robingimblett
Member
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If flaps are individually controllable, this can make a huge difference to the centre of lift point and righting moment lever length. Might be my next diagram.....
INEOS Team GB
- Thread starter Stingray~
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If flaps are individually controllable, this can make a huge difference to the centre of lift point and righting moment lever length. Might be my next diagram.....
Kiwing
Super Anarchist
They have to be symmetrical about the arm so not much chance of that.
The_Alchemist
Super Anarchist
But remember that the use of the flaps will be kept to a minimum to reduce drag. But they could be major factor in maneuvers.
Feels like we're revisiting some of the hot topics from last cycle.
When I made that VPP, I realized that for a balanced boat, foil cant angle is determined by the geometry of the sails' center of effort and the lateral / vertical force vectors. Foil lift has to be in line with the sum of lateral forces on sails and weight + rudder vertical:
Whether it's a W, Y or T foil, doesn't matter as long as the inside and outside flaps are set symmetrically. Where the anhedral Y foil makes a difference is that it adds a bit more adjustability. As conditions / sail forces change, with the T foil you can only react with changing cant angle (slow) or with sail trim. With a Y foil, you can change the angle of the foil lift vector faster without having to change the cant angle by setting inside/outside flaps differentially.
I'm pretty sure, you get lowest drag when the flap angles are symmetric, so the Y foil gives more control but at a cost of higher drag.
Apparently I also made an analysis on how the max righting moment differs between T and anhedral foils, but even I have a hard time understanding now what the hell I was trying to show here
.
One thing for sure is that sail COE and righting moment can be higher with a Y foil, if the flaps are set asymmetrically.
BTW this was the foil cant angle prediction from the VPP for TWS = 17.5 kts. Correlates pretty nicely with the summed cant angle data you show.
enigmatically2
Super Anarchist
Now that's some proper engineering guesswork, still guesswork but supported with graphs etc
To address one of the points, it is possible to adjust the flaps independently and asymmetrically on any of the shapes, not just the w, if they have multiple flap segments. But that goes back again to multiple actuators and space issues.
Anyone have a view on the merits of moving the flap axis outside the flap as Ineos seem to be doing? Sure you can lengthen the foil cord that way, so get more.lower end lift, but at the cost of more drag. That is is really independent of the w shape isn't it?
To address one of the points, it is possible to adjust the flaps independently and asymmetrically on any of the shapes, not just the w, if they have multiple flap segments. But that goes back again to multiple actuators and space issues.
Anyone have a view on the merits of moving the flap axis outside the flap as Ineos seem to be doing? Sure you can lengthen the foil cord that way, so get more.lower end lift, but at the cost of more drag. That is is really independent of the w shape isn't it?
robingimblett
Member
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Yes I remember all the great work you posted. I resurrected my AC36 CAD and calcs and brought it up to AC37 dimensions in recent months. I haven't got into the 3rd dimension of rudder downforce though.
Why did you arrive at 'inside and outside flaps are set symmetrically....'?
Would you agree that the the centre of lift point can be off the foil centreline provided the combined sail + gravity force vector pass through that centre of lift point?
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enigmatically2
Super Anarchist
So the logic of Ineos foil is as follows?
1) W reduces frontal section drag, offset by external hinges to be roughly the same as a T
2) external hinges allow inside flap segments to be extended, massively increasing lift as per aircraft wings for take-off or stability in bad conditions
3) at speed in more stable conditions only the external flap segment is used, reducing drag due to flaps
4) w keeps the foil deeper in water than a Y
Downsides.
More front section than a Y
More complex
Additional Drag at at the segment boundaries when flaps deployed
1) W reduces frontal section drag, offset by external hinges to be roughly the same as a T
2) external hinges allow inside flap segments to be extended, massively increasing lift as per aircraft wings for take-off or stability in bad conditions
3) at speed in more stable conditions only the external flap segment is used, reducing drag due to flaps
4) w keeps the foil deeper in water than a Y
Downsides.
More front section than a Y
More complex
Additional Drag at at the segment boundaries when flaps deployed
robingimblett
Member
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More complex without question and so much higher risk of breakdown. Not sure about front section area between the two but frontal length is less for the W.
I wonder if the W can provide more stable lift by using the opposing lateral vectors when canted.
I wonder if the W can provide more stable lift by using the opposing lateral vectors when canted.
enigmatically2
Super Anarchist
I would imagine it can. Meant to include that
The_Alchemist
Super Anarchist
How does the windward heel change these balances for increased speed?
enigmatically2
Super Anarchist
Not sure it does much. More an impact on end plating (up) lift(up) and righting moment (down)
But I dont immediately see much impact on the trade-offs between foil designs. Though I'm sure in the Sims it is possible to see some impact-2nd order perhaps
dg_sailingfan
Super Anarchist
You got to hope that this works out as intended. If not things will go down really fast for the British Women's & Youth AC Hopes!!!
www.athenapathway.com
Captains Log | Looking ahead to the ETF26 circuit!
Captains Log | Looking ahead to the ETF26 circuit!
www.athenapathway.com
enigmatically2
Super Anarchist
You are fcuking weird.You got to hope that this works out as intended. If not things will go down really fast for the British Women's & Youth AC Hopes!!!
Captains Log | Looking ahead to the ETF26 circuit!
Captains Log | Looking ahead to the ETF26 circuit!
Why will one non-scoring event have any more impact on GB hopes than anyone else?
Every team hopes they will do well. But they won't all. This is how competition works. And the AC will be at a different time in different conditions in different boats.
Kiwing
Super Anarchist
This W foil discussion seems to be dragging Ineos down. While I tend to agree we wont see W foils in the cup, there might be something there.
But as long as Sir Ben is beaten into the helm position I see them up with LR, AM, and TNZ?
But as long as Sir Ben is beaten into the helm position I see them up with LR, AM, and TNZ?
JALhazmat
Super Anarchist
Watch moths and kite foilers, the answer is a shit ton better vmg
ChairborneRanger
Anarchist
A standard shit ton, or a metric shit ton?
The_Alchemist
Super Anarchist
That is what we all hear, but I was asking how it fits into the COE and foil cants, etc... All of the above diagrams have a level boat.
Jethrow
Super Anarchist
It's the force vector of the foils, not necessarily the angle of the hull, although they (moths, kites, wing & windfoilers) do benefit from getting the weight to windward of the foil. I would guess one of the benifits of windward heel on the AC's is getting the correct angle of foil while keeping the arms as low as possible?
robingimblett
Member
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Unlike AC yachts, Moths and foiling kite boards are symmetrical with the foil directly beneath the hull/board. Sailing them heeled to windward is a more forgiving way to balance weight with sail / kite force and to make maximum use of sail / kite power.
AC yachts being asymmetrical in normal sailing position approximate the windward heel of a moth whilst the hull / mast of the AC yacht is still vertical.
enigmatically2
Super Anarchist
I agree, windward heel in a month or kite board increases RM, whereas in an AC boat it reduces it.
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