This sounds a bit more complicated than I was envisioning, but I'm still willing to do it. The stars are going to have to align to find a time when I can get multiple willing pilots of significantly different weights to do this on the same day in smooth conditions, but it would be great to finally get some data on how weight affects tension. I doubt I'll be able to do it with different tugs with the same day/conditions, but hopefully Lookout'll let me use the gauge so I can get something for comparison.
Tad Eareckson wrote:This cylinder/gauge combo is the same one I use for my load tester...
So I take it your load tester will be out of commission as long as I have it.
Tad Eareckson wrote:A barrel release is installed on the cylinder's fixed/upwind end.
Any way I can rig one of my current releases? I figure they'd be too far forward to reach. I guess if all else fails I could use a Bailey (don't worry, I'll have a hook knife), or maybe a Mason with a long release lanyard.
Tad Eareckson wrote:The barrel release engages the back end of 324 pound (18 stitch) Towline Shear Link...
Will Shear Link abrasion be an issue? If not for aerotowing, it seems like it would be a problem for winch towing...we don't use a parachute on the end of the line (due to air traffic concerns).
Tad Eareckson wrote:We're only interested in the steady state climb reading. Lows and highs are meaningless - we already know they can go down to zero and up to weak link.
Still, I'd be interested in seeing how it varies (both how much and in response to what)...
Tad Eareckson wrote:Have the tug plan to end the tow at five hundred feet
This sounds a bit more complicated than I was envisioning...
Yeah, there's a reason that you don't hear a whole lot of actual numbers on aerotow tens- pressures - especially from a culture that's been perfecting aerotowing for nearly twenty years and has no freakin' clue what a weak link is, let alone what the crap it's using blows at.
The stars are going to have to align to find a time when I can get multiple willing pilots of significantly different weights to do this on the same day in smooth conditions, but it would be great to finally get some data on how weight affects tension.
Doesn't hafta be on the same day or extraordinarily smooth conditions and we don't need lotsa varying weight guinea pigs.
- A few seconds of smooth climb is all you need to get a good reading.
- I think if we get just a couple/three data sets we can figure out the math to predict what happens in between and off the ends - tensions, lift to drag ratios, flying weights, rates of climb...
I doubt I'll be able to do it with different tugs with the same day/conditions, but hopefully Lookout'll let me use the gauge so I can get something for comparison.
Do it over a period of years. (And make sure not to mention my name at Lookout.)
So I take it your load tester will be out of commission as long as I have it.
No, it's a duplicate assembly.
Any way I can rig one of my current releases?
If you've got any good/better ideas then go for them.
I figure they'd be too far forward to reach.
I got into a moderately ugly situation on my first flight with this thing.
I had been DYING to get a number for a couple of DECADES and I was so happy to FINALLY be seeing one on the gauge that I locked onto it early on takeoff and was all over the place really fast and pretty low.
I was heading for a lockout and I had badly underestimated what the tow tension would do to move the configuration forward. I hadn't considered how much slop would be taken out of my harness and the distortion that would occur on top of that.
I had my arm fully extended and was real happy to get a few fingertips on the back end of the barrel.
I guess if all else fails I could use a Bailey...
No, don't put any releases aft of the cylinder.
I'm gonna be stitching you a fixed bridle just long enough to keep you from getting strangled by your shoulder straps being pulled together in order to make sure the release is within comfortable range no matter what.
This configuration is NOT optimized for a worst case scenario but you're not gonna be flying in conditions in which a worst case scenario situation is gonna be a possibility.
And you're still gonna be multiples more bullet resistant than all the Davis clone pro-towers launching at Zapata.
I'm normally no fan of K.I.S.S. but for this specialized application...
...(don't worry, I'll have a hook knife)...
I'm worried that you'll have a hook knife. Promise me you'll leave it in the car.
...or maybe a Mason with a long release lanyard.
That wouldn't be bad but the barrel is simpler and better. Better slack line performance and at weak link you can blow tow with a sixteen pound pull.
Will Shear Link abrasion be an issue?
I designed them, as best as I could, to be dragged - on grass anyway. I'd prefer they didn't get dragged on pavement - especially with the thimbles installed - but I'd be real interested to see how they hold up on grass and maybe a bit of dirt.
Still, I'd be interested in seeing how it varies (both how much and in response to what)...
Wanna see the needle go:
- up really fast? Push out.
- down really fast? Pull in.
Pretty dramatic.
Why five hundred?
That should be plenty enough to get all the information you need, deal with the cylinder after release, and land - but pick whatever number you like.
It's a function of the particular hydraulic cylinder I'm using - a Bimba H-091-DUZ.
The inside diameter is one and a sixteenth - the smallest I could get in that flavor and something that rather nicely covers the range of forces we're dealing with in towing.
The pressure on the piston if you pump vegetable (soybean) oil into the piston face end of the cylinder at one pound PSI is 0.88664 pounds 'cause that's the surface area of the piston face - as determined by the pi(r squared) thing.
But I'm trying to compress oil by pulling on the piston rod coming through the other end of the cylinder. Its diameter is three eighths inches and it takes a 0.11045 square inch circle out of the middle of the piston face on that side.
0.776 square inches of exposed piston face.
So if you pull a hundred pounds on the piston rod a gauge measuring the oil pressure will read 77.6 PSI.
(I hate to admit how long it took me to understand that when I first started getting into this.)
I definitely missed that detail. But the numbers were given in the specs for the cylinder.
Seems obvious in retrospect but I could not figure out the low one or why there even was a low one. Wasn't until I found an online explanation that the lightbulb finally came on.
What pound test do you use for weak links (aero tow)?
Gee hangster, I'da thunk that after fourteen pages on the subject in the June issue of Hang Gliding by the highly (self) esteemed Dr. Trisa Tilletti... http://www.kitestrings.org/post2230.html#p2230
...that it would be absolutely impossible for anyone to be the slightest bit confused on the issue of aerotow weak links - or really much of anything about aerotowing 'cause everybody and his dog knows that...
Towing Aloft - 1998/01
A weak link is the focal point of a safe towing system.
...a weak link is the focal point of a safe towing system.
Thanks Allen. I was tied up on a forum housekeeping project today so I wasn't checking the Jack Show traffic. Now I know why lots of my hit counters started flying up this evening.
Paul Hurless - 2012/08/13 17:49:45 UTC
The link will take you to a website that is mostly the raintings by a couple of outspoken, ill-manndered individuals who denounce everyone else as idiots.
Not everybody, Paul. Just actual idiots.
For example:
Most folk who fly hang gliders are idiots who have no business modifying critical systems they don't have a snowball's chance in hell of understanding.
Yeah Paul, that's from: http://www.kitestrings.org/post6.html#p6
Appreciate your patronage - and your instincts for reading the material most relevant to your particular needs and limitations.
A typical post by one of those individuals.
Guilty as charged, dude. Go fuck yourself.
Last edited by Paul H on 2012/08/13 19:59:33 UTC; edited 2 times in total
Edited twice and "mannered" still has an extra consonant and "rantings" still has an extra vowel. See what I mean about actual idiots and most folk who fly hang gliders having no business modifying critical systems they don't have a snowball's chance in hell of understanding?
2012/08/13 18:53:37 UTC - 3 thumbs up - Sam Kellner
Dennis Wood - 2012/08/13 17:54:59 UTC
Suffolk, Virginia
Jim, as I am starting to play with Elektra Tow (ET) at Quest Air (the battery powered "scooter" tow system you and Adam got me jazzed up about up at Highland) I've watched this thread closely. We all can learn.
Enjoy your posts, as always, and find your comments solid, based on hundreds of hours / tows of experience and backed up by a keen intellect/knowledge of the issues when it comes to most things in general and hang gliding AT/Towing in particular. Wanted to go on record in case anyone reading wanted to know one persons comments they should give weight to.
Tommy.
First, I sent Steve a bunch of info offline. Hopefully it clears things up a bit for him.
Unfortunately, he's stumbled onto some of Tad's old rantings and got suckered in. So most of this was just the same old story of debunking Tad's lunacy... again .
See, the thing is... "we", the people that work at and run aerotow parks, have a long track record.
This stuff isn't new, and has been slowly refined over decades.
We have done quite literally hundreds of thousands of tows.
We know what we're doing.
Sure "there's always room for improvement", but you have to realize the depth of experience you're dealing with here.
There isn't going to be some "oh gee, why didn't I think of that?" moment. The obvious answers have already been explored... at length.
Anyway...
Weaklink material... exactly what Davis said.
It's no mystery.
It's only a mystery why people choose to reinvent the wheel when we've got a proven system that works.
You have to realize the depth of experience you're dealing with there. They've got a proven system that works.
Works to what I've never really heard or understood but it's really hard to go wrong trusting people with that depth of experience.
hangster - 2012/08/13 18:06:59 UTC
I was told 150 -solo
It won't do you a goddam bit of good to be told by some total moron like Rooney or Davis what to use for a weak link. To stand a snowball's chance in hell of becoming an actual PILOT you first hafta know what a weak link IS.
Tost Flugzeuggerätebau
Weak links protect your aircraft against overloading.
If you understand THAT and that we're trying to keep our gliders under three Gs - you know just about everything you need to about weak links.
Or...
If you'd rather go down the rabbit hole, then you can try to understand the rationale behind the 150 solo - independent of flying or maximum certified operating weight. Be sure to get back to me when you think you've got something that makes sense.
Davis Straub - 2012/08/13 18:08:42 UTC
Boise
Used to do 130 lbs. Now do 200 lbs.
And the good news is that since 130 pound Greenspot blows at...
Then again, Russell Brown had us double up behind him after six breaks in a row at Zapata. We couldn't figure out why we had so many breaks so quickly. Maybe just coincidence.
...you can just keep on using 130.
Enjoy yourself in Boise and be careful not to choke to death on the smoke. (Fucking asshole.)
2012/08/14 00:50:18 UTC - 3 thumbs up - Allen Sparks
miguel - 2012/08/13 19:24:31 UTC
That is what T** at K***S***** advocates isn't it?
No. T** at K*** S****** (two words, plural) advocates one and a half times the maximum certified operating weight of the glider - which is pretty much in the middle of 0.8 to 2.0 range mandated by the FAA.
Also...
- When in doubt, go a notch higher.
- You can go higher on smaller solo gliders 'cause they're proportionally stronger than bigger solo gliders.
2012/08/13 21:54:02 UTC - 3 thumbs up - Allen Sparks
Allen Sparks - 2012/08/13 22:06:46 UTC
Kinda like MST3K for hang gliding...
...only different
There's really no mystery...
Tost Flugzeuggerätebau
Weak links protect your aircraft against overloading.
...about this Allen. It only gets confusing when you get total douchebags like...
Dr. Trisa Tilletti - 2012/06
We want our weak links to break as early as possible in lockout situations, but be strong and reliable enough to avoid frequent weak link breaks from turbulence. It is the same expectation of performance that we have for the weak links we use for towing sailplanes.
...Dr. Trisa Tilletti who fly with such pieces of shit for releases that they try to use their weak links as Swiss army knives.
And lemme tell ya sumpin' hangster. There've been A LOT of people really fucked up and really killed trying that lunatic strategy.
But if that's the route you wanna take - and I have very little doubt that it will be - you just stay on The Jack Show and keep listening to total douchebags like Jack, Paul, and Davis.
If, on the other hand, you'd rather not spend the rest of your career as a stupid clone then come over here, listen to the raintings by a couple of outspoken, ill-manndered individuals who denounce everyone else as idiots, and learn something.
Hey hangster...
We've been aerotowing (not that the flavor of towing is the least bit relevant to the issue) hang gliders since the early Eighties.
You ask:
What pound test do you use for weak links (aero tow)?
Allen tells you to go to Kite Strings.
This asshole:
Paul Hurless
tells you that the website that is mostly raintings by a couple of outspoken, ill-manndered individuals who denounce everyone else as idiots - without actually saying that there's anything wrong with the raintings.
Here is the requirement from the 2007 Worlds local rules (which I wrote) for weaklinks:
Pilots must use weaklinks provided by the meet organizers and in a manner approved by the meet organizers. All weaklinks will be checked and use of inappropriate weaklinks will require the pilot to go to the end of the launch line to change the weaklink.
Weaklinks will consist of a single loop of Cortland 130 lb Greenspot braided Dacron Tolling line and should be placed at one end of a shoulder bridle.
But now, based on several decades of experience and hundreds of thousands of tows conducted by numerous aerotow operators across the county, the de facto standard is no longer a 260 pound weak link made as a loop of 130 pound Greenspot IGFA Dacron braided fishing line attached to one end of the pilot's V-bridle.
Now do 200 lbs.
It's a 200 pound weak link made as a loop of 130 pound Greenspot IGFA Dacron braided fishing line attached to one end of the pilot's V-bridle - or shoulder bridle (really doesn't matter).
Have you noticed that NOBODY'S:
- talking about the purpose of the fucking weak link?
- asking you your:
-- flying weight?
-- glider model and size?
I would like to add, however, that at least my reading of accident reports suggest that a fatal glider accident is more likely when the towline fails prematurely. For that reason, I like to stay near the stronger end of the FAR 80 to 200 percent range.
Actually, reading the Pilot's Operating Handbook for several German gliders, I note the weak link for aerotow is specified as an exact figure. For example, the weak link for both aero tow and winch for my Nimbus 2C is specified as 600 KG (1323 Lbs) or a blue Tost weak link. The tolerance is plus or minus ten percent. The US Airworthiness Certificate specifies that the Nimbus 2C is to be flown as specified in the POH. Considering the possible flying weights, this ranges between 95 and 160 percent which is a narrower range than specified in the FARs.
Makes me wonder if we should be using Tost weak links instead of old bits of rope.
So why don't we just go to your Pilot's Operating Handbook and see what it says?
Wills Wing
Always use an appropriate weak link with a finished length of 1.5 inches or less.
I found your conclusion that Tad is a "whack job", and that because of that, you find it justifiable and even "entertaining sometimes to bait that type" to be an indicator of sadistic tendencies.
Such comments make me wonder if those who make them also go around diagnosing then kick sick puppies.
Tad's goal has been to make the towing of hang gliders safer. You can disagree with how he approaches that goal, but he should be respected for being motivated enough to make a serious effort in that direction.
Ridicule him ONLY if you can do better.
Paul Hurless - 2009/05/15 01:43:43 UTC
Yes, I can do better. It took me all of two minutes to come up with a simple (darn, the KISS principal keeps popping up) system that only has two moving parts; the cord to actuate it and the actual release that holds onto the tow line. It's almost completely internal in the control bar and a downtube, only emerging at the control bar for the hand to actuate it and at the top of the downtube where it goes to the release mechanism. No pulleys, springs, or bungees needed. If you are doubting me I could send you a sketch.
Red Howard - 2009/05/15 01:55:35 UTC
Utah
Yes, sketch please. I do not doubt you, though; I am just looking to learn, here.
Paul Hurless - 2009/05/15 03:02:47 UTC
I'll have to draw it out legibly and then scan it so it may be a day or so.
Tad Eareckson - 2009/06/18 12:23:50 UTC
C'mon Paul, it's been over a month. A SIMPLE system with only two moving parts? Should've only taken you half this time to produce a sketch.
I'm REALLY curious to see how you've done this 'cause it takes Wills Wing TEN additional parts - half of them moving (including a bearing and two of the dreaded pulleys) - just to get a Talon's VG actuation system up from where you can get to it to out the top of the downtube and pointed forward on the keel towards the core VG system itself (more complexity and pulleys up there than can easily be described).
So can you at least give us a guesstimate of how many more weeks, months this sketch is gonna take?
Zack C - 2011/01/10 14:28:40 UTC
When I first saw your release years ago on the Oz Report forum my impression was the same as most people's. I didn't know what the pictures were showing but it looked way more complicated than it needed to be. After seeing the problems that even the best releases on the market have and learning more about your release, however, I understand why you made it the way you did and the advantages it provides.
I've seen a lot of towing ideas and equipment over my 33 years of towing hang gliders and being towed in hang gliders.
The procedures and equipment that Tad advocates, to me, look to be the best.
Anyone that has a sharp eye for safety will take some time to study his posts.
So how's that sketch comin', Paul? I'd really like to see it 'cause, while we've been waiting, four more people - including a sixteen year old girl - have died 'cause they couldn't abort tows in time and while maintaining enough control to avoid slamming back into the runway.
If the problem is that you don't have enough cocktail napkins please lemme know - I'll happily send you a dozen or so for just the cost of shipping.
