So, how do you plan on feeding that EDF? A gap in the fuselage, cheater holes (inquiring minds want to know.)
Have you flown delta type planes or anything with elevons before?Valid Question, thank you for your interest. I have put a large gap at about 1/3 of the way down the fuse from the nose to make sure I have adequate airflow. It is not Ideal, but hopefully I will be able to make it look good in the end. Suggestions on that would be greatly appreciated as well. I have also played around with cheater holes in the nose area but decided to hold off if I can to preserve the airliner looks. this is my first edf design so I am flying blind for the most part here.
Have you flown delta type planes or anything with elevons before?
Bigger motor=more power=more good
Others more versed in EDF setups will fill in the finer details, but as somebody who may use them in the future, I know that: You want 5-15% reduction in diameter at the exit hole from the part where your EDF is. If you want more static thrust for easier launches and whatnot, go with closer to 5%. If you want higher top end speed but less static thrust, go with a more drastic reduction, up to 15%.Time for another project update:
Got the EDF in today and man, does it have a lot of power! I am running a 4s 1300 which seems a little small but that is ok. I went for a 40a esc per the reccomendation of the edf manufacturers and it is running a little warm, even on the bench.
My main issue is the thrust tube setup. I want to maximize power but I literally have no idea or prior knowledge of anything related to EDFs or thrust tubes. My current tube is a 15in long cone that tapers from ~3.75 inches to 2 inches in diameter. Please Help! If it is a quick fix, we might be looking at a maiden tomorrow! View attachment 126206 View attachment 126207 View attachment 126208 View attachment 126209
Others more versed in EDF setups will fill in the finer details, but as somebody who may use them in the future, I know that: You want 5-15% reduction in diameter at the exit hole from the part where your EDF is. If you want more static thrust for easier launches and whatnot, go with closer to 5%. If you want higher top end speed but less static thrust, to with a more drastic reduction, up to 15%.
I heard that the best length for a thrust tube is 4x the diameter of your EDF unit. A short thrust tube is preferable to no thrust tube. Too long and you probably start losing a bit of performance.
Time for another project update:
Got the EDF in today and man, does it have a lot of power! I am running a 4s 1300 which seems a little small but that is ok. I went for a 40a esc per the reccomendation of the edf manufacturers and it is running a little warm, even on the bench.
My main issue is the thrust tube setup. I want to maximize power but I literally have no idea or prior knowledge of anything related to EDFs or thrust tubes. My current tube is a 15in long cone that tapers from ~3.75 inches to 2 inches in diameter. Please Help! If it is a quick fix, we might be looking at a maiden tomorrow! View attachment 126206 View attachment 126207 View attachment 126208 View attachment 126209
I don't know a thing about ESC cooling. For air flow, I would suppose you could put it behind your intakes, cheater holes in the path of the air getting sucked into the EDF, but not really obstructing it like taped along the wall.
I think for a thrust tube you want 85-80% So 3 to 2.75 inches at the end of the tube.
As long as the ESC is exposed to airflow it should be pretty much fine.
As a general rule to maximize static thrust, the outlet area of the EDF should be the same as the "Fan swept area" or FSA - that is, the outlet is 100% of the FSA. Reducing the output diameter reduces the FSA, which decreases static thrust but increases efflux velocity, meaning a higher top speed but less acceleration.
The FSA is computed simply by the total disk area of the fan (pi * fan radius ^ 2) minus the hub area (pi * hub radius ^ 2), the stuff taken up by the spinner and motor. Multiply this by the desired % FSA (in decimal form, e.g. 90% = 0.9). Divide this by pi then take the square root of it to get the output diameter.
I've heard that tube length matters, although I don't really know where that comes from. In my limited testing with a 70mm 10-blade freewing unit on 4s, I lost around 100g of thrust (1600g -> 1500g) by adding any sort of exhaust tube. Maximum static thrust was achieved at 100% FSA, as expected. Thrust dropped off by another 100g upon reduction to 88% FSA, and dropped to 1300g (200 down from 100%) at 85% FSA - this is where the static thrust really started to drop off on my specific fan.
Personally I would recommend sticking to 100% FSA to be on the safe side and then constricting it if further performance is needed.