I know there has been a lot of chatter about the 10-12 blade fans and the sound they make. I've done a fair amount of testing and reading on air flow and the function of an EDF unit. I also have an advanced degree in physics and I'm very familiar with particle motion and sound waves. What people seem to be forgetting is that the "vacuum cleaner" sound is mostly coming from the air flow over the sharp edge of the fan shroud and not the motor itself. Just run the motor with no fan and you don't hear any high pitch noise. If you spend some time listening to some of the YouTube videos, you'll hear that some planes sound good and other don't. Sure, the 10-12 blades do dampen the noise and helps smooth out the air flow thus providing that neat jet sound, but I've gotten the same with the 5-blade fans. Take a fan unit which has the flux ring included (this is the rounded piece you can put on the intake of the fan unit). Try the fan both with and without this and you'll hear a big difference.
Case in point. I've put a 80mm fan unit into a plane that was designed for a 90mm fan. This fan unit was from my crashed Habu 32 which did have a high pitched sound when flying. I used my lathe and turned an adapter ring to fit the fan shroud with the outside diameter fitting the 90mm duct of the new plane. This adapter has a rounded inside shape and smooths the air flow between the intake ducts and the fan. The plane sounds more like a turbine than some turbines I've hear and has most people believing it is a turbine until I show them the insides. One other thing I should point out, and most EDF owners already know this, a 10-12 blade fan pulls more current than a 5 blade fan with the same motor and battery. The 10 blade fan creates more thrust but not much extra speed. For me at least, I'd take a little less thrust and gain another 30-60 seconds of flight time with no real loss in speed.
So, if you can get to the fan unit and smooth out the transition between the duct to the fan, you might be surprised to find that much of the vacuum cleaner sounds goes away. It is always a good idea to clean up all of the ducts and edges that the air has to pass by so this is a nice benefit in both duration (less current draw) and a more pleasing sound. I'm sure there will be a few folks that may dispute this or say this has little effect. All I can say to try it first. I have and I have a couple of EDF jets to prove (at least to me) this is a valid point. Hope this helps at least one person, if not in the enjoyment of a better sounding plane, but to learn a little bit by doing some tests themselves. Cheers
Case in point. I've put a 80mm fan unit into a plane that was designed for a 90mm fan. This fan unit was from my crashed Habu 32 which did have a high pitched sound when flying. I used my lathe and turned an adapter ring to fit the fan shroud with the outside diameter fitting the 90mm duct of the new plane. This adapter has a rounded inside shape and smooths the air flow between the intake ducts and the fan. The plane sounds more like a turbine than some turbines I've hear and has most people believing it is a turbine until I show them the insides. One other thing I should point out, and most EDF owners already know this, a 10-12 blade fan pulls more current than a 5 blade fan with the same motor and battery. The 10 blade fan creates more thrust but not much extra speed. For me at least, I'd take a little less thrust and gain another 30-60 seconds of flight time with no real loss in speed.
So, if you can get to the fan unit and smooth out the transition between the duct to the fan, you might be surprised to find that much of the vacuum cleaner sounds goes away. It is always a good idea to clean up all of the ducts and edges that the air has to pass by so this is a nice benefit in both duration (less current draw) and a more pleasing sound. I'm sure there will be a few folks that may dispute this or say this has little effect. All I can say to try it first. I have and I have a couple of EDF jets to prove (at least to me) this is a valid point. Hope this helps at least one person, if not in the enjoyment of a better sounding plane, but to learn a little bit by doing some tests themselves. Cheers
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