NZilla vs AZilla vs BatZilla – compare and contrast.

[michaelkeogh1970]

The three designs are out for all to see. But what do they have in common and what differences?

Hulls. They all seem to have some rocker to help in tacking (according to threads here – I have no idea but love reading this stuff!) Do the hulls make a huge difference, as they will be either skimming – or more likely clear above the water when sailing?

Wings. I have no idea here, but to my eye the wing on BatZilla looks pretty much identical to the one on DogZilla (just a bit smaller). The wing on NZilla looks a bit agricultural in comparison.

Foils. We have only seen one set of first generation foils yet. But they seem to be doing the trick!

Aerodynamics. Only one player at the races there as far as I can tell.

Overall design. Don’t see a Y frame on BatZilla. Do the cross beams along with the central structures give enough stiffness to stop the boat twisting? Again no idea but would like to learn.

Any thoughts?

 

[SimonN]

The three designs are out for all to see. But what do they have in common and what differences?

Hulls. They all seem to have some rocker to help in tacking (according to threads here – I have no idea but love reading this stuff!) Do the hulls make a huge difference, as they will be either skimming – or more likely clear above the water when sailing?

Wings. I have no idea here, but to my eye the wing on BatZilla looks pretty much identical to the one on DogZilla (just a bit smaller). The wing on NZilla looks a bit agricultural in comparison.

Foils. We have only seen one set of first generation foils yet. But they seem to be doing the trick!

Aerodynamics. Only one player at the races there as far as I can tell.

Overall design. Don’t see a Y frame on BatZilla. Do the cross beams along with the central structures give enough stiffness to stop the boat twisting? Again no idea but would like to learn.

Any thoughts?

Too early to comment on much, but your comments on the wings are, I believe, incorrect. The DogZilla wing was the most basic, agrucultural wing it is possible to build. The BatZilla wing is rather different. Besides being beutifully detailed, it seems to have a flap to control the slot between the 2 bigger elements. We haven't seen close enough photos to see whether the leading element twists. If it does, it is very similar to the NZ wing. If it doesn't, then it is a more simple, less sophisticated solution. It would be very interesting if it doesn't twist, to see the comparison between a "twister" and a non twister.

 

[nav]

The apparent difference in thickness of the OTUSA and ETNZ #1 wings surprises me.

 

[Loose Cannon]

BZ wing is a 3 element most likely with lead element twist. Very clean aero. NZ wing is a cleaned up development of dz wing, and Artemis's first wing was very much a development of Dz wing.

The hulls - artemis and tnz are going for a development of cheezezilla platform with y trusses. Their hull shapes are different reflecting their theology and which current catamaran hull they like (NZ like f18 thinking, adn Artemis like a-cat thinking.) Batzilla hull is a maxed out development of the west coast usa a-cat.

all beautiful, and I suspect that for all their differences, this course will restrict the impact of any speed differences. I will likely eat my words for saying that, but if I do, I will have seen a 72 foot cat foiling after the windward mark for a whole leg at such pace that they are aiming for the leward gate. and that would be well worth eating my words for.

I don't care what anyone says, these last 2 cups -for me at least- have included so much excitement about the boats that I don't miss the old matches. I remember watching the Fox web cam in SD for Jimmy's sunday drive on Dz, and the excitement that created. And now these unveilings feel the same. I can't say that even the unveiling of the winged keel in 83 was anything near this....

 

[SimonN]

BZ wing is a 3 element most likely with lead element twist. Very clean aero. NZ wing is a cleaned up development of dz wing, and Artemis's first wing was very much a development of Dz wing.

Seriously, I don't know where you get this stuff from.
First, I thought we had settled on the convention used in the aerospace industry that says that an element needs a slot and therefore, the OR wing is a 2 element wing. Technically, it is a 2 element wing with a flap on the trailing edge to control the slot between the 2 elements. To date, we have seen nothing that indicates whether the OR wing twists. Have you seen anything? If so, please share, otherwise your comments are simply speculation. having said that, the thin section does suggest that a twisting leading edge is likely.

The NZ and Ertemis wings have very little relationship to the DZ wing. The DZ wing was a very simple, 2 element, not flap, no leading edge twisting wing. It doesn't get more basic than that. The NZ wing is a 2 element, 1 flpa, leading edge twisting wing. If your assumption about the OR wing is correct, the 2 wings are from exactly the same family. The Artemis wing is slightly different again. There is some debate about exactly what it is but I believe that it has froint element twist (but controled differently from OR and NZ) and, depending on the height, is either a 2 element wing with flap or is 3 elements.

Overall, the Artemis wing is the outlyer. However, as Blunted has been pointed out , you have to be careful in comparing certain things as the percentage of cord in each element doesn't have as much influence as you might think.

There is no doubt that the OR wing has been detailed around the principal of reducing drag from controls to the point of obsession. How much that is a game winner, I am not sure. If all the wings were equal in section and configuration, then of course it makes a difference but i doubt it is a game winner on its own.

More interesting is the section being used. It does seem that the OR wing has a far thinner section than the NZ wing. This is all about trade offs. My understanding is that the thinner section has the potential for higher speeds but is far harder to trim as there is less margin before you get seperation. This is why I think the leading edge needs to twist, becaus ethe section isn't forgiving enough to work at all the angles it would need to if it didn't. The NZ wing is likely to accelerate better and be more forgiving to trim.

Of course, there are those who are far more knowledgable than me on this forum and I post my views as a way of getting the debate started on a technical level

 

[chris360]

From the pics we have seen, between oracle and TNZ, the big difference I can see is in the foil setup.

ETNZ- conventinal setup, angled boards giving a resulting lifting vector, automatic height control- the ore the boat lifts the less lift is created as less foil in the water.

They can control the angle of the board inboard to outboard changing the lift vector.

Oracle- vertical L shaped foil, more efficent at lifting the boat, the boards apear to more fore and aft changing the angle of attack of the bottom of the foil. Harder to control as it can lift to far out of the water and stall. But should be faster. I suspect they have some sort of gyro in the center pod controlling it, same as what they had in the wing of their 45 at one stage. Foils quite far forward give better control for the rudder to lift as well. Just my thoughts.....

 

[phomchick]

From the pics we have seen, between oracle and TNZ, the big difference I can see is in the foil setup.

ETNZ- conventinal setup, angled boards giving a resulting lifting vector, automatic height control- the ore the boat lifts the less lift is created as less foil in the water.

They can control the angle of the board inboard to outboard changing the lift vector.

Oracle- vertical L shaped foil, more efficent at lifting the boat, the boards apear to more fore and aft changing the angle of attack of the bottom of the foil. Harder to control as it can lift to far out of the water and stall. But should be faster. I suspect they have some sort of gyro in the center pod controlling it, same as what they had in the wing of their 45 at one stage. Foils quite far forward give better control for the rudder to lift as well. Just my thoughts.....

Hmmmm. So the bulge on the wing of the foiling AC45s contained a gyro? That raises interesting possibilities for the mysterious white tube. But wouldn't a spinning gyro be stored energy?

 

[chris360]

What ever is hiding in the pod is in the center section but is steamlined. Only thing I can think of is foil control as the setup is very hard to control manualy.

 

[Brian Weslake]

From the pics we have seen, between oracle and TNZ, the big difference I can see is in the foil setup.

ETNZ- conventinal setup, angled boards giving a resulting lifting vector, automatic height control- the ore the boat lifts the less lift is created as less foil in the water.

They can control the angle of the board inboard to outboard changing the lift vector.

Oracle- vertical L shaped foil, more efficent at lifting the boat, the boards apear to more fore and aft changing the angle of attack of the bottom of the foil. Harder to control as it can lift to far out of the water and stall. But should be faster. I suspect they have some sort of gyro in the center pod controlling it, same as what they had in the wing of their 45 at one stage. Foils quite far forward give better control for the rudder to lift as well. Just my thoughts.....

Hmmmm. So the bulge on the wing of the foiling AC45s contained a gyro? That raises interesting possibilities for the mysterious white tube. But wouldn't a spinning gyro be stored energy?

Well seeing as modern MEMS gyros are small enough that I have a 3 axis gyro in my iphone, I'm not sure they need such a large a centre pod to house one.

The basic problem with inclined lifting foils is that they move the centre of lift inboard, reducing the available righting arm and therefore the amount of heeling moment that the rig can be allowed to generate. Oracle is maximising its righting moment by getting the lifting foil as far to leeward as possible, but sacrifices some automatic ride control in exchange. ETNZ and Artemis are being more conservative by having canted foils, but will sacrifice some power in exchange for this.

In ETNZ's case they have daggerboard slots that are close to vertical, so they just need to put in straight boards to mimic Oracle. Artemis on the other hand looks to have committed to inclined boards with the daggerboard slots exiting on the inboard side of the hulls, they are going to need some surgery to reconfigure. I think this is Juan K's first big cockup (well maybe second after the broken rig), the Artemis boat looks very pedestrian so far.

 

[Swanno]

I think this is Juan K's first big cockup

Where have you been?

 

[chris360]

From the pics we have seen, between oracle and TNZ, the big difference I can see is in the foil setup.

ETNZ- conventinal setup, angled boards giving a resulting lifting vector, automatic height control- the ore the boat lifts the less lift is created as less foil in the water.

They can control the angle of the board inboard to outboard changing the lift vector.

Oracle- vertical L shaped foil, more efficent at lifting the boat, the boards apear to more fore and aft changing the angle of attack of the bottom of the foil. Harder to control as it can lift to far out of the water and stall. But should be faster. I suspect they have some sort of gyro in the center pod controlling it, same as what they had in the wing of their 45 at one stage. Foils quite far forward give better control for the rudder to lift as well. Just my thoughts.....

Hmmmm. So the bulge on the wing of the foiling AC45s contained a gyro? That raises interesting possibilities for the mysterious white tube. But wouldn't a spinning gyro be stored energy?

Well seeing as modern MEMS gyros are small enough that I have a 3 axis gyro in my iphone, I'm not sure they need such a large a centre pod to house one.

The basic problem with inclined lifting foils is that they move the centre of lift inboard, reducing the available righting arm and therefore the amount of heeling moment that the rig can be allowed to generate. Oracle is maximising its righting moment by getting the lifting foil as far to leeward as possible, but sacrifices some automatic ride control in exchange. ETNZ and Artemis are being more conservative by having canted foils, but will sacrifice some power in exchange for this.

In ETNZ's case they have daggerboard slots that are close to vertical, so they just need to put in straight boards to mimic Oracle. Artemis on the other hand looks to have committed to inclined boards with the daggerboard slots exiting on the inboard side of the hulls, they are going to need some surgery to reconfigure. I think this is Juan K's first big cockup (well maybe second after the broken rig), the Artemis boat looks very pedestrian so far.

I dont think it is a gyro as i know they can be small but like a gyro that is not affected by acceleration, deceleration or turning. Not to sure what else it could be. If Oracle can make this work they will be very fast. Its looks on oracle that the boards can more fore and aft. They are also less affected by wave action.

 

[Brian Weslake]

I think this is Juan K's first big cockup

Where have you been?

I meant in AC34, not the rest of his career.

 

[Boybland]

From the pics we have seen, between oracle and TNZ, the big difference I can see is in the foil setup.

ETNZ- conventinal setup, angled boards giving a resulting lifting vector, automatic height control- the ore the boat lifts the less lift is created as less foil in the water.

They can control the angle of the board inboard to outboard changing the lift vector.

Oracle- vertical L shaped foil, more efficent at lifting the boat, the boards apear to more fore and aft changing the angle of attack of the bottom of the foil. Harder to control as it can lift to far out of the water and stall. But should be faster. I suspect they have some sort of gyro in the center pod controlling it, same as what they had in the wing of their 45 at one stage. Foils quite far forward give better control for the rudder to lift as well. Just my thoughts.....

Not really an engineer or anything, but to my mind this is what it looks like they are trying to achieve.

I definitely think it is a significantly more complicated concept than just conventional angled boards, the most interesting thing to know is how close to horizontal the lower lifting surface is when she is flying.

I think ETNZ have come up with a very clever shape where a very effective flat lower section supports the majority of the boats weight at speed and curved shaped part above takes up the slack in a manner that is somewhat passively self correcting, I think this arrangement is what is resulting in the skimming effect we have seen on some of the videos (which looked fast actually even in light conditions)

 

[pbenett]

I've just seena video of ETNZ with L-daggerboards and T-foils. Having just been in San Francisco, I wander how much pure speed will count angainst reliability and fast tacking: in 24 knots true the Ac45 where screaming along incredibly fast, but constantly nose-diving when bearing away, and halting on tacks.

A bad tack will probably erase any straight-line speed advantage, and a lot of tacks wil be needed in such a narrow course.

First of all, they need to finish in one piece...

 

[SimonN]

Artemis on the other hand looks to have committed to inclined boards with the daggerboard slots exiting on the inboard side of the hulls, they are going to need some surgery to reconfigure. I think this is Juan K's first big cockup (well maybe second after the broken rig), the Artemis boat looks very pedestrian so far.

I love comments like this. JuanK is a world class designer surrounded by world cloass multihull specialists and you think you have spotted something that they haven't thought of. I find that rather unlikely. I would bet a fair amount of money that the boards will be able to be set out at max beam. You also seem to be a bit ill informed about the wing. As has been hinted at on this very forum, the wing failure was almost certainly not due to a design issue but instead, it was due to an issue in manufacture which was done by a 3rd party. PC as good as said so in an interview and he has said a number of things "off the record" that suggest that as well. (As an aside, it's funny how he doesn't seem to be able to keep quiet when he should.)
IMO, the OR and ETNZ foil approach looks pretty conventional. It is the Artemis set up that hints at something rather different and it will be very interesting to see what comes out of the shed. It is the only boat without a conventional slot in the bottom, the ability to adjust the foil looks to take a dufferent approach to the others while the ports in the hull at around the centreboard case level suggests we will see something very different and revolutionary. Nobody has managed to come up with a really good answer to what that is, except maybe for it being a point at which hydrolics might be connected.

The other thing I don't really understand is how people can so accurately predict how these boats will eprform against each other from so little info. Maybe some of you should be working for one of the design teams.

 

[SimonN]

The basic problem with inclined lifting foils is that they move the centre of lift inboard, reducing the available righting arm and therefore the amount of heeling moment that the rig can be allowed to generate. Oracle is maximising its righting moment by getting the lifting foil as far to leeward as possible, but sacrifices some automatic ride control in exchange. ETNZ and Artemis are being more conservative by having canted foils, but will sacrifice some power in exchange for this.

In ETNZ's case they have daggerboard slots that are close to vertical, so they just need to put in straight boards to mimic Oracle. Artemis on the other hand looks to have committed to inclined boards with the daggerboard slots exiting on the inboard side of the hulls, they are going to need some surgery to reconfigure. I think this is Juan K's first big cockup (well maybe second after the broken rig), the Artemis boat looks very pedestrian so far.

This really bugged me, so I went back and looked at the photos again and you have this so arse about face it makes me wonder what you are looking at.
On OR, the exit of the c/b case is on the inside edge of the hull. Of the 3 boats, it looks the most inboard. It also seems that BZ has the least ability to adjust the top of the board inboard and outboard. This is further compounded because of the cant on the boards the opposite way to the cant of the hulls. It seems pretty clear to me that the OR boards will be the most inboard of the 3.

On ETNZ, they seem to have a very conventional case and exits, relying on the s shape of teh board plus being able to mover the head inboard and out.

As mentioned above, the Artemis cases look to be the most radical and, I suspect, have the most possibilty for adjustment. I also suspect that they have a very radical solution as to how the boards are moved. We will know more when we see the boards, but that is the system I am most interested in.

 

[Enzedel92]

Nzilla has 2 hulls

Batzilla has 3 hulls

 

[Loose Cannon]

BZ wing is a 3 element most likely with lead element twist. Very clean aero. NZ wing is a cleaned up development of dz wing, and Artemis's first wing was very much a development of Dz wing.

Seriously, I don't know where you get this stuff from From the picture of the wing horizontal, about to be lifted for the first time where you see the shroud attachment.

Of course, there are those who are far more knowledgable than me on this forum and I post my views as a way of getting the debate started on a technical level

Simon - yes there are those far more knowledge than you. Yes, you do post your views... but beyond disparaging others thoughts, I don't know what you are doing to get a debate started on a technical level.

Seriously, once you leave the UK and move to Auz you are supposed to stop being a prick. Welcome to ignore...

 

[Brian Weslake]

This really bugged me, so I went back and looked at the photos again and you have this so arse about face it makes me wonder what you are looking at.

On OR, the exit of the c/b case is on the inside edge of the hull. Of the 3 boats, it looks the most inboard. It also seems that BZ has the least ability to adjust the top of the board inboard and outboard. This is further compounded because of the cant on the boards the opposite way to the cant of the hulls. It seems pretty clear to me that the OR boards will be the most inboard of the 3.

On ETNZ, they seem to have a very conventional case and exits, relying on the s shape of teh board plus being able to mover the head inboard and out.

As mentioned above, the Artemis cases look to be the most radical and, I suspect, have the most possibilty for adjustment. I also suspect that they have a very radical solution as to how the boards are moved. We will know more when we see the boards, but that is the system I am most interested in.

From photos so far it is pretty clear that with its straight boards and near vertical daggerboard slots, it is Oracle that will have its lifting surfaces furthest outboard. From what I have seen of the Artemis boat (only a few photos admittedly) it looks like it is set up for significant cant on the boards, but you are right, lets wait and see what they have come up with