Proposal for Dyneema / D12 Lower Shrouds for Laser Vago

Proposal for Improved and Safer Dyneema / D12 Lower Shrouds for Laser Vago

By Gerry Fisher, Vago #578 “Kingfisher” (November 2015)

Standard Laser Vago Lowers and their difficulties

The standard lowers are 3mm stainless wire, shackled at the bottom and tied at the top to an eye on the mast with a 3mm Dyneema strop as mentioned in the Vago rigging manual. The strops are difficult to reach. Inverting the lower shroud makes the strops easier to tie.

There is a potential safety problem. After a capsize the crew may be trapped in the lowers. Cutting the stainless steel to release the crew is difficult. Rope would be easier to cut.

One approach is to replace the wire and short strop with an all rope lower. Dyneema is a suitable material as under load it stretches or elongates very little. I have used 3mm Dyneema cord. To give strength and ease of adjustment the Dyneema is tripled up, as explained below.

Dyneema Lowers – Design and Fitting

Materials – 5.5m/side of 3mm Dyneema, 11 m in total.

Remove the original lower leaving the shackle at the bottom. Tie one end of the Dymeena cord to the mast eye. Then thread the other end through the shackle, back up mast eye and back down to the shackle. Loosely tie off the cord with a round turn and quite a few half-hitches.

To tension the lower shroud, hoist the jib. This puts tension into the main shrouds. It is easy to over tighten the jib halyard so it is a good idea to use a Loose Gauge to check the tension in the main shrouds. It should be 70 kg max.

Re-tie the lowers to be just tight. Check the mast is not pulled sideways by uneven tensions in the lowers. You can also measure the lengths.

In light winds my Vago sails faster when the lowers are slightly shorter. To achieve this, ease the jib halyard and re-tie the lowers to take up 1 cm of the Dyneema cord. As there is a 3 to 1 “gearing” this reduces the overall length of the lowers by 1/3 cm. Re-Tension the jib.

Adjusting the lowers with jib halyard tight can be tricky. Where the Dyneema cords go through the mast eye some cords can get trapped below other cords. Easing the jib halyard before adjustment avoids this problem. A series of reference marks on the Dyneema (use a permanent marker) makes adjustment more accurate. Re-tighten the jib halyard.

Alternative – Use D12, and splice rather than tie knots.

3mm D12 is a braid of 12 strands of Dyneema with a hollow core. A locking eye splice joins the D12 to the mast eye. (Google – marlowropes d12 locking eye). For the bottom end a non- locking splice is used. It is similar but the rope is not inverted during the splice and has a longer tail. The extra tail length is left coming out of side of the braid. When not under tension the loop is pulled to lengthen or tail pulled to shorten. With the jib halyard eased and with reference marks accurate adjustment is easy.

Note: For a quick trial the top splice can be made without the inversions.

2x 5.5 meters of 3mm Dyneema ie 11 meters total. Cost £14.63

(Marlow Excel Racing – Dyneema @ £1.33 / meter – Purple Marine)

2x 6 meters of 3mm D12 ie 12 meters total. Cost £39.12

(Marlow Excel D12 Max @ £3.26 / meter – Purple Marine)

(D12 needs to be a little longer to allow for the length of the splices)


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s