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#21
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Parachute source for gliders and winches
On Sunday, November 11, 2018 at 4:10:07 PM UTC-5, Dan Marotta wrote:
...On days without cross winds, just carry enough power to keep the chute inflated until it lands. I've never driven the winch, but I've sat in the cab and watched an international cadre of winching masters practice their art. At the two sites that I've done winch launches, operations continued in significant crosswind. Crosswinds seem to be less of a no-go with modern winches. Additional factors make landing the parachute right in front of the winch challenging for even expert winch operators: 1)2000 foot launches means more time to drift 2)less experienced pilots (like me) that insufficiently compensate for the crosswind (by flying the launch to the upwind side of the field). |
#22
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Parachute source for gliders and winches
On Mon, 12 Nov 2018 20:06:57 -0800, son_of_flubber wrote:
I've never driven the winch, but I've sat in the cab and watched an international cadre of winching masters practice their art. At the two sites that I've done winch launches, operations continued in significant crosswind. Crosswinds seem to be less of a no-go with modern winches. On sites with severe cross-wind there's always the parachuteless option. I've seen (and flown with) this setup at The Mynd, The Mynd is on top of a long, steep north-south ridge with the runway parallel to the ridge and close behind the soaring slope. Beyond the runway there's an additional small rise with a valley containing moorland and trees. When the ridge is working, launches and landings are flown in a 90 degree cross-wind. Obviously they can't use a parachute on the launch cable because, when the ridge is working well, the end of the cable would end up over the hill and probably in the downwind forest: the airfield is 250m across at its widest and scrub and trees start 100m downwind of its lee edge. They use a single drum winch with no parachute and the retrieval winch at the launch point: the main cable ends in a metal triangle with the retrieval cable on one corner and the shock rope and strop on the other. No parachute. During the launch a light cable streams off the small retrieval winch. When the glider releases, the main winch is put in neutral and the retrieval winch engages, causing the cable to snap down onto the main runway, and shortly after that, its business end is back at the launchpoint ready for the next launch. The two winch drivers co-ordinate agreement about who is in gear and when by radio. -- Martin | martin at Gregorie | gregorie dot org |
#23
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Parachute source for gliders and winches
On Monday, November 12, 2018 at 9:06:59 PM UTC-7, son_of_flubber wrote:
On Sunday, November 11, 2018 at 4:10:07 PM UTC-5, Dan Marotta wrote: ...On days without cross winds, just carry enough power to keep the chute inflated until it lands. I've never driven the winch, but I've sat in the cab and watched an international cadre of winching masters practice their art. At the two sites that I've done winch launches, operations continued in significant crosswind. Crosswinds seem to be less of a no-go with modern winches. Additional factors make landing the parachute right in front of the winch challenging for even expert winch operators: 1)2000 foot launches means more time to drift 2)less experienced pilots (like me) that insufficiently compensate for the crosswind (by flying the launch to the upwind side of the field). I've operated quite a number of different winches and always found it easy to drop the parachute exactly where I wanted it to land. My technique is to rip the 'chute down from the sky at high speed then stop the drum to drop the 'chute directly in front of the winch. A fast recovery of the rope and 'chute minimizes crosswind effects. Obviously, this depends on a powerful brake which can dependably stop the drum exactly when you want - some testing is required to determine this. Despite occasional screams of panic from onlookers, I have never pulled a 'chute through the rollers nor tangled the cable/rope on the drum doing this. |
#24
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Parachute source for gliders and winches
On Tuesday, November 13, 2018 at 3:37:00 AM UTC-8, Martin Gregorie wrote:
On Mon, 12 Nov 2018 20:06:57 -0800, son_of_flubber wrote: I've never driven the winch, but I've sat in the cab and watched an international cadre of winching masters practice their art. At the two sites that I've done winch launches, operations continued in significant crosswind. Crosswinds seem to be less of a no-go with modern winches. On sites with severe cross-wind there's always the parachuteless option. I've seen (and flown with) this setup at The Mynd, The Mynd is on top of a long, steep north-south ridge with the runway parallel to the ridge and close behind the soaring slope. Beyond the runway there's an additional small rise with a valley containing moorland and trees. When the ridge is working, launches and landings are flown in a 90 degree cross-wind. Obviously they can't use a parachute on the launch cable because, when the ridge is working well, the end of the cable would end up over the hill and probably in the downwind forest: the airfield is 250m across at its widest and scrub and trees start 100m downwind of its lee edge. I don't understand. At glider release the cable is pointing up into the sky at an angle of ... well, I don't know ... let's just say more than 60 degrees. I've never seen a cable being wound in drop below an angle of ... let's say 30 degrees (more like 45 probably, but let's go with 30) until the parachute is within 100m of the winch and speed is falling off. Half your 250m airfield width plus 100m to the trees is 225m. Even if the cable swings around directly downwind the parachute is going to be at least sin(30)*225 = 112m up when it crosses the trees. Your trees aren't that tall. It's a different story if the cable breaks, of course. |
#25
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Parachute source for gliders and winches
On Wednesday, October 31, 2018 at 10:06:09 AM UTC-6, JS wrote:
Saw the ad in the AMA flyer for their Expo in Pomona. SSA Region 12 has a presence there. AMA Expo: https://amablog.modelaircraft.org/am...m-2018-web.pdf Fruity Chutes looks like a good source for chutes, including ballistic chutes. Anything from 12" diameter up. Jim https://fruitychutes.com/ Winch 'chutes need to be VERY robust. I think the best scheme to get cheap winch 'chutes it to obtain an old Tost 'chute and have a parachute rigger make a copy using the Tost as a pattern. I've seen quotes of about $40 where Tost wants about $400. Obviously, you don't need a professional rigger to do this but they will have the heavy sewing machines required. |
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