Monday, 26 August 2013

Why ETNZ will win the AC





It is hard to predict who will win the AC is the common opinion. Both Oracle and ETNZ are improving all the time and both teams have another two weeks for practice and mods.

If we look at available data (see: cupinfo.com)
We see that ETNZ outperforms both Luna Rossa and Oracle. The aerodynamic advantage of Oracle due to the smaller hulls shows in their performance in a TWA of 60 degrees but not at other angles, which makes sense as the boats sail with very low AWA's.

The huge performance gap (see race data) between LR and ETNZ can be decomposed in:
- better start 1%
- better handling 1-2%
- better tactics 1 %
- better angles 1-2%
- higher endspeeds 2-4%

The boats are pretty similar, though I expect ETNZ to be the lighter boat. LR is probably close to max weight and ETNZ to min weight (just guess, not confirmed).
Looking at the data we see that ETNZ can sail deeper downwind and higher upwind. Two probable causes: the lighter boat is slightly more efficient and superior wing trim and co-operation between helmsman and wingtrimmer. High consistent speeds have always been Glenn's trademark.

One should realize that if the performance gap is bigger than 3 %, the fastest boat will only fail to win due to breakdowns or odd mistakes.  The performance delta between LR and ETNZ is one third boat and two third crew (my best guess)

The data of Oracle are old and probably not too reliable. The main difference between the teams are in wing design see: the 4 wings crew and reserve buoyancy in the hulls.
The last point did ETNZ  help a lot in learning how to sail the boat but will not be relevant in the cup as lighter winds are expected. The supposed lower drag upwind of Oracle see: article is not too relevant as the race will be decided downwind. Basically the boat which is ahead a few hundred meters after he first mark is likely to win that race.

The difference in wing design can be the deciding factor. I expect Oracle's wing to be a bit more forgiving due to the slightly rounder and wider first section. The wing which twists the best and has the lowest drag will  be the better wing (efficiency over power). If we see a relevant difference in speed between the teams it might be caused primarily by the difference in wing philosophy. The wing of Oracle looks more smooth and slick, the wind of ETNZ seems to be weapon in the hands of Dean and Glenn due to their fine tuning and great twist profile.

The teams are both strong. Oracle misses some hours on the water due to their capsize, but Jimmy has shown in the AC45 races that he is the man to beat. Jimmy is know for his aggressive style in match racing but I do not think that this will help him a lot. Dean showed that he is very capable of staying out of problems. If he can prevent dialups close to the start line as he did in the last race of the LV cup little is here to be gained by Oracle.
ETNZ may have some mods up their sleeve, if anything I think we will see  improved fairings and  perhaps a slightly smaller daggerboard (more high aspect tip, thinner tip). Due to their practice advantage they will know best how to do the last tweaks. Two weeks is too short for Oracle to match a daggerboard swap (see article in Seahorse about board construction).

The whole AC might be decided in the legs to mark one. If ETNZ can keeps its reaching advantage they are the most likely team to win the cup. The flatter bottom of the hulls do help the team to get the boat earlier on the foils.

After mark one racing can be close but if non of the two teams makes a handling mistake it will be very hard to find a passing lane for the trailing team.

This my layman's assessment based on watching video, visiting internet sites, racing against Glenn and my experience as A-class designer/developer.  May the best team win and I will salute the winner who ever it will be.

Two more weeks....

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