Posted 9/26/2023 14:06 (#10417117 - in reply to #10415619) Subject: RE: Dji T40
I've been trying to follow as many studies as I can for drone use (for herbicide and fungicide both). Still LOTS of learning to be done here, but take a look whats out there as well. (Some Weed Extensions have their own posted, otherwise theres also some reviews/trials listed on Sprayers101 as well)
Pretty much a few noteworthy things to mention:
1. For a DJI T40, I think they come by default with a rotary atomizer nozzle only. The T20/T30 come with a nozzle cluster (same kind of spray nozzles you'd use on a ground rig).
-The rotary atomizer makes a huge change in spray than traditionally used nozzles. Instead of having a variety of droplet sizes that hit different parts of the plant/etc, it intends to make all the droplets the same size. While it sounds good, a lot of good things happen having different droplet sizes (larger droplets cut down off-target movement of the smaller droplets in the mix. Smaller droplets give finer coverage, but only as long as they can get into the target area without being off target or evaporating, etc.)
So, not necessarily saying which is better (again, for transparency, we manufacture flat fan nozzles, so we'd have bias that way of course), BUT just bear in mind that a rotary atomizer is not the same as a spray nozzle. While targetting a median droplet size of like 300 microns might be great for fungicide coverage with a flat fan, if you calibrate a rotary atomizer to 300 micron size droplets, the coverage will be WAY less than the flat fan due to the lack of the smaller droplet sizes that are also made. So, if you go rotary, you might HAVE to spray with a smaller droplet size to get the same coverage (or better), BUT pay super close attention that your spray isn't evaporating before it does anything good (due to being super small drops) AND make sure the spray is actually getting to where you want to hit consistently.)
So, if you need better coverage, you can just put on more carrier volume, AND flying slower as it'll do a better consistent application at 5MPH than 16MPH.
2. Comparing fixed wing versus rotary drone is not a good comparison. The main thing is the rotor wash. With a fixed wing, it literally does a super job in getting those small droplets that would be otherwise having a tough time getting to the target. With a drone though, the rotary wash is a very different thing. It'll create more of a blade force that isn't equal across under each part of the blade during a revolution. My understanding drone manufacturers are trying to kind of 'redesign the blades' to improve this, but if you watch drone application videos or the actual application upfront, you'll see exactly what I mean. And rotor wash when it is used effectively is nice, but also with the tank being the largest payload on the drone, your rotor wash will decrease as you spray as well.
Again, doesn't mean drones are no good by any means, it just means its another thing for an operator to be aware of and address when it comes to application paths and offset spraying giving account for the wind. It also means that downforce will dramatically lessen from a full tank to empty situation as well, so the amount of force is dramatically changing through a flight.
For the speed side of things, drones can do a lot of things as well, but keep in mind your speed will generally set your spray height (or spray height will set your speed), and with that comes a HUGE difference in spray swath. That'd be the same as a field sprayer having one nozzle spraying at 20" boom height, and then adjusting boom height to 6' off crop and expecting the same spray rate and coverage. The higher you spray (without increasing flow), the less actual applied coverage you put down.
3. Time intensity of the drone and running the drone is no joke as well. This is where you make up time or can make it crazy time-consuming to spray with a drone. Make sure you have an efficient setup if you are doing anything as far as serious acres to be sprayed. This also brings into question the application rates as well. Overall, this would vary by coverage required, chemistry being used (and how sensitive it is to coverage/etc) and a whole lot of things, BUT the main thing it impacts is water useage, which directly changes the acres/hour that you can actually apply.
Probably more reasonably would be to assume 20acres/hour for nominal 5gal/acre work. I know some manufacturers tote more around the 40GPA, but that's probably like 2-3 GPA at speeds that are probably 10mph+ with very little downtime for filling/etc
So, a few things to keep in mind for sure, and while some of it is pretty critical of a drone spraying, the main purpose is that drones have their place for sure, we just have to be clear in where they fit into each operation. For operations that literally have huge hurdles for access and rough terrain and those kind of things that also cannot allow aerial application easily, drones are a solid option to get where you cant. If fields are full wide open and not much turning/ruts, then might not make the most sense unless you have the drone for other spraying jobs already.
Anyways, not a full story on the whole thing, but a few things to be aware of maybe getting into it and comparing drone makes/models/etc.