Today with help of Glenn Hansen (Hansen Rigging) we did a successful load test of a complete shroud. The main objective was to test the breaking strength of the dead eyes and the dead eye fittings but we got some interesting additional data out of this destructive test.

Last time we did this test we used traditional Lignium Vitae wood for both the upper and lower dead eyes. At that time the lower dead eyes failed at 12,000 Kg load and the upper dead eyes failed at 18,000 Kg. In order to meet the 3X safety factor for the highest loaded shroud we need these dead eyes to have a breaking strength of at least 23,000 Kg. Rather than changing the design in a significant way (we did some very minor adjustments to the design) of these components we changed material to increase the strength. The team at Ventis Scheepstimmerwerk fabricated several prototype sets for us in two materials, Tufnol and Delrin. Tufnol is about 3.6 times stronger than good quality Lignum wood and Delrin almost 4 times stronger than Lignum. Tufnol (cotton textile-phenolic resin, essentially cotton-reinforced Bakelite) is a material that was available in the 1920s so it is a bit more authentic than Delrin which is a modern synthetic material. After the parts were fabricated we varnished the Tufnol parts with two coats of Epifane varnish. It looks very authentic and to the untrained eye it could easily be mistaken for varnished wood.

Varnished Tufnol dead eyes.

TEST 1

We tested a complete 16 mm Dynex Dux shroud with the small bronze fitting and Tufnol dead eyes until it failed.

Configuration:

Upper and lower dead eyes in Tufnol material

Lower dead eye fitting (75mm - small fitting for the 75 mm chain pates)

10 meter long 16 mm Dynex Dux shroud with a double braided black jacket on

SK 75 Dynema lanyards (11 mm)

Test results:

The 16 mm Dynex Dyx shroud broke at 67,800 lbs (30,750 Kg) load. The shroud failed where it normally does, which is just where the splice for the eye tapers off.

What we learned:

1. 1)The upper and lower dead eye components in Tufnol have a safety factor of 4X compared to the highest working load of the highest loaded shroud on the boat which is 7,615 Kg. For all other shrouds the Tufnol components has a safety factor far in excess of 4X. Lloyds requires a 3X safety factor for standing rigging so we are in a good shape with that design and material choice.
   

2. 2)The 16 mm Dynex Dux breaks exactly at the load that the manufacturer predicts for a spliced line. The Dynex Dux 16 mm line exceeds the working load of the highest loaded shroud by a safety factor of 4X. Lloyds requires a 3X safety factor of standing rigging so in theory we could used 16 mm Dynex Dux for all shrouds on the vessel. However, the stretch of both 16 mm and 21 mm Dynex Dux far exceeds acceptable levels of stretch compared to what a correctly sized 1x19 mm galvanized wire would be (the most authentic type of shroud wire rope for this vessel).
   

3. 3)The small (75 mm) bronze fitting has a breaking strength that exceeds 30,750 Kg load. The highest loaded shroud where the small 75 mm bronze dead eye fitting is used has a max working load of 3,400 Kg which means that this fitting has a safety factor that exceeds 9X thanks to the design by yours truly and the strength of CuNiAl bronze :-)
   

Test 1 set-up, Dynex Dux shroud break point, and damage to the upper dead eye when it hit the test rig after the shroud failure.

TEST 2

Although the upper dead eye became damaged when the shroud failed and the dead eye hit the test rig we decided to re-use that dead eye for the second test where we replaced the 16 mm Dynex Dux shroud with a 21 mm Dynex Dux line (estimated breaking strength of 52,00 Kg, so that we could load up the fittings more than in Test 1).

Configuration:

Upper and lower dead eyes in Tufnol material

Lower dead eye fitting (75mm - small fitting for the 75 mm chain pates)

10 meter long 21 mm Dynex Dux shroud with a double braided black jacket on

SK 75 Dynema lanyards (11 mm)

Test results:

The upper Tufnol dead eye failed at 60,500 lbs (27,400 Kg) load.

What we learned:

1. 1)The only thing we learned is that a severely abused upper Tufnol dead eye of this design still has a safety factor of 3.6X. Most likely the impact of the dead eye at Test 1 created internal cracks and/or de-lamination that resulted in this failure. As the upper dead eye so far appears to be the weakest link next time we will test an undamaged upped dead eye in Tufnol until if fails to establish the real breaking load which will exceed the 4X safety factor that we observed in Test 1.
   

Test 2 set-up and upper deal eye failure.

TEST 3

For Test 3 we replaced the dead eyes with Delrin material and we switched to the large bonze dead eye fitting (for the 90 mm chain plates).

Configuration:

Upper and lower dead eyes in Delrin material

Lower dead eye fitting (90mm - large fitting for the 90 mm chain pates)

10 meter long 21 mm Dynex Dux shroud with a double braided black jacket on

SK 75 Dynema lanyards (11 mm)

Test result:

The upper dead eye failed at 82,000 lbs (37,200 Kg).

What we learned:

1. 1)The large bronze 90 mm fitting has a breaking strength that exceeds 37,200 Kg. The highest loaded shroud where the large 90 mm bronze dead eye fitting is used has a max working load of 7,615 Kg which means that this fitting has a safety factor that exceeds 4.8X.
   

2. 2)As we have yet to test either one of the bronze fittings to failure we really don’t know how much additional safety factor we have but both bronze fittings well exceed the required 3X safety factor.
   

3. 3)The upper Delrin dead eye has a safety factor of 4.8X and as Delrin is marginally stronger than Tufnol it is likely that the upper Tufnol dead eye has a safety factor somewhere between 4X and 4.8X if we get to test an undamaged Tufno version until failure in the future.
   

4. 4)The lower dead eye design has a safety factor that exceeds 4X for the Tufnol part and 4.8X for the Delrin part.
   

Test 3 set-up and upper dead eye failure.

Conclusion:

1) The Bronze fittings for both the 75 and 90 mm chain plates exceeds the design requirements and will be used “as is” on Wolfhound.

2) The Tufnol dead eyes exceeds the design requirements and will be used “as is” on Wolfhound.

Next set of tests:

We have yet to find a suitable, inexpensive, and authentic looking line for the shrouds. If we find such a line we will test it for stretch next time to make sure that it does not exceed the stretch of equivalent 1x19 galvanized wire rope that is the fallback choice of material for the standing rigging. The only reason we are experimenting with synthetic rigging is that the weight savings is very large (> 1,000Kg savings with Dynex Dux) in this rig.

We will also attempt to test an upper dead eye in Tufnol to failure to verify the safety margin which so far we know exceeds 4X. An educated guess is that we will find that it is slightly below 4.8X.

Next time we will also test the breaking strength of the final choice of the lanyard line. This will become the “weak link” (fuse) in the standing rigging to make sure that the breaking strength safety margins for a complete shroud is approximate 3X, and less than the 4X of the chain plates, as per Lloyds requirements.

Picture below: Glenn is studying the real heavy duty stuff on the test site