Surface towing for teaching

[Steve Davy]

http://lh3.googleusercontent.com/-jTx0B3gp83o/UfPVVtKTkXI/AAAAAAAAACA/v9muXahvVSg/w503-h377-no/DSC00074.JPG


Boosted first stage released.

[Tad Eareckson]

Suggestions...

http://lh5.googleusercontent.com/-GjRUYbVOJpk/UfPhhXHy9AI/AAAAAAAAACk/lCXAymMqoVQ/w503-h377-no/DSC00071.JPG


Make the pin symmetrical.

http://www.flickr.com/photos/aerotowrelease/8312399698/


The more offset the more sideloading and less strength, mechanical advantage, efficiency.

http://lh6.googleusercontent.com/-QUoBgXoIwvI/UfPUiMKAMAI/AAAAAAAAABw/ROPsBWxJ2o8/w503-h377-no/DSC00054.JPG


That would be a real good place for the damned M111C curved pin from ParaGear. That's the sort of application it's intended for.

However... I wouldn't expect that to work under a whole lotta load - especially unsplit load. I did something like that for my first aerotow secondary release and got the crap scared out of me when I tried to blow it under load - fortunately on the ground.

You could probably do that but you'd be dependent upon the guy at the other end to ease up on the tension to be able to blow the first stage. That's not a safety issue but it is a hassle / climb efficiency issue.

Keep these approaches:

http://www.youtube.com/watch?v=il3YPp3Rfq8

http://www.youtube.com/watch?v=PyPaFa-m5rc


in mind. Those are the bars you've gotta beat - or at least meet. And they're pretty high.

[deltaman]

Hi,
The french tow comittee told me they need 5daN for paragliders and 7daN for hanggliders to maintain a lockout.
A good release should dump the line under these values.

[deltaman]

A student died this we. He was surface towing by scooter with a forwarding pulley in the ground.



My report is actually a bush telegraph.
It was the 4th day of the initiation week.
The instructor, operator was still a student (grade) for towing.
The student, 43yo, didn't release and started a lockout.
(don't know the height, neither the release type)
The operator would have cut the line but it would have wrapped around the pulley.
The lockout went to the ground.

[Tad Eareckson]

Oops.

Forgot to mention that that yellow line looks like nylon/perlon. Avoid elastic materials like the plague in the finished product.

And a bit more on pin based releases...

To increase strength, mechanical advantage, efficiency you wanna reduce offset.
- You don't wanna accommodate offset with an asymmetrical pin.
- Engaging a loop of diameter material is major in reducing offset.
- Equally important in reducing offset is minimizing the diameter of the base material from which the release is constructed.

That last point occurred to me only now. I could've made stronger, more efficient, better barrel releases by using Dyneema/Vectran sorta line but I started off with eighth inch Dacron leechline 'cause:
- I was familiar with it
- it's nice to work with
- it fitted the barrel ID pretty well
- it was more than strong enough to deal with the weak link range in which I was interested

And I never - before now - questioned that assumption.

[Tad Eareckson]

The french tow comittee told me they need 5daN for paragliders and 7daN for hanggliders to maintain a lockout.

The French tow committee's full of shit (but we knew that already 'cause Scott Sigal has no fuckin' clue what a weak link is). You don't need ANY decaNewtons to maintain a lockout on ANYTHING that flies - paraglider, hang glider, sailplane, Cessna, Boeing 777.

This free flight glider:

http://www.youtube.com/watch?v=1yFUkMBhXEg


between 0:13 and 0:16 is locked out. The reason he's still alive is because there were no trees or rocks in his way before Mother Nature let him have his glider back.

I was almost killed on 1984/07/05 at Jockey's Ridge when - while I was resisting with both hands on the basetube and everything I had - an unbelievable thermal blast rolled me seventy degrees, turned me 180, and dumped me back towards the face of the dune with a twenty-plus mile per hour tailwind. That was a lockout.

When Donnell wrote all his Skyting Theory crap one of the many issues his assumptions and vector diagrams didn't account for was anything other than dead air. Ditto with respect to Trisa and their Cone of Safety bullshit.

Comparing/Contrasting free flight and a tow lockouts...

- You can die if you lock out near something hard - tree, rock, mountain, cliff, dune, runway, putting green, narrow dry riverbed with large rocks strewn all over the place...

- If you lock out with 1, 5, 7, 70, 140, 280 decaNewtons / 2, 11, 16, 157, 315, 629 pounds of towline tension pulling in the direction you used to be going that's gonna make things like - roll, roll rate, ability to resist - worse.

- If you lock out on a towline with nothing to regulate tension - as is the case with aero - that tension is go is gonna keep increasing and things are gonna get exponentially worse.

- If you lock out:

-- early on tow you WILL - at best - soon be making an unscheduled and possibly exciting landing.

-- at any point on tow you will before you get to start flying again, assuming that's still a possibility, be dealing with the effects of maybe two or three hundred pounds of suddenly subtracted towline tension - and that's almost always gonna require a fair bit of altitude.

Yeah, ideally you want to be able to dump a slack line with both hands on the basetube - and the less required opposition tension the better. But:
- there's no magic number at which a misaligned pull abruptly ceases to be a problem
- in the vast majority of real world situations gliders aren't having serious problems with thirty pounds of misaligned pulls

And if you're really worried about low tension the Koch two - or one - stage is gonna be pretty hard to beat for surface.

[Tad Eareckson]

A student died this we...

Aero...
- 2011 national champion - dead
- passenger of 2011 national champion - severely injured
- regular pilot - badly broken
Scooter...
- fourth day student - dead

Might be a good climate in which to get some good standards/SOPs/regulations into place.

The operator would have cut the line but it would have wrapped around the pulley.

I'll bet if they had been dolly launching him with one of Joe's releases he'd still be happily advancing through his lessons.

Try to find out what the weak link was. We need it to be light. Then we can show how an aero guy at under fifty feet was blown off by a two G weak link and did way better than a scooter guy at under fifty feet who wasn't blown off soon enough / at all by his three quarter G training weak link and died.

[Steve Davy]

Make the pin symmetrical.

I'm not going to make any more pins. I'll buy them at two bucks a pop.

The more offset the more sideloading and less strength, mechanical advantage, efficiency.

I noticed some side loading when tensioned, but thought it was from some twist in the base.

That would be a real good place for the damned M111C curved pin from ParaGear. That's the sort of application it's intended for.

I think it needs to be a straight pin so it can be pulled like the pin on a three string.

However... I wouldn't expect that to work under a whole lotta load - especially unsplit load.

It won't, but boosted twice it seems to work ok. That idea is on the back burner for now.

Keep these approaches in mind.

I will.

Those are the bars you've gotta beat - or at least meet.

1. I disagree. Edward's setup is what I'm aiming to beat.
2. That second video gave me the idea to engage a boosted straight pin bite release to a boosted barrel rather than a three string.

And they're pretty high.

Edward blows them away.

Lockout
http://www.youtube.com/watch?v=jUdtyB8xlag
Edward Zernaev - 2013/07/01
dead
13-1423
http://c2.staticflickr.com/2/1867/44534752601_5cd2d77ef7_o.png

[Tad Eareckson]

I'll buy them at two bucks a pop.

The M111S? It's pretty good in the off-the-shelf department but it would be nice to have something longer for some applications.

I think it needs to be a straight pin so it can be pulled like the pin on a three string.

On a three-string you're pulling straight back in opposition to the tension. With a straight pin in your application you'd be pulling perpendicularly to it and anything at another angle would reduce your efficiency. A curved pin would allow more of an aft pull and I would guess would work better with one's body geometry. But I wouldn't bet more than five or ten bucks on that being right and it may not be that big of an issue anyway.

Also... This statement:

That's the sort of application it's intended for.

wasn't very well thought through or particularly accurate. The curved pin is used for opening parachute containers with various directions of pull but there's no significant load/resistance involved.

I disagree. Edward's setup is what I'm aiming to beat.

Yeah. I didn't mean in terms of actuation - just stuff like:
- the transition from first to second stage
- weight, drag, cost, stowability

Steal all the best ideas and tweak, adapt, integrate them.

That second video gave me the idea to engage a boosted straight pin bite release to a boosted barrel rather than a three string.

Like that.

Edward blows them away.

Yeah. But that trick Sander uses to transition is just so fuckin' cool. I can't bear the thought of not incorporating it. But it seems to be dependent upon keeping the release point real close to the pilot. And that appears to be dependent upon using all that expensive, heavy, bulky Koch-type spreader hardware. If you use a bridle - as I'd prefer - you've pretty much by definition moved crap forward of the basetube. And I can't think of any real great ways to get around that.

[Steve Davy]

Found some info on splicing: http://www.samsonrope.com/Pages/SpliceInstructions.aspx