Metals in a Marine Environment

 

To understand the use of metals - or indeed any other material - it is helpful

to know a little about three properties; stress, strain and stiffness.

What could Dyneema do for you?

(download this article)

 When it comes to boats and rigging, we are surely no cleverer than our predecessors. What we have is better materials. Now if you subscribe to the view that classic boats result from a process of evolution (and also represent the leading edge of their day), then it makes sense to make best use of these materials. One obstacle is they are often introduced in such a fog of marketing hype, techno-babble and endorsements by handsomely paid celebrities that it can be hard to work out if they are actually any use. So here is my attempt to see how Dyneema, or Dyneema based rope might be used in traditional rigs. 

Rope makers seem to delight in confusing us with science and/or extraordinary polysyllabic names. Let me try to cut through the guff a little.

Block Configurations - Ash Blocks (stainless bindings)

Confusion quite often reigns, so a few words of explanation might help here.

With blocks, the "number" ie single, double, treble and so on refers to the number of sheaves (pulley wheels, if you must!).

If the binding - in these cases the metal bit, extends past the shell of the block, it forms a "becket" to which you can attach the end of the rope.

And that gives you the basic variations eg double, single & becket etc.

 

 

     

 

   

 

   

 

   

Specifications

Shell Size

Rope Dia

Sheave Dia

Sheave width

SWL

3”

8-10mm 40mm 12mm 1500kg

3½”

10-12mm 50mm 14mm 1750kg

4”

12-14mm 60mm 16mm 2000kg

Winch Selection Guide

 

 
Mainsail Area (ft2/ m2) 120/11 150/14 180/17 210/20 250/23 325/30 750/70  
Genoa Area (ft2/ m2) 200/19 300/28 350/33 470/44 575/53 825/77 1500/139  
Boat Length (ft/ m) 23/7 27/8 30/9 34/10 38/12 45/14 52/16  

Murray Winches

 
Main Halyard - 1 1 1/4 4/5 4/5 5

 

Genoa Halyard - 1 4 4 4/5 5 5/6
Genoa Sheets 1 4/5 4/5 5/8 5/8 8 8
Spi. Sheets etc - 1 1 1/4 4/5 5 5/6
Outhaul/Reefing - - - 1 1/4 4 4/5

Wilmex Winches

 
Main Halyard 8 8 10 10 25/26 31/40 40/41

 

Genoa Halyard 8 8/10 10/25 25/26 31/40/41 40/41/51 51
Genoa Sheets 8/10 10/26 25/26 31/40 40/41/51 51/70/71 70/71
Spi. Sheets etc 8 10 10 25/26 31/40 40/41/51 51/70/71
Outhaul/Reefing 8 8 8 10 10 25/26 40/41

Please note that the above figures are provided as an initial guide only