Discussions

To all you multi rotor guys, I think you are doing great work and I hope to  use one in my business soon. I'm starting to see a lot of designs coming on now with shielded props. These would be great for me in my busness of aquatic weed control. Spraying by Rotary UAV in a swamp would be full  of hazards for open props, e.g. dead sticks, trees, reeds, vines etc. It seems to me, most of the shielded designs seem to be for looks (UFO's) or for pure prop protection. No one seems to be applying the ducted fan principle to the props and I'm wondering why? Is it the perceived weight issue or is it the uncool looks that could emerge from such a design? I know from my work with hovercraft, the ducted fan was much more efficient than an open prop. The whole point was to slow the airspeed down after the prop, yes slow it, The duct would taper slightly after the prop slowing and increasing the air presure under the prop. At the rear of the duct are slats, directed against the swirl of the prop. These seem counter intuitive but they redirect the air flow and keep the aerodynamic forces perpendicular to the prop, producing more thrust. The design of the duct in front of the prop is important too. With the correct curve and distance from the prop, a low pressure dome in front of the prop is created, producing more thrust. The intakes on fan jets are not there for looks. All these improvements are measurable, there are correct ratios for the duct based on the prop size, in fact there is a whole science dedicated to ducted fans and I'm wondering why you guys are not applying it.  By the way, I know what I'm doing using a small UAV re the payload to spray Ag Chemical. You don't need  loads of water to kill weeds, just atomise active ingredient, (one or two litres per Hectare) please don't debate me on that.

Luke Joseph

Farm & Dam Control