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Spray drone questions
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Posted 7/8/2024 11:23 (#10802840 - in reply to #10799544)
Subject: RE: Spray drone questions

Yup, they'll be out there.

With CDA nozzles, there are some perks and some significant hurdles.
Overall, the CV of a CDA nozzle at generally used spray height/swath is worse than flat fans on a drone, and in many cases might be best equated to using your broadcast sprayer with a mix of nozzles that are a size or two larger/smaller than eachother. Again, CV of flat fan nozzles/clusters isn't near perfect either, so it isn't just a CDA nozzle versus flat fan on drone. Both application methods on drones suffer with CV.

It doesn't mean you can't have a perfect spray, but it'd be akin to having 100% kill on 40% of your acres with poor CV or consistency between swath/etc (with the added risk of resistance with greater CV variance).
I don't mind that rough concept to compare, again this is a ROUGH idea just to illustrate it, as it doesn't take sprayer applicator experience or training or any of that stuff in the mix, as it makes a significant difference:

I'd reckon using:
CDA nozzle on Drone might be like 100% kill on 40% of acres
Flat fan nozzle (proper sized) on drone might be more like 90% kill on 55% of acres
Broadcast acre (lets say as the baseline) might be 80% kill on 100% of acres

Again, rough concept, but just a top level concept. So, flat fan nozzles on drone might improve consistency of application, at the cost of some droplets coverage as they produce a MIX of droplets instead of nominal droplets of the same size.

With CDA nozzles, you get to the point where EVERY droplet is generally the same size. Again, sounds like a great thing, but there are significant shortfalls when it comes to spraying with a drone.
Back in the 70s+ with CDA nozzles, some of the constraints were how much power they used (like 1amp per motor, which you could imagine as an issue on a 100'+ sprayer). Also, making the same size droplet is handy, but it also doesn't produce as nice as a linear swath as flat fan nozzles.

Again, the intent of it isn't to throw mud at CDA nozzle manufacturers at all. The process and the equipment has been around since the 70s and works as it is intended, its just with field spraying there is a great need of efficiency (fields sprayed) as well as consistency in realistically inconsistent situations or environments (wind, location, drift susceptibility, etc.). A fair bit of the efficiency is lost on drones when you are using water volumes that help improve consistency of application and such.

With drones spray applications, the bread and butter is swath width and coverage therein.
Compared to a broadcast sprayer, where it is moreso coverage ONLY, as swath width/overlap is generally more than covered as most are running their booms higher than ideal.

I guess back to your original question, yup, there'd be studies with CDA nozzles for sure. They aren't really just a newer machine as CDA nozzles have been used on drones in Asia for a long time. Again, different application targets from what we are spraying and other significant logistical issues that make drone spraying the only realistic method to spray (e.g. tiered rice paddies, etc, etc.), to which drone sprayers are a huge help to get where a ground sprayer cant. They are much more consistent than a boomless sprayer in those tough to reach areas and will make huge strides in use-cases in those really tough to get to sensitive areas.

On the RPAAS website (drone spraying conference/research group), Dan Martin has compiled some of the studies as well. There should be old videos of presenters from previous RPAAS conference presentations that break it down as well. I think these were public videos, but maybe they were only hosted for attendees/participants.

On the lower part of that site is a dropbox link to Dan's list of some of the studies that can be downloaded.

Also, a good way to also find related studies would be to review the list of previous speakers at the RPAAS conference. The site has changed now, but used to be hosted by the folks at HSE-UAV.

Most of the speakers from previous sessions that are from a institute would have been presenting testing or research that tied into papers or more research related to efficacy in specific use-cases or investigating consistency in drones. There are also speakers from alternate drone manufacturers (fixed wing, helicopter, etc.) that can fix certain aspects that are in shortfall from small rotary wing drones.

Again, drones (with CDA or flat fan) are totally useful and will be useful, but there are significant changes and calibration needed that often drone retailers don't highlight probably near as they should. If you catch some of the videos of speakers nd other professional/commercial drone spraying outfits, you'll probably get a feel for how critical spray height is depending on where and what part of the field is and how there are literally sweet spots in spray height that WILL dictate the height you are spraying at to a large extent, which means it will directly effect your swath width and # of passes which has a direct change to your productivity of that field.

You can't just force it as a 'I'll be spraying 20' swaths, so that means I'll have X acres/hour'. It'd be more of a situation where "OK, I can see where the sweet spot is for the drone height, lay out a swath length to calibrate the coverage across that swath. Measure the swath, and then you'd have an idea that my swaths will be X feet, and you run with that spray height and that many passes to finish the field. Again, different setup compared to fields we can get a ground sprayer in, but super crazy important.

Anyways, lots of info tossed out there. I just want folks to realize there is a pretty heavy difference in training and operator experience in making a spray drone a viable application that is net-useful.
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