| Changing the stays or trap wires #149472 07/14/08 08:12 AM 07/14/08 08:12 AM |
Joined: Oct 2006 Posts: 186 Chattanooga, TN jody OP
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Posts: 186 Chattanooga, TN | I am thinking of changing from the wire stays and trap wires to an all high strength line system for the blade. Anyone done this yet? Should the same lengths be used or do I need to adjust it some?
Thanks jody
Jody
Blade F16 724
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| | | Re: Changing the stays or trap wires
[Re: jody]
#149473 07/14/08 08:48 AM 07/14/08 08:48 AM |
Joined: May 2003 Posts: 4,451 West coast of Norway Rolf_Nilsen
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Posts: 4,451 West coast of Norway | Jody, check out what Eric Precourt has to offer: http://www.precourt.ca/I would prefer a system which was easy to adjust, so some kind of adjustment on the stays like erics would be an idea. Synthetic stays on beachcats are not well tested, and reports have been mixed. Trapeze lines are well tried and a "no-brainer". Go for the same length, but look out for chafe. Spectra/Dynemaa 3mm is good enough in my experience. | | | Re: Changing the stays or trap wires
[Re: Rolf_Nilsen]
#149476 07/14/08 10:52 AM 07/14/08 10:52 AM |
Joined: Oct 2006 Posts: 186 Chattanooga, TN jody OP
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Posts: 186 Chattanooga, TN | Ok I think I am gonna try it. Anyone know the lenghts needed for the VW blade, would save me from dropping the mast this week and measureing. Thanks Jody
Jody
Blade F16 724
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| | | Re: Changing the stays or trap wires
[Re: jody]
#149477 07/14/08 11:34 AM 07/14/08 11:34 AM |
Joined: Aug 2005 Posts: 2,921 Michigan PTP
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Posts: 2,921 Michigan | A friend did this on my old HT with 1/8 (I think) vectran. What kind of line are you going to use? Unless you use PBO or dynex dux (pretty certain they don't come in small enough diameter and they are very pricey) then make them several inches shorter because they will creep. On the HT I think the side stays crept like 4 inches or so. Makes it difficult to really make them to a length that you can still use the staymaster adjusters. On trap lines it isn't as big of a deal. In the end, I think the trouble of line as stays from a length, creep point of view outweighs any advantage they have.
If you do go ahead and do it then use a lashing type system on both sides so you can have plenty of play to tighten them. My friend's vectran (at least 20-25 feet maybe) may have even crept 5-6 inches.
Last edited by PTP; 07/14/08 11:37 AM.
| | | Re: Changing the stays or trap wires
[Re: jody]
#149478 07/14/08 01:55 PM 07/14/08 01:55 PM |
Joined: Sep 2007 Posts: 571 Hamburg Smiths_Cat
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Posts: 571 Hamburg | I am just doing it. I discovered some abrasion on my sail, where it comes to contact with the wires. Hence I decided to take synthetic fibres. From a pure technical point I would take PBO from 'easyrigging'. I dropped this idea, when I saw the price. There are only a few fibres which are ok for wire replacement (apart from PBO): Vectran, Aramid and Dyneema. Vectran would have a too large diameter for the same load. I didn't find any offer for covered Aramid, which I could splice, hence my choice was dyneema. I decided for Liros regatta 2000, because it has a cover, which adds UV protection. The drawback is that I needed one day for making half the splicing work (I only spliced single braid ropes so far). I think that I will use single braid Dyneema in future and replace it more often. This would reduce the rope diameter as well, since the cover adds 1mm more diameter. For the trapez lines I took 3mm (BL 500kg, hence margin of safety 10 to 5), for the shrouds 5mm (BL 1200kg, normal load would be around 200kg, but 'missuse' could lead to significant higher loading). Since I have no jib, I have two long bridle wires (each 5.8m) and a short fore stays (0.5m). The fore stay is 6mm rope (BL 2200kg, normal load about 700kg, hence m.s. only 3, but the stay of the hooter acts as a back-up). The bridle wires are 3mm wire. The higher gauge of fore stay and shrouds adds about 2% more drag. That is nothing compared to my skill. The lower weight, I didn't calculate it. Length. Each rope creeps, even wire. Dyneema creeps more than other materials. However my boat is already fitted with 'adjustment devices', which are again dyneema ropes. Safety. I will test my splicing work by tensioning each of the ropes (two trees, main sheet, ....) Though I am still a bit thrilled. As I am still in the process, I don't have any live expierence yet. But I will tell you I have buy a new mast (hopefully not). Cheers, Klaus | | | Re: Changing the stays or trap wires
[Re: PTP]
#149480 07/14/08 02:56 PM 07/14/08 02:56 PM |
Joined: Sep 2005 Posts: 893 waynemarlow
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Posts: 893 | On the HT I think the side stays crept like 4 inches or so have alook at http://www.marlowropes.com/public/pageManager.cfm?page_id=132 where you will be surprised at the versatility of the D12. As to creeping, actually creep is the wrong word, the fibres tighten upon themselves under load and thus lengthen once first used. I tend to make up an approximate length, tie it between two supports and then sit on it, you can then readjust the end ( splicing only takes afew minutes )to the correct length minus about 25mm on the stays. After a few days they settle down and don't really move much. The only down side I think is that you really need to change every couple of years the forestay as the spinnaker seems to " fray " the rope a little but 3.5 mm is much stronger than wire so theres a bit of tolerance left. The other thing I would recommend is that on the 3mm trapeze line the loadings are fairly light and consquently the slippery rope tends to " creep " through the splice as its not tightening hard enough on itself. I now insert the end of the line 3 times through itself rather than the 2 as marlow recommends and have'nt had any bother since. <img src="http://www.catsailor.com/forums/images/graemlins/cool.gif" alt="" /> As to increasing the drag by 2%, can you check that as my instinct would say .002 as that is a huge increase in drag
Last edited by waynemarlow; 07/14/08 03:00 PM.
| | | Re: Changing the stays or trap wires
[Re: waynemarlow]
#149481 07/15/08 04:12 PM 07/15/08 04:12 PM |
Joined: Sep 2007 Posts: 571 Hamburg Smiths_Cat
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Posts: 571 Hamburg | As to increasing the drag by 2%, can you check that as my instinct would say .002 as that is a huge increase in drag cD_shrouds = diameter_shrouds * length_shrouds * 2 * cd / area_sail, with cd of tubes, ropes etc. of about 1. Going from 3mm to 5mm of 2 * 6m shrouds for a boat with 14m² sail area creats a delta drag of 0.0017. If the total drag of your boat is around 0.1, than you have an estimated drag increment of 1.7% = 2%. Cheers, Klaus | | | Re: Changing the stays or trap wires
[Re: Mark P]
#149486 07/24/08 01:45 PM 07/24/08 01:45 PM |
Joined: Sep 2005 Posts: 893 waynemarlow
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Posts: 893 | The Brummel Splice won't work with the D12as its plaits are too close together, try the Marlow Web site http://www.marlowropes.com/public/pageManager.cfm?page_id=207 which has a nice simple piccie sequence <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" /> | | | Re: Changing the stays or trap wires
[Re: waynemarlow]
#149489 07/26/08 12:48 PM 07/26/08 12:48 PM |
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Posts: 571 Hamburg | It is covered 12 strand SK75, should be comparable.
Well, I have pre stretched them with about 300kg 10 times. Than put them on the boat and streched again. After one week (without sailing, but mast up and tensioned) I went sailing (strong winds) and after a few minutes they were stretched another 6cm. At the end that means the windward forstay and the main sheet has to take nearly all the load). Back on the beach I had to tension again. That is what I meant with "difficult to tension".
Regarding stiffness, it depends on the rope diameter of course. If you select the diameter by breaking strength (equal diameter for wire and D12), D12 will stretch 1% at 20% load and wire 0.2% at the same loading, hence wire is 5 times stiffer. To get the same stretch, you have at least to double the diameter. However I don't know how important shroud stiffness is, if your boat is conventional rigged (left and right shroud + one forestay). However if you have two forestays, it plays an important role.
If I have to re-tension again after the next sailing or if the leeward forsetay constantly comes slacky, I will switch back to wire <img src="http://www.catsailor.com/forums/images/graemlins/frown.gif" alt="" />.
Cheers,
Klaus | | | Re: Changing the stays or trap wires
[Re: waynemarlow]
#149491 07/27/08 01:00 PM 07/27/08 01:00 PM |
Joined: Jan 2005 Posts: 6,049 Sebring, Florida. Timbo
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Posts: 6,049 Sebring, Florida. | Given the dificulty, cost, drag, durability, etc. of switching from wire to dyneema (or what have you) I wonder what is the benefit supposed to be?
Is this all just to reduce total weight on the boat? What about the wind drag of the fatter line vs. the skinny wire? Has anyone weighed their 3 wires (ok, 7 if you include both trap lines) vs. the lines? How much total weight savings is there?
Even most A cats are still using wires vs. line, at least for the rigging if not the trap wires too.
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