Zack,
Tad, can your single-point four-string mouth release be used for foot launching?
I wouldn't recommend it - especially not the way I do my Four-Strings. It's a totally awesome release and I adore it but...
I optimize and adjust it for the individual - it's a one time deal but it's something of a bitch.
You want the Clamcleat directly under the pilot's teeth and the Trigger Line length such that the pilot can adequately turn his head to look around but no more. And when the pilot's towing there's a lot of pull on the harness so you've pretty much gotta stick him in the air with it once to see how it feels. And if the Trigger length is wrong I've gotta swap in another unit 'cause that length determines the construction of the entire assembly. So I can't really do this long distance very easily.
(Just for reference in case anyone wants to experiment... Have the pilot hold the end of the Trigger Line lightly between his lips prior to and during launch. That way if it's too short the line is pulled away without arming or blowing the release.)
The upside is that normally you just hold the Trigger in your teeth to about two hundred feet then spit it out. If you're low and things start getting iffy you tilt your head back to disengage the Trigger Line from the Clamcleat and arm it. Now all you gotta do is relax your bite and you're off. But if you get things back under control you're stuck with holding it in your teeth all the way up. (In an OFF NOW situation you'd just tug and leggo.)
If you used this for a standing launch the geometry would go to hell with the tow tension pulling your shoulder straps out away from your body when the tug started rolling.
A better option would be the:
Barrel Release - Remote
http://www.flickr.com/photos/aerotowrelease/8312402264/
Not quite as cool but perfectly effective and a no brainer to set anybody up with 'cause there's absolutely nothing critical about the lanyard length. But you'd still have issues at launch and this wouldn't be a great idea either.
You'd really hafta go with something cable actuated like the Russians have or Paul Farina has done. And in any case my two are useless if you wanna tow two point.
Last weekend we were told we could no longer dolly launch off the runway because of this.
That's totally despicable. What those sonsabitches are saying is that they're more concerned about one of their lights maybe getting broken than one of your necks probably getting broken. It's a public airport, I'm guessing it gets federal funding, maybe you've got some avenue of recourse - in the absence of any vestige of decency.
The gist of it was...
And don't forget that you're towing from your armpits with your harness up around your chin until/unless you can kick into the boot.
This is insane. When Ridgely was at about the fifty thousand tow point I asked Sunny what percentage of them were foot launch. He just laughed imagining the carnage. I think they had had one or two (flights - not percent).
And combine foot launch with 130 pound Greenspot... Do me a favor and keep a couple of cameras rolling at all times.
I've heard it said that since payout winches keep a constant tension the line is effectively of infinite length. I'm not sure if that makes sense, but in my experience initial line length on a payout winch doesn't seem to make much difference.
It's not, not much, and not much. Yeah, it's nice to have a lot of line out when shit's hitting the fan but on payout you tend to be pulling line out when shit's hitting the fan and that's reasonably nice.
A lot of this terror of platform launching stems from Donnell's sound-great-until-you-think-about-them Skyting theory assumptions. If they were the tiniest bit valid we would no more be capable of aerotowing the way we do than bumblebees would be capable of attaining flight.
The first of Donnell's Criteria is that:
The direction of the towing force must remain essentially constant throughout every phase of the towed flight.
the assumptions being that:
- a glider on tow is incapable of being maneuvered by its pilot
- the glider won't be turned away from the direction of tow by turbulence (inconveniences like thermals never figured into Donnell's vector diagrams)
- there can be no value in a driver maneuvering in front of the glider - somehow turned, impossibly, off line - to help it out
His primary weapon for attaining Constant Direction is a towline - nylon, to keep the tension "constant" so's you don't hafta spring for a winch - of infinite length. And he goes on for years contradicting himself all over the place about what a safe infinite length actually is. (It seems to get a lot shorter for student pilots - the opposite of what one would predict.)
Peter Birren reveres Donnell as a god, starts controlling towing in the Chicago area, himself gets revered as a god for solving all of mankind's problems with his invention of the Linknife, and predicts that all manner of death and destruction will arise from platform launching.
He has to wait twenty years for somebody to give him a lockout he can twist into something resembling ammunition but John Woiwode finally comes through, doing something of a level of stupidity unrivaled in the history of towing until Shane Smith hooks up his bridle through a weak link. And then he has an absolute field day.
I now feel platform launching is the safest way to get a hang glider into the air (in the widest range of conditions).
My two point aerotow release / bridle / weak link system is bulletproof. But I still think/agree that - even with the serious limitations of available releases - platform launching is still the safest way to get into the air - including free flight options. (And a couple of other advantages it has are that there's only one weak link in the system - under control of the pilot - and it's a lot harder for the driver to help you out by dumping the towline.)
I think I'd want to minimize the amount of time I had my hand off the bar in rowdy conditions. And those paddles are mighty close.
But:
- You are, by definition, doing it:
-- a long ways from the ground
-- when there's no shit hitting any fans
- There's a very wide window available for doing it.
- The penalty for:
-- not doing it in a timely manner is climb limitation, not instant death.
-- screwing it up is you're off tow. The only times the penalty for being off tow is more serious than being on tow is when you're relatively low and standing on your tail or rolled and stalling. If you're in either of those situations you're not gonna be trying to trip Stage One.
- If conditions are rowdy and you're starting to get kicked when you're reaching for Stage One then put your hand back on the basetube and give it another shot five seconds later.
Larry,
Butt seriously, I don't enjoy putting things in my mouth but do feel comfortable pushing buttons on my fingers, but all the actuators and power and stuff sounds more prone to failure than either a pneumatic or hydraulic actuator you bite down on.
- Soarmaster and Mosquito jockeys have been putting things in their mouths just fine since well back into the Seventies.
- The Russians, Steve Kinsley, Yours Truly, and Craig Stanley just LOVE putting things in their mouths.
- If you don't enjoy having things in your mouth just spit them out at two hundred feet.
- Buttons on fingers can be problematic if you're shifting your hands from down to base tubes during critical stages of tow.
- Just 'cause something SOUNDS prone to failure doesn't mean it IS prone to failure. There's a lotta very complex and critical stuff on passenger and military jets that sounds very scary but performs very well.
- Hang glider parachutes ARE VERY prone to failure. But somebody with a snapped outboard leading edge section is NEVER gonna regret at least having a shot at getting something clear and inflated before it gets eaten up.
- None of the emergency actuation modes takes the normal actuation mode off the table.
- Pneumatic ain't gonna do it - except as a trigger for something with enough oomph to make it happen.
- Hydraulic could work.
- But I think that electric with solenoids is the way to go. Note that jets have gone from hydraulic to fly by wire.
Mike,
By platform I assume you mean any wheeled takeoff (?)
No. Similar benefits but...
By platform I mean off the back of a boat, truck, or trailer. The front end guy controls the direction and the tow angle is down and constant - thus eliminating the need for a two stage.
Dolly, cart - synonyms.
- Remote from the front end of the towline.
- Just pretend directional control - good enough just about all the time at an airport, no freakin' way on a crowned road.
- Tow angle constant and straight ahead for aero - which makes release design REAL EASY - and constantly increasing for a while from straight ahead to really steep for surface - which makes two stage necessary and release design a real bitch.
Most tandem aerotow gliders have built in dollies that go up and come down with them.
When I say "payout" I'm usually thinking and meaning platform - although people using stationary winches in high winds and/or for step towing are also doing payout.
And another flavor of wheeled takeoff would be a glider with regular (non castering) wheels launching prone with a keel runner.
Regarding your dolly/trolley gathering dust in the shed...
Hassle, slowed operation, preference for foot launching... Yeah, those are all perfectly legitimate reasons for eschewing the thing. And the more competent and careful your pilots and crew the less of a factor it becomes.
But lemme throw out a few things that may weigh on our perspectives...
You're at a WAY higher latitude than I am and a WAY WAY higher latitude than Zack and Larry. And Larry lives in a state the name of whose English translation is "Dry Zone" and he starts out a mile higher than we other three do.
I don't know what conditions are usually like in your neck of the woods but even here where I've done most of my flying - Pennsylvania, Maryland, Virginia - dust devils are not all that uncommon. I've had my glider hit by them on the ground - fortunately when I've been there or within real close dashing distance - at least twice.
Ridgely is a high volume operation. On a good weekend day in the summer the launch line never disappears. There are two tugs, four dollies, several golf carts, and gliders launch every three or four minutes. As soon as a glider separates from a dolly there's a golf cart chasing it. It gets lassoed by somebody with a hook on the end of a pole and immediately delivered to the foremost person in line without one.
Fairly strong cross and tail winds are total non issues. We build up really good airspeed and really scary groundspeed before committing to aviation. (Lemme use present tense 'cause it's easier.) I come off the dolly a little earlier than I'd really like to in order to make things a little easier for the recovery crew. (You're welcome, motherfuckers.) And I'm usually thinking, "Thank GAWD I'm not running right now."
Despite the high volume, often potentially dangerous conditions, total shit rigged releases, sloppy dolly maintenance (flat tires ALL the time), and clueless tug and glider drivers the ONLY - and I mean ONLY - crashes at launch arise as a consequence of 130 pound Greenspot. I one hundred percent guarantee you that if you duplicated that operation foot launch only it would be a bloodbath - people WOULD die.
Once launched line tensions do not have to be that high, there is no need to be going up like a rocket or to drop prone until the pilot is comfortable. When all is steady the pilot goes prone...
I LOVED starting out prone, launching under high tension, going up like a rocket, and watching the truck turn into a Tonka Toy in one and a half seconds. It was like a carrier launch without the possibility of engine or catapult failure, rolling of the deck, falling six stories onto the ocean, and being immediately run over by a 97 thousand ton boat. The first time people do it their eyes are like saucers. Then they land and say, "AGAIN!!!"
A short line can get 45 degree off to one side much much quicker than a very very long line...
True, but with the glider bolted trim and level up to the instant of launch, that much excess airspeed, and the ability to pull line off the drum it simply doesn't happen.
