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Monofoil or "riding stabless", setup and riding

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fluidity
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Re: Monofoil or "riding stabless", setup and riding

Postby fluidity » Wed Feb 24, 2021 1:28 am

PrfctChaos wrote:
Wed Feb 24, 2021 1:09 am
fluidity wrote:
Thu Feb 04, 2021 9:37 am

I can tell you the characteristics that will make a poor foil to control in unifoiling mode:
characteristics that will make the foil want to dive:
Concave rear underside profile.
High assymetry including wings with a very flat underside.

For performance I believe you need a foil with around 2:1 top:bottom curvature profile.

Are these statements backed up by any calculations Fluidity? Showing that those changes cause less "dive" with increased speed.

Hi PrfctChaos,
I think we both know that you are the gun on here for general hydrofoil calculations as attested to by your very popular thread in gearbuilder.

However its over complicating matters to require mathematically proof that a curved surface likes to ride over a fluid pivoting around the projected centre of the curve. Simple, right?

The curves of an assymetric foil can be cancelled against each other to leave a remainder assymetric curvature which is the significant factor in built in pitching moment of the foil independent of external pitching considerations.

As for my comment "2:1 top:bottom curvature profile", this is ball park but is based on requirement for pumping and net lift with stable characteristics over use-case angles of positive and negative attack.

You could also put it another way and say I just fluked it with my first non naca design that rides "real sweet" and break down its possible weaknesses based on a direct link to my lack of certification in the field!
(kind of like faulting a dog based on poor pedigree documentation) :-D

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Re: Monofoil or "riding stabless", setup and riding

Postby PrfctChaos » Wed Feb 24, 2021 2:44 am

fluidity wrote:
Wed Feb 24, 2021 1:28 am
PrfctChaos wrote:
Wed Feb 24, 2021 1:09 am
fluidity wrote:
Thu Feb 04, 2021 9:37 am

I can tell you the characteristics that will make a poor foil to control in unifoiling mode:
characteristics that will make the foil want to dive:
Concave rear underside profile.
High assymetry including wings with a very flat underside.

For performance I believe you need a foil with around 2:1 top:bottom curvature profile.

Are these statements backed up by any calculations Fluidity? Showing that those changes cause less "dive" with increased speed.

Hi PrfctChaos,
I think we both know that you are the gun on here for general hydrofoil calculations as attested to by your very popular thread in gearbuilder.

However its over complicating matters to require mathematically proof that a curved surface likes to ride over a fluid pivoting around the projected centre of the curve. Simple, right?

The curves of an assymetric foil can be cancelled against each other to leave a remainder assymetric curvature which is the significant factor in built in pitching moment of the foil independent of external pitching considerations.

As for my comment "2:1 top:bottom curvature profile", this is ball park but is based on requirement for pumping and net lift with stable characteristics over use-case angles of positive and negative attack.

You could also put it another way and say I just fluked it with my first non naca design that rides "real sweet" and break down its possible weaknesses based on a direct link to my lack of certification in the field!
(kind of like faulting a dog based on poor pedigree documentation) :-D
Not sure I understood much of that, but as long as you are enjoying it mate. I just think it is worth-while explaining where info comes from when giving advice to others.

The change in foot pressure that comes with a change in speed comes from a few main things, as far as I can see.

- Firstly the front wings lift force (The centre of lift can change as the angle of attack changes), if the centre of lift moves backwards more back foot pressure is needed. If it moves forwards then more front foot pressure is needed.
- As speed increases the front wing induced drag decreases, meaning more front foot pressure
- As speed increases the front wing parasitic drag increases, meaning more back foot pressure
- As speed increases the mast/fuse/other parasitic drag increases, meaning more back foot pressure

So theoretically someone might be able to design a monowing where foot pressure doesn't change much as speed increases. But it might not be very efficient, since I think it will require a non-ideal profile (selected for parameters other than just low drag over the speed range) and more importantly will probably need artificially high induced drag at low speed, so that it can help with balance as speed increases (the dropping induced drag can be used to cancel out increased parasitic drag as the speed increases). Pretty complicated. I still think one would need to test if it is better or worse than a ideal wing with fuse and small stabiliser...

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DIY CAD ultra-concave wave twintips 1500 and 130mm with my own fin designs. Easy upwind, awesome carving. Switch Nitro 10m V7, Naish 5.3m Wing.
Now focussing on Wingsurfing to rise to a new challenge. Building my own foils from my CAD design and 3D prints, built a CNC machine last year and now cutting designs with CNC as well as 3D printing.
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Re: Monofoil or "riding stabless", setup and riding

Postby fluidity » Wed Feb 24, 2021 10:41 am

PrfctChaos wrote:
Wed Feb 24, 2021 2:44 am
fluidity wrote:
Wed Feb 24, 2021 1:28 am

I'm sure you understand most if not all of this in your own way but there are my understandings with some more fleshing out:

"However its over complicating matters to require mathematically proof that a curved surface likes to ride over a fluid pivoting around the projected centre of the curve. Simple, right? "
Think of the white's concave in a Ying-Yang symbol rotating around the black bulb. It's an exaggeration of the above foils.

"The curves of an assymetric foil can be cancelled against each other to leave a remainder assymetric curvature which is the significant factor in built in pitching moment of the foil independent of external pitching considerations."
Positive above foil centre line, negative below. For an assymetric foil you can analyse by going from joined top and bottom curves to a single line curve indicating the net assymetry and likely behaviour if free to pivot.(add + Y to -Y for each X top and bottom foil coordinate)

"As for my comment "2:1 top:bottom curvature profile", this is ball park but is based on requirement for pumping and net lift with stable characteristics over use-case angles of positive and negative attack."
Imagine the foil at multiple positive and negative angles of attack, for high climb angle the soft front curve to a higher top of foil curve is friendly to coanda effect and reduces stall speed by maintaining clinging flow without breakaway. At descending angles, unwanted flow separation can(also) occur at the under leading edge if it is too sharp. Critical on a mast which has many angles of attack and for a pumping foil for the same reason.
The change in foot pressure that comes with a change in speed comes from a few main things, as far as I can see.

- Firstly the front wings lift force (The centre of lift can change as the angle of attack changes), if the centre of lift moves backwards more back foot pressure is needed. If it moves forwards then more front foot pressure is needed.
- As speed increases the front wing induced drag decreases, meaning more front foot pressure
- As speed increases the front wing parasitic drag increases, meaning more back foot pressure
- As speed increases the mast/fuse/other parasitic drag increases, meaning more back foot pressure

So theoretically someone might be able to design a monowing where foot pressure doesn't change much as speed increases. But it might not be very efficient, since I think it will require a non-ideal profile (selected for parameters other than just low drag over the speed range) and more importantly will probably need artificially high induced drag at low speed, so that it can help with balance as speed increases (the dropping induced drag can be used to cancel out increased parasitic drag as the speed increases). Pretty complicated. I still think one would need to test if it is better or worse than a ideal wing with fuse and small stabiliser...
Foil shape's net assymetry has less implicit pitching influence for short chord wings and all those other factors you mention above are also factors in the mix. Horst seems fine with high aspect foils though I think he likes even more the handling of a severe delta design due to it's pitch stability.

I'm sure there are many non complex ways to dynamically modify stabiliser angle or delta elevon angle in motion for different speeds to match drag induced pitching moment.
And complicated too.
From mast strain guages being read by a microcontroller and outputting a look-up table compensation angle to the stabiliser/elevons, controlled by stepper motor or heated memory wire or voltage multiplier Jacob's ladder to a Piezo electric jack, many options :D

Or simpler like small very high pitch prop bleeding power from speed and driving a hydraulic piston to adjust the stabiliser angle to be more severe with more speed, slow bleed of pressure for relaxation of piston at lower speeds.

Or use the driver on top of the board! We have natural ability to incorporate many natural processes and cycles and semi autonomously respond... "Muscle memory" to best adjust our tensegrity body mechanics in near real time to these real world situations.

Give it time and there will be a whole lot of silly patents based on obvious applications of electronic gyro and g-force sensor chips to make electric foil boards ride as simply as Segway ballance scooters. People will come on these boards and say: "my battery only lasts 5 minutes and the magic smoke leaks out of the speed controller hatch but look at my selfies!" and you will look and they will be perched on the front corner of the board wondering why it's not working well 8)

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Re: Monofoil or "riding stabless", setup and riding

Postby Horst Sergio » Wed Feb 24, 2021 9:56 pm

fluidity wrote:
Wed Feb 24, 2021 10:41 am
Foil shape's net assymetry has less implicit pitching influence for short chord wings and all those other factors you mention above are also factors in the mix. Horst seems fine with high aspect foils though I think he likes even more the handling of a severe delta design due to it's pitch stability....
Trying to take part in the quoting session: :wink:

Yes, I just had the interesting experience that high aspect wings are not a limitation in general for mono foils and that you may set some upwind angle records on them and also good jumping hight when the wings are also small.

But I would not advise to try or build such wings for monofoiling as the idea to me is that the monofoil is the perfect and safe alrounder. Trying to use super high AR wings with sharp tips may destroy this idea as well as super low AR wings and you may end with a one trick pony in the best case or even something completely unrideable. Exaggerating delta shape may cause the same if in combination with high AR the wings may get instable by flexibility and it can easily become unrideable in my eyes.

To just give a new experiende from last days:

Quite sure that I will do a video of a galactical (around the world) on a mono coming summer, tried it these days and passed the kite quite compfortably, but till now it collapsed always, so didn't made it yet, but have seen the light. Just prefer to do the always necessary relaunch jobs in warmer water. :wink:
Galactical is just a great way to evaluate overall performance of a hydrofoil. To be able to do it, the foil has to shine in many disciplines as good glide, stability at speed and manouverability. A one trick pony doesn't go through a galactical and also most cheap foils will never do so.
With the wing a downwind 360 is the most similar trick, even if way simpler, as also mentioned here:
viewtopic.php?f=201&t=2408431&p=1129841#p1129841

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Re: Monofoil or "riding stabless", setup and riding

Postby PrfctChaos » Thu Feb 25, 2021 1:22 am

Horst Sergio wrote:
Wed Feb 24, 2021 9:56 pm
most cheap foils will never do so.
Not sure water knows or cares how much currency was handed over in exchange for a product... and so many different types and sizes of foils even in the more economical price bracket. Just saying all of them perform badly is a bit extreme.

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Re: Monofoil or "riding stabless", setup and riding

Postby Horst Sergio » Fri Feb 26, 2021 8:45 pm

PrfctChaos wrote:
Thu Feb 25, 2021 1:22 am
Not sure water knows or cares how much currency was handed over in exchange for a product... and so many different types and sizes of foils even in the more economical price bracket.
I think the currency may feel it, if going around a wing that was optimised by CRD and professional riders in many steps, instead of just selling cheap the first design that comes out of production. But this is just IMHO after testing many wings at different price levels not with the influence of a stabi, but pure as they are as mono. And yes there are many types also at low price, but sometimes when I read comparisons of wings I know, it feels to me that evaluation is not about the real quality of the wing to behave well in many disciplins all together but it sometimes just sounds as if the tester just found a wing that by size or another single factor fits better to his style or skill level, but that doesn't tell anything about the wing quality it self.
PrfctChaos wrote:
Thu Feb 25, 2021 1:22 am
Just saying all of them perform badly is a bit extreme.
Agree, as anyway I didn't said that :wink: , just "most" what IMHO I feel and as I have never seen anyone on a cheaper foil doing an around the world, but maybe Florian Gruber, Fred Hope, Steven Akkersdijk or others can do it also on cheap foils.
Well still a bit hard to do good statistic here, to evaluate the "most" :wink:

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Re: Monofoil or "riding stabless", setup and riding

Postby Horst Sergio » Sun Mar 07, 2021 7:06 pm

And here is Nr. 2
(serial mono foil)

and the first with a serial mono only wing: No compromise :thumb:

Image

also with a very nice drifting video:

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Re: Monofoil or "riding stabless", setup and riding

Postby a99 » Fri Aug 27, 2021 10:47 pm

Nice monofoil video, still wing desing itself is not mush different from bigger wings, just a little more added surface in mast connection place, but it is hard to imagine that it gives so much comparing with usual bigger 1500cm2 wing. Maybe somone can comment this wing desing? By the way surface area is 1500 cm2, and even from view it has similarities eith moses 790 wing. Horst or someone, have you tried monofoiling with this moses wing, maybe it is better than smaller Moses wings for monofoiling? As i remember you used onda 633 or 683w mostly. But tritone and spleen as we see released monowings with surfase bigger than 1500, probably it means that monowings working more properly only in bigger surfaces and with less than 1500 it more to struggle side or a lot of lit or practice.


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