40
P
E
I
J
 
 
 
 
 
 
Ordering Midrange Blocks
1. Determine block size and type
The tables below are guidelines for typical applications. Additional rigging tips are available at harken.com. 
2. Contact 
If you have questions, please contact your dealer or Harken Technical Service.
Note: Multihulls and heavy displacement monohulls should reduce the maximum sail areas 
shown by as much as 25%. 
Running Backstays
The table below shows if Midrange or high-
load Midrange blocks are strong enough for 
the backstay, based on the breaking strength 
of the runner wire.
Spinnaker: Symmetrical/Asymmetrical 
Use the spinnaker’s sail area to determine what 
size Midrange or high-load Midrange blocks to use 
for the sheet and afterguy controls. See page 269 
for common configurations.
Genoa Footblocks
Determine the area of your foretriangle and 
how many degrees the footblock will deflect 
the line to select footblock size. For system load-
ing details, see the Block Loading vs. 
Angle of Deflection and Genoa System 
Loading sections on page 279. See 
page 259 for common configurations.
Vang 
See page 265 for common configurations. 
Mainsheet 
The farther forward a mainsheet system is on 
the boom, the higher the loads. Systems with multi-
ple attachment points spread the load over the 
boom. Use the table to determine if Midrange 
blocks are strong enough for your mainsail area. 
See pages 262 - 263 for common configurations.
*Assumes 10% roach.     †Assumes two or more shackles share load on both boom and deck.          
Maximum mainsail area (P x E x .5 x 1.1*)
ft
2
m
2
End-boom system
Single attachment
500
46
Multiple attachment†
540
50
Mid-boom system
Single attachment
425
39
Multiple attachment†
500
46
Mainsheet
Maximum 100% foretriangle sail area at 35 knots (I x J x .5)
ft2
m
2
180˚ turn
150
14
90˚ turn
215
20
Genoa Footblocks
*Assumes maximum deflection of 45°.
Maximum spinnaker area  (P x E x .5 x 1.8)
Standard
High-load
ft2
m
2
ft
2
m
2
Sheet
Plain
1100
100
1300
120
Ratchet
900
83
—
—
Afterguy*
Mounted amidships
1100
100
1250
115
Mounted on transom
900
83
1000
93
Maximum "I" dimension
Masthead halyard
48
14.6
53
16
Spinnaker
Mastbase Lead Blocks
Attach blocks to padeyes or 1634 Midrange 
ESP stand-up bases, or mount mastbase halyard 
leads to the deck. Use mainsail luff length and 
foretriangle height to determine what size 
Midrange or high-load Midrange blocks to use. 
Carbo blocks or 1986 mastbase halyard leads may 
be appropriate for applications with lower loads. 
See page 268 for common configurations.
Standard
High-load
ft
m
ft
m
Maximum "P" dimension
Main halyard lead
48
14.6
52
15.8
Genoa halyard lead
Maximum "I" dimension
46
14
50
15.3
Spinnaker halyard lead
Maximum "I" dimension
48
14.6
53
16
Mastbase Lead Blocks
Maximum breaking load of runner wire
Standard
High-load
2:1 fl ying blocks
lb
kg
lb
kg
1:1 afterguy deck
2200
998
2800
1270
2:1 afterguy becket deck
3600
1633
3600
1633
2:1 afterguy single deck
4500
2040
5000
2268
Running Backstays
Maximum mainsail area (P x E x .5 x 1.1*)
ft2
m
2
Fiddle
400
37
Triple
450
42
*Assumes 10% roach.
Vang

View this content as a flipbook by clicking here.