Hi Mojo, we have continued to rig boats, monohulls and multihulls. 65' MacGregor just completed in the Caribbean. Many large cats as they are just crying out for a synthetic solution, for both function and cost. In addition we have rigged the diamond stays on a number of boats now and that application is working great and a validation of our sizing process for creep as the static loads are generally high on diamonds. Spreader ends are turning out to not be as big of a challenge as previously thought, most can be modified and some need to be retrofitted. We are also doing alot of boats now with turnbuckles as we can splice to a specified length with very little variation and good accuracy. We are rigging an Open 60 now with a mast ram that has extremely high pretension requirements and this has really presented a challenge for us to design around the creep. In addition, it is an offshore boat, so the dynamic loads will have quite a time value to them so we have to factor those in also. The designer has provided us with all the loads and that certainly makes it easier.
We are continuing to learn more about dyneema and its wonderful properties but, more importantly, how to design around its limitations. Its a great material but it certainly puts more responsibility in the hands of the sailor, especially for chafe inspections. For sizing standing rigging with Dux we are using a template of properties in decending order of priority.
1. Stretch
2. Creep
3. Chafe
4. UV resistance
As data comes in, the UV concern is becoming smaller and smaller. Initially some UV damage is experienced but then the material becomes relatively opaque to UV so the rate of damage slows down considerably. We have seen first year damage as high as 15% of Mean Breaking Load. But, couple this with the fact that when we size for stretch and creep the line is 2-5 times stronger than the steel equivalent so the factor of safety is high. Based on UV limitations, we think that we will probably end up with a recommended 8 year replacement interval (in the tropics) which is similar to steel. Covered Colligo Dux Rigging is an option also and makes for an even longer replacement interval than steel.
For Chafe, IMO, Dux is the toughest synthetic line you can get. For example, we are using ceramic knifes to cut the line and can ussually do about 10 splices on 9 mm line before they need to be sharpened. These are knifes that the manufacturers say never need to be sharpened! Having said that, Dux is certainly not as tough as steel. We see this as the biggest pardigm shift that is needed when going to synthetic standing rigging, it needs to be inspected regularly. When sized correctly (2-5 times stronger than steel) you certainly have a relatively large window of opportunity to see chafe issues and address them. The good news is our style of synthetic is easily inspected and chafe issues are highly visible.
Stretch and Creep are issues that need to be specifically addressed in the design (sizing) phase but can easily be designed around.
The other really important fact here is the the end terminations need to be sized such that you can get the most from the line to keep the safety factor up (for reasons stated above). A minimum 5/1 bending ratio is needed on all dyneema products to retain minimum 80% of break strength. Most of our products are 7/1 or higher. I was in St Malo for the start of the Route Du Rhum and it just made me cringe to see how dyneema was abused. It was spliced to all sorts of things, rings, padeyes, etc. that were mostly really too small, this is fine for race boats (especially running rigging) that rerig before every race and inspect often but to transition this material into the cruising world the high factor of safety is crucial, especially in standing rigging. In my mind the high factor of safety is the big enabler of this material as it buys you time to deal with the chafe and UV issues, and gives you a big warm and fuzzy when moving to a new technology. I tell customers all the time "your rig is not going to fall down, if we don't size it correctly you might have some performance issues like stretch or creep but it won't fall down".
Notice, also, that breaking strength is not on our list. This is generally a box that we check off when sizing the line (is it strong enough?) but it is never the driver. We do not size Dux or any Dyneema for breaking strength as the other parameters are the limiting ones.
One other issue that we have run into is discontinuous rigging. The best way to take advantage of synthetic rigging is to have a continuous rig. In fact, discontinuous rigging leads to so many end fittings that the amount of complications in the rig, windage issues, tensioning, etc start to overcome the weight savings factors of going to synthetic.
Sorry about the long windedness here. I hope this helps and I certainly hope this does not lead to any caustic replies. I don't mind professional feedback, I even welcome constructive criticism as this is a new technology, but lets keep it professional.
John Franta, Colligo Marine
That is damn scary!
