Tornado-Cat
Super Anarchist
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I don't think so, higher speed and sailing like a trimaran when foiling will make it behave like a multi
Team UK
- Thread starter Barnyb
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Tri's point higher upwind than cats do - stiffer, deck stepped rig, aligned centre board, just like a mono. Not totally comparable to the offset foils of the AC75 concept, but I'd be surprised if they don't point higher at a similar speed to the cats. All just speculation on my part though.
Terry Hollis
Super Anarchist
You're probably right Terry, but Mini Fracks sails did look to have pretty good shape for a soft sail setup. Whether the twin sail mains of the AC75 can make up for the efficiency of the wing is unknown yet, but I suspect it will be closer than you imagine, with respect to the larger windage of the cats, and side slippage, as well as having the extra element in the water (dual rudders).
Ben Ainslie interview in the last Tip & Shaft (sorry if already posted) :
https://us12.campaign-archive.com/?u=1e692787e2c4cc3370813fca1&id=1c8adeddde
https://us12.campaign-archive.com/?u=1e692787e2c4cc3370813fca1&id=1c8adeddde
dogwatch
Super Anarchist
Tip and Shaft. Good grief.
Works for me; there may even be a YT posted above somewhere, I forget.
anyway, some freeze frames
Agreed, however, remember we are still looking at a testing "mule" for comparison to auto industry. So what we are seeing here in no way represents the finished product.
I would expect to see everything faired to within in an inch of its life come race time. Much in the way, back in Godzilla vs. Alinghi - they pulled out beam fairings for everything and stripped off all unnecessary items - netting for one.
I dont imagine that you will see the floats at all - possibly an airbag type of device that could be deployed by stab buttons to try and save a capsize from either hull side or outrigger tips - but nothing as clunky and draggy as seen here.
The rigs also will mature rapidly into endplated and efficient power sources.
The interesting thing about this video is that bow modification - reminiscent of the JK/Origin "Star" bowed TP52. Must be in response to something, and tripping over a sharp knife like bow shape is as good a guess as any. Its rudimentary look suggests pure "mule" like treatment - what can we do that maximises testing time whilst giving a clearer path forward to a workable solution - they are marching into winter conditions where reduced daylight and suitable weather opportunities will be driving the programme as much as anything.
Time on water for both sailors and physical concepts, that can be validated for real life opration has just got to be so valuable, for what is otherwise pure speculation and simulation, albeit by the sharpest minds in modern NA.
Overall, most would be pleasantly pleased with the indications that this test boat has for the new AC class
nav
Super Anarchist
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Boybland
Super Anarchist
The test boat is significantly narrower than the AC75 (being designed for a completely different purpose originally), all the bits sticking out of it are simply to bring the geometry into line with what the AC75 will actually perform like. Expect the AC75s to be much much cleaner than this.
surfsailor
Super Anarchist
Increasing anhedral allows them to further separate control of 'heave' (vertical lift) from leeway resistance (horizontal lift) when the foil arm is set to maximum extension. This could be a very useful tool, and you can clearly see that they have increased the anhedral from the initial design. Typical scenarios:
Upwind: vertical lift* set quite high due to lower speed, horizontal lift* set to max, to induce negative leeway (this is already happening on kite and windsurf foils to varying degrees, with the kites being clear leaders)
Downwind: Vertical lift* set lower (less required due to much higher speed), horizontal lift* set to zero or even negative to maximise VMG towards a downwind mark.
* In each case, I am referring to the lift coefficient of the submerged (leeward) foil relative to the two axis (Z = vertical, Y = horizontal)
Can you elaborate the part in bold? - seems to be counterintuitive.
Agree about the separation of anhedral - but surely having each operate in their separate X and Y axis (i.e. 90 degree perpendicular surfaces) is the optimum for running both at minimum sizes with resultant reductions in drag.
The_Alchemist
Super Anarchist
ok guys, how fast? I grabbed a clip of the video that shows the length of the GB boat passing by the stern of the spectator boat. my software says that it take 0.6 seconds for the length of the GB boat to pass by. Some of you may have better timing software and know the length of the GB boat so we can calculate the speed. We can also look up the wind speed at the time. have fun...
View attachment tm2sm.mp4
View attachment tm2sm.mp4
surfsailor
Super Anarchist
It is counterintuitive, and it might not turn out to be fast, but it is definitely possible. Imagine a wing with 90 degrees between the two legs - at some point when rotating the foil arm, one leg of that wing will be horizontal (parallel to the water surface, which means it can ONLY generate lift in the Z axis) and the other leg will be vertical (perpendicular to the water surface, which means it can ONLY generate lift in the Y axis). Since the flaps can be controlled independently, you would set the horizontal leg at whatever Cl was required to support the weight of boat plus/minus what ever downforce/upforce is being created by the rig, and have total freedom to set the vertical leg however you wanted. One possible upwind setting would be with so much lift that the leeway angle went negative - IE, the boats course thru the water is closer to the wind than the direction the bow was pointing.
I get all that. That is what I was trying to convey to you that I did understand.
What I do not get is your use of the language "to induce negative leeway". It is, frankly, confusing and too open to interpretation - which you have not provided.
I am hoping that you are trying to describe that you could generate sufficient (even excess) lift that the craft no longer generates leeway - but actively climbs to weather (upwind at least). Downwind this trait is actually deterimental to VMG.
So. assuming that this IS what you are describing - what needs to be carefully considered here is what is actually happening to the whole platform when the vertical foil is twisted to do as I think you are saying.
What I think is being missed her is the important distiction between Kite Foils and Windurfers to any other foiling platform with a stayed rig - be that Test Boat or AC75.
What occurs is that on kite foilers and windsurfers the vertical element can be rotated independently of the rig which can continue to generate its power irrespective of platform direction. I think that the foil riders can feel throughtheir feet the amount of twist that the foils can run, without stalling or slowing too much. However, this is not the case with a stayed rig.
What will hapen is that if the foil is set to generate excess lift - the whole plarform will instead rotate the bow down to leeward until the foil runs back into the equilibrium mode of runnings at an angle in the water where it's drag and lift are restored - i.e. normal(ish) angle of attack through the water.
What you have proposed is the eternal debate of gybing centreboards and all that they entail. So if history of these forums is anything to go by ( I think it was a discussion about 14's or David Hollom) ............ well I wish you luck.
I do not believe it can currently be done any better than trying to run the whole show at zero leeway with a foil that can trimmed in AOA (either bodilly or through trim tabs) and mimimal size to give the lowest drag possible and thereby create the highest VMG achieveable.
Happy to stand corrected and educated by anyone who can make a reasoned argument.
surfsailor
Super Anarchist
Ok, I totally missed the point of your question. My bad. By 'negative leeway' I simply meant that the course relative to the TWA would be a tighter angle than the angle between longitudinal centerline of the hull and the TWA. And yes, another way to unpack that is - given a course relative to the TWA - that more lift on the vertical foil leg would let you rotate the entire hull and rig away from the TWA, and less lift would rotate the entire rig and hull towards the TWA.
On the cats, they could just rotate the wing, since the slot was part of the wing architecture, and the jib was largely inconsequential. But the AC 75s will be using head sails, so all of a sudden, there is a trade off between widening the slot and platform drag (since both increase as you increase foil lift in the Y axis. I could imagine there might be gains to be made doing that in light foiling conditions.
As for downwind, as I noted in my original post, you could invert the flap on the vertical foil leg to increase leeway, kind of like leeway coupling on steroids.
My overall point here is that - since these designs introduce multiple additional foil control parameters - there are a huge range of potential sailing modes that need to be explored. INEOs - with the increased anhedral on the foil in the latest video - seems to be going down the path of more control isolation.
nav
Super Anarchist
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It might make it easier to think about, keeping the two foil wings separate. The angle between the frackers' wings makes this even more tempting, but in the end it is all resolved by one resultant force. Given that the entire foil including both wings on the end can be set as high or low as you like, (unlike most foils to date), isn't using both wings in parallel to generate the lift and setting the arm 'height' to control the direction of that lift also a consideration? That thinking is certainly suggested by the relatively 'straight' wings offered in early graphics from the other 3 teams.
The counter argument would include the loss of rm by not being at max beam all the time........
Let's see if the others actually build to with their early ideas - as INEOS has so far.
Someone above suggested the angle between ITUK's wings had increased recently. Not sure it's any different from earlier, but I do think the boat has been running with different port and starboard patterns at times
The counter argument would include the loss of rm by not being at max beam all the time........
Let's see if the others actually build to with their early ideas - as INEOS has so far.
Someone above suggested the angle between ITUK's wings had increased recently. Not sure it's any different from earlier, but I do think the boat has been running with different port and starboard patterns at times
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