We also could construct one by our own or make adjustments. I’m curious to see if the impeller is also great in giving thrust as it is in creating vortexes.
Mantaray, the Solas propeller tested very well. It would require a higher kV motor than I’ve chosen to attain good foiling speed.
I think a higher kV Alien c80100 and the Solas prop may be a very good choice.
This chart below will help match motor speed and prop pitch for the desired. For max efficiency use 85% of max kV x voltage. Also allow about 10 to 15% slip.
Example for my case:
65kV x 44 Volt (average) x .85 = 2,860 rpm
I’m using 10" pitch for now; from the chart then top speed would be about 26 mph with no slip
Add 10% slip and the top expected speed is about 23.5 mph average. A little more when the battery is fresh, a little less as the battery is used up and the voltage starts to drop.
Please note this assumes your drive system has the power to attain the rpm. Too small a motor and you won’t reach the predicted rpm ever.
Morgan. the Solas propeller is manufactured and sold for small outboard motor use. I’m not aware of any step files…seems unlikely the manufacturer would release them.
I’m using passive cooling.The motor will be mounted inside a failrly tight fitting aluminum housing. Heat transfer is a combination of radiant heat transfer and forced convection between the motor and the (well cooled) aluminum housing. This arrangement has already been proven to work well on my first prototype efoil with a much less efficient (meaning more heat) drive.
With the Alien c80100 motor and best prop combination, the flume shows we need 255 watts for 15 lbs. of thrust and 360 watts for 20 lbs. of thrust. The 15 lbs of thrust should provide me with a 15 mph cruise, the 20 lbs more than 20 mph cruise as calculated by the hydrofoil deign tool.
The nice thing about an efficient motor/prop combination is that the benefit of the low power consumption is also reflected in the operation of the esc, wires and batteries as well as the motor. The result is less power wasted as heat everywhere.
You can do this. Please try it. Take this heavy motor, place it into a pod adding low volume and ventilate air through the windings using part of the motors torque by an integrated fan system. Make sure the air flow is systematic. Try to build lighter than a torqu?do with more peak power. Think about the duct and the motor pod will influence each other. Your flume measurements are a best case, i do not want to critize this. Only to keep it in mind, no gear, everything well cooled and underloaded, prop without duct and motorpod, short time measures without resistance in the waterflow.
I admire your work, but i do not believe the conclusions yet. Anyhow i want to support you with ideas because i feel its a promising way.
I agree, this flume is best for comparative data. It is a great tool (not perfect) and has helped reduce electric power requirement by a great, great deal. The Leopard motor and prop used in the video below was tested in the flume. Here are the comparative results with the best motor/prop combination so far:
To further clarify the pod setup. The motor will be bolted to an aluminum firewall which will be welded to the aluminum pod. Distance from the motor to the aluminum tube shrouded in water is less than 3 cm. I have all the confidence that the head dissipation will be adequate. With the Leopard motor we were pulling upwards of 50 amps with no heat issues. The new setup, as you can see from the numbers, we are expecting to pull less than 10 amps.
Mike
If the power requirements prove correct in practical testing that’s a huge improvement on existing setups in terms of battery requirements. I.e same batteries for alot longer runtime, or less battery/cost for same runtime.
That sounds great. With 20lbs ~ 100N and 7m/s you have a power requirement of 700Watts. With prop efficiency of 75% and motor the same you will have around 1244Watts input power from the batteries. Maybe you drive slower, than your power requirement drops further.
What is the diameter of the pod?
I use windsurfboard without a wing so i calculate with 200-400N thrust, so i need around 3-5kW battery output.
So i cannot cool the motor by air in a pod. Anyhow i understand, i need some wing.
15 lbs. (14.7 actually) at 15 mph is predicted by the design tool. 66.7N x 6.71m/s = 447.6 Watts.
Propeller efficiency and pod drag already included in the calculations.
Design tool predicts .74 hp or 552 watts at 15 mph with the propeller efficiency factored in.
Hello Winging-it, great work you are doing with providing this data.
I also think that it should be able to foil with less power that a lot of people assume.
There are videos of people foiling just pumping their boards. How much power do they need?
Common understanding is that Joe average can produce about 100 Watts sustainable on a bicycle. A very fit athlete maybe 300 Watts sustainable and a maybe around 1kW over a very short period of time.
So I would assume that the pump foilers also produce around 200 Watts and not a lot more. And that’s enough to keep flying. Agreed, they have slow foils, very good technique and don’t have the drag of a pod, but not a lot of power.
