I'm not sure I'm following you.
- Joe's using red Spectra line to which runs between the quick link and pin eye through the barrel mechanism.
- Spectra is essentially - for the purpose of this exercise - zero stretch AFTER it's loaded up under normal tow tension.
- But it's gonna elongate a bit as it's loaded up from zero tension - at which point it's short and fat.
- The barrel release performance - minus the spring - is absolutely linear. If the load to actuation ratio is fifteen to one you'll need to pull an extra pound for every fifteen of load you add.
- My keel mounted barrel release system:
http://www.flickr.com/photos/aerotowrelease/8306258400/
is under tension all the time - whether or not the bridle is connected to it. It's tensioned to the nose primarily because it needs to be to be functional in a slack line situation. So there's no (significant) slop to be taken out of the system as the tow tension loads things up.
- Joe's assembly could easily be rigged the same way.
- If it were rigged that way fifteen pounds of direct loading would require a fixed eleven pounds of spring compression plus another pound to overcome the friction of the mechanism.
- But it isn't, so at low tension while the Spectra is still short and fat you hafta pull the barrel farther back - and compress the spring more - to clear the pin.
- So for some of that low range increasing the load could DECREASE the required pull.
The easiest way to deliver a lot of force is with a jab (how Lookout recommends you actuate their releases).
They also advise that...
There is no product liability insurance covering this gear and we do not warrant this gear as suitable for towing anything.
...their "releases" aren't suitable for towing anything and that...
The new GT aerotow release, new as of July 11th 2009, is designed to be used with a V bridle and a 130-pound green stripe Dacron tournament fishing line weak link. At this time it is not recommended to use this release with a higher value weak link.
...at this time it is not recommended to use this release with a weak link of a higher value than 130 pound green stripe Dacron tournament fishing line. And the value of a 130 pound green stripe Dacron tournament fishing line weak link is comparable to the combined value of parachute in a container with no pins and worn out velcro and a hang check in the setup area twenty minutes before launch.
If you don't deliver enough force with one jab, you're going to have to do two...
If you live that long.
...including the second release in the video in my previous post).
I'm less concerned with the spring issue in Joe's release than I am with Matt's crap. At least I know that the spring issue CAN be overcome fairly quickly and easily.
Ralph Sickinger - 2000/08/28 18:18:20 UTC
Under sled conditions, I decided to borrow Brian Vant-Hull's glider instead of setting up my own, since we both fly the same type of glider. Brian's release is a different style, but I tested it twice during preflight to make sure I was familiar with it. After towing to altitude, Sunny waved me off; I pulled on the release (hard), but nothing happened! After the second failed attempt to release, I thought about releasing from the secondary, but before I could move my hand the tug stalled and started to fall; Sunny had no choice but to gun the engine in attempt to regain flying speed, but this resulted in a sudden and severe pull on the harness and glider; I was only able to pull on the release again, while simultaneously praying for the weak link to break. The release finally opened, and I was free of the tug.
Brian Vant-Hull - 2000/08/28 22:49:13 UTC
I purchased my release (the one Ralph used) at Lookout Mountain over a year ago, but never had any problems until the Ridgely Fly-In, where the same thing happened. I pulled three or four times on the release, then finally went to the secondary, by which time I was high above the tug and Sunny (is there a connection here?) was frantically waving me off.
No way in hell I'd go up on that piece o' shit. And that piece o' shit is way more reliable than Matt's new and improved piece o' shit.
If that's all you need, I think a basetube-mounted brake handle would be fine (assuming it worked...).
- Yeah, but given their record on the downtube where the cable bending is minimized...
http://www.hanggliding.org/viewtopic.php?t=11497
Aerotow release options?
Axel Banchero - 2009/06/20 04:57:01 UTC
I just kept hitting the brake lever for a few seconds in WTF mode, and the instructor used the barrel release.
...no way in hell would I do that.
- IF you had a reliable basetube mounted brake lever system it would be safer to trigger than my own system. You could white knuckle clamp your hand to the basetube and blow tow with an index finger.
- But I still wouldn't use it 'cause I can blow mine by just twisting my grip, I wouldn't put all that crap in the airflow, and the lever gives you something you can use to snag a bridle.
Are you saying that it could be better with a lighter spring?
Yeah. It could be 10.9 pounds better.
Or is your issue that it requires too much force at lower loads?
I'm not real worried about it but if something can EASILY be made better it should be made better.
At any rate, I don't think a lighter spring would address the difficulty I had under higher loads...only normal loads.
It would address over ten pounds of it.
I'm going to go back to having a longer pull...it worked better that way.
You're adjusting your procedure to compensate for an engineering problem rather than fixing the engineering problem.
http://www.chgpa.org/forums/viewtopic.php?f=2&t=3600
Weak link question
Lauren Tjaden - 2008/11/20 22:50:53 UTC
I practiced releasing using varied types of release under load (on the ground) at Highland this year, and found it very educational. When pro-towing the method the pilot uses to release can be very important (something I'd never realized, since I've -- knock on wood - never locked out while pro-towing). I found that the only way to release under strong loads (with either curved or straight pin releases) was to grab the TOP of the barrel instead of just grasping around its sides.
(Lauren wasn't using a sane straight pin barrel like mine - she was using one of those idiot short fat barrel / webbing pieces of crap like Steve Wendt punches out, a Bailey release with a straight pin swapped in.)
It would require surgery.
- I performed no surgery in my initial designs. I mounted a spinnaker shackle at the keel, lashed some guide rings to the port downtube and ran a 205 leechline lanyard down to the basetube. And I NEVER had a problem blowing it - or any of my later evolutionary stages.
Unboosted, the performance wouldn't be significantly better.
Negligible spring resistance, no cable resistance, no cable flex at the bottom, minimal required hand motion.
- By delaying or not doing surgery on your glider you're increasing the probability of someone needing to do surgery on you. You're not increasing it much - but you ARE increasing it.
Boosting will require more surgery (not sure how much...I'll let Tad speak to that).
Nope. Once you've got a basic installation - with or without surgery - it's a very simple matter to start adding pulleys at the top.