Synthetic rigging

[Guest]

I love the idea, just waiting fo rthe technology to get to the point where I canswap out the SS, have something at least as strong, lighter, long lived and repairable/replaceable by little old me

 

http://www.chicagoyachtrigging.com/18-d ... el-splice/

[TimB 7]

Why wait Ogre, the future (fibre) is already here... this really is BACK to the future, looks like a 19th century rigging job with 21st century technolgy.

 

 

tb

[Guest]

Ok - that is cool, all through the video I was wanting to know how long it will last, my requirement would be 7 years, he said 5 but maybe longer - I'm impressed.

[Clipper 343]

A lot of multis in auckland are running all synthetic rigging (aside from forestays). even my 37 year old GBE is mostly synthetic rigging now. Lighter and cheaper than stainless.

[Guest]

For the same size as wire its meant to be twice as strong. Careful what you do with weight aloft though, more is better for stability. Why not replace one at a time, keep a record and when 5 years old replace. Apparently the stretch is the same as wire. The yacht may sing a different tune in a gale though.

[TimB 7]

Soft Hanks and the forestay can be synthetic too... goodbye wire!

[Guest]

I thought I was the only one still using hanks on the forestay.

[Guest]

Nope, I'm another hank user, since the majority of the SA is behind the two masts sail changes are exceedingly rare, thus the simplicity and reliability of hanks overrules the usefulness of a furler.

So costwise synthetic still a little above SS?

On a skinny tippy Spencer this could be significant (not going to Carbon masts $$$$$$)

[Guest]

Careful about weight aloft. From my research more is better for stability. I'm experimenting by hauling a 20 kg lump of lead up the inner forestay. Mine is very beamy and this gives her a sharp motion in a beam chop or sea. So I'm thinking of ditching the ali mast and going to timber so as to have more weight aloft. I may just make it a freestanding rotating wing mast thats 2 metres taller.

[Grinna 2]

Bbay, the idea of more weight aloft giving greater stability seems counter intuitive to me.

 

I can imagine that spreading the mass of the vessel over a larger area can have effects on the speed of motion or the feeling of motion on the vessel (like figure skaters spinning slower with their arms extended vs with arms tucked in) but surely having a larger proportion of the vessel's mass higher just raises the centre of gravity and lessens the righting moment by decreasing the leverage against the roll centre? I was under the impression that race yachts do all they can to reduce weight aloft and get the mass as low as possible.

[Clipper 343]

Careful about weight aloft. From my research more is better for stability. I'm experimenting by hauling a 20 kg lump of lead up the inner forestay. Mine is very beamy and this gives her a sharp motion in a beam chop or sea. So I'm thinking of ditching the ali mast and going to timber so as to have more weight aloft. I may just make it a freestanding rotating wing mast thats 2 metres taller.

 

I think it would be more to do with resistance to rolling, or an increase in inertia, not stability in the purest sense.

 

A heavy rig will cause a boat to roll slower perhaps, but in a knockdown situation, weight aloft is bad

 

And in multis, I cant imagine there is ever a benefit to weight aloft?

[rigger 47]

The more weight aloft the more tender the vessel - lesser the stability.

In some cases you may want a vessel to be less stable / more tender as too much can be unsafe from the point of crew getting flung about due to violent rolling.

 

A tender vessel will roll more gently than a stiff vessel.

 

Some of thee ships I worked on had so much stability that if we had not actively reduced (part filled ballast tanks was one method) it we would have lost cargo in rough seas.

[Kiteroa 8]

Best to ask an opinion of someone how's using fibre rigging. The guys on Prawn Broker have UHMWPE standing rigging currently.

 

Different situation on a multi hanging the rig off 3 cables. 0.5% stretch on the caps isn't going to matter much as the boat is probably wracking too much to notice. On a mono it is going to be scary.

 

Weight aloft reduces the boats righting moment and decreases it's 'sailing power' if you like. A boat with a heavy rig and low righting moment will wallow slowly an a sea way. A boat with a light rig and high RM will jerk around more in a chop, but has more stability and as a result will sail faster.

[Guest]

Yes it seems counter intuitive but in tank tests performed by Marchaj he showed that a hull without mast was much easier to roll than one with a mast. It seems its the initial impact of the wave that is resisted by weight aloft. I'm sure too much weight aloft would have an adverse affect but that to have that much weight in the mast it would need to be made of something ridiculous such as cast iron. From the Junk rig folks, who muck about with this often, less than 5% of the weight of the hull is good.

Also, the weight in the mast is very unlikely to have a serious righting moment impact on a yacht more than say , just off my head, 7 tons or so. Especially if its made in wood, which floats, possibly and ali mast would float for a while at least so they would help to right the yacht to an extent. There's apparently very little that can be done to increase a yachts resistance to knockdowns but more weight in the mast helps somewhat.

Mine is a double ender designed by Bill Atkin way back when timber mast was the norm so having a ali one detracts from the design.

But in regards to this thread, it seems WONDERFUL to have twice the strength with stuff you can make up yourself.

[Island Time 1,239]

BB, different scenario to what most are thinking of.

 

In a severe storm, with breaking wave impacts, a yacht with a rig is better than a yacht without. Without a rig the yacht has a very "quick" motion, and less inertia to be overcome to cause a capsize. However, even though it is easier to capsize, it is also more likely to self right. Hulls with low freeboard and little reserve buoyancy also fair better in this situation.

 

Conversely, when in the normal state (not in extreme storms, 99.99.... % of the time), weight aloft is bad! It slows the roll period, reduces ultimate stability (angle of vanishing stability) etc, therefore causing the vessel to heel more, carry less sail, pitch more, and generally be less of a sailboat.

 

Everything in yacht design is a compromise...

Even though you are correct in your thoughts, you are also mistaken!!

[Guest]

I'm happy to be corrected IT Just like to see some real science behind the reasoning. Just for the aspect of comfortable motion I would use caution. I speak with experience here, mine is harsh in beam seas and thats why I've put lead aloft to see how the weight affects the motion. Also, you could haul a weight aloft when anchored to give a more comfortable time. I'm trying 20 kg but it might need more. Yacht designers are very careful with this aspect and mine is not as designed.

Till Marchaj is proven incorrect I'll go with his theories.

If the yachts motion was affected it wouldn't be too hard to fix some weight aloft to correct it. Going the other way thats hard and expensive.

[Island Time 1,239]

In that situation it really would change your roll period, so could well make it more comfortable.

 

It has been proven that it's possible to capsize a fairly large fishing vessel with only 2ft waves - if the wave period matches the roll period. Simply changing course a few degrees, or hauling a weight aloft would have the same effect, and prevent the capsize.

 

I would not leave ANY weight aloft while sailing if I were you. The naval architect has gone to a lot of effort to put weight below your center of gravity...

 

I'll see if I still have the stability testing results somewhere that I got my info from. You are correct in breaking seas, but not otherwise...

Matt

[Guest]

But in regards to this thread, it seems WONDERFUL to have twice the strength with stuff you can make up yourself.

6mm stainless 1x 19 wire - 4110kg bust - 0.245 kg/mt

10mm stainless 1x19 wire - 10100kg bust - 0.597 kg/mt

 

1/4" (6mm) SK75 Dyneema - 8600lb bust (3900kg odd) - 1.6lb per 100ft (0.02kg/mt)

3/8" (9.5mm) SK75 Dyneema - 19600lb bust (8900kg odd) - 3.6lb per 100ft (0.05kg/mt)

 

The wire is just the wire and using old school numbers. The Dyneema are the 'average break load' for Amsteel Blue by Samson in the US. Samson uses 50% of the world entire dyneema production, most goes into BIG mooring lines for oil rigs and stuff like that. It can be noted here that Mr Rigger himself has rooted lots of Amsteel over the years by tugging it hard..... yes I do mean a Tug boat

 

There are a few monos with fibre rigging in NZ or at least the kiwi No 8 type fibre rigging. Very few, if any, boats would have the real McCoy that top end race boats use. Do knot confuse what the TP52's, AC, Volvo and that lots use with what Colligo Marine and NZers use. They are very very differing beasts.

[Island Time 1,239]

For anyone interested in what weight aloft does to stability, and stability in general, this is a good start

http://marsh-design.com/content/underst ... ity-curves

 

There is a bit of maths and physics involved....

[rigger 47]

On the Amsteel Blue - we sent (not where I work now) a line back to the factory for testing.

It had minor chaff and had reached its allotted number of jobs.

It broke at less than 40% of it's rated avg - it broke at one of the splices.

 

KM do you have any data on fatigue cycling in dyneema