fstz28 0 #1 December 3, 2003 besides different canopy sizes, once under canopy how can you get more forward travel into winds(~15knots guess). had a jump today where winds were picking up and luckily stayed on the dz. Think i only covered about two hundred yards in the descent from 3k. sabre 230 at 1.1 canopy control class in the future yep Quote Share this post Link to post Share on other sites
tinfoil 0 #2 December 3, 2003 If I remember right, I've been told to pull down both rear risers. “- - Sumo is the greatest of sports. It has power, grace, speed and cluture. And most importantly, two fat bastards smacking the shit out of each other. ” Quote Share this post Link to post Share on other sites
ianmdrennan 2 #3 December 3, 2003 Into winds (the 15mph stated) rear risers/toggles will not help you gain distance, you'll cover less ground over a longer period of time, but it'll still be less ground at those speeds. You can use front risers, but that comes at the expense of altitude or you can let your canopy fly on full drive. General rules of thumb: With the wind or no wind - Rears or toggles (depending on canopy some will go further than others in those configurations) Into wind - Full drive or front risers (be careful with this one). Blue skies IanPerformance Designs Factory Team Quote Share this post Link to post Share on other sites
tinfoil 0 #4 December 3, 2003 Oops, I was wrong, thanks for the correction. “- - Sumo is the greatest of sports. It has power, grace, speed and cluture. And most importantly, two fat bastards smacking the shit out of each other. ” Quote Share this post Link to post Share on other sites
Hooknswoop 19 #5 December 3, 2003 Get small. Tuck your legs up and bring your arms in, qnything to reduce drag. The faster you are going (airspeed) the bigger a difference this makes. The only other thing you can do is sacrafice altitude (you'll descend faster) by pulling down both front risers. I wouldn't recommend this in turbulence. If you have plenty of altitude, like 3,000 feet, it might be better to turn, run with the wind and find a better landing area besides the DZ. Trying to make it back in marginal conditions has been a factor in a number of injuries and fatalities. Derek Quote Share this post Link to post Share on other sites
kallend 1,623 #6 December 3, 2003 QuoteInto winds (the 15mph stated) rear risers/toggles will not help you gain distance, you'll cover less ground over a longer period of time, but it'll still be less ground at those speeds. You can use front risers, but that comes at the expense of altitude or you can let your canopy fly on full drive. General rules of thumb: With the wind or no wind - Rears or toggles (depending on canopy some will go further than others in those configurations) Into wind - Full drive or front risers (be careful with this one). Blue skies Ian A year or so back there was a longish thread about penetration into wind in which some numbers were crunched. IIRC the conclusion is that front risers only help increase distance covered over the ground when the wind speed is comparable to the canopy flight speed (30kt or thereabouts). Reducing drag by getting small has less of an effect than you might think too, because the extra speed turns into extra lift and keeps you up longer in the adverse winds. Getting small helps more when running downwind. To a first approximation the forward speed of a canopy is the speed at which the lift produced equals the suspended weight. Which leads to the conclusion that wearing additional weight is probably the best way to go. (NOTE - glider pilots carry extra ballast to increase penetration when required).... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
freakydiver 0 #7 December 3, 2003 But don't glider pilots also have positive lift at their disposal? I would think given all factors being equal - two canopy drivers under identical canopies at different weights - wont the heavier of the two simply descend faster? Just curious... -- (N.DG) "If all else fails – at least try and look under control." -- Quote Share this post Link to post Share on other sites
Hooknswoop 19 #8 December 3, 2003 QuoteReducing drag by getting small has less of an effect than you might think too, because the extra speed turns into extra lift and keeps you up longer in the adverse winds. Getting small helps more when running downwind What would estimate the increase in speed is and decrease in rate of descent is? Derek Quote Share this post Link to post Share on other sites
JumpCrazy 0 #9 December 4, 2003 Double fronts has worked for me before. The winds were strong but steady (not gusting). In full flight I was coming straight down above a fence and was at about 100'. I applied some front riser pressure (only pulled 2-3") and moved about 10-15' past the fence. I released the front risers by about 50' and landed safely (not on the fence). I jump a silhouette 150 loaded at 1.1Flying Hellfish #470 Quote Share this post Link to post Share on other sites
fstz28 0 #10 December 4, 2003 thanks, hopefully the weather down here will be nice tommorrow and i'll give it a try and see how much difference that makes! thanks for all the help all! Quote Share this post Link to post Share on other sites
ianmdrennan 2 #11 December 4, 2003 Not to overstate the obvious, but I want to make sure we've not assumed you realize this....let go of the fronts WAAAAAY up high. Don't ride them low at your experience level. Sorry if you already knew this, just want to make sure Blue skies IanPerformance Designs Factory Team Quote Share this post Link to post Share on other sites
Hooknswoop 19 #12 December 4, 2003 Long Spot Techniques There are several things you can do to increase the chances of getting back to the landing area from a long spot. If you are up-wind of the landing area, as soon as safely possible, turn using you rear risers to face the landing area. Turn quickly, but as flat as possible to reduce the amount of altitude lost in the turn. Don’t make a long spot worse by flying in the wrong direction while stowing your slider, loosing your chest strap, etc. Different canopies and even different wing loading react differently to techniques for increasing the glide ratio, allowing you to cover the most ground and keeping you in the higher upper tailwinds longer. One method is to simply leave the brakes stowed, which allows the canopy to “float”, and steer with rear riser input or harness steer. Another is to release the brakes and pull down slightly on the rear risers, flatting the canopy and getting a longer glide. Sometimes, canopies will glide the most with the brakes set and the rear risers pulled down an inch or two. Experiment and determine what works best for your canopy and wing loading. Try to use harness steering to keep the canopy pointed back to the landing area as any toggle input adds drag and decrease you chances of making it back to the landing area. Reducing drag by pulling your legs up in front of you and collapsing your slider will help you cover more ground back to the drop zone. The faster the canopy, the more this will help. This is also where a collapsible pilot chute can help. If you are downwind of the landing area, the amount of headwind will affect which technique will yield the best results. Given the following figures for a hypothetical canopy's performance in braked, full-flight, and front risered flight, the best technique for different headwinds can be calculated. Example 1: Zero Wind Rear Risers (RR): Full flight (FF): Front risers (FR): Airspeed = 25 mph (2200 fpm) Airspeed = 35 mph (3080 fpm) Airspeed = 45 mph (3960 fpm) Ground speed = 25 mph Ground speed = 35 mph Ground peed = 45 mph Rate of descent = 750 fpm Rate of descent = 1250 fpm Rate of descent = 2000 fpm Time of flight = 2.67 minutes Time of flight = 1.60 minutes Time of flight = 1.0 minutes Glide ratio: 2.9:1 Glide ratio: 2.5:1 Glide ratio: 2:1 Ground distance covered = 5874 ft Ground distance covered = 4928 ft Ground distance covered = 3960 ft For Example 1, Rear risers (RR) yields the best glide ratio and the most ground distance covered. Example 2: 5 mph Headwind Rear Risers (RR): Full flight (FF): Front risers (FR): Airspeed = 25 mph (2200 fpm) Airspeed = 35 mph (3080 fpm) Airspeed = 45 mph (3960 fpm) Ground speed = 20 mph Ground peed = 30 mph Ground speed = 40 mph Rate of descent = 750 fpm Rate of descent = 1250 fpm Rate of descent = 2000 fpm Time of flight = 2.67 minutes Time of flight = 1.60 minutes Time of flight = 1.0 minutes Ground distance covered = 4699 ft Ground distance covered = 4224 ft Ground distance covered = 3520 ft In Example 2, with a 5 mph headwind, the best technique is still rear risers, but with 1175 ft less ground distance covered. Example 3: 10 mph Headwind Rear Risers (RR): Full flight (FF): Front risers (FR): Airspeed = 25 mph (2200 fpm) Airspeed = 35 mph (3080 fpm) Airspeed = 45 mph (3960 fpm) Ground speed = 15 mph Ground peed = 25 mph Ground speed = 35 mph Rate of descent = 750 fpm Rate of descent = 1250 fpm Rate of descent = 2000 fpm Time of flight = 2.67 minutes Time of flight = 1.60 minutes Time of flight = 1.0 minutes Ground distance covered = 3524 ft Ground distance covered = 3520 ft Ground distance covered = 3080 ft In Example 3, rear risers and full flight produce almost the same result in ground distance covered. Example 4: 15 mph Headwind Rear Risers (RR): Full flight (FF): Front risers (FR): Airspeed = 25 mph (2200 fpm) Airspeed = 35 mph (3080 fpm) Airspeed = 45 mph (3960 fpm) Ground speed = 10 mph Ground peed = 20 mph Ground speed = 30 mph Rate of descent = 750 fpm Rate of descent = 1250 fpm Rate of descent = 2000 fpm Time of flight = 2.67 minutes Time of flight = 1.60 minutes Time of flight = 1.0 minutes Ground distance covered = 2350 ft Ground distance covered = 2816 ft Ground distance covered = 2640 ft In Example 3, full flight moves up to the best technique, front risers moves up to the second best technique and rear risers goes from the best to worst technique. Example 5: 20 mph Headwind Rear Risers (RR): Full flight (FF): Front risers (FR): Airspeed = 25 mph (2200 fpm) Airspeed = 35 mph (3080 fpm) Airspeed = 45 mph (3960 fpm) Ground speed = 5 mph Ground peed = 15 mph Ground speed = 25 mph Rate of descent = 750 fpm Rate of descent = 1250 fpm Rate of descent = 2000 fpm Time of flight = 2.67 minutes Time of flight = 1.60 minutes Time of flight = 1.0 minutes Ground distance covered = 1175 ft Ground distance covered = 2112 ft Ground distance covered = 2200 ft In example 5, front risers moves up to best technique and full flight drops back to second best technique. * Information based on a hypothetical canopy with the following performance: On rear risers, Airspeed = 25 mph and rate of descent = 750 fpm. In full flight, airspeed = 35 mph, and rate of descent = 1250 fpm. On front risers, airspeed = 45 mph and rate of descent = 2000 fpm. As the headwinds increase, the best to worst techniques do not change after a 20-mph headwind, for this hypothetical canopy. Which technique that will work best for the amount of headwinds you are fighting depending on your canopy. Experiment in controlled conditions to determine which technique qorks best for you and your canopy. Generally wind speed decreases with altitude from the friction of the earth's surface. Remember that landing at the drop zone is secondary to landing safely. If you are not absolutely sure you will make it back to the drop zone, select a safe alternate landing zone early and plan your approach. Jumpers pushing the limits of a long spot, determined to land back at the drop zone has been a factor in numerous landing injuries. When in doubt, land out. Derek Quote Share this post Link to post Share on other sites
marks 0 #13 December 4, 2003 QuoteOne method is to simply leave the brakes stowed, which allows the canopy to “float”, and steer with rear riser input or harness steer i have two good freinds that have been paralysed because they didnt unstow there brakes till about 500-800 ft just because of a long spot.. then the canopy collapesed when they did.. make sure the canopy is square stable and steerable.. then you can hang in half brakes if you like Quote Share this post Link to post Share on other sites
Hooknswoop 19 #14 December 4, 2003 Quotei have two good freinds that have been paralysed because they didnt unstow there brakes till about 500-800 ft just because of a long spot.. then the canopy collapesed when they did.. make sure the canopy is square stable and steerable.. then you can hang in half brakes if you like Excellent point, release your brakes high enough to deal with a brake problem. Derek Quote Share this post Link to post Share on other sites
johnny1488 1 #15 December 4, 2003 this was less than 3 weeks ago Hang on to your legstraps if you want to float in brakes. Johnny --"This ain't no book club, we're all gonna die!" Mike Rome Quote Share this post Link to post Share on other sites
kallend 1,623 #16 December 4, 2003 QuoteQuoteReducing drag by getting small has less of an effect than you might think too, because the extra speed turns into extra lift and keeps you up longer in the adverse winds. Getting small helps more when running downwind What would estimate the increase in speed is and decrease in rate of descent is? Derek Good question. To get a proper estimate you'd need the slope of the lift and drag curves, which is the kind of information only manufacturers would have. However, I'll make a stab at a rough calculation tomorrow. Do you have any feel for the % drag reduction achievable by getting small? I'd imagine it's not much, given the total drag of the canopy/lines/skydiver system. For a 200lb skydiver the drag in freefall at 180fps terminal is 200lb force. At 45fps under canopy that drag (for a basically similar body position) will be 200*(45/180)^2 = 12.5 lb. If the glide ratio is 3:1, the total drag will be around 70lb force. If you can cut your body drag by 1/3 by getting small, this is still only 6% of the total system drag. Rest to follow, I'm going to bed.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
Hooknswoop 19 #17 December 4, 2003 QuoteGood question. To get a proper estimate you'd need the slope of the lift and drag curves, which is the kind of information only manufacturers would have. However, I'll make a stab at a rough calculation tomorrow. Cool, thanks. QuoteDo you have any feel for the % drag reduction achievable by getting small? Nope, that's why I asked you. I figured you could come up with something I could work with. I do know it makes a difference. It makes a huge difference under my 60. QuoteI'd imagine it's not much, given the total drag of the canopy/lines/skydiver system. For a 200lb skydiver the drag in freefall at 180fps terminal is 200lb force. At 45fps under canopy that drag (for a basically similar body position) will be 200*(45/180)^2 = 12.5 lb. If the glide ratio is 3:1, the total drag will be around 70lb force. If you can cut your body drag by 1/3 by getting small, this is still only 6% of the total system drag. I'll work w/ 6% and see what I come up with. QuoteRest to follow, I'm going to bed. Night, Derek Quote Share this post Link to post Share on other sites
kallend 1,623 #18 December 4, 2003 QuoteQuoteGood question. To get a proper estimate you'd need the slope of the lift and drag curves, which is the kind of information only manufacturers would have. However, I'll make a stab at a rough calculation tomorrow. Cool, thanks. QuoteDo you have any feel for the % drag reduction achievable by getting small? Nope, that's why I asked you. I figured you could come up with something I could work with. I do know it makes a difference. It makes a huge difference under my 60. QuoteI'd imagine it's not much, given the total drag of the canopy/lines/skydiver system. For a 200lb skydiver the drag in freefall at 180fps terminal is 200lb force. At 45fps under canopy that drag (for a basically similar body position) will be 200*(45/180)^2 = 12.5 lb. If the glide ratio is 3:1, the total drag will be around 70lb force. If you can cut your body drag by 1/3 by getting small, this is still only 6% of the total system drag. I'll work w/ 6% and see what I come up with. QuoteRest to follow, I'm going to bed. Night, Derek OK here goes: Assume 200lb weight, 30mph (44fps) forward speed, 3:1 glide ratio initially. Descent rate is 10mph = 14.67fps. It takes 68 seconds to descend 1000ft, covering 3000ft forward in still air in this time. Distance covered for various headwinds is as folllows: wind (mph) distance (ft) 0 3000 15 1500 25 499 35 - 499 (backing up) Drag is then reduced as in previous post. I don't believe the lift and drag coefficients change significantly because although there will be an angle of attack change due to a change (reduction) in glideslope angle by about 1 degree, it will be almost exactly canceled by the trim change (increase) due to the drag reduction being located below the canopy, which will cause the jumper to move forward slightly (The line joining the skydiver's CG with the center of lift of the canopy will tilted by around 4 degrees due to the drag force on the skydiver, and this will change by a degree or so as the drag is reduced). SO we will ignore changes in Cl and Cd as alpha will be assumed constant. The net change in drag increases the lift/drag ratio to 3.18. In still air the new glide ratio will also be 3.18 In equilibrium, the vector sum of lift + drag = gravitational force. In the original configuration this requires the lift force to be 189.7lbf. The new low drag configuration requires the lift force to be 190.4lb. The canopy must accelerate to 30.06mph (44.09fps) to achieve this. The new descent rate is 44.09/3.18 = 13.9fps, so it takes 71.9 seconds to descend 1000ft Distances covered in various headwinds: wind(mph) distance(ft) 0 3180 15 1582 25 527 35 -527 So comparing before and after: wind change in distance (ft) 0 180 15 82 25 28 35 -28 The advantage of reducing drag disappears as the headwind gets stronger, due to the decrease in descent rate leading to more time spent in the adverse winds. ... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
kallend 1,623 #19 December 4, 2003 Quote*** Nope, that's why I asked you. I figured you could come up with something I could work with. I do know it makes a difference. It makes a huge difference under my 60. Derek I don't wish to repeat the calculation for all possible configurations but the following observations come out: The faster the canopy flies the greater the % of drag contributed by the skydiver's body, so the drag reduction effect will be greater and you will see a better improvement both in glide ratio and in forward speed. The improvement in penetration is positive up to the point that the headwind is equal to the airspeed of the canopy. So a small highly loaded canopy will see a benefit of getting small at a windspeed where a large student canopy would see no improvement at all. For a tailwind, there is always an improvement in distance covered if you reduce drag (there is no "sail" effect). All of the above assume a lifting (airfoil) canopy where the primary force opposing gravity is aerodynamic lift. Does not apply to rounds.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
Hooknswoop 19 #20 December 4, 2003 I agree with both your posts completely. Thanks for taking the time to run through this stuff. Derek Quote Share this post Link to post Share on other sites
kallend 1,623 #21 December 4, 2003 Slightly OT. When I typed in the speed - distance tables they were nicely formatted, but they come out wrong on the posts. Does anyone know a way of forcing the format using markup or some other way?... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
twnsnd 1 #22 December 4, 2003 Holy shit prof! It would take me all day to write a post sounding half as intelligent. -We are the Swoophaters. We have travelled back in time to hate on your swoops.- Quote Share this post Link to post Share on other sites
Jimbo 0 #23 December 4, 2003 Slightly off topic for the forum, but what the hell. Using the (pre) (/pre) tags will keep the text formatting. Line item 5 Line item 4 Line item 3 Line item ... - Jim"Like" - The modern day comma Good bye, my friends. You are missed. Quote Share this post Link to post Share on other sites
marks 0 #24 December 5, 2003 Quotethis was less than 3 weeks ago Hang on to your legstraps if you want to float in brakes. thats what i do.. i hold my brakes low down and loop my thumb through my hip ring ..... very relaxing.... nice! Quote Share this post Link to post Share on other sites
