STATIC TOW SETUP

Launch style discussed uses the 2:1 Hewett Center-of-Mass Bridle

The idea behind any release is to be easy to set up, and not activate until it's needed (not a moment sooner). When it is needed - at the top of tow or in an emergency - it has to work the first time, every time. The Linknife does that quite efficiently and works by cutting the weaklink, simple as that.

See below for setting up a 2:1 bridle.

Aug 2012: Video of foot-launching ATOS using an over/under bridle with 2 Linknife Releases.

MAIN RELEASE PLACEMENT
As a MAIN release, place the Linknife between the bridle and towline. Pass the weaklink loop through the loop on the towline end. Pass the two loop ends of the weaklink through the slots in the Linknife and into the 1/4" rapid link on the bridle. Tie the release pull string to your harness shoulder loops or straps, in easy reach by either hand.

Note in the illustration below how the lower part of the bridle is routed UNDER the control bar. Route it above just once and you'll quickly see why the word UNDER is in all caps. If such a thing should happen, release at your first opportunity, if not sooner, before you get pulled down.

VIDEO: Pilot view of static tow launch at Bong Park, WI

AFTER (normal) RELEASING
1. First and foremost, FLY THE GLIDER!
2. Release the main bridle from the waist shackle.
3. FLY THE GLIDER!
4. Gradually roll up the bridle and stow in the harness.

If you land with the bridle dragging behind you, it's possible that it could snag on something. As much of a possibility as that is, in more than 20 years of static line towing, I have yet to see it happen during a landing approach. Still, it's good style to fly clean.

BACKUP PLACEMENT
Place alternate backup - for emergency use only - directly on the bridle at the keel or on the upper bridle line in front of the pilot. Backups like this are not really recommended for Hewett 2:1 bridles as pilot injury is possible when the bridle whips through the waist shackle. Your hook knife is the best option for a release failure (not that the Linknife is going to fail or anything, but no release in 100% foolproof. You might set it up wrong... who knows?).

Optionally, add 6 inches of small shrink tubing (diagram below) to the pull string, snug against the Linknife, to prevent the Linknife from twisting around the weaklink. You can also customize the setup by mounting a small dog leash reel to your harness for the pull string. (Make sure you lock it with some slack line out before launching!)

WEAKLINKS
A 4-strand weaklink will set up easily between the towline and the bridle. My personal favorite for a weaklink is 130-pound braided dacron kite string, tied with a grapevine knot. I weight 170, those heavier will probably want to use something like 150# line.

Starting with 18-20 inches of string, this gives me a large enough loop to work while wearing gloves. Insert the first loop through the towline, then pass the 2 end loops through the Linknife above the O-ring as shown below. Place both loop ends in the rapid link. Don't forget to close the rapid link.

 

Here's how it works

ORDER HERE

The Linknife can also be used as an emergency release at the tow vehicle when static line towing.
More info and photos at this page on towing equipment

 

Hewett Bridle Considerations

The Reel Pilots use the Hewett Center-of-Mass bridle for foot launched static line towing of our hang gliders. It's basically a 2:1 pulley that's arranged thusly:

Main Bridle

The main bridle must be much stronger than the towline to prevent snap-back. Bridle measures 20-24 feet (7+ meters). Material should be a no-stretch line like perlon, spectra, or a particular 900-pound test like I found at a skydiving supply house. (You can order a bridle kit for static or aero towing here.)

Affix the bridle to the keel from 1" to 14" forward of the hang point (the newer you are, the farther forward it should be attached for the first few dozen or so tows). Important: Attach so that it will not slide forward on the keel tube, probably with a restraining line to the kingpost or top of downtubes.

Beginning at the keel, the bridle line passes through a ring at the "apex" or towline attach point, through a 1/4" rapid link ("B" in photo below) and routes back to the pilot's waist UNDER the control bar.

At the pilot's waist (D) there's an attachment like a sailboat shackle. There are 2 purposes for the shackle: to disconnect the bridle from the pilot after the tow, and as a second "pulley" to permit smooth sliding of the bridle. Bridle routes through this shackle and back UNDER the bar to the apex where it's firmly tied to the steel ring/link. Bowline is a good knot for this setup.

Black = Bridle: non-stretch line for main and waist bridle
A (Red) = weaklink through Linknife
B (LtBlue) = 1/4" (6mm) rapid link
C (Orange) = Release line with slack
D = Shackle on waist line to allow "pulley" action

Waist Bridle

At the pilot's center-of-mass -- usually the waist -- a short bridle retains the shackle and is formed to limit side to side movement. Tie a knot, weave a loop, whatever... keep it solid and keep it short.

This bridle must be short enough to keep the shackle from contacting the control bar. Appropriate size would allow one fist-width between bridle and harness. It can be attached to waist loops on most modern harnesses or can be a sewn loop on the harness skirt; grommets can be placed in the skirt for the bridle to wrap around the leg loops... it's your choice depending on what type of harness you own.

My friend Wes Schield developed this waist bridle release using a welded ring and non-stretch cordage. This design permits one-handed dropping of the bridle after releasing from the towline. The photos show a prototype for concept, not material type or size, though in practice it works great.

 A sailing snap shackle is also a good choice, like this one from West Marine (their model #121046)

 

Bridle In-Flight

Here are a couple of views of how the static towing bridle looks in flight:

This illustration above shows the pilot/glider/bridle orientation at maybe 200 feet off the ground. Illustration based on one from the Canadian Towing Manual.

At the top of tow (no matter how much towline used) the upper bridle line will contact the base tube. It's not necessary to push hard against it as that will likely cause the glider to stall. A little pushing may be OK to maximize the climb but the conditions of the day will have a lot to do with it. Upon release, the release line is first wrapped up and stowed, then the bridle is disconnected from the waist allowing it to stretch to full length, then wrapped up and stowed. The whole procedure takes about 30 seconds. It is important to have the bridle stowed prior to landing so it doesn't catch on anything on the ground.

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Basic Details of Launch

Don't try this without expert supervision and training.
You could seriously hurt yourself
by not knowing what you are about to experience.

Aside from recent flying experience and a good working knowledge of hang glider flight, foot launched towing requires the pilot to hold AoA (Angle of Attack) against the upward pull of the low part of the bridle when tension is applied. As tension is applied, the pilot must RESIST the towline force so that tension builds in the line. As forward movement is attained and the wing produces lift, the glider will rise and find its trim point... pull in a bit to get better flying speed until well away from the ground, then let the bar slowly to trim and climb away.

Basic rule of control:
If any part of the bridle touches
the front flying wires,
RELEASE!

Corrections are made by "bumping the bar" to maintain a straight-ahead heading – yaw and roll corrections are NOT done by "turning" the glider. Fully shifting weight will result in increasing PIO.

After releasing, roll up the bridle and stow it in your harness or side wires. DO NOT let it drag behind you on landing.

A little aside to comparing static line to payout: One of our pilots moved to Missouri several years ago after becoming an accomplished static tow pilot here. He of course brought his reel/gauge with him. Was told by the locals that they "used to do static but have graduated to payout". So he set up his static line and beat their pants off on every launch... they could never get as high on payout as he did on static line. :-)

More details on the above

Do not mount anything on the base tube. It must be kept free of things that would snag the bridle in any way. A little snag, combined with a little roll while on tow, can make for setting up a lockout.

A straight base tube is better than a speed bar for static towing. The bridle has less of a chance of locking in on one side of a speed bar. (Just a suggestion)

Lower line and harness bridle

I don't know what kind of harness you fly in, but most have hip loops. Using 1/4" or so rapid links and material similar to the main bridle, make a short waist bridle that attaches to both sides of the harness. Sew or tie a loop into the middle of the line with a shackle or beener that can't move side-to-side. The length of the bridle should be set so there's maybe a "fist" of room between it and the harness. One reason for the "fist" space is that at launch you don't want the shackle/ beener/ whatever catching on the base tube. KISS!

You should be able to easily attach all bridles while on the ground during setup, and very easily remove the main bridle after release. No fabric-on-fabric... but you know that.

On my old AirFlare pod and on an Airstream dorsal fin pod, I set grommets in the "skirt" so the hip-bridle could wrap around the leg loops. I can't do this with my Airtime LaZer harness now but must use the sewn-in hip loops.

Some pilots pull only from the chest. In this arrangement there is no tow force applied to the glider. I have only seen the over/under "Euro release" used a couple of times and have not yet flown with this arrangement. It's reported to have good success, but within our club the one pilot who did attempt it experienced his first lockout.

A chest-only bridle being used with a "Scooter Tow", a variation on the stationary winch.
Photo provided by Dave Broyles, Allen TX

Backup release

I do not recommend using one on the pilot for static line towing. The arrangement for such a backup would add far too much complexity to the system. Your best bet is to become intimately familiar with your hook knife and make sure it's where you can quickly reach it. A backup at the car is a wonderful idea to dump all towline tension immediately, however this can present new problems like the pilot could be left dragging several thousand feet of towline that can snag on a ground obstacle.

In my 1000+ tows, I've had to use my hook knife three times... the first was on a pulley tow when an old 2-string release didn't work. Sure did need that hook knife... and RIGHT NOW! Though it worked fine and I lost the bridle and release, it gave me the inspiration to come up with the Linknife.

Linknife

The Linknife is a release that cuts the weaklink. It's small and light and can be used in a number of ways with a tow bridle system for static, payout and aerotowing.

I use one Linknife only as my main release for both static line and aerotowing. For aerotow, I place the release at the same position as with the static Hewett system. Not only does this keep things simple (same release for all systems) but it eliminates any unthreading hang-up potential and saves weight and complexity.

My release line is attached to the harness shoulder. I use a small dog leash reel at the harness, so after releasing it's a simple matter to pull the tab and - zip- the release line is automatically rewound. Gotta make sure to lock the reel before launching so at the time of release, especially in an emergency, you will not hit the line and just pay out more line (can you guess how I found this out? Yup, the hard way).

Backup at the keel

You might be tempted to experiment with a secondary release. One place you might think to place it is at the keel. When we first were towing in 1982 to about '86, there were pilots who had their main release there... we referred to it as a threaded bridle. Couple of pilots got hurt when the bridle line came whipping back at them. We've since banned 'em.

Launching from a dolly using a Hewett 2:1 bridle.

ORDER LINKNIFE AND BRIDLE HERE

DISCLAIMER: As with all aviation endeavors, your choice and use of equipment is totally up to you. It is assumed you are an experienced HG or PG tow pilot who is intimately familiar with the style of towing you will be doing. As such, YOU ASSUME ALL RISK AND LIABILITY in the use of the Linknife, as well as all other parts, functions and personnel involved in the towing and flight operations. If you do not have experience in towing, please contact an instructor for expert training. Trying to learn on your own can, and probably will, result in your injury and even death. Many pilots have paid the ultimate price so we may now tow as safely as never before possible. Please learn from their lessons.

Note: Using PayPal is very simple. You do NOT need to be a member of PayPal to make a purchase. You may use a credit card like any other system. If your order is to be shipped outside the US, please let me know via email: peter@birrendesign.com PLEASE LET ME KNOW IF YOUR ORDERING BUTTON DOESN'T WORK!

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Thank you!

and keep looking up.