Dyneema SK78 12 strand rope has very similar strength and stretch qualities to 1 x 19 stainless steel wire rope, size on size, making it very suitable as an incredibly strong but light-weight alternative. It is commonly used for Removable Inner Forestays as a means of hoisting a storm jib where headsail roller reefing is present. They are easily fitted and require no expensive tensioning devices, in fact it's back to basics; tensioning is done by conventional means using rope lashings with 4:1, 6:1 or 8:1 purchase and deadeyes.
Another advantage over stainless wire as a removable inner stay is, that for the most part, it will not be in use and must be conveniently kept away from the foredeck, which usually means attaching to the sidedeck by the shrouds or by the mast. With a stainless wire stay, when brought back to the mast is commonly too long to tension and so the tensioner has to be removed and the stay lashed if possible (it might still be too long). With the Dyneema stay, the main part is made about 750mm short of the total length needed to allow for tensioning both when in use and when not.
Dyneema SK78 rope is also great to carry as a spare stay in case of an emergency; it is lightweight, coils easily and there is no need to carry numerous, expensive, swageless Norseman or STA-LOK terminals of various sizes and configurations. All you need is and eye spliced in one end (the upper) and to be able to perform a simple splice around the lower terminal wqhen the desired length of stay is known.
| || || || |
|Deadeye ||Chainplate Terminators |
|8:1 purchase ||4:1 purchase female ||8:1 purchase male ||8:1 purchase female |
|Dyneema Rope Diameter ||5mm ||6mm ||8mm ||10mm ||12mm |
|Rope Break Load daN ** ||2600 ||4300 ||5000 ||7500 ||8500 |
|Purchase ||4:1 ||6:1 ||6:1 ||8:1 ||8:1 |
|Top Terminal ||Soft Eye |
|Lower Terminal ||Colligo Line Terminator |
|Deck Deadeye ||Colligo Chainplate Distributor |
** daN = deca Newtons = approximate to 1.02 kilograms of force. Therefore 1000 deca Newtons is very approximate to 1 metric ton of force.