Foiling downwind at 10kts vs 13kts+

[tkaraszewski]

Here's a track I recorded the other day. The blue highlighted part is one downwind leg and through a gybe. The average speed below it is in MPH, so an average of 28.4 mph, or just under 25 knots. The protractor on it shows a gybe angle of 79.1 degrees.

So, sailing (79.1/2 = 39.55) degrees off the wind, we have a VMG of (cos 39.55 degrees) * 28.4 mph = 21.9mph, or 19 knots.


Ok, what was the wind doing? Here's the wind that day:


This track starts at 5:02 PM and the gybe above is 1 hour and 17 minutes into the track, making it 6:19PM. You can see from the wind graph that the wind was averaging about 9-12 knots at this time, with gusts to ~15 knots. This wind meter is right next to where this track was recorded. Maybe 500m away at most. It is accurate for this spot.

So yes, this was recorded on race gear, but that's not really the point, the point is that you can go downwind *faster than the wind* by sailing VMG angles. Your fastest downwind angles depend on keeping board speed high more than they depend on keeping angle low. This is fundamentally true even with freeride gear, even though your angles will be somewhat higher and speeds lower, it's still faster than just doing a bunch of kite loops straight downwind.

If you really want to sail straight downwind you will need to loop to keep the kite flying, but it's not fast.

[alekbelia]

...So yes, this was recorded on race gear...

I can provide tons of racing tracks (I'm a racer too. ). But we here are not talking about racing gear.

[alekbelia]

...This is fundamentally true even with freeride gear, even though your angles will be somewhat higher and speeds lower, it's still faster than just doing a bunch of kite loops straight downwind...

Why snowkiters are doing loops when going up? Kites with low AR are not so effective and foils with 1000 size have a lot of drag. Compare them with racing gear is like compare a F1 car 1000 hp with a tractor 1000 hp.
The real difference is when the wind is light, the kite is small enough to produce enough static pull and the kite have ability to loop in front of the kiter (big racing parafoils can't do that). Here is the short video. Even on halfwinds I moved the kite to keep the speed of the foil. Downwind was not possible without loops.

[rnelias]

The kite makes a big difference in this kind of wind if you have 10 knots and you are going downwind at at an angle but let's say 5 knots to the wind there isn't much wind left on the kite because you are running away from the wind. A kite that drifts very well and that is super light like a single strut, strutless or foil kite will be able to stay up there and handle this while keeping enough tension in the lines. A heavier freeride kite designed to go upwind will struggle. I haven't tried the EVO SLS but I don't think it's designed for ultimate drift in very light wind.

The most important factors, in marginal winds, are: 1) Rider skill and 2) right equipment and, if you're not experient enough (like me), the equipment will make a huge difference. Maybe a Neo SLS would make your life easier since it's designed to be a drift machine, however, it doesn't make miracles and LEI kites, even the SLS ones are still a pig in the air compared to foil kites or 0 and 1-structs.

Here's an example.

Wind NE 7-8k (look the water surface)
F-One IC6 850cm^2 wing with IC6 400cm^2 stab (95 cm mast)
Flysurfer Soul 12m
I have 73kg



There's no straight DW leg in this ride but I had an earlier session, in the same conditions, where I had tested other up and dw angles.

I usually ride with an 1-struct kite (Boxer 9m) but it was too small/weak for a marginal 8 knots condition. Boxer is already a good while drifting but it can't be compared to the Soul.

BTW, in the 10-13kts range this Boxer 9m is enough for me going up and dw with no issues.

[1234567Simon]

I foiled with about 10kts ......,

The wind was such that there was little chance of relaunch even with my light Duotone Evo sls. This was the lightest wind I ever foiled in till date.

Just my oppinion... Everything is OK.... 10knots is Low.....

10knots is Low.... Tube EVO SLS will stay Up longer.....
13 knots ist full fun!!!!

If my heavy core section 8 m is barely flying.... 9-10 knots.... I try to go fast ( Not racing fast.... Foil and Kite are both slow).
And then go steady more and more downwind..... My target: Kite deep in Wind Window but Not stalling.... And giving the Kite enough Back Line to go as fast as possible......
At a certain Point :there suddenly ist some self Made Wind.


Looping I am Not confident enough.... If I fall the Kite will drop for sure.


As I know Relaunch is Not possible anyymore, I stay Close to shore, an have to Gybe a Lot (with or without Looping) (still can Not Tack). So no need to go downwind .




Just my Experience.... With my Equipment, and my little Experience...

[Peter_Frank]

It is REALLY interesting now, if there is a point where slower wings and inefficient kites will make dw looping the kite at slower speeds give you higher VMG than going as fast and deep as possible (like used to on "other" gear)

I still doubt it, but you could be right, there is a point where the fastest way downwind change?

Based on a huge amount of parameters, so not that simple, and even IF looping is faster, there are so many factors involved, so WHEN is it faster


Overall my take would always be, that when turning/looping the kite you have loss, versus keeping it steady.
And as the "power" for speed is from sweeping the kite in the loop downwind, or going faster across the wind at a deep angle - I would say the loss when looping means less VMG too.

I might be corrected though, great topic eventhough difficult

Keelboats are slow, and has highest VMG dead downwind?
Or can they go faster even with a spinnaker when bearing deep?

Faster boats or dinghys always go faster at deep angles, but slow boats might be fastest dead downwind?
OR, it might depend on how much wind you got (and the specific boat/dinghy) and in low winds dead downwind is faster, in more wind bearing deep is faster.

Not completely the same as looping a kite, but related.

Peter

PS: I have to wear my GPS the next time out in 9-10 knots and test this

[alekbelia]

...Not completely the same as looping a kite, but related...

Kite with good looping ability can be described like a one blade propeller.

[purdyd]

I think what is important is the kite has to move. By sining and looping you generate more power.

So running down wind I would start sining the kite. That will help.

There does come a point where the kite won’t climb so you have to loop.

Anyone who has flown a kite in really light of winds or perhaps run very fast down a wave face toward the kite has experienced this.

My experience would be the best way to lose ground in light wind is a series of turns with a back loop before the turn and then a loop during the turn to unwind the lines. Repeat.

[Peter_Frank]

purdyd, it might be correct for inefficient wings and kites (which is the core of this topic now ), I dont know.

But I disagree for fast gear.

Here I would say, that no matter how light wind, you go faster and most efficient downwind keeping board speed up and kite steady not even sinus'ing (=no loss).
Kiteracers should be able to answer this?

When light wind, do you get the highest downwind VMG keeping kite steady or sinus'ing?

As when you sinus you sweep across a larger area of the wind indeed, but is it a benefit or disadvantage?

Its just, I have never seen kiteracers (here) sinus downwind, not even in 5 knots of wind

Peter

[leeuwen]

Its just, I have never seen kiteracers (here) sinus downwind, not even in 5 knots of wind

I don’t think you can compare that, their gear dictates what they can do:
The racers I know are on super short lines with huge slow steering kites.
They don’t have “the space” to sine or loop a kite even if they wanted to.
Eg for boardstarts they need to backstall their kite all the way to the water line to get enough space to create some room to get speed into the kite for the required power spike….

Meanwhile I am easily getting on my board looping a smaller foilkite on long lines.