Propellers and Ducts


#208

Not to mention that our thrust acts on the opposite side of the board as with a kite.


#209

As the propeller rotation ? I change to left rotation with FR propeller , may be that is why it took some time …


#210

Yes but dont forget we dont need a racefoil here… and if you say the moses 683 is not the best profile this is relative. Best profile for kitefoil windfoil or efoil or race foil?
It all depends where you want to use it, and for e-foil Moses 683 is quite ok in respect of easy flying handling and efficiency. And with our profile we have similar handling but 20% more efficiency, so we are quite happy.
For an efoil you want to have a wing that runs from 20 to 40km/h at a weight of 100kg and it should start flying at 15km/h. And should be stabel at that speed.
All the kitefoils are used totaly different…mostly at 40km/h+ and at only a third of the weight…
So don`t compare apples with pears…
And yes you can increase efficiency with canard setup (that we use as well) or with less stabilizer force. a.s.o…but as I said the main goal is easy stable ride for e-foil with big speed range…second was efficiency…


#211

I love your approach. this is exactly what I want to do. I think the amount of current people are drawing with their designs is insane and the weight of the batteries you’ll need, and the safety of that much amperage as well…and all the over specs components you need. High efficiency isn’t talked about enough.
How big is your front wing? High aspect ratio? I have a few wing designs I’ll test but first I need to get my propulsion unit working…finally have all parts. I’m trying to use as low of a prop pitch as possible.
What size of prop are you using? Your efficiency is impressive.


#212

I follow the same strategy. First get as much thrust as I can out of my motor to get around 35kg of thrust. That seems to be a common requirement here. Then try my kitefoil and cnc different wings.


#213

Elevate, like MikeL I appreciate your approach too. Especially for the first time in hydrofoil history, eFoils provide an objective environment with figures (volts, amps, speed) and I’m sure that kitefoils and windfoils development in return will beneficiate from that too.

Yes, speed and weight range do matter. I mentioned Banga and its Chubanga heir because a lot of CFD has been carried out, extensively tested before and during competitions and their high AR front wing is surprisingly easy flying and very tolerant according to the people who have tested them.

As you mentioned “profile efficiency” my answer was targeted at that point.
Moses 683: not obviously optimised for least drag as it is a freeride front wing. It would be interesting to test your new wing back to back with the 639 (windsurf competition with high aspect ratio) more optimised to that aspect which doesn’t necessarily mean unpleasant flying handling.
As a conclusion, if you have the same footprint as the 683 with same profile thickness but use a more efficient airfoil section and get the same speed with 20% less power, congratulations. :wink:
I would appreciate your 639 figure comparison if available.

By the way, do you have an availability date for your line of products ?

Moses%20639%20vs%20683

As per:

I have to politely disagree. Seems to me that the kinematic viscosity in the Re formula was not switched from air (10-5) to water (10-6)
200.000 is 5 to 8 times too small. According to the values you gave us (40 kmph that is 11m/s), water temp = 10°c
Moses 639, Windfoil competion low drag high AR, Re = 1.600.000 max at wing root
Moses 683, Freeride fun, low AR, Re = 1.100.000 max at wing root
Reynolds%20Moses

http://www.airfoiltools.com/calculator/reynoldsnumber?MReNumForm[vel]=11&MReNumForm[chord]=0.122&MReNumForm[kvisc]=1.267E-6&yt0=Calculate

One thing to notice is that if one decides to use the same wings on a kitefoil with a wingspan shorter by 40% (40cm typical value), the Re doesn’t change because only the chord length is considered in the Re formula.


Biplane and box wing hydrofoils
#214

You understood me wrong. I said the moses 683 works quite well… but they use the wrong profile as well…It works good but it is not optimized for our use, and theerefore another wrong assumption.
You dont optimize it for 40km/h but for the point where you want a stable ride and that is much less speed therefore you end up with REnumbers below 400000. If you want to create a race efoil yes you can go your approach…


#215

What profil would you use for the rear wing? I am using a less than ideal kite foil that has some negative lift and I had to compensate with a shim


#216

You should play with XLFR5 for some time… very nice analysis features and it’s a good starting point. Take time to read the user manual, for analysis readong


#217

great discussion. I feel like I just learned a bunch about foil design. I think I’ll read more. It seems to me that optimizing for about 20km/hr would be a good cruising speed.


#218

Yes thats the way you go:wink:

We decided to share our research. You can order our optimized front wing profile for e-foils already for 229€ in full carbon. If your interested you can buy it directly from manufacturer. Just order it with email under: info@RLkite.com

Needs about 7days for shipping :wink:


#219

Yes I saw these photos on their Facebook page back in May. Looks really nice guys- well done!


#220

Will order one for sure if my current one doesn’t work out.


#221

Yes quality and the efficiency is great…


#222

Hi guys is there any online shop selling props?


#223

I did share this propeller and impeller generating software last year on the forum but things get buried. The company just came out with new free and instant STL and STEP file download of impeller design if you enter in specs. https://www.wageningen-b-series-propeller.com/


#224

You can make some nice looking props with that. Thanks


#225

Nice article! Does that mean you are working with centrifugal pumps?


#226

We, not centrifugal pumps. inducer impellers are used on high-end jet boats to get more flow and thrust as low end speed.

We just tested a ton of different setups with impellers and nozzles today. Learned a ton and preping for more testing with new knowledge within a couple days.


IMG_1056


#227

I was thinking about not using two-blade propellers? I was seeing racing boats with thai propeller just worth a try? I know it manufactures it turns very well at high rpm

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