I see in the description of many foils they talk about the foils top speed and often give a specific number. What does this actually mean when your on the water? Does a foil just get to a certain speed and then level out and not go any faster? Does the handling become more difficult at top speed?

I'm not an expert, but did some reading on hydrofoil design. From what I understand , the combination of wing profile and overall design elements of aspect ratio, sweep and anhedral of wing, plus effects of mast profile, and fuselage design are determining the top speed. Of course stabilizer is playback roll too.
The wing will reach a top speed and the water flow over wing will become turbulent and even cavitate ( water vaporized due to pressure) leading to instability. So there is definitely a top speed, even if you apply more power, it won't go faster.

I'm on a 2016 Moses Fluente mast, 548 front wing and 330 stabilizer. I've done 42km/hr on it and that felt blistering fast. A fellow foiler with one more season than me, and 20 years less wear and tear, took it out and he did 49 km/hr according to his Locosys watch, without pushing particularly hard. I'm not sure what the top end is....im not near it, it's supposed to be the slowest wing they sell.
Hurts a lot to fall at 40km/hr.

Hurts when you fall at 20kts.
Hurts when you fall at 40kts.
may as well do 40

Thanks for the replys guys, that makes sense that the design has limiting factors which govern speed

20 30 40 knots sounds painful

So far in my learning I have had some really solid crashes a couple times doing a sort of body drag Waterski thing

I have been doing alot of Surf /Sup foiling on low aspect foils and we thought they had a max speed around 30km but as we got better we are now cracking 50km paddle in free surfing on waves. It's just rider ability that max's you out. I also kite on kite foils and tow in on both kite and Surf foils. The kite foils are way more stable at speed but pretty unforgiving on an over foil , you cavitate that front wing and you are down hard , the lower aspect surf foils don't drop as fast on an over foil giving you that chance to save it. The other thing we have found kiting on a surf foil lets you glide alot faster without the pull of the kite so you can free surf the swell alot more which is really fun downwinding as long as you can keep your kite from back stalling and it also gets you up and going in less wind and more glide on transitions.

The Kai Go Foil is what we have been using for all 3 and the shorter mast (600mm) also feels really good on the kite plus you can ride in shallower water. Kiting has been dominated by very high aspect foils with long mast but if you want to kite foil waves these new surf /Sup foils are so much fun. The other really good thing about the Go Foil no sharp edges , which is a huge plus.

To answer your question what is the top speed , I don't know but you don't need a super high aspect long mast , razor sharp kite foil to go really fast unless you want to race and compete. This is a shot of the Kai Go Foil we have been testing. We mounted it on a Slingshot Dwarf craft board. ( it's on a Sup in this pic) To a kiter it's probably the ugliest thing you have seen with it's big fat lip leading edge and shouldn't work on a kite but it does really well. Disclaimer nothing to do with Go Foil.

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Piros said..
I have been doing alot of Surf /Sup foiling on low aspect foils and we thought they had a max speed around 30km but as we got better we are now cracking 50km paddle in free surfing on waves.....

50 km/hr paddle in foiling, 30 mph / 25 knots? That is pretty fast, especially on these super low aspect surf type foils. Was that measured by a GPS or other device?

Garmin Fenix 5X and boat GPS multiple runs , we are Qld based and the Sup/Surf foil crew in NSW are getting similar speeds on the Naish Sup/Foil as well.

Thanks for your contribution Piros. I was originally asking the question out of curiosity not necessarily because I just want to go super fast. What you are describing with the surf foil actually sounds amazing, I guess with a big low aspect foil like the go foil you could really ride the waves and you could probably use the tiniest kite possible and back it right off when your on the wave, that would be a dreamy way to foil

Thanks for your contribution Piros. I was originally asking the question out of curiosity not necessarily because I just want to go super fast. What you are describing with the surf foil actually sounds amazing, I guess with a big low aspect foil like the go foil you could really ride the waves and you could probably use the tiniest kite possible and back it right off when your on the wave, that would be a dreamy way to foil

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Youngbreezy said..
What you are describing with the surf foil actually sounds amazing, I guess with a big low aspect foil like the go foil you could really ride the waves and you could probably use the tiniest kite possible and back it right off when your on the wave, that would be a dreamy way to foil

That is exactly what I've been playing with last season. I'm using a 5m kite and freeride foil and just trying to ride the swells. I'd love to try a super low AR foil like the Takuma or Gofoil. Slower the better I reckon !! Got my foiling gybes sorted now - I just ride toeside and don't bother switching. Basically I can ride the same downwinder as my mates on SB too which is cool.

I wonder how slow you could go using the Zeeko XLW windfoil wing?

all top foils:ML, LZ, KFA, Enata you do over 30knots.top guys go more towards 40knots on reach.23knots upwind and 35knots downwind..