Ordering Midrange Blocks

5/5/2012

1. Determine block size and type

The tables below are guidelines for typical applications.

2. Contact

If you have any 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%.

    MASTBASE
    VANG

Mainsheet
The farther forward a mainsheet system is on the boom, the higher the loads. Systems with multiple attachment points spread the load over the boom. Use the table below to determine if Midrange blocks are strong enough for you mainsail area.

 
  
Maximum mainsail area
(P x E x .5 x 1.1*)
  ft² m² 

 
End-boom system Single attachment50046

 
Multiple attachment**54050

 
Mid-boom system Single attachment 42539

 
Multiple attachment**50046

 
*Assumes 10% roach.
**Assumes two or more shackles share load on both boom and deck.


Genoa Footblocks
Determine the area of your foretriangle and how many degrees the footblock will deflect the line to select footblock size. For system loading details, see the Block Loading vs. Angle of Deflection and Genoa System Loading sections.

 
Turning blocks
 
Maximum 100% foretriangle sail area at 35 knots
(I x J x .5)

 
180° turn
15014

 
Turning blocks
  

 
90° turn
21520

 

Spinnaker Blocks: 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.

 
  Maximum spinnaker area
P x E x .5 x 1.8
  StandardHigh-load
  ft2m2ft2m2

 
Sheet
Plain
11001001300120

 
Ratchet90083--

 
Afterguy*
Mounted amidships 11001001250115

 
Mounted on transom 90083100093
 

Maximum "I" dimension

 
   

 
Masthead halyard
 48 ft 14.6 m 53 ft 16 m

 
*Assumes maximum deflection of 45°

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 used for applications with lower loads.

 
 Maximum "P" dimension
 StandardHigh-load
 ftmftm

 

 
Main halyard lead
4814.65215.8

 

 
 Maximum "I" dimension

 

 
Genoa halyard lead
46145015.3

 

 
 Maximum "I" dimension

 

 
Spinnaker halyard lead
4814.65316

 

Running Backstays
The table below shows whether Midrange of high-load Midrange blocks are strong enough for your backstay, based on the breaking strength of your runner wire.

 
  
Maximum breaking load of runner wire
  StandardHigh-load
  lbkglbkg

 
Flying block
2:13600163346002086

 
Afterguy
1:1220099828001270

 
2:1 Becket 3600163336001633

 
2:1 Single4500204050002268

 

Vang
Common vang configurations

 
  Maximum mainsail area P x E x .5 x 1.1
  ft2m2

 
Fiddle
 40037

 
Triple
 45042
    

 
*Assumes 10% roach
   

 
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