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How to turn a hydrofoil - and what is YAW ?

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Mitaka
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Re: How to turn a hydrofoil - and what is YAW ?

Postby Mitaka » Wed Dec 13, 2017 9:13 am

plummet wrote:
Wed Dec 13, 2017 8:04 am
I was out today on the mutant boosting and watching myself yaw the board aggressively multiple times. I was doing this well before foiling and my yawing experience did not help me on the foil.
I think that most people misunderstand the problem in turning when foiling. It is not how to redirect the hydrofoil in a new direction, not at all. Just redirect the kite - it will start to pull you in a new direction and problem solved - the foil is redirected/yawed.

The main problem is the fine roll and pitch control in order to keep your balance during the turn, not the initiation of the turn. Every kiter has some kind of roll and pitch control, otherwise he won't be able to kite at ll but since all other kite boards have much more pitch and roll stability most kiters, when turning with a hydrofoil, lack the refined roll control to withstand the pull of the kite combined with the centrifugal forces and they lack the refined pitch control to keep stable height (or even worse - they have wrong muscle memory and put too much weight/pressure on the back foot).

With simple words you have experienced some problems when learning to turn or jibe not because you lack the ability to yaw the hydrofoil but because you lack the ability to keep your balance during the turn. :D
Last edited by Mitaka on Wed Dec 13, 2017 9:14 am, edited 1 time in total.

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Re: How to turn a hydrofoil - and what is YAW ?

Postby joyrider1 » Wed Dec 13, 2017 9:14 am

Thank you Kevin and all.

This is all right BUT: Just be aware that you have to constantly (!) correct your roll level (with or without kite) all through the turn. Even going straight you constantly (!) are correcting roll (and pitch of course at the same time) , just like riding a bike on the street you have to constantly (!) correct and countersteer not to fall off the bike. If you locked the handlebar of your bike on the street whilst a long turn: Good luck! You can imagine what I mean. Same with the KBHF. If you somehow locked your body/kite/strut together in the middle of a long turn: ??????? Every single split of a second you are correcting your roll to not fall, right? So every single split of a second you have to create that correcting roll and this is done by every single split of a second changing the yaw (or if you want to: twist) of your body. The attached kite is just helping, you can be “lazier” and not as precise with your twisting of the body. That’s all. Just like a unicycle rider who would be helped all the time by a leash hanging from the sky.

As KBHF beginners we are quite comfortable with the kite power as steering tool so we try to use it to correct our balance. This is what we are used to. BUT: You could not ride for longer just trying to correct you roll with sheeting/powering/steering the kite and the rest of your body being like completely locked with the foil. (Even the chair HF rider has to correct the foil by his correction of his body tension). On the other hand: it is perfectly possible to ride a HF just Kai Lenny or other HF surfer oder HF SUPs. Kitepower for steering a KBHF seems natural because we are comfortable with it but it is overestimated way too much.

SO: The kite as a steering tool for turning a KBHF is the way minor part. It is worth nothing (!) without your body constantly (!) twisting to control roll and pitch. On the other hand: Just you and your surfing HF (no kite): Perfectly possible 
This is what even most good riders are not aware of.
Beginners could be helped a lot if they knew…..

Revhed thank you for the link, it describes perfectly what I mean and why countersteering is so important. Tells it all.
Plummet: Yes, of course there is always (a little) pitch correction in a turn as well. But pitch alone is not able to create roll, but yaw can create roll ver well (in HF). Airplanes I don`t consider here.

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Re: How to turn a hydrofoil - and what is YAW ?

Postby joyrider1 » Wed Dec 13, 2017 9:19 am

Mitaka wrote:
Wed Dec 13, 2017 9:13 am
With simple words you have experienced some problems when learning to turn or jibe not because you lack the ability to yaw the hydrofoil but because you lack the ability to keep your balance during the turn. :D
You are on the right path but have to think just one little tad further: Keeping balance in the turn IS the constant need to always recorrect twist and YAW!

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Re: How to turn a hydrofoil - and what is YAW ?

Postby joyrider1 » Wed Dec 13, 2017 10:05 am

We all are fooled by what we FEEL. But just feeling something does not mean that it is this way. Example: I guess nobody felt the countersteering in riding a bike. But it is there, check the link from revhed.

Plummet: Considering airplanes one would have to take a weight steered airplane with the plane beeing the rudder itself. Even hanggliders (not paragliders) don`t work exactly as KBHF. Think of a hangglider where the pilot is above the wing AND (!) you have an extremely leading/pointing component as the must/strut is for the HF in the water. The hanggliders don`t have that, therefore the comparison would not be completely correct.

Thank you all for interesting input, very helpful.

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Re: How to turn a hydrofoil - and what is YAW ?

Postby Mitaka » Wed Dec 13, 2017 11:09 am

joyrider1 wrote:
Wed Dec 13, 2017 9:19 am
Mitaka wrote:
Wed Dec 13, 2017 9:13 am
With simple words you have experienced some problems when learning to turn or jibe not because you lack the ability to yaw the hydrofoil but because you lack the ability to keep your balance during the turn. :D
You are on the right path but have to think just one little tad further: Keeping balance in the turn IS the constant need to always recorrect twist and YAW!
I think that you just found yourself what is primary in turning a hydrofoil - roll or jaw. :D

If you lean your body to the inside (roll the foilboard) you need to yaw in order to keep you balance (CORRECT !!!) otherwise your inclined body will fall. When you lean to one side during hydrofoiling you can keep your balance only in two ways:
1. Use the support of the kite.
2. Turn the hydrofoil to create centrifugal forces which will compensate the gravity forces making your body to fall.

It is also very well explained in the link provided by revhed:
"... causes it (rider) to lean to the left.
The rider, or in most cases the inherent stability of the bike, provides the steering torque necessary to rotate the front wheel back to the left and in the direction of the desired turn."

The rider initiates the turn by leaning to the inside but that action alone is NOT turning the bike!!! NOT AT ALL!!!
Imagine a rigid bike with a fixed front wheel (no steering) - lean to the inside with such a bike and you will fall down immediately because the lack of redirection (lack of centrifugal force to withstand the gravity).

In many 'surface' sports we initiate the turn by leaning to the inside but that simple action is NOT causing the turn alone. Examples:
- Incline a bike - the front wheel rotates and the bike turns.
- Incline a skateboard - the steering mechanism turns the wheels and the skateboard turns. Now imagine a rigid skateboard with firmly fixed wheels - it will not turn if you incline it.
- Incline a carving snowboard - only the edge is contacting with the snow, the board is bending and the edge shape (arc) makes the snowboard to turn. Now imagine a rigid snowboard with parallel edges and try to initiate a turn only by leaning to the inside - not possible.

We all are used to initiate the turn simply by leaning to the inside and we expect the bike, the skateboard, the snowboard, etc. to do the rest.

Well, it does not work like that with the rigid structure of the hydrofoil fully submerged in the water. If you just lean to the inside (especially at lower speed like beginners do) you will immediately loose your balance and the kite support and/or board yaw is the only way to regain your balance again.

I think the essence of the Peter's post was: Initiate the turn by yawing the board and I fully agree with him! Do not lean to the inside (roll the board) and expect somehow miraculously the foil to turn like bike, skateboard, snowboard etc. Of course immediately you must combine the yaw with roll and pitch control in order to keep your balance during the turn. :D

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Re: How to turn a hydrofoil - and what is YAW ?

Postby joyrider1 » Wed Dec 13, 2017 1:27 pm

Mitaka wrote:
Wed Dec 13, 2017 11:09 am
If you lean your body to the inside (roll the foilboard) you need to yaw in order to keep you balance (CORRECT !!!) otherwise your inclined body will fall. When you lean to one side during hydrofoiling you can keep your balance only in two ways:
1. Use the support of the kite.
...

You don`t need the support of the kite necessarily at all, it only makes it easier. Using the kite only for turning the KBHF will teach yourself the necessary effect of countersteering much later. OK, you will learn some day but is it useful just to try and error?
When you are experienced rider then it is even very much fun using the kite for "pulling yourself" into a turn, yes :thumb: But how would Kai Lenny on his SUP and the other surfboard hydrofoilers turn without a kite then? We all know that we don`t like at all to give up the alignment between body and mast/strut.

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Re: How to turn a hydrofoil - and what is YAW ?

Postby Mossy 757 » Wed Dec 13, 2017 2:35 pm

plummet wrote:
Wed Dec 13, 2017 8:04 am
The more I think about this the more I disagree that yaw is the primary turning function of the foil. I was out today on the mutant boosting and watching myself yaw the board aggressively multiple times. I was doing this well before foiling and my yawing experience did not help me on the foil.

So. Yaw input is not the primary turning mechanism of a hydrofoil. Much like yaw is not the primary turning mechanism of an aircraft.

My take on this is that you must pitch, roll and yaw seamlessly and in unison to make an effective foil turn.
This is a better version of what I've been trying to say.

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Re: How to turn a hydrofoil - and what is YAW ?

Postby Peter_Frank » Wed Dec 13, 2017 10:41 pm

Interesting aspects and views shared in this thread now - have been away and not read in detail nor time right now, but like that there are so many who gives their input and share :D

However, I will say one thing, being an engineer working with design, analytics, and aerodynamics/design and a lot of flying - that for me when not trying to make something "new", I find joy in exploring how things works in real life, say windsurfing or hydrofoiling or whatever you do, and then make deductions and find the theory behind and how everything could or does interact, and share (or discuss).

And not the other way around - as if you have some idea beforehand of how things SHOULD work from other dynamic objects or even book studies or knowledge, you will most likely get this to work with what you experience out there, based on this often "pre"formed thesis, eventhough it is not really fully true in terms of what happens nor its significance, IMO.

To get back to the first post - I am still saying, that no matter if you use countersteering or kitepull or leaning over or combinations more likely, to start a turn, it is still the yaw input that is essential for a tight good hydrofoil turn.

It is all done in coordinated sync yes, also things like pushing the rear wing down in the carve, etc, we all agree on that I think, not in doubt.
It is IMO an incredible complicated sequence of motion and forces applied that makes a hydrofoil turn, and not just a single thing, of course.

A bit more precise, I could also say, that the skills we know from other, usually boardsports, are easy for us to implement without thinking, they are "natural".
The only thing that is really different for most or all of us, and makes such a huge impact on whether you succeed when learning to turn, is the twist or yaw input.

Later when learned to carve fully, one can even easier see how much yaw helps in terms of doing tight carves and not racing carves.

Maybe a few of us are born with the natural talent so we just "do it" without knowing we twist (good, as this is not how I nor most of those I know are), and this could very likely be why a few say they can not feel it (but be happy, you just do it without knowing)

I am, on purpose, not even discussing the theory behind what makes a foil turn - not necessary (eventhough another really interesting aspect indeed that we could talk about for infinite time yes) to deduct that yaw is such an essential part of hydrofoil turning :thumb:

A few of you disagree or got their own thesis, it will always be like that.
I dont know everything either....

It is nice to read most have found the same and can reckognize the importance of yaw in tight carving turns, from themeselves :rollgrin:
And to those of you learning to turn, TRY it, combined with all your othe natural skills, and see how you can suddenly carve much better and tighter when you get the hang of it :naughty:

8) PF

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Re: How to turn a hydrofoil - and what is YAW ?

Postby fun2kite » Fri Dec 15, 2017 4:28 am

This is a great topic. I never thought of YAW being important in how tight my carves are. In fact this was exact problem I was thinking: Why can't I make tight turns. I always just lean into the turn, never twist.. So This is an eye opener and I will defiantly try if I can add the twisting (yaw) to the way I turn and see if that makes a difference.

I also ride OneWheel on land. Today I monitored how I turn on OneWheel and noticed that also, I only lean, never twist. I attempted to twist (yaw) on OneWheel and it felt very uncomfortable first. But the radius of my turn was greatly reduced.. The feeling of twisting was /is definitely very new to me and I now know for sure that I do not do it at all. But i could experience that feeling on ONeWheel and will try transfer that to the water next time I ride.

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Re: How to turn a hydrofoil - and what is YAW ?

Postby kas911 » Fri Dec 15, 2017 7:09 am

How to turn on a foil? Efter 20 sessions you Will figure it out. The end

Why does a foil turn? Well thats a different story :-D


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