Part 2 · J/70 North American Championship · Chesapeake Bay, Annapolis

What the wind changes.
What the numbers measure.

A local wind estimate and a consistent VMG calculation, with the uncertainty left visible.

Whole-leg results include routes and turns; steady VMG counts only straight-line sailing beside other boats on the same leg, each race weighted equally.

Legs Measure Only races with a result for both selected boats

All races start included. Comparisons without sufficient evidence remain blank.

One measure, consistent aggregation

Matched steady sailing · local wind direction

100 is the reference and above 100 is better VMG. The reference is nearby boats sailing steadily on the same leg at the same moment.

Sagara

102.3VMG index

7 of 7 comparison races with a result

96% of eligible steady samples matched · 60.8 minutes

±5° direction sensitivity: 101.4–103.2. This is not a confidence interval.

OceanPact

99.0VMG index

7 of 7 comparison races with a result

86% of eligible steady samples matched · 55.8 minutes

±5° direction sensitivity: 97.6–100.4. This is not a confidence interval.

Speed and direction, reconciled with VMG

Right is faster; up converts more of that speed into progress along the chosen direction. The curves are equal-VMG indices, calculated exactly from these two factors. Direction efficiency is a projection ratio, not a measured pointing angle.

The plotted VMG value is the same equal-race mean used below. Direction efficiency is derived as VMG index ÷ speed index × 100, so the two factors reconcile exactly; it is not an independent angle median.

The race-by-race check

Same selected measure, same race cells. A blank means there is no qualifying result, not zero performance. Other boats may cover fewer races; compare their coverage before ranking them.

Matched steady sailing · local wind direction; equal-race mean in the Mean column
Boat	R1	R2	R3	R4	R5	R6	R7	Mean	Races	Speed index	Direction index	Matched / eligible min
Sagara	104.7	99.1	98.0	100.7	102.1	99.2	112.3	102.3	7	100.5	101.8	60.8 / 63.6
OceanPact	102.7	97.5	100.7	100.8	95.6	98.5	97.0	99.0	7	100.0	99.0	55.8 / 64.8
GARM	106.4	103.2	104.1	104.8	102.9	97.5	92.3	101.6	7	101.3	100.3	58.3 / 67.3
Wicked	103.0	98.3	102.9	101.0	100.2	101.7	111.0	102.6	7	101.1	101.5	67.0 / 73.3
Level5	100.7	99.6	101.7	103.2	103.7	98.8	109.0	102.4	7	102.2	100.2	64.3 / 67.7
Progress	103.8	94.6	107.3	98.6	103.1	103.7	91.0	100.3	7	98.9	101.4	59.3 / 70.4
Empeiria	101.7	101.6	104.4	98.2	104.7	95.1	102.9	101.2	7	99.4	101.9	72.8 / 85.0
MINDSET	99.5	96.0	102.9	101.0	100.8	111.2	102.5	102.0	7	101.2	100.8	60.8 / 63.3
Hedgehog	104.3	99.6	102.8	101.2	103.4	91.2	100.9	100.5	7	99.5	101.0	65.4 / 71.7
Savasana	100.3	98.8	93.4	102.4	99.2	102.7	91.0	98.2	7	99.2	99.0	70.5 / 87.2
Midlife Crisis	98.9	99.5	96.9	98.8	105.7	100.7	99.4	100.0	7	99.7	100.3	59.8 / 63.7
Patakin	99.7	98.5	101.7	102.4	99.9	105.3	99.5	101.0	7	100.5	100.5	51.1 / 56.4
Bazinga!	106.5	96.7	102.2	98.0	97.3	—	102.4	100.5	6	100.3	100.2	16.8 / 17.8
Aretê	102.3	100.9	100.4	101.4	99.6	99.9	103.8	101.2	7	98.7	102.6	70.7 / 79.2
TÔ NESSA	99.9	105.9	107.6	100.8	118.3	98.9	87.6	102.7	7	103.3	99.4	32.9 / 35.9
Stampede	104.0	99.8	99.4	96.5	96.6	99.1	102.6	99.7	7	98.4	101.3	76.8 / 81.8
Ellie	102.3	99.3	100.9	101.1	97.1	104.2	114.3	102.8	7	100.5	102.3	54.8 / 56.1
Jelvis	100.5	96.9	104.5	107.3	103.0	99.3	114.3	103.7	7	101.0	102.6	57.2 / 62.8
7th Heaven	99.2	99.3	98.7	110.1	99.4	103.2	96.5	100.9	7	102.0	98.9	67.7 / 76.5
Elvis	98.8	99.6	97.7	104.9	102.7	104.3	97.5	100.8	7	101.1	99.7	76.5 / 79.8
DJ	101.3	96.5	99.5	106.8	98.7	102.6	95.7	100.2	7	98.7	101.4	60.3 / 63.3
Rowdy	102.3	102.7	106.3	99.4	101.7	106.0	107.3	103.7	7	101.9	101.8	58.3 / 66.1
Tangerine	98.6	98.6	101.2	103.6	99.9	102.7	92.2	99.5	7	100.4	99.1	72.4 / 75.5
What? NoooWaaay!	104.9	102.4	100.7	100.0	99.5	95.3	106.9	101.4	7	97.9	103.5	66.5 / 70.2
Lifted	103.5	93.8	100.4	95.2	106.3	99.8	96.6	99.4	7	102.1	97.3	38.3 / 42.5
Vale Night	100.9	100.2	96.2	107.0	103.3	97.0	106.1	101.5	7	100.9	100.7	53.3 / 56.9
Good Guy	100.2	102.8	99.9	103.3	98.7	105.8	104.0	102.1	7	101.4	100.7	67.7 / 75.6
Wild Card	101.1	98.9	100.7	91.3	94.8	104.4	101.4	98.9	7	97.3	101.6	62.8 / 65.8
Proof	98.0	99.5	103.1	105.1	99.4	98.6	108.3	101.7	7	101.2	100.6	33.8 / 35.8
Sitella	105.3	97.4	99.8	98.2	95.7	105.4	98.7	100.1	7	100.4	99.6	69.6 / 78.5
Yolanda	102.2	102.3	96.6	97.5	98.2	98.5	119.2	102.1	7	98.8	103.3	62.8 / 70.6
Surprise	105.1	98.2	99.4	—	105.0	99.5	95.0	100.4	6	98.7	101.6	49.8 / 52.9
Truckin’	96.5	101.9	99.0	97.2	100.4	92.7	98.0	98.0	7	95.7	102.4	70.8 / 73.9
Who Dat	94.5	100.0	99.8	103.1	100.4	102.2	87.1	98.2	7	102.7	95.6	57.7 / 59.6
Wild Child	91.2	98.8	90.9	97.8	103.2	82.7	102.3	95.3	7	97.6	97.6	84.3 / 91.0
Aquaholiks	98.0	102.3	97.9	98.5	100.3	98.7	101.5	99.6	7	97.8	101.8	51.9 / 53.4
Osprey	93.2	96.7	95.8	99.9	100.2	98.7	—	97.4	6	99.5	97.9	57.0 / 62.8
Ayacucho	94.8	101.2	100.6	100.1	101.2	88.9	107.4	99.2	7	97.4	101.8	49.3 / 50.5
Johnny Thunder	100.3	102.0	103.0	98.0	101.1	107.4	95.1	101.0	7	99.0	102.0	52.9 / 55.5
Coalition	95.0	97.5	98.4	97.6	103.3	98.7	101.3	98.8	7	99.8	99.1	67.6 / 72.5
Phoenix	92.6	99.3	85.1	95.3	97.6	112.7	100.4	97.6	7	100.3	97.3	33.6 / 35.0
Danger Mouse	99.5	103.6	99.5	94.9	103.2	90.8	102.8	99.2	7	99.6	99.6	52.9 / 54.3
Minimax	100.8	102.4	100.6	105.3	101.6	104.0	100.8	102.2	7	100.4	101.8	71.4 / 72.8
Miss Killer	101.0	103.2	101.7	91.9	102.0	100.2	—	100.0	6	97.9	102.1	51.3 / 51.5
Tea Dance Snake	100.2	97.2	—	101.5	101.1	98.0	107.5	100.9	6	100.2	100.7	37.6 / 39.5
Black Pearl	90.7	102.5	97.5	97.5	95.9	108.3	100.1	98.9	7	101.2	97.7	52.7 / 54.6
Toro	102.1	100.9	99.6	100.8	101.3	99.9	85.2	98.6	7	100.0	98.6	54.8 / 55.8
Celerity	108.5	93.3	96.0	102.8	98.3	96.2	—	99.2	6	103.0	96.3	24.2 / 27.8
Fuzz	91.1	97.7	96.8	104.1	109.8	88.3	96.1	97.7	7	99.7	98.0	56.4 / 64.3
Margaritaville	95.4	98.7	103.2	102.2	106.5	102.8	98.1	101.0	7	101.0	99.9	65.7 / 68.7
VOODEUX	94.1	101.2	99.7	107.1	97.6	105.9	99.7	100.8	7	98.2	102.7	44.9 / 48.2
Kings Point	102.2	99.4	97.5	98.4	101.5	93.7	87.6	97.2	7	109.2	89.0	68.1 / 74.1
Derecho	95.5	103.5	94.4	92.4	100.5	95.4	109.0	98.7	7	104.1	94.8	54.8 / 73.4
Foreign Affairs	96.6	94.2	98.5	94.8	105.9	99.0	—	98.2	6	105.7	92.9	32.0 / 34.7

Does the answer depend on the wind neighborhood?

For Sagara, this rebuilds the wind fit with its spatial and temporal support 25% narrower or wider. Peer distance stays at 600 metres. These choices can change which samples qualify, so the matched minutes are shown too. A large change is a reason to treat the result cautiously.

Wind-neighborhood sensitivity · Sagara · downwind
Race	Narrow index / min	Default index / min	Wide index / min
R1	104.7 / 11.3	104.7 / 11.3	104.3 / 11.7
R2	99.9 / 8.3	99.1 / 8.3	98.9 / 8.3
R3	97.9 / 4.9	98.0 / 4.9	99.1 / 4.9
R4	101.7 / 12.3	100.7 / 14.9	100.1 / 15.2
R5	102.1 / 11.4	102.1 / 11.4	102.5 / 11.4
R6	98.9 / 6.3	99.2 / 6.3	98.7 / 6.3
R7	110.0 / 3.4	112.3 / 3.6	111.3 / 3.7

Inspect the evidence

Wind direction across the course

The map shows the fitted ground-referenced direction at supported locations. Empty areas have insufficient evidence. This fleet overview uses all donors; the performance calculations refit with the scored boat excluded.

Inspect race