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#1
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Experiences with Dyneema
This started from a thread on winch cable breaks, but I thought I should
start a new thread: On Tue, 28 Jun 2005 20:20:23 +0000, Andreas Maurer wrote: Flying on the same airfield as the Landau Aero Club, I'd like to add a few comments: - There have been lots of cable breaks with Dyneema ropes now (also of other Dyneema cable users - these plastic cables are used by many clubs in Germany now). At the moment my club is not sure if the Dyneema cable is really cheaper to operate than steel cable on the long run. I have been wondering when we would start getting real feedback about Dyneema. I never really believed that it would work out cheaper than steel on a life cycle cost per launch basis. But I had hoped that it would suffer less from cable breaks and snarl-ups etc and be easier to handle, which would make winch launching more user friendly. (After a day of winching it sometimes feels like we spend more time farming than flying.) What does concern me is: - it may be more susceptible to damage due to being mishandled (eg damaged by rubbing on steel parts) leading to a shortening of its useful life. - that on high wear surfaces (eg gravel or tar) it will wear out long before the high capital costs can be recovered. If anybody has first hand experience, please pass it on. Thanks Ian |
#2
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Ian wrote:
This started from a thread on winch cable breaks, but I thought I should start a new thread: On Tue, 28 Jun 2005 20:20:23 +0000, Andreas Maurer wrote: Flying on the same airfield as the Landau Aero Club, I'd like to add a few comments: - There have been lots of cable breaks with Dyneema ropes now (also of other Dyneema cable users - these plastic cables are used by many clubs in Germany now). At the moment my club is not sure if the Dyneema cable is really cheaper to operate than steel cable on the long run. I have been wondering when we would start getting real feedback about Dyneema. I never really believed that it would work out cheaper than steel on a life cycle cost per launch basis. But I had hoped that it would suffer less from cable breaks and snarl-ups etc and be easier to handle, which would make winch launching more user friendly. (After a day of winching it sometimes feels like we spend more time farming than flying.) What does concern me is: - it may be more susceptible to damage due to being mishandled (eg damaged by rubbing on steel parts) leading to a shortening of its useful life. - that on high wear surfaces (eg gravel or tar) it will wear out long before the high capital costs can be recovered. If anybody has first hand experience, please pass it on. Thanks Ian Ian -- We call it Spectra but it's the same material. There is hardly any comparison between our use of 5000 ft (1500 m) stranded steel vs. Spectra working off of a hard-surfaced runway. We have had zero breaks in four or five hundred starts as compared to one break every three or four starts using steel. The Spectra is still not even getting fuzzy after two years of use. The pavement wears out the bottom of the waves in the steel whereas the Spectra is so light it practically floats over the surface on pull-back. On grass steel may work fine, but I don't have any first-hand experience. As far as getting higher tows goes, we don't see a lot of improvement, about 1700 ft (500 m) either way. This is with about 1600 to 2000 lb (700 to 900 kg) of line tension (as best as I can estimate) and 15 kt headwind using a Blanik L-13 and its wishbone cg harness. Bob |
#3
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hello, now we have more than 2800 starts with each drum of dyneema ( 5mm ) and we have somes breaks in the cable with big gliders .. We project to change dynnema by new and we doen't want to use steel cable because if the preise per start is more , for security, and for repar and so one dynnema is the best and our winch is like new : no impact in the winch .. see you Pascal internet site : www.planeur-stflo.net |
#4
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"Ian" wrote in message news This started from a thread on winch cable breaks, but I thought I should start a new thread: What does concern me is: - it may be more susceptible to damage due to being mishandled (eg damaged by rubbing on steel parts) leading to a shortening of its useful life. - that on high wear surfaces (eg gravel or tar) it will wear out long before the high capital costs can be recovered. If anybody has first hand experience, please pass it on. Thanks Ian The feedback I have been getting is that the stuff lasts longer on almost any surface. The key, as Bob Johnson pointed out, is that the weight bearing down on the runway is far less with Spectra/Dyneema. On turf, the stuff should last much longer. Breaks, when they occur, are almost always due to the material getting nicked by a sharp edge - usually where the termination hardware attaches. There seems to be some room for improvements in attachment hardware. It's clear that with extremely long cables, Dyneema delivers higher launches but the benefit is much smaller with short winch runs. If you are fortunate enough to have 2000 meters or more, really high launches are possible. Bill Daniels |
#5
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My very limited experience with Spectra (Dyneema, etc), about 50
launches, was very positive. I've driven maybe 2000+ launches with steel cable. One of the nicest things about the synthetic lines is that they have very little tendency to throw themselves into a tangle when there is a sudden release of tension on the launch (cable break or simulated cable break). Also, a drum of synthetic has much lower inertia than a drum of steel cable so it's easier to control. My only problem, and a very slight one at that, with the synthetic line is that it doesn't sag under it's own weight on launch. The sag of steel cable is a prime indicator of tension. Too much sag means you need to add power, too little means you have too much power on. With the synthetic, this clue is lost. It just looks like a laser beam from the winch to the glider. I still miss the winch... -- Take out the airplane for reply |
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On Thu, 30 Jun 2005 05:19:05 -0700, jouanarp wrote:
now we have more than 2800 starts with each drum of dyneema ( 5mm ) and we have somes breaks in the cable with big gliders .. We project to change dynnema by new and we doen't want to use steel cable because if the preise per start is more , for security, and for repar and so one dynnema is the best and our winch is like new : no impact in the winch .. This is a good indication of what to expect. This is the kind of information we need to justify the investment. Can you please give me some more details: Are you still using the original cable after 2800 launches? Are their any plans to replace it yet? How many launches per break do you get now with the worn cable? What surface do you operate from (it looks like smooth grass from the photo on your web site)? How long is your runway? Thanks Ian |
#7
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In message , Ian
writes On Thu, 30 Jun 2005 05:19:05 -0700, jouanarp wrote: now we have more than 2800 starts with each drum of dyneema ( 5mm ) and we have somes breaks in the cable with big gliders .. We project to change dynnema by new and we doen't want to use steel cable because if the preise per start is more , for security, and for repar and so one dynnema is the best and our winch is like new : no impact in the winch .. This is a good indication of what to expect. This is the kind of information we need to justify the investment. Can you please give me some more details: Are you still using the original cable after 2800 launches? Are their any plans to replace it yet? How many launches per break do you get now with the worn cable? What surface do you operate from (it looks like smooth grass from the photo on your web site)? How long is your runway? And a set of equivalent answers from someone using it on a tarmac runway, ideally with it going across another one would be very useful as it would map directly to our site. Robin Thanks Ian -- Robin Birch |
#8
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At 16:30 30 June 2005, Wallace Berry wrote:
(snip) My only problem, and a very slight one at that, with the synthetic line is that it doesn't sag under it's own weight on launch. The sag of steel cable is a prime indicator of tension. Too much sag means you need to add power, too little means you have too much power on. With the synthetic, this clue is lost. It just looks like a laser beam from the winch to the glider. Does anyone have any experience of what happens with a 'low' cable break. One of the advantages of a 'heavy' wire is that it assists in preventing the tendency of the launch parachute to fly up or is the parachute unecessary with synthetic line? |
#9
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Ian wrote:
This started from a thread on winch cable breaks, but I thought I should start a new thread: On Tue, 28 Jun 2005 20:20:23 +0000, Andreas Maurer wrote: Flying on the same airfield as the Landau Aero Club, I'd like to add a few comments: - There have been lots of cable breaks with Dyneema ropes now (also of other Dyneema cable users - these plastic cables are used by many clubs in Germany now). At the moment my club is not sure if the Dyneema cable is really cheaper to operate than steel cable on the long run. I have been wondering when we would start getting real feedback about Dyneema. I never really believed that it would work out cheaper than steel on a life cycle cost per launch basis. But I had hoped that it would suffer less from cable breaks and snarl-ups etc and be easier to handle, which would make winch launching more user friendly. (After a day of winching it sometimes feels like we spend more time farming than flying.) What does concern me is: - it may be more susceptible to damage due to being mishandled (eg damaged by rubbing on steel parts) leading to a shortening of its useful life. - that on high wear surfaces (eg gravel or tar) it will wear out long before the high capital costs can be recovered. If anybody has first hand experience, please pass it on. Thanks Ian I don't think anyone really ever said it would be cheaper. On a winch launch, rope weight and rope diameter are the only two variables that will have an impact on launch performance (given that there is sufficient power and length). The longer the run, the more impact. All Dyneema/Spectra ropes are not equal. There are more expensive products that have superior strength and abrasion resistence. Superior strength means even less weight and diameter. The performance variables are most significant at the glider end of the rope. Cheaper and larger diameter ropes may enable cost savings at the winch end without impacting launch performance. We have some limited experience with exactly this, steel wire rope at the winch end and a Spectra sample at the glider end. 1000ft or so over a mile run. We achieved 200-400ft/launch improvement. There are several opportunities for improving on this concept. Frank Whiteley |
#10
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The August-September issue of Sailplane & Gliding (out
July 25 in UK) includes a report from the first UK club to trial Dyneema. Helen Editor, S&G www.gliding.co.uk |
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