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#1
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Best Rope to purchase for Auto Tows?
I am looking for the benefit of recent experience with modern ropes
for auto tows. We fly off a 5000 foot grass runway (with a couple of rocky spots). What size and type of rope would be best? Bill Snead |
#2
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Best Rope to purchase for Auto Tows?
On Oct 15, 9:21*pm, " wrote:
I am looking for the benefit of recent experience with modern ropes for auto tows. *We fly off a 5000 foot grass runway (with a couple of rocky spots). *What size and type of rope would be best? Bill Snead Arguably the 'best' would be Amsteel Blue from Sampson Rope (~$0.41/ Ft.) 3/16" diameter would give you 5400 Lbs-F breaking strength and weight about 1Lb/100 feet. It has about 10x the strength/weight and 15x the abrasion resistance of steel. If you prefer, it's available in other colors. http://www.samsonrope.com/index.cfm?rope=192 |
#3
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Best Rope to purchase for Auto Tows?
please see http://www.wingsandwheels.com/page30.htm
I offer all types including Poly ropes, Dacron and Spectra all at very competative prices thanks tim Please visit the Wings & Wheels website at www.wingsandwheels.com wrote in message ... I am looking for the benefit of recent experience with modern ropes for auto tows. We fly off a 5000 foot grass runway (with a couple of rocky spots). What size and type of rope would be best? Bill Snead __________ Information from ESET NOD32 Antivirus, version of virus signature database 5536 (20101016) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com __________ Information from ESET NOD32 Antivirus, version of virus signature database 5536 (20101016) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com |
#4
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Best Rope to purchase for Auto Tows?
On Oct 15, 10:21*pm, " wrote:
I am looking for the benefit of recent experience with modern ropes for auto tows. *We fly off a 5000 foot grass runway (with a couple of rocky spots). *What size and type of rope would be best? 1: Based on personal experience, I would advise against using polypropylene rope for autotow: it's much too elastic. The amount of rubber-banding during the initial part of an autotow launch of a 1000 ft - plus poly rope is very interesting, and adds one extra, unnecessary safety consideration to the first phase of launch: having the rope go completely slack d/t elasticity just about the time the glider is 15 or 20 feet off the ground and barely above stall is, in my judgment, not desirable. 2: After the initial poly experience, our club switched to low-stretch 1/4" dacron rope in 1500' lengths from David Bradley (now via Wings & Wheels). We actually strength-tested our ropes at first; found that new rope broke at about 1700-1800 lb as claimed, and as the rope abraded through being (inevitably) dragged along our highly abrasive 5000-ft runway, during a season the 100 yards of rope nearest the tow vehicle decreased to about 1100-1200 lb (and became the actual weak link). Your experience will be better on grass, though the fibers will pick up sand, that will chafe internally and decrease strength. 3. Jacketed rope would wear longer but is more time-consuming to splice in attaching hardware or when it does break, and is more expensive. We did not try it. 4: I replaced the 1/4" steel cables of my hangar door with 1/4" Spectra, and am very pleased with its durability and the lack of steel slivers We are thinking of changing from Dacron to Spectra next time we buy rope. I would expect tow-vehicle traction to be a concern on a grass runway, as grass is slippery. This would be mitigated with a (slow) running start: use about 50 ft of slack rope, drive the tow vehicle about about 10-15 mph until the slack comes out. Withf 1500 ft of woven rope, this does not jerk the glider; meanwhile, there's less tire spin and it's much easier on the engine and transmission. (Only an automatic transmission is safe and durable; staying in a single gear through the tow is highly desirable, as shifts take the power out of the tow at poor times.) |
#5
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Best Rope to purchase for Auto Tows?
On Oct 17, 3:11*am, danlj wrote:
On Oct 15, 10:21*pm, " wrote: I am looking for the benefit of recent experience with modern ropes for auto tows. *We fly off a 5000 foot grass runway (with a couple of rocky spots). *What size and type of rope would be best? 1: Based on personal experience, I would advise against using polypropylene rope for autotow: it's much too elastic. The amount of rubber-banding during the initial part of an autotow launch of a 1000 ft - plus poly rope is very interesting, and adds one extra, unnecessary safety consideration to the first phase of launch: having the rope go completely slack d/t elasticity just about the time the glider is 15 or 20 feet off the ground and barely above stall is, in my judgment, not desirable. 2: After the initial poly experience, our club switched to low-stretch 1/4" dacron rope in 1500' lengths from David Bradley (now via Wings & Wheels). We actually strength-tested our ropes at first; found that new rope broke at about 1700-1800 lb as claimed, and as the rope abraded through being (inevitably) dragged along our highly abrasive 5000-ft runway, during a season the 100 yards of rope nearest the tow vehicle decreased to about 1100-1200 lb (and became the actual weak link). Your experience will be better on grass, though the fibers will pick up sand, that will chafe internally and decrease strength. 3. Jacketed rope would wear longer but is more time-consuming to splice in attaching hardware or when it does break, and is more expensive. We did not try it. 4: I replaced the 1/4" steel cables of my hangar door with 1/4" Spectra, and am very pleased with its durability and the lack of steel slivers We are thinking of changing from Dacron to Spectra next time we buy rope. I would expect tow-vehicle traction to be a concern on a grass runway, as grass is slippery. This would be mitigated with a (slow) running start: use about 50 ft of slack rope, drive the tow vehicle about about 10-15 mph until the slack comes out. Withf 1500 ft of woven rope, this does not jerk the glider; meanwhile, there's less tire spin and it's much easier on the engine and transmission. (Only an automatic transmission is safe and durable; staying in a single gear through the tow is highly desirable, as shifts take the power out of the tow at poor times.) I would agree with the above. UHMWPE/Dyneema/Spectra/Amsteel Blue are essentially the same thing and due to their high strength and light weight are the preferred rope material. (It's good to see Tim Mara selling Spectra at a very good price.) We did a bunch of math on auto tow on the winch interest groups. Straight auto tow requires a lot of room so doesn't make good use of runway length. Going to a 2:1 "two-pulley" system with the rope anchored at the upwind fence next to a pulley and a pulley on the tow car converts the operation to essentially a winch and reduces the tow car speed by half - but it also doubles the traction effort required. The heaviest gliders require a black 10,000 DaN (2200 LbF) weak link so the tow car would need to produce up to a 4400 LbF tractive effort which is probably more than a grass surface can support. Most operations serious about ground launch convert to a winch which isn't limited by traction and does less damage to airfield grass. Well run, a winch his faster to cycle than auto tow. |
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