Emirates Team New Zealand.

Sailbydate

Super Anarchist
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Kohimarama
Where & When?
7 May 2020. Wetapix:

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Lickindip

Anarchist
758
525
Auckland
quite clearly they are evaluating the bulb vs no bulb. my money is still on No-bulb during the actual AC races

the bulb theory is good for evaluating multiple shapes due to the mass ruling ... when it comes to practicality and performance during actual racing, what's the point in having them?

 

phill_nz

Super Anarchist
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internet atm
that's to be seen

im guessing that different programs have come up with different results depending on what parameters not factored into it changed the answers ( its unlikely anyone has created a perfect program )

and almost everything has a pro and con

bulbous bows and reverse angle / wave piercing bows don't look like they would work either .. yet

 
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See Level

Working to overcome my inner peace
quite clearly they are evaluating the bulb vs no bulb. my money is still on No-bulb during the actual AC races

the bulb theory is good for evaluating multiple shapes due to the mass ruling ... when it comes to practicality and performance during actual racing, what's the point in having them?
I thought the whole idea of building a test boat smaller than an actual surrogate was that it allowed the team to do whatever they want without breaking the rules?

 

JonRowe

Super Anarchist
1,801
958
Offshore.
I thought the whole idea of building a test boat smaller than an actual surrogate was that it allowed the team to do whatever they want without breaking the rules?
It is, ETNZ are more likely checking all the boxes and validating their modelling surrounding the bulb.

 

The_Alchemist

Super Anarchist
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USA
quite clearly they are evaluating the bulb vs no bulb. my money is still on No-bulb during the actual AC races

the bulb theory is good for evaluating multiple shapes due to the mass ruling ... when it comes to practicality and performance during actual racing, what's the point in having them?
Didn’t all you guys say that the NZ simulator was so good that they developed these revolutionary new bulbless foils that nobody else thought of?  Why would they need to test a bulbed foil if they already know their foil is better?  Why waste the time.  Also, is it just a coincidence that they are now sailing faster?

 

The_Alchemist

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Where & When?
I just spent over 2 hours trying to find our discussion on foils where NZ was the outlier and all the other teams went with the bulb.  It must have been in the "old NZ" thread that was deleted.  I said that I thought NZ would eventually change over to the bulb foils.  The idea was that all of the other teams had already tested the bulb-less foils on their test boats and all of them decided independently to change to the bulb foils.  And all of the bulbs had the anhedral foils where as NZ started with one T-foils just like AM did on the Mule.   Most of the NZ posters said that I was missing the brilliant design of the NZ foils, I said that NZ was playing catch-up because they didn't have the "on the water" test boat experience of the other teams.

 

Tornado-Cat

Super Anarchist
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quite clearly they are evaluating the bulb vs no bulb. my money is still on No-bulb during the actual AC races

the bulb theory is good for evaluating multiple shapes due to the mass ruling ... when it comes to practicality and performance during actual racing, what's the point in having them?
The rule does not apply on the test boat so it's clearly to test its performance.

 

Lickindip

Anarchist
758
525
Auckland
Isn't the junction improved hydrodynamics? 
probably depends on a few factors, but the way I see it is you are accelerating the flow for it to go around the bulb, the bulb still has a junction with the wings similar to a fuselage of an aircraft, accelerated flow when nearing the cavitation zone cant be a good thing

have a look at this video from memory 40mins in - yes I know it is an aircraft but it discusses the principles of what the flow is doing around the junction without any bias with simple diagrams and explanations

the teams with the bulbs aren't doing much fairing in the zones between the wing/bulb IMO



another thing to note is that aircraft generally need a fuselage to house the pilot/passengers and engines, figure out they can fit all that into the wing they end up with a much more efficient design

image.png

 

Lickindip

Anarchist
758
525
Auckland
Didn’t all you guys say that the NZ simulator was so good that they developed these revolutionary new bulbless foils that nobody else thought of?  Why would they need to test a bulbed foil if they already know their foil is better?  Why waste the time.  Also, is it just a coincidence that they are now sailing faster?
sailing simulator or CFX simulater?

all teams will have similar CFX programs, ETNZ is using ANSYS from memory

CFX data output: lift drag weight etc etc at different angles at different speeds will be input as a pretty complicated yachting polar into the team-specific yachting simulator

the first thing you are told with using CFX is "crap in = crap out" so if the person producing the CFX data is making the wrong assumptions/conditions you will have a shitty polar that won't represent the actual yacht

 

uflux

Super Anarchist
Do we have to keep going on about this bulbs are faster nonsense!?!

The only real hydrodynamic reason for a bulb is the all allows the use of thinner wing designs (potentially faster than a thinker wing) by placing the required weight in a bulb. That’s it...every thing else from a hydro perspective is a negative (surface area drag, parasite drag etc). So it all come down to whether thin is faster even with the negatives.

 

breezie

Member
176
91
coromandel
Well if teamNZ are really sure that bulb-less is the way to go then obviously they will fly a bulb-ed version now and then to keep the others guessing.  

 
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