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Confused about pitch control

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slowboat
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Confused about pitch control

Postby slowboat » Mon Feb 18, 2019 7:45 pm

I hope this makes sense to someone because it is very confusing to me. I think my stance is pretty well balanced over my foil’s center of lift. When I get on a wave and start to feel the push of the wave and increased speed, I find myself increasing front foot pressure. Makes sense so far. But when I carve HARD, I have to increase my back foot pressure throughout the carve, otherwise my foil breaches. And the harder I carve, the more back pressure I have to apply and maintain. Does this make sense? I have noticed this with several different foils. Thanks for your input.

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Re: Confused about pitch control

Postby edt » Mon Feb 18, 2019 8:21 pm

slowboat wrote:
Mon Feb 18, 2019 7:45 pm
I hope this makes sense to someone because it is very confusing to me. I think my stance is pretty well balanced over my foil’s center of lift. When I get on a wave and start to feel the push of the wave and increased speed, I find myself increasing front foot pressure. Makes sense so far. But when I carve HARD, I have to increase my back foot pressure throughout the carve, otherwise my foil breaches. And the harder I carve, the more back pressure I have to apply and maintain. Does this make sense? I have noticed this with several different foils. Thanks for your input.
Whenever you carve hard the wing looses lift so you have to compensate by increasing attitude
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slowboat
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Re: Confused about pitch control

Postby slowboat » Mon Feb 18, 2019 8:36 pm

Shows how little I know. I thought they maintained lift during a turn.

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Re: Confused about pitch control

Postby Peter_Frank » Mon Feb 18, 2019 10:20 pm

slowboat, this does not make sense...

You write it breaches (ventilates meaning wing getting too high) if you dont push with your rear foot?
This is not what happens, more likely that you dont turn much and the foil continues to tilt over till you crash...

But apart from that, it is very true what you write, and how it is.

Going straight, some foils more than others, need more front pressure when going faster or down a wave, others are almost neutral - simply foil specific and trim specific differences.

And when turning, you need to push harder and harder with the rear foot, the more narrow you want to turn, this is how it is.

Can be compared to when you fly a glider, if you bank the glider (ailerons or rudder) and doing nothing else, it will either almost not turn at all, or turn a bit only, but in both situations (again, trim dependant) it will drop fast into a (death)spiral instead of turning :o

So for the wing to keep its lift during this acceleration (changing direction IS an acceleration), you pull the elevator.
In narrow turns you pull HARD on the elevator.

As a hydrofoil dont have an elevator, because the stabilizer is at a fixed angle, we have to push hard with our rear foot to get narrow turns, so it is like it should be slowboat :thumb:

We control the "lacking" elevator for pitch control, with our weight distribution instead.

And carving around hard and narrow, we need to push with the rear foot.

This is why I like a really wide stance, and rear foot as far behind the mast as possible, I find this gives me the best control and feel.
BUT, this is only me, as I know, and can, stand with a very narrow stance and carve just as hard, so simply a matter of what feels best for you.

8) PF
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Re: Confused about pitch control

Postby Mossy 757 » Mon Feb 18, 2019 10:22 pm

Imagine the wing riding through the water level, perfectly vertical. All of the lift is pushing upwards. When you initiate a turn, the lifting vector is now no longer pushing upwards, it's pushing towards the center of the turn, so some component of your upwards lift is now gone and needs to be replaced somehow.

In an airplane when you begin a turn, you initiate the roll with the ailerons, step on a little outside rudder to push the nose up in the air (to account for the loss of upward lift), and then pull back on the controls to load up the wings and push into the turn with elevator.

When you're foiling you don't have dynamic control surfaces like a plane, so it would make sense you'd have to drastically adjust body weight in order to replicate the arrangement of forces that results in a nice smooth turn.
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Peter_Frank
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Re: Confused about pitch control

Postby Peter_Frank » Mon Feb 18, 2019 11:04 pm

Hmmm, that is a VERY bad way to turn a plane :o

You should use the inside rudder pedal instead, and even better use it before or simultaneously with the ailerons.

Otherwise you will make a non coordinated turn, which can be fun for aerobatics and special motorplanes yes, but it will be loss and drag and feel bad for both yourself and if you have passengers.

Keeping a coordinated turn on planes, require banking and rudder to the same side, and elevator.

To compensate for the loss in lift when banked, you can do nothing - using the rudder the other way "to the outside" will make it even worse.
So you will have a higher sinkrate in a turn, and a lot higher if you use the outside pedal.

To make a narrow turn keeping the same height all the way around, you can dive to more speed, and use this speed to be able to have sufficient lift when banked over hard, thus keeping level height throughout the turn, really fun to do :D

Are we talking about extremely motorpowered aerobatic planes, then it is a way to turn around pylons, banking 90 degrees and keeping height with the huge rudder alone, and then pull the turn with the elevator, that is very true (and also fun).

Got nothing to do with carving as I see it.

But this is off topic, sorry....

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Re: Confused about pitch control

Postby slowboat » Mon Feb 18, 2019 11:07 pm

Ok got it. Thanks for the clear explanations. They sync with my experience.

Is it also true that the more I lean into a carve, the more lift I lose?

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Re: Confused about pitch control

Postby edt » Mon Feb 18, 2019 11:12 pm

If you are leaning harder because you are driving the kite somehow so it generates more power, you also gain speed, this generates lift but it's not really clear to me if the additional speed compensates for the extra pressure.

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Re: Confused about pitch control

Postby Regis-de-giens » Tue Feb 19, 2019 12:08 am

I would add a reflexion, not sure of myself but worth thinking (sorry maybe it was mentioned above , i did not catch all subtilities due to my english level).

So, even independantly of the lift loss (which also appear when you go upwind hard with foil angle by the way ) :

- during the carve you incline the foil centerward. If you do not change your balance the foil will still go forward but just inclined (simplification not taking into account the lift decrease, ok), like a racer pointing upwind but straight

- now the foil is inclined, straight. Say 45 degree inclination. If you add pressure on the rear foot, the lift will increase, the foil will go up... but inclined ... this means that :
- ok there is still an additionnal vertical part of the pull that will make it higher on the water
- but also an additionnal centerward force (of same absolute value) that will push the foil toward the center of the curve. Hence the higher rear foot pressure, the higher this force appears, and the smaller radius you carve.

=> you turn tigher if you incline more and can then apply more rear pressure, and your brain knows it by cumulative reflex learning


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