Standing rigging sizing, options and expected loads

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EdS
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Standing rigging sizing, options and expected loads

Post by EdS » Sun Aug 19, 2012 11:00 pm

I have been looking into replacing the old PBO forestay on the boat which is tired.

How are all the standing rigging materials chosen and sized and what do most people use

I dont know what the expected loads on different parts of the rig are and therefore what diameter material to chose.

It appears that there are several options:
- Wire
- Rod
- Dyneema
- Hand wound PBO or dyneema or similar
- Carbon Rod http://www.marskeaircraft.com/carbonrod_p2.html

Is there any reason that I couldnt use carbon rod.

On the other hand it may be sensible to go with wire or rod.
The rest of my rigging is currently rod.

Any thoughts?
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Hendo
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Re: Standing rigging sizing, options and expected loads

Post by Hendo » Mon Aug 20, 2012 6:33 am

Ed,
these are great questions, OK, this is what I got , your forestay can be vectran, or dyneema in about the 1/4" flavor.
the shrouds we usealy go with wire around the 1/8' or 3mm. dyform is the stuff,
some people go fore PBO and all that expencive Sh!@#$$%^&* but what if ..
Kris Bundy rigged his whole new mast with (Starboat,Rod rigging) , did his own swagging and it turned out great! at low cost..
all the orders I get from the Bay , and Aus. thay want wire!..
My currant rig has as follows with no problems;
Foerstay vectran 1/4"
shrouds: Dyform wire 3mm.
lowers; vectran !1/4"
cap shrouds; 1/8" 1-19 SS. wire.

Dan H
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Re: Standing rigging sizing, options and expected loads

Post by Dan H » Mon Aug 20, 2012 7:23 pm

3mm dyform on all but caps which are 2.5mm is the basic standard in the UK anyway.
Breaking strain on 3mm dyform is very close to a tonne.
I would avoid carbon rod if I were you - even if you get the terminations and junctions correct, you have to deal with the total lack of robustness - tap it on something in the wrong direction in the dinghy park and it will just snap.
My impressions regarding PBo is that it is expensive, and that once you have sheathed it in something to mitigate the poor uv and chafe performance you have lost a lot of the benefit of its excellent tensile performance.

Terminations notwithstanding, I think that there are some good braided sk78 dyneema strings on the market now which offer similar modulus (I.e stretch per unit cross section ) and strength to dyform at approx 1/4 the weight. The new stuff had much better creep performance, is robust against chafe, and has uv protection coatings.
I think that it beds in a fair bit on the first few uses, lending itself to an adjustable rig,

Sorry if that muddies the waters!

EdS
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Re: Standing rigging sizing, options and expected loads

Post by EdS » Tue Aug 21, 2012 12:42 am

Sorry if that muddies the waters!
Not at all, I was hoping for a little discussion. It is good to hear what is the standard or atleast widespread set up.

OK it seems sensible to stick with resilient materials. I only ask because a rigger friend did a 16ft skiff with the carbon rigging and suggested it to me.

For the forestay I am tending towards the SK78 or vectran. I mentioned PBO because that is what is currently on there.

Hendo are you lowers adjustable? and if so is it a bottle screw or block system.
I currently have a bottle screw on wire, but it would be good to go to dyneema any suggestions.
Although I dont need anymore string, the boat is like a birds nest.

The rig is adjustable, so a bit of creep isnt a big deal. I just need to adapt my marks.

What do you mean about terminations for the dyneema Dan?
Have people moved towards Dog bones and strops or are they still linking splices with shackles.

Thanks for the input chaps
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Katie
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Re: Standing rigging sizing, options and expected loads

Post by Katie » Tue Aug 21, 2012 10:36 am

HI Ed,

I'm using 5mm Marlow SK78 Max for my forestay. The Max is the elongated, low stretch version. Although the breaking strains of the 3mm and 4mm are massive on paper, I went for the 5mm because I was nervous about it breaking through chafe, eg if I capsized on a sharp bit of mooring buoy/got it caught on splinters on the Itchenor staging etc etc. So far, it's been pretty good. Stretch while sailing is minimal. If I'm sailing a couple of days in a row, I can pull the forestay to the same marks each day, but if i haven't sailed for a while it seems to shrink and needs to be "restretched".

Previously, i was using woven PBO (Maffioli VZ) with a long splice. This was brilliant - zero stretch and exactly the same settings every time - and only about £6 a metre. But it kinks easily, and, when i tried to replace it, I couldn't get hold of any in the UK. So I did a lot of research at that point and concluded that the SK78 Max was probably the next best thing...

Dan H
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Re: Standing rigging sizing, options and expected loads

Post by Dan H » Tue Aug 21, 2012 4:35 pm

Ed,
Dog boning not hugely in evidence in the UK 14 fleet....

Whilst a swaged tball and socket are the most cost effective way of terminating with wire/dyform, if you are going nonferrous you would ideally have a spliced loop going around some kind of pin built into the mast. A bit going on with that these days, and some integrated spreaders / stay / trapeze attachments around.

All very nice but prob not worth retrofitting to an old mast.
I think there are swaged t terminal fittings with ends suitable for splicing onto.
Integrating the lowers onto thje mast can be done fairly neatly with rope - whether to the gnav fitting itself, or round the front of the mast with a bonded on piece.

EdS
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Re: Standing rigging sizing, options and expected loads

Post by EdS » Wed Aug 22, 2012 12:34 pm

Katie, thanks for that. I hadn't considered the wear risk from bouys and moored boats. I thought once you caught one that was rig broken.
Going bigger isn't much of a weigh penalty and adds a safety factor so good plan.

Dan, I have carbon connections on the mast which take the pin from a small shackle so I have a way of attaching the lowers.
But what I meant is how do I make it vaguely adjustable rather than just fixed. I guess I could find a way of connecting the splice to the stainless bottle screw.

The other option is an adjustable splice with thread sown in to show the corresponding lengths between each side.
How often do you adjust the lowers anyway?
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Dan H
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Re: Standing rigging sizing, options and expected loads

Post by Dan H » Wed Aug 22, 2012 10:47 pm

Tbh I reckon chafe is more a long term rubbing problem of moving ropes on other ropes or mast or fittings rather than a one off disaster situation. Dyneema is quite robust.
Prob worth trying to stay close to dyform diameters for windage, though this matters less in the jib luff.

Pretty sure I've seen rope lowers onto bottle screws. I guess it's just a case of getting a stainless eye onto thread that'll go in that ronstan bottlescrew.

As far as I can tell, lowers are pretty important as you go from light to med to windy.
Plus you'll have to adjust them if you rake to keep things even.

I reckon that I'll speak for most when I say that it's not one to adjust round most racetracks - cunno kicker foil and sheets are usually plenty!

But if it's a long race with a big wind change and you have a rope system, then it's another gear.
I think that if you adjust rig tension on shrouds rather than forestay, that your lowers may ease slightly with increasing rig tension.
Opposite is true on pinned rigs - lowers increase significantly with increased rig tension.

EdS
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Re: Standing rigging sizing, options and expected loads

Post by EdS » Fri Aug 24, 2012 5:51 pm

But if it's a long race with a big wind change and you have a rope system, then it's another gear.
Depending on competence it may be a higher gear but I think I might find a lower gear or even neutral.
A theory lesson on the lowers and general rig set up is probably not a bad idea.

I guess it keeps the mast straight lower down keeping the fullness in the sail whilst also counteracting the force applied by the GNAV

The ability to maintain the correct rig tension with a fully adjustable rig also appears to be a bit of a mystery.
I guess you can associate a force on the forestay adjuster to be close to the correct rig tensions ( again not sure on that, Tom helped me down at Weston but in more of a experienced based way.

Anyway this is off topic from the original question. Thanks for the input everyone, I am going with Sk78 of some diameter TBD.
Tbh I reckon chafe is more a long term rubbing problem of moving ropes on other ropes
On the long term abrasion, sleeving the high wear areas is probably not a bad idea using the same diameter dyneema.
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Dan H
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Re: Standing rigging sizing, options and expected loads

Post by Dan H » Fri Aug 24, 2012 8:47 pm

Ed, you have it spot on with the lowers effect.
slack when its windy going on to tight (anything from 10 to 20 depending on mast / sail) in the lighter stuff. If your mast / sail combo is well known it should be easy to come by numbers.
The pain with tuning it is that it will change with rig tension, also depending on whether you tension with the forestay or shrouds.
It will also affect / be affected by the caps in dock tune - i.e if lowers are 15 on the beach without main up, and you pull on caps from 15 to 20, the lowers will come on too, but will effectively be the same on the water as pulling up the main usually takes most of the tension out of the caps.

Re maintaining rig tension you probably need to mark 1 - 10 on the ranges of all your controls somehow, then get a good base, then some plausible windy and light numbers, note the positions that give you the right tensions, then mark them on a matrix that you keep on the boat. You may end up getting a good feel for the nmbers and get slicker at changing stuff.

I'd recommend finding a nice base set, then worry about how it changes at the light and heavy ends of the spectrum.
See how you get on with lowers on 10 to 15
Shrouds on 33
Caps on 15 - 20
Rake 8100 (+/- 100mm for light heavy)

It is deffo easy to pull on too much lowers and bind up the lower part of the main

Anyhow, find something that works and then forget about it if you can! Less you can worry about all but major cntrols and sheets the better as far as I can tell.

EdS
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Re: Standing rigging sizing, options and expected loads

Post by EdS » Fri Aug 24, 2012 10:36 pm

Thanks Dan, those numbers will be useful.

On the rig tension it is a little complicated on my boat.
I have adjustable shrouds and forestay on continuous line systems.

The first thing is to check the rake and then mark off the shrouds so that they are fixed.
The forestay adjustment can be marked infront of the mast, so that can be referenced to the each of the shroud positions.

On the mast rake doesnt that depend on the location of the mast and foils in the boat and how much caps are on?

Do you go to the transom or the top of the rudder gantry or do you do it on the forestay? and what caps setting?
that is possibly a stupid question, I hope not.
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Dan H
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Re: Standing rigging sizing, options and expected loads

Post by Dan H » Sun Aug 26, 2012 6:40 pm

Ed,
Your rig tension sounds interesting - I guess again it is just playing around on the beach to see the effects.
Rake is from white band at mast tip to bottom edge of transom.
Assume rig all pulled on inc caps as if you were about to hoist and go out.

Rake measurement is actually quite insensitve to "J" measurement - I loked at the trig a while ago and moving the whole rig back 100mm makes about 15mm diff in the rake value on the tape assuming nothing else changes - i.e. caught in the noise.

Dont think you want to adjust rake to affect f/a balance - just assume the designer has that correct. too mch rake will make the boat sluggish in the light, too little and it will be a bit staggery in breeze.

Dan

EdS
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Re: Standing rigging sizing, options and expected loads

Post by EdS » Sun Aug 26, 2012 8:30 pm

Dan,

Sorry I made sound like the shrouds and forestay were on one line.
I meant they have seperate systems but it does mean you have alot of adjustment and unknowns.

When i get back next week i will do the rake adjustments on the shrouds and stitch the dyneema so i can see the settings.
Then go with the forestay from rig tension from there.

Thanks for the input on measuring rake. I guess the only thing which is a slight unknown is caps being correct and of course the spreader angle.

Ed
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Dan H
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Re: Standing rigging sizing, options and expected loads

Post by Dan H » Tue Aug 28, 2012 11:56 am

Ed - if I were you I would set rake on forestay and adjust rig tension on shrouds - means that the lowers ease and jib twists as you pull rig on. Opposite happens if you increase tension by forestay.
Caps less critical than the other settings as far as I can tell - just stops the mast falling sideways whilst sailing. 15 - 20 will be fine.
Dont think upper spreader length and deflection are that critical given that the leeward one is always slack when sailing upwind. Just affects how much slacker it goes with more f/a bend.
Lower spreaders are important - bit dependant on mast / sail combo - best get sailmakers advice there.

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