I have noticed most SUP foil stab wing tips are down and kite foil are up.
Anyone know the logic especially when foil profile is symetrical?
I know a guy who has tried a SUP foil stab wing both ways for kiting and has not noticed any difference.
Up tips provides better damage protection.

JB can you advise, I have Naish medium thrust.

All foils are different , the rear wing is designed to drag for stability but can also be used for additional lift , like Naish & GoFoil. The Naish rear wing 100% points down. There are other brands that face up but are very different to GF or Naish. Kiting is very different you are getting lifted so you can still get going on an incorrect set up foil.

Things change a lot when you start adding in different angles.

Angles (usually down) help with constant turning like with SUP and Surfing. However flat is actually more efficient and great for straight line lift like with Kiting or Windsurfing.

Kiting and Windsurfing you use a power source like your sail to deliver the power and speed you need to hydrofoil, where as a surf foil requires forces and gravity to create the equation.

I have had a lot of time between the Naish WS and the Naish Surf Windfoiling in waves and it is very apparent the differences.

Naish Thrust Surf

Naish Thrust Windsurf.

The Naish Surf tends to lift very early and with a lot of stability at low speeds. It also continues this stability when you do turns, even at super low speeds. However the Surf foils do have a limited top end, and will reach a point where you are learning so far forward (seemingly) to control the lift.

The Naish Thrust WS1 is very smooth and constant with it's lift. It is not far behind the Surf with it's foiling speed, but it tends to want to go faster, and it naturally does go faster. Now when you go to turn the WS1, that's when you'll notice the different. Large open turns are fine, and the foil feels naturally stiffer, but when you try to tighten up your turns like achievable on the Surf, smoothness and lift is compromised.

When I have used the WS1 rear wing on the Thrust Surf Foil, I notice similar to the WS1 Foil characteristics, which shows that the rear wing really does influence the turn-ability of the foil.

When I change up the rear wing on the Thrust Surf XL is also interesting. The XL Rear wing king of makes the foil feel like the Thrust Surf Large does with the WS1 rear wing. It is more efficient and great for pumping, but tight turn are difficult and stiffer. By simply changing the rear wing to the Surf rear STD, I can get a lot more mobility in the XL.

I think that when a flat wing is leaned over the combined forces change (please be kind on my tech diagram ;) ). The reason a surf wing keeps consistence in lift though turns is because the lift co-efficient remains similar, where as the flatter wing changes. This feels fine on the wind wings because generally you are riding in a straight line with a lineal power souce, but surfing your power source if not so constant and directional.





Anyway I am sure there is a much more technical reason behind much of this, but there is definitely a different, especially with aggressive turns.

I'll speak with the engineers and see if I can get a better response.

Ride safe,

JB

I think JB is spot on. I'll add my experiences to further help our understanding...I hope

I used to own a surf foil with flat (meaning no anhedral) front and rear wings. It had slightly more low speed lift than the Naish L (I now ride Naish) yet it did not surf near as well because it would side slip to the inside of turns when banked. So anhedral is good for carving.

At SurfExpo last year, I met Kai Lenny. He told me because these huge front wings are so naturally stable, they like to do the rear wing with anhedral. Anhedral hurts stability. So anhedral rear wings help counter the massive front wings. Better turning.

When I made the switch from that flat wing surf foil to Naish, the two things that stood out the most......wobble under my rear foot. I swear, I could feel exactly what Kai said about anhedral. The second, was how great the Naish carved compared to my old flat wing set surf foil.

Good info tonhelp my understanding.
Look forward to more from JB.
I will do some on water testing and this information helps my understanding of what is happening and why.

OK guys, here's the direct quote I got from Michi Schweiger, Foiling Product Manager for Naish Foiling International.

- Hi JB!
I can give you the run down from the riding side of things and Nils can follow up with the technical info.
We have tested with flatter wings/ less wingtips.
Those foils obviously still ride but they are extremely sensitive when it comes to turning.
Wings with down turned wing tips allow you to turn and transition smoothly between riding the wing in an angle or flat.
Flatter wings are more critical in that transition and have the tendency to jump out once the speed decreases while turning.
Same scenario for backwings. Every time we use some that are flatter we find that they are by far not as forgiving in turns."


So very similar to my findings from a riding perspective. Nils Rosenblad, the Engineer and designer for the Thrust Foils along with many other Naish products such as sails will give me his technical angle soon which I'll share up also.

I hope this helps you all tech out a little, I love it!

Ride safe,

JB

And here's the more technical answer I received from Nils Rosenblad Naish Engineer and Thrust Designer. Although he is mainly describing the front wing, the theory is the same. Again, not to dis-similar to my thoughts above.

Hi JB
The simplest and clearest explanation is that kite (and WS) foils are primarily optimized for steady state flight - you want to get up and go, and then keep going in a roughly linear direction - whereas surf foils are primarily optimized for turning, with steady state flight being secondary. Think of the difference between a glider and a stunt plane.
Interestingly enough, even downwind SUP foiling is much closer to surfing than kiting - we tried both, and the flatter wings were a disaster because they simply didn't respond to the constant rider input (which of course is the opposite of steady kite foiling). I was initially imagining that scenario to be closer to steady state, and turned out to be completely wrong.
The reason the geometries are very different is also quite simple.
Kite foils cant (to windward) to shave off excess lift and increase lateral resistance at speed. The higher aspect ratio, flatter wings have much better L/D ratios (especially at the higher Reynolds number/speed regime kites operate at) and have a normal elliptical load distribution that results in efficient, steady, controllable flight. Any wingtip treatment (winglets etc) is solely there to mitigate tip vortices (drag).
Surf foils are designed to generate most of their lift in the center section, and the large down-turned wingtip sections are there to both keep the lift fairly constant through a wide range of cant angles (the speed range is relatively narrow once you are on a wave), and to minimize side slip thru a carving turn. They are also shaped to make the transition from one extreme cant angle to another - think 'S' turn - as smooth as possible.
An easy way to look at it is to imagine that the center part of the foil wing is the tail of a surfboard, except fully submerged - the tip sections are the thruster fins.Hope this helps, and that you are doing well and having fun!
Best Regards

Nils Rosenblad

Here is a link to the definition of the Reynolds numbers - en.wikipedia.org/wiki/Reynolds_number

I hope this all helps.

Ride safe,

JB

Update
I tried stab upside-down on medium Naish - bad idea just did not work.
Well it sort of did but just far from right.
Put on the right way up and it performed like a real one.

Slingshot Foil Designer Tony Logosz discusses the basic concepts and function of a foil's stabilizer rear wing.

I'm a little confused about the rear/stab concepts discussed at 2:15.

In my opinion, the smaller rear/stab is no where near as affective as a larger one for pumping and the smaller rear/stab is far better for turning. I have tried many combo's with big front wings and I basically put it down to;

- Non breaking waves, fat and lots of pumping = XL rear/Stab.
- good walls and great for carving and turning = Std Rear/Stab.

Now, obviously I am referring to the Naish Thrust Set up, and it may be different on the SS.

The larger rear does however offer up a lot more stability. Makes your glide ridiculously stable.

Great vid though, and appreciate the time getting info out, just wanted to share my thoughts there as to me, the message seems a little odd.

Ride safe,

JB

Select to expand quote

Windgenuity said..
In my opinion, the smaller rear/stab is no where near as affective as a larger one for pumping and the smaller rear/stab is far better for turning. I have tried many combo's with big front wings and I basically put it down to;

I am not a pumping expert, but all the good pumpers I know (the ones able to pump back to the lineup and catch a 2nd wave still flying) told me that a smaller stab helps a lot for pumping, as it is less stable it frees the rider to perform all the small movements needed for efficient long distance pumping.

Basically what helps turning helps pumping. Just like with surfboards, actually.

Select to expand quote

Windgenuity said..
I'm a little confused about the rear/stab concepts discussed at 2:15.

In my opinion, the smaller rear/stab is no where near as affective as a larger one for pumping and the smaller rear/stab is far better for turning. I have tried many combo's with big front wings and I basically put it down to;

- Non breaking waves, fat and lots of pumping = XL rear/Stab.
- good walls and great for carving and turning = Std Rear/Stab.

Now, obviously I am referring to the Naish Thrust Set up, and it may be different on the SS.

The larger rear does however offer up a lot more stability. Makes your glide ridiculously stable.

Great vid though, and appreciate the time getting info out, just wanted to share my thoughts there as to me, the message seems a little odd.

Ride safe,

JB

Hey JB

I think the technique used to pump the Naish foils is to use a bit weight to push off the rear wing?

While with the Slingshot foils the pumping technique is a little different and using much more weight on the front wing

We have definitely found it easier to pump the smaller rear wing than our larger one, no matter the wing size. Meaning you can use the smaller better turning rear wing for almost all conditions.

The one exception was our Spaceskate (H4) wing which because of the accentuated delta outline and a dihedral underside, which makes it super lively from side to side, with sharp carving, tight turning, and agile handling. (The shortboard of wings) You can pump it in the turns, like a skateboard with loose trucks. It's a wing that advanced riders will use to create speed in the turns.

This wing actually was easier to pump with the larger rear wing as you were using that to push off as well.

Select to expand quote

7-Nation Aust said..

Windgenuity said..
I'm a little confused about the rear/stab concepts discussed at 2:15.

In my opinion, the smaller rear/stab is no where near as affective as a larger one for pumping and the smaller rear/stab is far better for turning. I have tried many combo's with big front wings and I basically put it down to;

- Non breaking waves, fat and lots of pumping = XL rear/Stab.
- good walls and great for carving and turning = Std Rear/Stab.

Now, obviously I am referring to the Naish Thrust Set up, and it may be different on the SS.

The larger rear does however offer up a lot more stability. Makes your glide ridiculously stable.

Great vid though, and appreciate the time getting info out, just wanted to share my thoughts there as to me, the message seems a little odd.

Ride safe,

JB

Hey JB

I think the technique used to pump the Naish foils is to use a bit weight to push off the rear wing?

While with the Slingshot foils the pumping technique is a little different and using much more weight on the front wing

We have definitely found it easier to pump the smaller rear wing than our larger one, no matter the wing size. Meaning you can use the smaller better turning rear wing for almost all conditions.

The one exception was our Spaceskate (H4) wing which because of the accentuated delta outline and a dihedral underside, which makes it super lively from side to side, with sharp carving, tight turning, and agile handling. (The shortboard of wings) You can pump it in the turns, like a skateboard with loose trucks. It's a wing that advanced riders will use to create speed in the turns.

This wing actually was easier to pump with the larger rear wing as you were using that to push off as well.

It's an interesting theory, I have done a lot of pumping on both. and agree that pumping on the smaller rear is good. I change back and forth all the time until I need to cover a long distance pumping, then the XL rear wins every time. It you keep your speed up and can maintain your speed the std rears work fine, and you'll likely travel faster with the std then the XL rear (I think my GPS reading are around 3-5km/h slower on the XL rear for the same day pumping). But I find with the std rear if I am going to link more than 2 or 3 waves or cover a lot of distance I absolutely have to keep my speed up, whereas the XL rear I can afford to ride a little slower and actually work a little less, slower cadence and conserve energy. I agree with you that the STD rear makes the foil feel free'er but just not "better" for pumping (I guess we need to define what better is). Also if I am paddling up onto the foil without a decent wave or swell on SUP, the XL rear makes a huge difference (like for down winding).

Interesting, and makes me want to play more :)

Ride safe,

JB