pacice

Foiling Monohull - what would it look like?

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4 hours ago, barfy said:

I'd say, grow some you two.

Tc modus operandi: make an observation, extrapolate to the nth degree, and make a conclusion based on that. Herfy not usually in that park, but yur working on it cuz.

Hey, I was just posting a question as to what might happen "if".  I am more interested in the design differences.  Hopefully we will see the first boats soon.

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10 hours ago, Herfy said:

I know many don't think it is possible, but "what if" the boat is deemed as being too unstable and the AC is postponed?  Would that degrade into another of those DOG fights like back in 1988?  Not trying to attack the Kiwi design, just wondering what would happen?

The AC75's are stable when the foils are down.  When racing in light or fluky air the potential for instability exists with the ballasted foil is raised to windward and the wind decides to take a break. Given that the crew weight exceeds the ballast weight and the fact that the foils can be lowered back into the water we are talking about the skill of the crew rather than the boat being too unstable.

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3 hours ago, Terry Hollis said:

The AC75's are stable when the foils are down.  When racing in light or fluky air the potential for instability exists with the ballasted foil is raised to windward and the wind decides to take a break. Given that the crew weight exceeds the ballast weight and the fact that the foils can be lowered back into the water we are talking about the skill of the crew rather than the boat being too unstable.

Like, running rail to rail? I would hope that more elegant methods of trim will be developed.

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3 hours ago, Herfy said:

Hey, I was just posting a question as to what might happen "if".  I am more interested in the design differences.  Hopefully we will see the first boats soon.

There are a lot of "ifs" to be revealed in short order!!

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5 hours ago, Terry Hollis said:

Given that the crew weight exceeds the ballast weight…

What are you counting as ballast? Even if only the foils an ignoring the arms, then per rule 10.1:

Crew weight: 960–990 kg
Foil weight: 2,430 kg (1,215 kg each)

Seems to me ballast is considerably more than crew weight. And the ballast is at the end of 3.4m arms mounted more or less on the gunwale. Crew weight can't be more than about 2.4m from the centreline if they're all on the rail, so better not rely on them to avoid a capsize. ;-)

Quote

 

…and the fact that the foils can be lowered back into the water we are talking about the skill of the crew rather than the boat being too unstable.

But they aren't allowed to race with both foils down except during manoeuvres, and not allowed to race at all with them fully down in the most stable configuration. I don't think they will race in less than say 6 kn of steady breeze, so kinda moot really.

 

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13 hours ago, Terry Hollis said:

The AC75's are stable when the foils are down.  When racing in light or fluky air the potential for instability exists with the ballasted foil is raised to windward and the wind decides to take a break. Given that the crew weight exceeds the ballast weight and the fact that the foils can be lowered back into the water we are talking about the skill of the crew rather than the boat being too unstable.

Well, then that raises the first questions that I had about the design of the boats.  With the LR mock up showing just one set of grinders in the center of the boat, they won't have the flexibility to adjust crew weight from side to side. 

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13 hours ago, RobG said:

What are you counting as ballast? Even if only the foils an ignoring the arms, then per rule 10.1:

Crew weight: 960–990 kg
Foil weight: 2,430 kg (1,215 kg each)

Seems to me ballast is considerably more than crew weight. And the ballast is at the end of 3.4m arms mounted more or less on the gunwale. Crew weight can't be more than about 2.4m from the centreline if they're all on the rail, so better not rely on them to avoid a capsize. ;-)

But they aren't allowed to race with both foils down except during manoeuvres, and not allowed to race at all with them fully down in the most stable configuration. I don't think they will race in less than say 6 kn of steady breeze, so kinda moot really.

 

In a situation where there is no wind at all the boat will be moving very slowly so the leeward foils ballast will exceed the hydrodynamic lift so the boat is more or less balanced.  If we have zero wind while the boat is still on the foils lowering the windward foil/ballast to avoid a capsize would be regarded as a manoeuvre, they might even go into a tack or gybe to avoid a capsize, it still gets back to crew work.

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14 hours ago, RobG said:

What are you counting as ballast? Even if only the foils an ignoring the arms, then per rule 10.1:

Crew weight: 960–990 kg
Foil weight: 2,430 kg (1,215 kg each)

Seems to me ballast is considerably more than crew weight. And the ballast is at the end of 3.4m arms mounted more or less on the gunwale. Crew weight can't be more than about 2.4m from the centreline if they're all on the rail, so better not rely on them to avoid a capsize. ;-)

But they aren't allowed to race with both foils down except during manoeuvres, and not allowed to race at all with them fully down in the most stable configuration. I don't think they will race in less than say 6 kn of steady breeze, so kinda moot really.

 

A simple addition to the rules making anything under foiling speed considered to be  maneuvering would resolve this, effectively moving the restriction to apply basically only during stable straight line foiling, which is probably the intent anyway as I assume it's primary intent is to remove using the windward foil to generate additional righting moment and the loads that implies. 

It would also allow two foil take off if that turned out to be useful.

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6 hours ago, Boybland said:

A simple addition to the rules making anything under foiling speed considered to be  maneuvering would resolve this, effectively moving the restriction to apply basically only during stable straight line foiling, which is probably the intent anyway as I assume it's primary intent is to remove using the windward foil to generate additional righting moment and the loads that implies. 

It would also allow two foil take off if that turned out to be useful.

Reading through rule 27 again, the boats can be sailed with the foils anywhere between fully down and "highest permitted sailing position", which means as high as possible but still in the water (80° to 90° above fully down). They can then go from there to "fully raised" (about 119° above fully down), but can't stop in between the two upper positions.

So my mistake, the boats can race with the foils fully down so the lower wind limit might be very low. I think that will make racing very interesting.

There is equivocating on downforce (27.4), the boats aren't designed for it but they'll see what happens. Once they work that out, they'll likely amend the rule to suit. But it will be hard to tell if both foils are down whether one is generating downforce unless they mandate a sensor as part of the ILS so the race committee can monitor or check later for compliance.

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Yes down force is muddy waters ATM, and it's been discussed here previously. I reckon some clarification will occur after a few months training.hopefully consensus and input from all concerned,  that's the way the show has been so far. And again, no amount of rail meat is gonna stop one of these beasts from laying down if mismanaged. Skill will be there, but it ain't gonna be dead wieght skill.

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1 hour ago, RobG said:

Reading through rule 27 again, the boats can be sailed with the foils anywhere between fully down and "highest permitted sailing position", which means as high as possible but still in the water (80° to 90° above fully down). They can then go from there to "fully raised" (about 119° above fully down), but can't stop in between the two upper positions.

So my mistake, the boats can race with the foils fully down so the lower wind limit might be very low. I think that will make racing very interesting.

There is equivocating on downforce (27.4), the boats aren't designed for it but they'll see what happens. Once they work that out, they'll likely amend the rule to suit. But it will be hard to tell if both foils are down whether one is generating downforce unless they mandate a sensor as part of the ILS so the race committee can monitor or check later for compliance.

To be honest I would think as long as the boats aren't foiling it's probably neither her nor there is they are generating down force as it would be negligible compared to the loads those arms are built for anyway.

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16 hours ago, Boybland said:

To be honest I would think as long as the boats aren't foiling it's probably neither her nor there is they are generating down force as it would be negligible compared to the loads those arms are built for anyway.

Yes, it's downforce while foiling that's the issue. And not for the arms, they can take it, but for the boats. The tested arm broke at 27.3 tonne, which is supposed to be about 3 times the max expected, so imagine 9 t lift on one side, with say 8 t downforce on the other with the rig taking 100% load. They might not sail steadily with those loads, but they might occur momentarily during gusts or manoeuvres.

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4 hours ago, RobG said:

, it's downforce while foiling that's the issue

Doesn't that mean both arms down which is precluded except during manoeuvres?

I think I get why down force has been fenced off, depend on stiction and if you loose it it goes bad fast. Like the max rudder diff with the slack rigs in 35, I saw some pretty loose moments very quickly.

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6 hours ago, barfy said:

Doesn't that mean both arms down which is precluded except during manoeuvres?

I can't find that in the rules anymore. Rule 27 seems to cover aspects of foil arm cant and it doesn't preclude it. I'd expect it to be slower except where downforce is being used. Even in marginal conditions where two down might be used to get foiling, once on foils, it should be faster with the windward foil raised. Just me speculating of course. ;-)

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Whatever is written in the rule now, due to the unknown of the boat the rule committee will have increasing power.

This is coming from Jack Griffin letter:

"The Rules Committee was not in the original Protocol. It was defined in the AC75 Class Rule in March 2018, and given the power to change the class rule at any time for supplied or specified equipment. The Foil Cant System and the Foil Arms are supplied equipment. The mast is specified equipment. Only COR/D need to agree to these changes; the other challengers have no vote.
Interestingly, it was not until Protocol Amendment 02 in August 2018 that we found out who appoints the Rules Committee: COR/D.


In addition, the AC75 Class Rule requires the Rules Committee to set the restrictions on using the Foil Cant System by 30 November 2019. Restrictions may include

·        limits on downforce generated by the foils

·        cant angle for the windward foil

and these restrictions may apply

·        for certain wind ranges

·        during certain phases of the race, e.g. pre-start"

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11 hours ago, RobG said:

I can't find that in the rules anymore. Rule 27 seems to cover aspects of foil arm cant and it doesn't preclude it. I'd expect it to be slower except where downforce is being used. Even in marginal conditions where two down might be used to get foiling, once on foils, it should be faster with the windward foil raised. Just me speculating of course. ;-)

Interesting.what version are you reading as current?

Both down may be interesting; being able to tack or gybe without notice, no energy restrictions on maneuvering as we saw in 35 could enable lightning quick moves in pre start and during duels. Like burling's handbrake turn r5? and subsequent hook.

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So the Ed puts boats on the front page that kinda foil “cos you know that’s cool”

yet throws a shit fit when a boat actually designed to foil appears.. twat.

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I know I've spent too much time here when I see this and think it's an AC75 shot I haven't seen before.

Annotation 2019-09-11 061240.png

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22 minutes ago, Ex-yachtie said:

I know I've spent too much time here when I see this and think it's an AC75 shot I haven't seen before.

Annotation 2019-09-11 061240.png

Their "scientific research" whalers can just follow behind Te Aihe and collect their sushi samples already sliced and diced..

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Be interesting to see if, when not up on foils, she sails faster than a 75 footer?

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19 minutes ago, Kiwing said:

Be interesting to see if, when not up on foils, she sails faster than a 75 footer?

Hard to imagine with so much drag.

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The whetted surfaces must be about equal.  stiffness be better with the foils (more upright (or healed to windward?) state?)

But it is really hard to tell apart from that I wonder if we will ever find out?

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