Push 0 #1 July 9, 2003 Ok, this is kind of long, but please bear with me. I have a Triathlon. It was built before they did that update, but the previous owner relined it, so the lineset has been updated. I've recently started jumping it and I'm noticing a built in left turn. It's a fairly slow turn, maybe a degree a second or so. If I wait a long time I will start drifting off heading, and it's just severe enough to require correction on final approach. This is, of course, annoying, since I need to keep the right control line under tension to fly straight. It doesn't seem to be my weight in the harness because moving around in it does nothing (the Triathlon is completely square, planform factor 0). Two riggers checked the length of the lines and found nothing except a 1/4 inch offset in the control lines, which will do nothing anyway because the slack in those lines is much greater than 1/4 inch in full flight, and the canopy is turning in full flight. Finally, I inspected the shape of the wing. Basically, I checked that the stitching on the canopy is symmetrical. Here's what I found. Basically, I start from the center cell and work outwards. So I would take the 3rd and 5th cells and check that all the stitches are the same length. Same with the 2nd and 6th, etc. I didn't check every single seam. I checked the nose and the tail, and they're symmetrical. Then I started checking the ribs. I compared the outermost ribs on the outermost cells (the 1st and 7th). These are the ribs that have no canopy to one of their sides. See my poor excuse for a drawing for more explanation. One of these ribs is about half an inch shorter than the other. The left rib is shorter, so that side would be generating less lift and my weight would effect it more, bringing the left half of the nose of the canopy down and causing a slow left diving turn. The other ribs seem even. My question is, it's a pretty small difference. Could this be what is causing the turn? If so, is there an easy way to fix it without ruining the performance of the airfoil and/or endangering the lineset? I was thinking of tying a knot in the other A line to pull down the right rib until they balance, but I'm not sure what effect that would have on the strength of the line. Do I have to send it to Aerodyne or could a rigger undo the bartack and move the line attachment point? Thanks for reading this far -- Toggle Whippin' Yahoo Skydiving is easy. All you have to do is relax while plummetting at 120 mph from 10,000' with nothing but some nylon and webbing to save you. Quote Share this post Link to post Share on other sites
darkwing 4 #2 July 9, 2003 The critical piece of missing information is how much toggle dies it take to correct the turn? At least in the old days and I suspect now also a manufacturer has a turn tolerance, that is, some specified number of inches of toggle to correct a built-in turn is allowed before any repair action is taken. I can perhaps justify the rib difference as causing the turn, and if it is worth the effort (and my sense with limited information is that it is not), then shortening the other rib is a fairly easy modification. -- Jeff My Skydiving History Quote Share this post Link to post Share on other sites
Push 0 #3 July 9, 2003 I will talk to my rigger tomorrow, maybe have someone more experienced jump that canopy and make the call. Either way, I will let this message board know, it can be educational. As to the toggle input, I need to pull the right toggle maybe half way down the riser. -- Toggle Whippin' Yahoo Skydiving is easy. All you have to do is relax while plummetting at 120 mph from 10,000' with nothing but some nylon and webbing to save you. Quote Share this post Link to post Share on other sites
rhino 0 #4 July 9, 2003 1. make sure your leg straps are perfectly even. 2. make sure their are no twists in your brake lines. 3. Make sure your brake lines are even. 4. If you have done 1-3 see your friendly neighborhood rigger Rhino Quote Share this post Link to post Share on other sites
usskydiver 0 #5 July 9, 2003 I think the winds the canopy is flying in would also make a difference. It is my exerience that all steerable round parachutes will eventually and on their own, turn and run with the wind. Something to consider. Tim Maggot Quote Share this post Link to post Share on other sites
jmidgley 0 #6 July 9, 2003 It's an immutable rule that any discussion of flight will eventually resolve into a debate about whether a wing 'knows' whether it's pointing into wind or downwind. I must say I'm delighted to see this happening after only four posts; I'll stand back and watch what happens next... John Quote Share this post Link to post Share on other sites
riggerrob 558 #7 July 9, 2003 QuoteIt's an immutable rule that any discussion of flight will eventually resolve into a debate about whether a wing 'knows' whether it's pointing into wind or downwind. I must say I'm delighted to see this happening after only four posts; I'll stand back and watch what happens next... John >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Hee! Hee! ... while pulling up a chair .... Quote Share this post Link to post Share on other sites
Push 0 #8 July 9, 2003 Believe it or not, I've done steps one through four and noone still has any idea what's causing the turn. Until now, that is. In fact, I'm gonna see my friendly neighbourhood rigger later in the day. As to the chute turning into the wind, that sounds impossible. When a canopy is in an airmass, it's irrelevant which way that airmass is moving, no? -- Toggle Whippin' Yahoo Skydiving is easy. All you have to do is relax while plummetting at 120 mph from 10,000' with nothing but some nylon and webbing to save you. Quote Share this post Link to post Share on other sites
fundgh 0 #9 July 9, 2003 I think it is like letting a rowboat go down a river...it may tend to turn up river if you are holding the nose from solid ground, but once free, it will go any which way it wants. Of course a canopy will fly straight (hopefully) without input, but does it seek wind ...um I don't think so....FUN FOR ALL! Quote Share this post Link to post Share on other sites
Gadget 0 #10 July 9, 2003 I had one of those triatlon's to.It also had a build in left turn.Because it was new i returned it to aerodyne.I don't know what they did with it because i got a new one and this runs straightIf people from Poland are called Poles, why aren't people from Holland called Holes??? My logbook Quote Share this post Link to post Share on other sites
usskydiver 0 #11 July 9, 2003 I stand by my statement that all steerable parachutes will turn (on their own) and run with the wind eventually. I've experienced this on Tandems, my Velocity 103 (Love it!!) and a T-10B from 500 feet while jumping into combat in Panama and trying to get my rucksack lowered before it broke my femurs (would have been the 2nd break for the Left femur...the orthopod would have had fun getting the pre-existing femoral nail out) Tim Maggot Quote Share this post Link to post Share on other sites
billvon 2,426 #12 July 9, 2003 >I stand by my statement that all steerable parachutes will turn (on >their own) and run with the wind eventually. I think the reason people believe this is that, if you're on final and thus actually care about facing into the wind, any turn at all is a turn downwind. I've seen it in countless students that I'm talking down - I'll say "hands up! Get ready to flare!" and the canopy starts to turn downwind. Of course, if I told them to turn downwind and do exactly the same thing, the canopy would be just as likely to turn, except then it would turning _upwind._ And it also does the same thing at 2000 feet, but at 2000 feet I don't care much that it's got a slow left turn going. Quote Share this post Link to post Share on other sites
cheneyneel 0 #13 July 10, 2003 Are you sure that it is the canopy? Have you had another canopy in that harness? Have you hooked it up to another harness to see? I had a harness that was not symetrical from the factory and it caused a slow drifting turn.. They fixed it but for months I thought it was the canopy and couldnt find anything wrong with it.. As far as your actual questions I know nothing!!Sorry! Quote Share this post Link to post Share on other sites
Push 0 #14 July 10, 2003 Hey, good point. I'll break out the measuring tape on the harness first thing tomorrow. -- Toggle Whippin' Yahoo Skydiving is easy. All you have to do is relax while plummetting at 120 mph from 10,000' with nothing but some nylon and webbing to save you. Quote Share this post Link to post Share on other sites
