How much thrust do we actualy need?


#1

Just wondering has anyone done any tests to see just how much thrust we actually need to get up and flying? I know for a fact its more than I can generate just trying to run as we tried testing that last weekend?


#2

It’s very dependent on rider weight and skill. Check out this guy who can paddle to foil up on a flat lake: https://youtu.be/aZp3p8Kbjwc. Very tempted to try smaller, less powerful but less drag and more efficient setups next and integrate the throttle in a paddle. Like a sup surf assistant to efoil instead of pump to the next wave in the ocean. :smile:


#3

Charlie, this guy does it running

Looks like a huge and high aspect wing.
There is also another video where he is powered by a bicycle. And another powered by a winch.

I think an average person on a bike can produce around 300 or so watts.


#4

we were very close to getting up by running but we were in 5mm wetsuit and wetsuit boots and not on a slightly wet and muddy surface so perhaps if we had had proper shoes and not in a wetsuit we could of just managed. we were trying it with my sup and large sup foil. The number I’m looking for really wants to regardless of technique. I had some fishing scales that max out at 22kg and I can easily max that out so I guess I will just have to try and find some large scales and try again.


#5

I’m sure you provided a great picture. Running around in 5mm suits, sweating and trying to foil…

The guy in the video runs horue, so he’s a very experienced foiler.

A luggage scale might do the trick. When you get up you know the thrust needed with a sup foil, we then need to add thrust to overcome the drag of motor, propeller and duct.

Thinking about it, it’s probably not only a matter of thrust but also speed. Maybe you couldn’t run fast enough in your wetsuits.


#6

it was near freezing conditions so feet were numb and there was defiantly no sweet happening, it probably didn’t make as much a spectacle as when we did a last resort of looping a rope round a hand rail as a turn around pully on the middle of a bridge and then tied the rope to the roof rack of the car haha

I just ordered a 50kg set of scales of ebay for £3 so will see how that goes. I think with the foil I was using the speed should be achievable running we were so close last time I think its more the power to over come the drag, I wasn’t running fast at all. I think maybe with a set of runners on or with a second person it would easily be achievable to get the numbers I need.


#7

That looks super ridicoulous : D


#8

At this moment I can ride with my second prototype and jet with very low voltage and speed, I confirm the most important is the good balance between volume of the board and front wing, both things are the most important in my opinion.
With my first prototype I can’t ride in the same conditions.


#9

https://www.facebook.com/kitesurf.reparaciones/videos/1928041110544697/


#10

they are basically two totally different values though the thrust to get out the water and then the amount it requires to cruz. I have to admit I’m slightly amazed that it seams know one has measured it and used it in there calculations for there design.


#11

Why does the volume of the board matter for you?


#12

Yes we have done testing , two different boards and a kite foil and a sup foil . The load cell indicated 30kg load to get the board to pop and then reduced to 7-12 kg load when foiling . the kite foil took 5-10 kg more to pop then was similar load . both pulled directly behind a boat. load cell was calibrated in the 0-50kg range and has 3000 increments.


#13

Interesting

Was that with a motor pod or a pure board and foil setup?


#14

Foil and board only aprox 100 kg auw. Prop would add drag even when spinning but it gives a good rough guide . We derived 48v and 3kw to be safe , i know of a rig running on less than 300w but its impactical for us. The foil is a scary aspect and roughly 1.5m wide


#15

cheers thanks for that that’s what I was looking for. I guess I will have a try with the scales I ordered when I get them. Many thanks


#16

If you want a system to start with less problems, choose a board volume 25-30 liters minimum more than your weight. Try to move the weight of the electronics forward near the nose of the board as possible. A front wing of sup like go foil, naish malolo, takuma, I think takuma is perfect.
I can lift with 8s direct and jet, my weigh 70kg.
And start working from here to reduce parameters.


#17

Too late. My board is about 80l and I have the Cabrinha foil from 2017.


#18

will be more difficult to start, you will need gearbox and power, the more power you need the more wear the elements will have and break before, so the ideal is to get a system good balanced and light, if possible.


#19

Well, its not light either. I am probably going only for fibre glass and the foil is very heavy : )
I hope there will be a direct drive motor by the time the board is ready. Didn´t buy the ESC or Motor yet.


#20

Great info Virus!
I agree larger/wider board will make it much easier to get up and ride, plus the larger boards require much less thrust to get moving and up also.

What is your setup with direct jet 8S? motor type/size/kv, ESC, are you still using the 56mm impeller you made?, and what is the diameter of your exit nozzle 40mm-ish?