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jeremyh

Synthetic rigging in A Cats

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I'm looking to lose a couple of pounds to get the boat close to minimum weight. I have seen people using sk90 in 3mm, but I have also heard that d12 max sk78 would be better because it is pre-stretched so much. The only problem is the d12 max is so hard to find in the u.s. Any thoughts?

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Jeremyh,

 

We have done a couple of sets of shrouds for A Cats in Marlow D12 Max SK78 3mm. We have it in stock.

 

Email me the pin to pin lengths of the shrouds and we will get them going for you.

 

My email is rod@velasailingsupply.com

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The boat was completed in December, it is a home built with curved boards and volume similar to the DNA. We just added to much weight in fairing and paint, and a boom. I am switching the boom to a windsurfing mast section and will sand some paint off and wet sand to get a good finish. Then I could also lose a couple of pounds on rigging.

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Hi. Several people talked about this at the most recent worlds and consensus was such rigging saved 2lbs or about .8 kg. It is pretty amazing, no doubt.

 

I will also vouch for Jeremy's boat. It is the latest iteration of a 2 year old design that continues to evolve by OH Rogers and is a really nice looking boat. I believe the entire platform including blades and beams are made from scratch.

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2 lbs is about right after doing the math, so I will save this project until I finish sanding the entire boat and assembling a new boom because I can only lose lbs.

 

Thanks, the entire boat was made from scratch, we used OH's hull, daggerboard and rudder molds and we made our own beam molds. The only things we didn't make were the mast, sail, and hardware.

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I have been using easy rigging for 5 or 6 years. Keep it on a spool when its off the boat. Amazing how light it is, when it shows up in the mail I wondered why they send an empty envelope....Finally broke a shrowd after 4 years? it had been rubbing on the lee diamond swage. Not sure how well it would do going around spreader tips.

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if you went with a set of rope stays you will be giving away some response from the rig as the stays will soften the boat a little bit. No matter how amaziing the new ropes are, they all have some give in them.

 

If you really want to do it and not sacrifice performance then i would suggest getting in touch with easy rigging, they make nice stuff, small and reliable too.

 

You can do your diamonds with it too, works well over spreader ends.

 

some guys have done the pultruded carbon rods and glue ends on, but most of the pultruded rods are quite low modulus and as such will stretch more than a PBO stay and they are very easy to damage.

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The easyrigging stuff isn't what it used to be. They changed the outer casing from a smooth finish to a braided one and this leads to a high pitched humming at speed on the really thin stuff that is used on A's. Not fast and very annoying. I would love to get hold of the old style rigging for my boat.

 

The guys I know who are making up carbon rigging are getting good results. Stretch hasn't been an issue on the A's and it hasn't proven to be anywhere near as fragile as they thought it would be. The most dangerous time is when somebody tries to help you pull the boat by grabbing a carbon stay.

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You can still get the Easyrigging stays with the simple plastic cover, just order it like that. simple.

 

The home made stuff from pultruded carbon is okish... but it is not reliable with cyclical movement and there is no warning of impending failure. Not so much of a big deal on a sidestay, but on your diamonds it gets expensive really fast.

 

There was a recent failure of such piece on a slightly larger cat, and the consequences were predictable..

 

If you cant afford to get these things done properly, then its ok to make your stuff at home for sidestays on an A Cat, worst case the rig falls over the side, you pick it up and go home. But unless you can afford a new mast section I would avoid it for diamonds.

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So that's got to mean you don't have a new gen boat.....minimum weight is the least of your worries

 

Maybe; but so what? Some sailors like to experiment, others like to do that and sail under the latest go-fasts. A pound aloft is a lot to me; besides, riding this boat has me jealous, new, old, first place or last.

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Got to agree with Macca. I wouldn't use carbon for diamonds, but then again, I haven't seen anybody using anything other than wire on the A's.

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Carbon rod is the go but defiantly not a game changer. Dyform and even 1x19 is still fine just a touch heavier. Majority of the top 10 at worlds and Euros are still on wire. The issue with Carbon it is extremely fragile so you need to take care when rigging and unrigging. I only use mine if the regatta is longer than 2 days. Can not use carbon on diamonds.

As for fiber rigging, you need proper parallel product like easy rigging. Anything braided you either have too much constructional stretch or the dia needs to be too large and windage is the issue. I would much prefer 2.5mm Dyform over 3mm SK78 or even 90 that is braided. Braided dyneema is ok for trap wires but that is about it.

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2 lbs is about right after doing the math, so I will save this project until I finish sanding the entire boat and assembling a new boom because I can only lose lbs.

 

Thanks, the entire boat was made from scratch, we used OH's hull, daggerboard and rudder molds and we made our own beam molds. The only things we didn't make were the mast, sail, and hardware.

 

Wouldn't you rather take weight out of the rig than anywhere else?

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2 lbs is about right after doing the math, so I will save this project until I finish sanding the entire boat and assembling a new boom because I can only lose lbs.

 

Thanks, the entire boat was made from scratch, we used OH's hull, daggerboard and rudder molds and we made our own beam molds. The only things we didn't make were the mast, sail, and hardware.

 

Wouldn't you rather take weight out of the rig than anywhere else?

I agree with you on that, but I can lose more weight in other areas such as paint and a boom. I can probably lose 6 or more lbs between the two. I am in a time crunch to finish these tasks before A cat mids, so I will put the tasks that lose the most weight first.

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yes you can build rigging in dyneema, but no I do not think it is a good idea.

self spliced rigging will have lots of construction stretch. on top of that most ropes will be dyneema, which develops creep when under tension.

the creep in dyneema varies with temperature, load (as a percentage of the breakload of the rope) and type of dyneema used.

 

If you want to limit the creep, you will need to go up in size quite considerably, resulting in thick, not so lite stays (but still lighter then steel wire) with more construction stretch.

 

so yes it is possible to build rigging in Dyneema.

It helps if you do not care if you have repeatable rigging settings. (or do not mind bigger diameter shrouds)

preferably low load stays as forestays and capshrouds on A cat.

For diamonds it will not be possible to get any repeatable rig tension. (especially if you sail in an area with temps higher then 25C)

 

If anyone is interested I can do a more elaborate piece about (composite)rigging

 

Cheers, C.

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I am trying out a set of the Marlow Dyneema that Mike Krantz from Layline made up for me. The stays and shrouds are 3 mm. Mike advised there would be about 1" of stretch. I think so far there has been about 1.5". I've done three sailing sessions in 12-14 knots, 7-9 knots, and 14-17 knots. I pulled some stretch out after the first two, I pulled none out after the last (and windiest session).

 

Here are my views/observations on what some are saying above:

 

Weight and ease of use - the weight savings is around 2 lbs and it's easier to rig and de-rig since the lines coil and uncoil like small lines.

Windage - I just don't believe there is a windage penalty you can measure in terms of performance between 2.5 mm standing rigging and 3 mm standing rigging. I always do my solo sailing sessions with a Speed Puck and I can see no issues so far with hitting my target speeds and tacking and jibing angles with the new rigging.

Noise - The new rigging makes some noise but I don't mind it. In fact I kind of like it. Sounds like speed!

Platform stiffness - Properly setup, so far I cannot detect any degradation in platform stiffness or response.

 

During my last sailing session in 14-17 knots of breeze and 1'-2' chop, I did a measured 1.9 nm upwind/downwind test. On the upwind leg, I did three tacks that were 89, 92, 91 degree tacking angles, pretty spot on for an A-class. My boatspeed results were 12.55 knots (best 100 meter average), 12.41 knots (best 200 meter average), 12.21 knots (best 500 meter average), and 12.11 knots (best 1,000 meter average). The top end (2 second average) was 13.01 knots. Downwind, I did four jibes and all had angles between 100-104 degrees. Speedwise, the best 100 was 17.46 knots, best 200 was 17.21 knots, best 500 was 16.78 knots, and best 1,000 was 16.7 knots. My top 2 second speed was 18.62 knots. I don't think the riggging is slowing me down. I was not trapezing downwind so if I had the balls to do that, the downwind numbers might have been higher.

 

I'll be at the Ronstan Midwinters next week. I'll post how the rigging does during that event.

 

Cheers to all,

 

Bob Hodges - USA 230

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Hi Bob,

 

the stretch you are mentioning is construction stretch. Stretch under load is not something you will easily see, because your windward stays will just stay tight, but will elongate (which means less wind energy transferred into speed)(Which is probably so small you will not see it on your GPS, as a direct speed difference).

 

I presume you have SK 78 for side rigging. When you calulate the EA for the 3mm dyneema shroud it is about 0.54 MN.

2,5 mm dyform has an EA of 0,82 MN.

 

This will result in 35% more stretch in your dyneema shroud, for the same load, compared to your dyform shroud.

You will have saved weight, but have lost stiffness.

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Hi Bob,

 

the stretch you are mentioning is construction stretch. Stretch under load is not something you will easily see, because your windward stays will just stay tight, but will elongate (which means less wind energy transferred into speed)(Which is probably so small you will not see it on your GPS, as a direct speed difference).

 

I presume you have SK 78 for side rigging. When you calulate the EA for the 3mm dyneema shroud it is about 0.54 MN.

2,5 mm dyform has an EA of 0,82 MN.

 

This will result in 35% more stretch in your dyneema shroud, for the same load, compared to your dyform shroud.

You will have saved weight, but have lost stiffness.

 

Constantijn,

 

Understand about the construction stretch but note the following. On Saturday, before I went sailing, I checked the tension on the shrouds with a black Loos Pro gauge to get a reference number. When I got back, I re-checked the tension and it was the same. So I have to believe minimal to no stretch during that 90 minute sailing session. Now while sailing, it certainly might not be as "stiff" as Dyform or carbon but I could not tell any perceivable difference. The boatspeed and tacking angle numbers I posted for that session seem to indicate no degradation in performance both in terms of boatspeed and tacking/jibing angles. I'll have a better perspective after the Midwinters next week but there is no reason at this point to change it out yet. I've always used Dyform and can certainly go back but this stuff looks promising so far. Stay tuned.

 

Bob Hodges

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Hi Bob,

 

You will get the same reading, but thats because the loads before and after sailing are the same (ie, only static rig tension) the stretch is happening when you are sailing.

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Bailey - Mike told me it was the Marlow product which I think is the SK 90 Dyneema.

 

Macca (and others) - I won't debate the stretch is occurring while sailing but if I don't have to re-tension (at this point) after sailing, I have to assume the system has some type of memory that brings it back to it's original length when dynamic loading is stopped. Like I said, we'll get a better perspective after the Midwinters next week.

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hi Bob,

if it is SK 90, the EA will be around 0.6 MN, so you will have 30% more stretch then with dyform.

If you would switch to 3,5mm or 4mm diameter the stretch could be similair as in 2,5mm dyform.

 

you seem to mix up the properties creep, stretch and construction stretch.

 

Stretch is elongation due to force. when unloaded it will return to its original length.

 

Construction stretch is what you have in a braided construction. When the fibres are loaded, the will compress and try to straighten themselves. Rope manufacturers try to do this in their factory by pre tensioning and heating with steam. This helps, but will not be able to prevent the construction stretch from occuring. each time you store and coil your rigging, you will have to pull it out again. (as the rope will shrinks a bit due to coiling). when you load up a rope higher then before it will compress (and elongate further)

 

Creep is non returning elongation under load. compare it to pulling on chewing gum. it does not shrink back after unloading. This is a property of polyethylene molecules (the stuff Dyneema is made of). Although rope manufacturers sometimes claim differently, there is NO way to take out creep in the production of the rope

while SK 90 has relative low stretch and high breakload, it also has the most creep of all Dyneema fibres.

 

You will see that after a day on the water in higher temps and a bit of breeze, that you will have lost rig tension.

Cheers, C.

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As mentioned before herewith a small write up. It compares different materials used in building of standing rigging, without going to much in detail about each materials up and downside:

 

When you design rigging there are 2 parameters;

- breakload

- stretch

 

breakload is understandable for everybody and quite easy to do/ match

 

stretch is a bit different. the engineering value for rigging is EA (MN), where E stands for the E modulus and A for area or cross section. Unit is in Mega Newton

When replacing steel rigging you can measure what you have, and look for an alternative.

As steel is the standard, most often we build to these equivalents.

 

- rod rigging is the standard on bigger boats (and has the least amount of stretch of the steel rigging), you can measure the diameter, calculate the cross section, multiply it with the E modulus of Steel, hussle with the zeros and out comes the EA in MN.

- for wire it is a bit different as it is spiral wound and has about 30% of air within the strands. furthermore due to the air it will compress and extend when you load it up. This is called construction stretch.

- dy form or compacted strand is in between the 2 above. basically it is wire which has been pushed through a dy, changing the shape of the individual strands from round to a compacted shape. due to this there is less air, so more steel for the same diameter and also less construction stretch.

 

We have measured the real stretch of lengths of wire and dyform to get their real EAs, as the values available from various suppliers are often not correct!

When you have the EA of the steel rigging it is easy to match in any other material (as long as you know the E modulus). does not mater if it is carbon, pbo, dyneema, polyester, shockcord or bamboo!

Obviously if the E modulus goes down the A must come up to keep the end result the same.

 

Herewith a comparisson of different E modulusses:

Carbon 295 GPa

Carbon (low grade extrusions) 240 GPa

PBO (Zylon) 245 GPa

Nitronic 50 (rod rigging) 190 GPa

Dyneema (SK 90) 130 GPa

Aramid (Kevlar 49 & Twaron 2200) 110 GPa

Dyneema (SK 78) 110 GPa

Dyneema (DM 20) 93 GPa

 

Carbon laminates always have between 30 and 50% resin. Dry carbon is not relieable. Carbon with resin can be fragile and hard to store/ coil

PBO needs a UV shielding. The thin sizes only come with a braided cover and no compression layer and environmental barrier like the bigger stuff. PBO loses breakload over time

Dyneema has creep (all grades, though the amount varies!!)

Aramid needs UV shielding

 

A braided construction (rope) will always have construction stretch, which can be pulled out, but which returns after coiling.

All UD dry fibre solution need some kind of cover to keep the fibres together.

 

A few words about creep:

this is something which is misunderstood by lots of people. Creep is elongation under load, but it does not shrink again after unloading (like pulling on chewing gum)

Creep is a property of the molecule of the fibre and cannot be taken out, whatever you do.

Most of the man made fibres have creep, the amount varies. Eg Aramid and PBO have so little creep that its already gone when the construction of the rigging is finished.

 

Dyneema has the most creep of the discussed fibres (and it never stops). Depending on load (load as a percentage of the break load) the creep will vary.

A higher percentage will result in more creep. The creep also depends on temperature.

 

Construction stretch:

All braided or twisted constructions have this. Compressing and pre tensioning can limit this (like in Dyform or heat threating dyneema rope). When the stay or rope is higher loaded then before it will compress / elongate further.

 

Hope this helps ;-)

 

Cheers, C.

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Constantijn,

 

Thanks for the spec writeup regarding Dyneema, etc.

 

Here's the deal - 2.5mm Dyform has a breaking strength of 1,500 lbs. 3mm SK90 has a breaking strength of 3,400lbs.

 

For a 24 ft A-cat shroud, I will splice the length to 23' 6" and place it on a frame with a 40,000 lb hydraulic ram.

 

Using the hydraulic ram and a load cell I will cycle the shroud up to 2,000 lbs and slowly pull it out to the 24' finished length, and then hold it at that length 30 mins or more. This eliminates the constructional stretch induced by the original construction process and the eye splices at each end.

 

I agree with your comments that Dyneema has creep when used in high load applications, more so than wire. But we are talking about A-cat shrouds, and using a product that is twice as strong as the wire that it is replacing at less than 1/4 it's weight. My guess is that we are operating at less than 20% of the breaking load of the 3mm SK90, which is approaching 50% of the breaking strength of 2.5mm dyform.

 

I may be wrong, but I have never heard of anyone breaking an A-cat shroud from shock loading - kink, chafe, or fatigue yes, but shock loading no.

 

I guess, what I need to do, is mount a load cell on my A-cat and go sailing in big breeze to measure the actual forces...

 

-Mike

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Certainly the load cell would tell the full story. I rig concert audio speakers and you would not believe the numbers the dyno gives us just by bouncing the cabinets up an inch. It is at least 10 to 20% of the static load.

 

 

In big wind and chop, the numbers of our A cat rig could be larger than one would guess. For testing purposes, it should be tested on both the forestay and shroud. It would certainly be cool to see.

 

 

 

My 2 cents.

 

Christopher

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Hi Mike,

 

You shroud will be more then strong enough, that will not be an issue (strength is not the limiting factor in most cases).

The only thing I am trying to point out is that stretch is also a very important property when building rigging.

 

the max (non dynamic) load on a multi hull will be when just flying a hull, while sitting in.

my guestimate is, that this will be your body weight + boatweigth.

 

If you keep the loads below 20% of the BL then creep will be less of an issue.

You then will have saved weight compared to wire, be bigger in diameter and will have a bit more stretch.

money wise it can be cheap, but is depends what work you can do yourself.

 

However, for a high tech, light weight boat like an A cat, stretch is a very important property ,as stretch equals energy absorbed in elongating the rigging, instead of being transferred into speed.

Keep in mind that we are discussing very small amounts. (but still a few boat lengths in a full leg)

 

my 2c

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As mentioned before herewith a small write up. It compares different materials used in building of standing rigging, without going to much in detail about each materials up and downside:

 

When you design rigging there are 2 parameters;

- breakload

- stretch

 

breakload is understandable for everybody and quite easy to do/ match

 

stretch is a bit different. the engineering value for rigging is EA (MN), where E stands for the E modulus and A for area or cross section. Unit is in Mega Newton

When replacing steel rigging you can measure what you have, and look for an alternative.

As steel is the standard, most often we build to these equivalents.

 

- rod rigging is the standard on bigger boats (and has the least amount of stretch of the steel rigging), you can measure the diameter, calculate the cross section, multiply it with the E modulus of Steel, hussle with the zeros and out comes the EA in MN.

- for wire it is a bit different as it is spiral wound and has about 30% of air within the strands. furthermore due to the air it will compress and extend when you load it up. This is called construction stretch.

- dy form or compacted strand is in between the 2 above. basically it is wire which has been pushed through a dy, changing the shape of the individual strands from round to a compacted shape. due to this there is less air, so more steel for the same diameter and also less construction stretch.

 

We have measured the real stretch of lengths of wire and dyform to get their real EAs, as the values available from various suppliers are often not correct!

When you have the EA of the steel rigging it is easy to match in any other material (as long as you know the E modulus). does not mater if it is carbon, pbo, dyneema, polyester, shockcord or bamboo!

Obviously if the E modulus goes down the A must come up to keep the end result the same.

 

Herewith a comparisson of different E modulusses:

Carbon 295 GPa

Carbon (low grade extrusions) 240 GPa

PBO (Zylon) 245 GPa

Nitronic 50 (rod rigging) 190 GPa

Dyneema (SK 90) 130 GPa

Aramid (Kevlar 49 & Twaron 2200) 110 GPa

Dyneema (SK 78) 110 GPa

Dyneema (DM 20) 93 GPa

 

Carbon laminates always have between 30 and 50% resin. Dry carbon is not relieable. Carbon with resin can be fragile and hard to store/ coil

PBO needs a UV shielding. The thin sizes only come with a braided cover and no compression layer and environmental barrier like the bigger stuff. PBO loses breakload over time

Dyneema has creep (all grades, though the amount varies!!)

Aramid needs UV shielding

 

A braided construction (rope) will always have construction stretch, which can be pulled out, but which returns after coiling.

All UD dry fibre solution need some kind of cover to keep the fibres together.

 

A few words about creep:

this is something which is misunderstood by lots of people. Creep is elongation under load, but it does not shrink again after unloading (like pulling on chewing gum)

Creep is a property of the molecule of the fibre and cannot be taken out, whatever you do.

Most of the man made fibres have creep, the amount varies. Eg Aramid and PBO have so little creep that its already gone when the construction of the rigging is finished.

 

Dyneema has the most creep of the discussed fibres (and it never stops). Depending on load (load as a percentage of the break load) the creep will vary.

A higher percentage will result in more creep. The creep also depends on temperature.

 

Construction stretch:

All braided or twisted constructions have this. Compressing and pre tensioning can limit this (like in Dyform or heat threating dyneema rope). When the stay or rope is higher loaded then before it will compress / elongate further.

 

Hope this helps ;-)

 

Cheers, C.

 

What about Dynex Dux. Is this stuff better than SK78 / 90??

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No, Dynex Dux is a brand of rope from Hampidjan.

Hampidjan is an Icelandic company, very big in offshore ropes and netting.

 

the DD is produced from SK 75, so not the best grade for this aplication (in my opinion)

 

 

Again, for high performance boats stretch is a more important value/ property then break load.

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After sailing for two hours in 14-17 knots with the SK90 rigging Mike made for me, I checked the rig tension and rake settings on my A-Class and they were the same as they were when I left the beach. I believe the forestays on an A-Class are more highly loaded than the shrouds. When you are on the trapeze, most of the load comes off the windward shroud and the leeward shroud is lightly loaded. I don't disagree with anything Constantin is telling us, I just believe the actual loads on an A-Class don't produce significant issues that affect performance based on the amount of stretch or creep that actually occurs. I tend to agree with Mike that creep is not going to be an issue at all and here's another data point. I also own a Corsair Sprint 750 trimaran. All of the standing rigging on this boat is 7 mm Dynex Dux. I have been using this rigging (by Colligo Marine) for nearly 5 years (3 years on the first set, 18 months on the current set). We went through one stretch cycle (with each set) and since that time, we have not had to make any changes to the tensioning of the rig. Again, while I will not dispute that the Dynex Dux might stretch more than the previous SS rigging (that weighed 14 lbs more) while sailing, we have had excellent racing results with it on the boat.

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Hi everybody,

 

Does anyone has experience with X-wire 90 from Gottifredi Maffioli? The core is a hybrid composition with SK90 fibers blended with PBO. The cover is made out of Dyneema and it exists in 3mm, so maybe quite interesting for A cats. Any comments are welcome because I am also looking for a change in my shrouds.

 

Patrick

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A few words about creep:

this is something which is misunderstood by lots of people. Creep is elongation under load, but it does not shrink again after unloading (like pulling on chewing gum)

Creep is a property of the molecule of the fibre and cannot be taken out, whatever you do.

Most of the man made fibres have creep, the amount varies. Eg Aramid and PBO have so little creep that its already gone when the construction of the rigging is finished.

 

Dyneema has the most creep of the discussed fibres (and it never stops). Depending on load (load as a percentage of the break load) the creep will vary.

A higher percentage will result in more creep. The creep also depends on temperature.

 

 

 

You are right about creep, all materials creep, even PBO, Aramid and Steel, this must be considered when sizing any material with a constant load. But, for a sailboat rig, this is certainly not a limiting factor with SK75 derivatives like Dynex Dux. For instance, our creep limit is 0.1" per year, maximium (10 years produces 1 inch). 9 mm dux, which has an equivalent stretch to 1/4-5/16 inch 1x19 steel wire, has a constant tension limit of about 1200 lbs (for a 50 foot long linea at 70F). Much more than the pretension you would normally use. Since creep is permanent elongation over time, dynamic loads are usually not considered in our calculations. So, you see, you only have an increase in cross sectional area of about 1-2 mm that produces equivalent stretch and virtually no creep issues. Dyneema can be used for standing rigging, It is just a matter of understanding the material properties and designing for a given application. Just to clarify, we do not use, or reccomend, 20% of break strength as a creep limit. You will more than likely get more creep that you want to deal with. Creep is exponential with load and depends on length so you can get into lots of trouble by using a simple percentage of break strength number for creep sizing.

 

Also, in braided line, constructional stretch is a much bigger factor than material stretch. This is why we use Dynex Dux (SK75), its construction consistently produces less constructional stretch than all the other braided lines, SK78, SK90, and DM20, even heat stretched (at the braided level) SK90 We have tested all of these from many manufacturers. SK90, in particular, is heat stretched at the fiber level which makes it less pliable at the braided level, and thus will not compact enough to eliminate most of the constructional stretch. All of the SK90 we have tested has higher stretch than Dynes Dux at the rope level, even thought the material stretch is less. If you take the time to cut a piece of Dynex Dux you will see what looks like a single strand of 12 cells. It is so tightly compacted that you virtually get no constructional stretch. The other lines just aren't that compacted so you get considerably more constructional stretch.

 

We have rigged over 300 boats now to 70 feet (with Colligo Dux Rigging) with no creep problems and much improved performance. In fact, the US Coast Guard calls our rigging the safest as it is fully inspectable. They are tired of investigation accidents that involve swage fittings.

 

Unfortunately, Hampidjan is not making anything smaller than 5 mm so for A cats you are limited in your selection. The best option, for performance, might be a unidirectional line.

 

 

 

John Franta, Colligo Marine.

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I can back up what John Franta is saying by practical experience using Colligo rigging on my Corsair Sprint 750. The shrouds and forestays are all Dux SK75 and after going through one stretch cycle, we've not had to make any adjustments in over a year.

 

Jury is still out for me over using the SK90 on the A-Class standing rigging. I sailed the A-Class Midwinters with it last month and finished 2nd in the event so I don't think any on the water dynamics were occurring that were limiting the performance of the boat. What I did see was shrinkage of the shrouds and forestays that occurred after I had sailed the boat at home in preparation for the event, thought I had all the stretching out and then when I re-rigged at the event site, I was one hole up on my shroud adjusters for a given rake setting. By the end of the event, I was back to where I was training for the event at home. So there was movement of approximately 1/2" in shrinkage and re-stretching. What this implies for me is to get to the event at least one day before and go sailing and then "re-calibrate" after the pre-regatta session to get the settings I want. A bit of a hassle but at this point not too bad considering it saves over a kilo on Dyform and you don't have to worry about it as much as carbon rigging.

 

Will be sailing the Admiral's Cup next month and will make a final determination whether to stick with the SK90 after that event.

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I have a questions about the thimbles used with Synthetic rigging. I am building two boats and have bought 3mm SK78 for the shrouds and Forstays. And some 2.5mm Dyneema for the trap lines.

 

Do you need to use the fully enclosed thimbles on the ends, or will the open thimbles work just as well. The closed ones are $5 each, and the open are $1

 

Thanks

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Another update on the SK90 I'm using after the Admiral's Cup this past weekend in Tampa. Again, no issues and my boatspeed and performance seemed very competitive in the fleet. I arrived on Thursday and sailed that afternoon. Did one tension adjustment after that warmup and did not touch it until Saturday morning when I changed the rig rake. At this point I have no reason to discontinue using it. Ben Hall is playing around with another type of heat treated SK90 also. We all want the stuff to work in this application as the cost is affordable and the weight savings are comparable to PBO and Carbon rigging.

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Hi there,

I am writing you guys, because I need to know an approximate avarage weight of some items on a A-class like:

single rudder (blade + tiller)= ?

single dagger board= ?

main sail with battens=?

boom = ?

shrouds + trapeezes= ?

front beam= ?

back beam= ?

 

If anyone can help me would be great :D !

 

Thanks

 

R.

 

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It has been a while since this topic was last dicussed and I'm wondering if there have been any new thoughts, products or improvements over the SK90 that was discussed a couple years ago for ACAT standing rigging. Maybe some new rigging at the Worlds?

 

A-man

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The rigging at the worlds varied widely from plain old stainless to carbon and dyneema. I am a big fan of the dyneema rigging for its ease of use and low cost. If you are in North America, you can get it made up for the A very reasonably from Mike Krantz. I think it is this stuff: http://www.dsm.com/products/dyneema/en_GB/sports-lifestyle/sailing-lines-cloth/dyneema-max-technology.html

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It has been a while since this topic was last dicussed and I'm wondering if there have been any new thoughts, products or improvements over the SK90 that was discussed a couple years ago for ACAT standing rigging. Maybe some new rigging at the Worlds?

 

A-man

SK99 is out now, as well as SK99MAX. The 99 is about 8% stronger than the 90 but still has the same creep characteristics that 75 and 90 had. I think that on an A cat you are working at a low enough % of the fiber's strength that Bob and others have sidestepped creep being an issue. 99MAX should be an incremental improvement over 90MAX for this application. We are getting mixed feedback on using it for standing rigging on larger boats (multis specifically), enough that I won't recommend it for that use, but will recommend 78 MAX or DM20 MAX instead.

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I am curious about the Max stuff, but have yet to see any stretch numbers on it. My understanding is that while it has effectively no creep, it suffers from pretty bad stretch characteristics.

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SK99 is out now, as well as SK99MAX. The 99 is about 8% stronger than the 90 but still has the same creep characteristics that 75 and 90 had. I think that on an A cat you are working at a low enough % of the fiber's strength that Bob and others have sidestepped creep being an issue. 99MAX should be an incremental improvement over 90MAX for this application. We are getting mixed feedback on using it for standing rigging on larger boats (multis specifically), enough that I won't recommend it for that use, but will recommend 78 MAX or DM20 MAX instead.

 

Thanks for the input. Who carries this and is it available under 3 mm?

 

A-man

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I was using (on my A Cat) STS 12-90 3 mm, but after over three seasons it was time for new shrouds so I ordered some Excel D12 MAX 78 2.5 mm from Landfall. Was happy with the service and I am happy with the product so far.

 

 

http://www.landfallnavigation.com/maexd12max78.html

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I'd be more positive about carbon rod than this thread suggests. Very stiff and light, and actually pretty reliable once you get used to it. Don't leave it coiled in the sun

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I'd be more positive about carbon rod than this thread suggests. Very stiff and light, and actually pretty reliable once you get used to it. Don't leave it coiled in the sun

Yes I've been using it on my A for three years. Very reliable, light and long lasting. Just care needed to maintain the chafe points and when rigging. And of course warn any helpers pulling the boat up the beach nit to pull by the forestay.

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30 years ago I used 3/32 kevlar core wire on all my 18 sq meter catamarans (L=5.5m x W=3.5m x SA= 18m2 x W= 93kg). This was 1x19 wire withthe inner 1x7 core replaced with uindirectional kevlar. Very light. Used for Shrouds, trap wires and diamond wires. From Defender marine. Double nicopress loops for ends.

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sk 99 has a very high creep, similair to that of sk 75.

The E modulus is higher the the other Dyneemas, which is nice, so low stretch.

Although more then strong enough it will creep considerably when sized to breakload only. (do not go too thin)

Please note that the creep is very temperature sensative. sailing in Auz summer will create creep problems, while in UK summers you are fine ;-)

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