he happens to have a page on a 7" build (I've never done one full disclosure)
7″ quadcopters have better efficiency and flight time for long range than 5″. You can use a lot of same components from 5″ racing drones on 7″. It is larger than a 5″, but you can still comfortably carry it around. Here are some tips about Long Range FPV. Learn about Mini Quad frames in […]
Regarding Lithium Ion vs Lithium Polymer, I think the differences for our case are largely negligible. To get the discharge current you are typically going to need to stack quite a few cells in parallel if using lithium ion and the weight from the packaging of the cells and connections between them (nickel strips spot welded typically) and other insulation needed would probably literally out-weigh any benefit in terms of better energy density. Lithium polymer is the typical go-to for flying things due to the size/weight and discharge capability combination... assuming typical 18650 cells will discharge 5-15A range safely if you want to match a 100C 1.5Ah battery (150A max discharge current), you need 10 of those 18650 cells in parallel (granted they are typically 2.5Ah a piece and so would be 25Ah battery which is huge capacity but only at 1S which is low voltage for a quad, go up to 6S and you have a 60cell battery, I use a 50cell battery on my electric skateboard in 10S5P configuration but good luck getting that thing to fly )
Li-ion 18650 cells are great for ground vehicles (personal transportation) or for all sorts of tools and laptops etc. etc. things that sit on the ground and don't have extremely high discharge current or can deal with being heavy to have lots of cells in parallel but for flying I think lithium polymer is still the way to go. As newer cells like 21700 size come out and have higher discharge current then it might come to a point that they are usable but as is I don't think it's ordinarily practical. Come to think of it Peter Sripol just build a personal plane using 18650 cells I think and at that scale it probably does make sense but for park flier type RC things it's going to be humongous to be worth doing.
Regarding your parts selection so far, FC F7 is a thumbs up.
4 in 1 that connects directly to F7 FC as a stack is a good call makes life easier (just got JBF7 and iflight ESC combo from racedayquads and fantastic combo so far!) Kakute F7 is nice too have a couple of them, can't really go wrong with F7 IMO though beware there have been some overheating issues with some of them so something to watch out for, overall though the STM32F7 chip at the core of them has highly configurable pins so can be very flexible.
About the 10" build I have a hexacopter that is around that size and it is frightening I enjoy it but have to respect something that size and with that much power and being flown remotely with hobby grade parts. Recommend you check out ecalc.ch website and probably get a license there to plug in all your actual parts/numbers to see what kind of flight time etc. you should expect but my guess is getting to an hour is going to be pretty much impossible. Thing is once you get flying being up in the air for 20-30 min is a really long time, you are doing something basically the entire time. If you are looking for camera you can set in the air for a long time and get some cool long shots to speed up or whatever from the air then would probably recommend check out DJI mavic or competitors since they will provide a much easier ready to go experience for that kind of flying but if doing manual flight to any degree then generally not bad to come down every ten minutes or so to change a battery and take a quick break out of the goggles or away from a screen.
Regarding 3 blade vs 2 blade, with 3 blade you have more weight/mass on the prop itself so the motor works harder to change speed and just can't change speed as quickly with a 3 blade prop as with a 2 blade prop so less responsive with 3 blade but each swing of the blade around pushes an extra 50% or so of air compared with a 2 blade prop, so each rotation gets more thrust out of it but takes more to make it go. Long story short this basically means 2 blade props are more efficient but 3 blade props allow you to halt your descent or change direction more quickly (more agile) for longer range and less diving/recovering or other acrobatic things you'll want 2 blade, for making faster turns or recovering from falls would want 3 typically or possibly more.
Thank you for your reply.
It is good to know that I am on the right track. Your answers to the questions I have are very helpful.
For the 10'' build, after more research, I realize it takes more responsibility to fly a big drone and I know I need to upgrade the parts and make sure it has as much fail-safe as possible. Do you know any professional grade parts/brands that are suitable/reliable for long distance flight or maybe know where to find more info about professional grade drones parts? I know pixhawk is well known in the rc community but I don't if it is the right part for the design I want.