45
Tattler II, 19.2 m (63'), Gaff-rigged Sandbagger, Van Dam Custom Boats © Alison Langley
Ordering Big Boat Blocks
Genoa Footblocks 
Footblocks route genoa controls from the lead car to a winch. Double footblocks or snatch blocks enable faster sheet changes. Determine the 
area of your foretriangle and how many degrees the footblock will deflect the line to select footblock size. For system loading details, refer to 
the Block Loading vs Angle of Deflection and Genoa System Loading sections on page 279. See page 259 for common configurations.
Spinnaker: Symmetrical/Asymmetrical
Use the spinnaker’s sail area to determine what size Black Magic, Element, or stainless steel blocks to use for the sheet and afterguy 
controls. See pages 269-270 for common configurations.
Maximum spinnaker area (I x J x 1.8)
45 mm Element*
57 mm low-load
Black Magic
60 mm Element*
57 mm high-load
Black Magic
80 mm Element*
75 mm low-load
Black Magic/
75 mm ESP
75 mm high-load
Black Magic/
75 mm stainless
100 mm
Black Magic/
100 mm stainless
125 mm
Black Magic
150 mm
Black Magic/
150 mm stainless
ft2
m
2
ft
2
m
2
ft
2
m
2
ft
2
m
2
ft
2
m
2
ft
2
m
2
ft
2
m
2
Spinnaker sheet, tack line
720
67
1200
111
1400
130
2000
186
2650
246
4300
400
5600
520
Afterguy**
790
73
1320
123
1500
140
2200
204
2900
269
4700
437
6100
567
 *Element blocks are appropriate for most cruising boats. For high-performance boats, choose Black Magic blocks.     **Assumes maximum deflection of 45° to winch.      
 Single Genoa Footblocks
Maximum 100% foretriangle sail area at 40 knots (I x J x .5)
45 mm Element*
57 mm 
Carga moderada
Black Magic
60 mm Element*
57 mm
Carga moderada
Black Magic
80 mm Element*
75 mm
Black Magic/
75 mm inoxidable
100 mm
Black Magic/
100 mm inoxidable
125 mm
Black Magic
150 mm
Black Magic/
150 mm inoxidable
ft
2
m
2
ft
2
m
2
ft
2
m
2
ft
2
m
2
ft
2
m
2
ft
2
m
2
180° turn
110
10
180
17
365
34
540
50
800
74
1100
102
120° turn
125
12
210
20
420
39
630
59
920
85
1256
117
90° turn
155
14
260
24
515
48
770
72
1130
105
1540
143
 *Element blocks are appropriate for most cruising boats. For high-performance boats, choose Black Magic blocks.
 Double Genoa Footblocks
Maximum 100% foretriangle sail area at 40 knots* (I x J x .5)
57 mm low-load
Black Magic
60 mm Element**
57 mm high-load
Black Magic
80 mm Element**
75 mm Black Magic
100 mm
Black Magic
125 mm
Black Magic
ft
2
m
2
ft
2
m
2
ft
2
m
2
ft
2
m
2
ft
2
m
2
180° turn
75
7
120
11
240
22
360
33
530
49 
120° turn
85
8
140
13
275
26
415
39
610
57
90° turn
105
10
175
16
340
32
510
47
750
70
 *Based on load on upper sheave.     **Element blocks are appropriate for most cruising boats. For high-performance boats, choose Black Magic blocks.

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