Tornado-Cat

Boats and foils comparison

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1 hour ago, GeeJay said:

Hi from a newbie - my first post although I’m a long-time lurker.  Used to sail Paper Tiger catamarans competitively but so old and knackered now that fishing from our runabout and riding motorcycles is about all I can manage.  I still follow anything to do with sailing though.

I’m a bit late to the party with respect to discussing the latest ETNZ foil design but admin took over a week to approve my membership. Seeing Weta27’s photo of the foil on the ETNZ thread, it so happened that I’d recently taken delivery of some enhancing software and wondered how it would work with Weta’s photo.  Obviously there is only so much you can do from that original but I thought that the result was quite interesting.  A direct post won’t show anything new but here’s a link to a downloadable photo after I ran it through Gigapixel AI: https://www.dropbox.com/s/g6pxmp1myn68r58/ETNZ foil-gigapixel-scale-4_00x.jpg?dl=0.  If you’re interested, you can download and zoom in on parts of it or zoom on Dropbox.

Cheers for now……
 

Appreciate your efforts here GJ.

Firmly of the belief that the Dark patches are just vestigial dampness drying out in the join between Foil and flap, which because there must be a zone of articulation has a void into which water gets held. No conspiracy or unobtainium materials. No secret squirrel attempts to store water in the structure - just mechanical voids that do hold water, and take a while to drain...... The crack is the point at which the water flows out and is most sheltered from the Apparent Wind so last place that remains damp on the whole structure - I liken it to the same effect that is seen on the flaps wings and nacelles of Commercial Jets when they take off in heavy rain, and how the water runs around and eventually dries on the junction of each.

Cannot be certain what the Midline structure is on the underside of the fairing/bulb - but again seems to involve a void that allows water to be held that has then drained out and further wetted the Hinge crack between Foil and Flap.

The dark patch of the flap is merely a hangover of being the closest to the water surface and therefore subject to spray and the occasional dunking - so least likely to ever get dry, or at least take the longest to dry.

 

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11 minutes ago, Boink said:

Appreciate your efforts here GJ.

Firmly of the belief that the Dark patches are just vestigial dampness drying out in the join between Foil and flap, which because there must be a zone of articulation has a void into which water gets held........

Cannot be certain what the Midline structure is on the underside of the fairing/bulb.....

 

 

Thanks Boink.  I recently bought the software to enlarge and tidy up old negatives, 35mm slides and prints that I'm busy digitizing and was just curious to see if it showed anything interesting.  I agree with respect to the dampness but I was mainly interested in the apparently asymmetric structure you mentioned.  The flattened underside of the fairing/bulb certainly looks similar to the lifting fuselage of the Boeing concept design photo that someone posted on the ETNZ thread.  I'm a retired mech engineer though, so what would I know?

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7 hours ago, JALhazmat said:

So what are you learning from running the foils in a deliberately wrong location? 
 

If the foils need to be further foreword on B2 and the way to do that is apparently moving the entire arm pivot forwards why would they not move the foil position forward on the arms in the picture so they get proper data on B1 

they spent enough time in the shed putting them on so why not put them in the correct place? 

what your saying is that knowingly they put the foils too far back so that they didn’t measure  on B1 and any sailing would be out of balance for what they want to do on B2 

if B1 is sailing about with the centre of lift 1m further back than it should be then trim and balance will be way off, the rudder more heavily loaded etc 

Except it's not 1m it's 200mm or 0.2m if you prefer, perhaps ETNZ simply feel they can adequately account for this with other trim options (i.e. rudder trim / foils, mast rake, etc...) and in their relative performance measurements, it's pretty clear looking at Defiant for example that their weight to lift distribution is somewhat different to ETNZ's, so there are definitely different ways to do this.

The foil arms are one design and you certainly wouldn't want to risk pushing those out of measurement.

The join between the foil arm and the foil is supporting about 90% of an 8 ton boat, it kind of needs to be where it's strongest...

As for what would you learn? Isn't that fairly obvious when running a pretty revolutionary new foil shape?

Like I said I'm sceptical, just playing Devil's advocate here and pointing out it's not an impossible scenario, there are plenty of negatives in my view, not least of all that the new boat would then be slightly out of balance with the other existing foils.

 

 

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23 minutes ago, GeeJay said:

I'm a retired mech engineer though, so what would I know?

More than most around here......

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5 hours ago, Boybland said:

Except it's not 1m it's 200mm or 0.2m if you prefer, perhaps ETNZ simply feel they can adequately account for this with other trim options (i.e. rudder trim / foils, mast rake, etc...) and in their relative performance measurements, it's pretty clear looking at Defiant for example that their weight to lift distribution is somewhat different to ETNZ's, so there are definitely different ways to do this.

The foil arms are one design and you certainly wouldn't want to risk pushing those out of measurement.

The join between the foil arm and the foil is supporting about 90% of an 8 ton boat, it kind of needs to be where it's strongest...

As for what would you learn? Isn't that fairly obvious when running a pretty revolutionary new foil shape?

Like I said I'm sceptical, just playing Devil's advocate here and pointing out it's not an impossible scenario, there are plenty of negatives in my view, not least of all that the new boat would then be slightly out of balance with the other existing foils.

 

 

it's interesting that all teams B1's have the foil arm at the Aft end of the Box. they have made an decisions about the loading/force balancing when designing and thought ' shit we have to have the centre of foil lift as far back as possible so lets put the arm there'

This is just my assumption but ETNZ once sailing could have figured out they can move it forward and i imagine B2 will have the foil arm forward and therefore the foil forward and back in the box.

happy to be proven wrong

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2 hours ago, Lickindip said:

it's interesting that all teams B1's have the foil arm at the Aft end of the Box. they have made an decisions about the loading/force balancing when designing and thought ' shit we have to have the centre of foil lift as far back as possible so lets put the arm there'

This is just my assumption but ETNZ once sailing could have figured out they can move it forward and i imagine B2 will have the foil arm forward and therefore the foil forward and back in the box.

happy to be proven wrong

One thing that might also add to this, is perhaps ETNZ have decided none foiling is simply a none event, so moving the lateral resistance from the arm (that was previously in line with the lateral force from the foil) is no longer an issue, thereby allowing the foil to be significantly trailing the arm.

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On 9/18/2020 at 7:29 AM, Ex-yachtie said:

Interesting clip.

Being a random sample I think we can all agree this is fully representative of each boat’s performance, and we should labour comparisons before we all fall out with each other. 
 


 

Something that's been bugging me is the difference between the flapping of Defiant's headsail and ETNZ's.  ETNZ's is much snappier with the sail trimmed quickly.

 

Anyone got any observations worth sharing?

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1 hour ago, Ex-yachtie said:

Something that's been bugging me is the difference between the flapping of Defiant's headsail and ETNZ's.  ETNZ's is much snappier with the sail trimmed quickly.

 

Anyone got any observations worth sharing?

Pretty simple really haves and have nots.

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2 hours ago, Ex-yachtie said:

Something that's been bugging me is the difference between the flapping of Defiant's headsail and ETNZ's.  ETNZ's is much snappier with the sail trimmed quickly.

 

Anyone got any observations worth sharing?

To be honest most of the difference is down to the helm. TNZ did a tighter turn

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4 minutes ago, mako23 said:

To be honest

So you aren't normally?

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Just now, mako23 said:

You have got me , everything I say is a lie 

The phrase shits me, sorry.  It's becoming the new "you know?".

You should stop it.  Interesting that it has now crossed into type.  Why the fuck would you type it?

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17 minutes ago, mako23 said:

To be honest most of the difference is down to the helm. TNZ did a tighter turn

To be honest no one has a bloody clue, 

system, functionality, turn radius, speed.

all variables amongst many others that we simply don’t know.

 

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On 9/21/2020 at 11:28 PM, JALhazmat said:

To be honest no one has a bloody clue, 

system, functionality, turn radius, speed.

all variables amongst many others that we simply don’t know.

 

Just for your interest, because we discussed this before. Ive placed a link to a paper that used keel design with a wind tunnel. Just thought you might be interested, if not no worries. Have a nice day 

 

http://publications.lib.chalmers.se/records/fulltext/148387.pdf

 

 

 

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7 hours ago, mako23 said:

Just for your interest, because we discussed this before. Ive placed a link to a paper that used keel design with a wind tunnel. Just thought you might be interested, if not no worries. Have a nice day 

 

http://publications.lib.chalmers.se/records/fulltext/148387.pdf

 

 

 

Just because I didn’t reply instantly on this? Why thank you for the reminder.

as you know tunnel testing and tow tests are not allowed this cycle,

this is why all the teams are going in so heavily with CFD, hence the latest puff piece from ETNZ on the subject. 
 

it’s also why none of the teams are hiring out fucking enormous wind tunnels and testing there. When wind tunnel testing is getting too expensive for Formula1 who test usually with 3rd scale models( as it’s cheaper) and the tunnel doesn’t need to be so bloody enormous.  it’s not going to be the first choice for the affordable low cost kiwi dream AC is it 


as you also know I was talking about the absurdity of comparing a prototype delta winged passenger plane with ETNZ latest foil. 
 

I know that you are grasping saying that if they can use air to model a bulbed keel (not a hydrofoil) then by your logic they should be testing planes in underwater flow tanks? Just re jig the Reynolds number and off you go... 

 

 

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1 hour ago, JALhazmat said:

Just because I didn’t reply instantly on this? Why thank you for the reminder.

as you know tunnel testing and tow tests are not allowed this cycle,

this is why all the teams are going in so heavily with CFD, hence the latest puff piece from ETNZ on the subject. 
 

it’s also why none of the teams are hiring out fucking enormous wind tunnels and testing there. When wind tunnel testing is getting too expensive for Formula1 who test usually with 3rd scale models( as it’s cheaper) and the tunnel doesn’t need to be so bloody enormous.  it’s not going to be the first choice for the affordable low cost kiwi dream AC is it 


as you also know I was talking about the absurdity of comparing a prototype delta winged passenger plane with ETNZ latest foil. 
 

I know that you are grasping saying that if they can use air to model a bulbed keel (not a hydrofoil) then by your logic they should be testing planes in underwater flow tanks? Just re jig the Reynolds number and off you go... 

 

 

Wow .....interesting response. I’m not saying anything other than you can use air  flow to simulate flow of water. Nothing more or nothing less. As for simulating air flow by using water. Don’t know haven’t a clue ? All I did know was about reynold numbers ( Hazy memory ) and that a previous syndicate had done air flow to simulate a keel. 
 

Has Boris Johnson got under your skin dude ?? 

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29 minutes ago, mako23 said:

Wow .....interesting response. I’m not saying anything other than you can use air  flow to simulate flow of water. Nothing more or nothing less. As for simulating air flow by using water. Don’t know haven’t a clue ? All I did know was about reynold numbers ( Hazy memory ) and that a previous syndicate had done air flow to simulate a keel. 
 

Has Boris Johnson got under your skin dude ?? 

Not a bit of it, yes it’s  blunt because the amount of stuff that has to be repeated because people can’t be bothered to read/research, draw stupid comparisons or run off down blind alleys saying that concepts that work at 600mph are easily transferable to 50mph (alchemist and the bloody plane) 

yes you CAN use air to simulate water. But Not in this ac you can’t and if your simulating anything why wouldn’t you click the button that says water on the CFD program instead? 

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1 hour ago, JALhazmat said:

Not a bit of it, yes it’s  blunt because the amount of stuff that has to be repeated because people can’t be bothered to read/research, draw stupid comparisons or run off down blind alleys saying that concepts that work at 600mph are easily transferable to 50mph (alchemist and the bloody plane) 

yes you CAN use air to simulate water. But Not in this ac you can’t and if your simulating anything why wouldn’t you click the button that says water on the CFD program instead? 

The bit I disagreed with is this statement from you 

 

are the ac boats doing over 600mph? No

 how can aero that works (theoretically) on a 300 person intercontinental jet powered passenger plane moving at 600+mph be applied to a hydro foil moving at 0-50kts in water? 

 

The point I was trying to make that the theoretical aero on a 300 person intercontinental jet CAN be applied to the foils of a yacht at 40 knots in the water.  You then have the audacity to moan about people not doing there homework, when it is  YOU that has not done your homework. 
 

in fact many CFD packages uses Navier Stokes equations to simulate both water and air flow around a foil 
 

 

 

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3 hours ago, JALhazmat said:

a bit of it, yes it’s  blunt

It's actually a lot of "it".

Please don't quote that particular troll? Thx.

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7 hours ago, JALhazmat said:

......

I know that you are grasping saying that if they can use air to model a bulbed keel (not a hydrofoil) then by your logic they should be testing planes in underwater flow tanks? Just re jig the Reynolds number and off you go... 

You mean like this pic from NASA:

image.png.6604cf9892fe9043659db10a72c0f59d.png

https://www.nasa.gov/centers/dryden/about/Organizations/Technology/Facts/TF-2004-05-DFRC.html

Looking into it further, here is an article that was declassified that states that water is very useful for testing lift and drag.  It can have some problems in supersonic high speed testing because of the inability to achieve high enough Reynolds number.  But this can also be the case with air tunnels not being able to achieve high enough Reynolds numbers for super high speed fighter jets.

In general, water tunnels can be a very good way to test the basic parameters of air flow at slower speeds.

https://apps.dtic.mil/dtic/tr/fulltext/u2/a582450.pdf

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Cool story, now show me a current ac team doing it..  I mean try an keep it relevant? 

I think NASA might have a slightly different budget but hey you know best 

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11 hours ago, JALhazmat said:

it’s also why none of the teams are hiring out fucking enormous wind tunnels and testing there. When wind tunnel testing is getting too expensive for Formula1 who test usually with 3rd scale models( as it’s cheaper) and the tunnel doesn’t need to be so bloody enormous.  it’s not going to be the first choice for the affordable low cost kiwi dream AC is it 

 

Screenshot 2020-09-24 0558172.png

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35 minutes ago, Lickindip said:

here is the reason why you won't see any AC team this round doing any tank testing

image.png.a768d4e2dcc34ba0c8430d1d8f7e15a2.png

THANK YOU!!!!

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28 minutes ago, Lickindip said:

here is the reason why you won't see any AC team this round doing any tank testing

image.png.a768d4e2dcc34ba0c8430d1d8f7e15a2.png

Spoil sport. 

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although ...

I'm assuming they are allowed to drive down the motorway with a mock foil out the window as that would be 'open-air' and the car is not a surrogate 

:lol:

 

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3 hours ago, JALhazmat said:

Cool story, now show me a current ac team doing it..  I mean try an keep it relevant? 

I think NASA might have a slightly different budget but hey you know best 

Why do you have to be such a pompous dickhead!  

You are the one stating that plane in air vs foil in water comparison are totally ridiculous.  

You are the one stating that if it was such a good idea then why don't they test planes in water tunnels.

I just gave you an example of how it has been done and you go off on another tangent asking about which AC teams are doing it.  

Who the Fck cares...  you know they can't do it for this cup.

Are you off your meds?

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2 hours ago, Lickindip said:

although ...

I'm assuming they are allowed to drive down the motorway with a mock foil out the window as that would be 'open-air' and the car is not a surrogate 

:lol:

 

Depend on if it is under 12 meters long... lol

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Lucky for ETNZ they have worked out how to take the tank testing into the Waitemata harbour with Hawk and their foil cameras/sensors. It is very interesting how they worded that rule. They obviously had that in mind.

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10 minutes ago, uflux said:

Lucky for ETNZ they have worked out how to take the tank testing into the Waitemata harbour with Hawk and their foil cameras/sensors. It is very interesting how they worded that rule. They obviously had that in mind.

I think the rule was in place to restrict scaled development. else teams could have made 10,000scaled foils and water tested them every day/night

this way you are restricted to bums on seats in front of computers which can be more of a dark art in getting relevant results.

My favourite equation from uni ... CrapIN = CrapOUT

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37 minutes ago, The_Alchemist said:

Why do you have to be such a pompous dickhead!  

You are the one stating that plane in air vs foil in water comparison are totally ridiculous.  

You are the one stating that if it was such a good idea then why don't they test planes in water tunnels.

I just gave you an example of how it has been done and you go off on another tangent asking about which AC teams are doing it.  

Who the Fck cares...  you know they can't do it for this cup.

Are you off your meds?

Aww poor baby, did the stranger on the internet not blindly agree with your bullshit? 
 

You think there is some hilarious comparison with that plane and the new kiwi foil.. oh they look “similar” so the tech must transfer...  

who cares? You and your hard of understanding mako chum seem to think it’s a thing so I guess you both do. 
 

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2 hours ago, JALhazmat said:

Aww poor baby, did the stranger on the internet not blindly agree with your bullshit? 
 

You think there is some hilarious comparison with that plane and the new kiwi foil.. oh they look “similar” so the tech must transfer...  

who cares? You and your hard of understanding mako chum seem to think it’s a thing so I guess you both do. 
 

I never said there was a tech transfer, someone else pointed out some similarities and I just noted that the Airbus engineers, who should know the most about that plane design, do not seem to be selling it to AM.

I really don't care what you think, just trying to carry on a conversation and correct your flippant assumptions.  You yell "no way", get called on it with examples of where it is taking place and then you change the subject and declare "who cares?".  Just grow up and be a man about it.

 

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let's just be realistic here ... AM B1 and Gen 1 foils had minimal to do with Airbus as I do not believe they were there from day 1

it was a rush to get something onto paper and get it under construction.

AM B2 is going to be a hell of a lot more refined in all aspects with the help of the Airbus knowledge and computing power

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4 hours ago, The_Alchemist said:

I never said there was a tech transfer, someone else pointed out some similarities and I just noted that the Airbus engineers, who should know the most about that plane design, do not seem to be selling it to AM.

I really don't care what you think, just trying to carry on a conversation and correct your flippant assumptions.  You yell "no way", get called on it with examples of where it is taking place and then you change the subject and declare "who cares?".  Just grow up and be a man about it.

 

You had me on block (apparently) I suggest you do it again. 

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10 hours ago, Lickindip said:

I think the rule was in place to restrict scaled development. else teams could have made 10,000scaled foils and water tested them every day/night

this way you are restricted to bums on seats in front of computers which can be more of a dark art in getting relevant results.

My favourite equation from uni ... CrapIN = CrapOUT

Also this favours TNZ with all their data collected from their boats. The more onboard telemetry you have the better you can validate your cfd package. People can leave your syndicate but they can’t take your telemetry data. It’s not worse the risk of being caught if you used another syndicate data. 
 

yes it does reduce cost which is a good thing but it’s also an advantage to existing syndicates who are not starting from scratch 

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18 hours ago, The_Alchemist said:

You mean like this pic from NASA:

https://www.nasa.gov/centers/dryden/about/Organizations/Technology/Facts/TF-2004-05-DFRC.html

Looking into it further, here is an article that was declassified that states that water is very useful for testing lift and drag.  It can have some problems in supersonic high speed testing because of the inability to achieve high enough Reynolds number.  But this can also be the case with air tunnels not being able to achieve high enough Reynolds numbers for super high speed fighter jets.

In general, water tunnels can be a very good way to test the basic parameters of air flow at slower speeds.

https://apps.dtic.mil/dtic/tr/fulltext/u2/a582450.pdf

Also were there are issues water can not be easily compressed which can happen at high speeds with air on the leading edge. Also air can’t replicate cavitation. 

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The Italian guys having a chat about various aspects of the two boats we now have in play.

Soon will be the full Monty!

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On 9/21/2020 at 7:18 AM, mako23 said:

You have got me , everything I say is a lie 

Therefore, you tell the truth...

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