Okay. The water police stopped me again, and told me that they loved what I build and what I was doing, but also warned me that what I was doing was in a “grey” area, and gave me an unofficial warning. (no fine / no notes taken) They even wished me a nice and fun day!
This was on my DIY jet board!
The lake I’m having fun on is a lake that officially has a max speed of 9 km/h.
Question. Is it possible to efoil at around 9 km/h?
If so, I might start building one.
This so the police can wish me even more fun
If possible, it will be quite difficult for the following reasons: You need a certain amount of lift to become foilborne. The formula for calculating lift, L = (rho/2) * v² * S * c(L) , tells you that the amount of lift doubles, if you double the surface of the wing, but quadruples, if you double the velocity.
Other way around: if your riding velocity is reduced to a half, you have to quadruple the wing surface to get the same lift. That means an automatically increase of drag.
rho density of water
c(L) lifting coefficient, depends on cross section of foil and angle of attac
9kmh is 5.6mph. That’s crazy slow! But, I can foil at about 6-7mph on my slingshot infinity 84 wing. There is one size larger slingshot infinity wing. The infinity 99. I think you could foil at less then 9kmh.
But, foiling this slow is difficult. The wing is partially stalled, the angle of attack is very high, and you are using more power, as pilots call it, you’re “behind the power curve”, “standing on the prop”.
Good luck. Try to make friends with the authorities. Try to go when less people are around.
Thank you all for the info.
The lake I’m talking about has about no one on it. One side of it is classified as “nature resort” and the other side has houses on it (one is our house).
Lot’s of owners have asked for an exemption so they can waterski on it, but a couple of owners are fighting this exemption (and winning) it.
I’ve been doing some more searching, and found the clearwaterfoils.com 2300 wing.
They are claiming that it will start to foil at around 5 mph (rider 77kg)