Windy conditions
- Thread starter leadpan
- Start date
turkeybird
Member
Higher rpm's and smaller props = more stable
I've built 3 different X 8 quads lately, and I'm a believer now. I love X8 configurations. My favorite to fly out of all of my copters ( helis 800 size to 450 and multis 1200 Octo to Estes micro) is my Hobby King Dead Cat frame set up as an X8. It doesn't matter how much wind there is, it holds. I built it from dji 550 motors and 30 amp esc's that I had sitting around with a nazav2. Totally cheap, and it flies better than any of the others!
I've built 3 different X 8 quads lately, and I'm a believer now. I love X8 configurations. My favorite to fly out of all of my copters ( helis 800 size to 450 and multis 1200 Octo to Estes micro) is my Hobby King Dead Cat frame set up as an X8. It doesn't matter how much wind there is, it holds. I built it from dji 550 motors and 30 amp esc's that I had sitting around with a nazav2. Totally cheap, and it flies better than any of the others!
Can you please explain why you believe this to be the case?
stevemaller
Heavy Lifter
Is it safe to say that high quality carbon fiber props are the best of both worlds (can go larger with lower weight)?
Strictly speaking, manoeuvrability relates to how fast thrust can be changed, not rpm. When comparing two props of different diameter, the amount of additional thrust available from a given rpm increase is not the same. Sure the mass of a smaller diameter prop may require less force to accelerate, but is the resulting change in thrust with respect to time greater than what is achievable with a larger diameter prop using a similar output motor? If you do not have to accelerate the larger prop as much to achieve the same thrust increase then perhaps not.
When a prop accelerates, it not only has to put power into accelerating the mass of the prop itself, but it in order to do the job it is designed for, it has to further accelerate the mass of air flowing through it. My gut feeling is that the amount of work the prop is doing on the air is orders of magnitude larger than the work it is doing just accelerating itself in which case the effect of the lower mass of a smaller diameter prop would be less significant.
In practice it is not such an easy thing to compare as an optimal setup with different diameter props requires different spec motors. I have never seen anyone do a proper comparison. It would require two motors of the same size/power output but different kv rating and matched props. You could then time how long each motor takes to accelerate between two set thrust levels. I would really like to see some actual data on this as my hunch is that bigger slower props can provide just as much 'manoeuvrability' but with better efficiency...
Scott Drysdale
Mixmaster
Under heavy load, most of the thinner props will deflect up towards the tips which reduces the lifting efficiency. Carbon fiber makes it possible to make the prop thinner but also stiffer.
If you work with eCalc for multirotors, you will see a P.const factor in the lower right of the data input form.... It is a parameter that is based on the prop thickness. The thinner the prop, the less drag it will produce relative to lift....... this is called the L/D ratio. Since carbon fiber makes it possible to make props both thinner and lighter, some of the CF props, such as the paddle props may give you more airtime.
If you work with eCalc for multirotors, you will see a P.const factor in the lower right of the data input form.... It is a parameter that is based on the prop thickness. The thinner the prop, the less drag it will produce relative to lift....... this is called the L/D ratio. Since carbon fiber makes it possible to make props both thinner and lighter, some of the CF props, such as the paddle props may give you more airtime.