free-lance designer, in business since 1975

"We didn't all use them, but I was one who did. When I had a release failure on tow behind a Moyes' tug, I went for it and it worked flawlessly!"

Jim Zeiset
Jan, 1997 (Green Team) at the Hay Tow meet, Australia

"NOTHING works better than the Linknife."
Jeff Sinason
Former Region 6 Director

The light weight, low cost, sure fire, place anywhere,
Tow Release for Hang Gliders and Paragliders

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AEROTOWING SETUP
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for chest-only or with main V-bridle

As a MAIN release, the Linknife can be place at the ARS (no, not the same arse the Oz pilots are fond of using, but at the Apex Release Site, between the bridle and towline, similar to Static Line). Also see the Linknife Operation (takes 1 minute to load).

Another MAIN release spot is at the keel, on the weaklink but not needing a rapid link because the direction of pull is mostly perpendicular to the weaklink. Run the pull string down your harness main to your shoulder. Some pilots have been tying the pull line to a whiffle ball and clipping the ball to somewhere convenient. (see below for a little more on this)

For backup, the Linknife can be used at the pilot's shoulder or at the bottom end of the main V-bridle.

A 4-strand weaklink (full strength) will set up easily at the ARS. My personal favorite for a weaklink is 130-pound test braided dacron kite string, tied with a grapevine knot (a large pilot may way to use 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.

If releasing from the keel, a weaklink 1/2 the strength of the above 4-strand should be used as the tow force is spread half-and-half between keel and pilot.

An alternate PITCH LIMITER line can be attached to the glider's nose. See Opinion Page for more information on this concept.

Aerotowing release placement (illustration)
The above illustration shows several arrangements:

Keel releasing –– as a Main releaseor as a backup (see below for more on routing this)

On the chest or in front of the harness bridle –– this would be only as a backup release position when using the release at the keel. When using a V-bridle (chest to keel) do not place the main release on the chest).

At the ARS (Apex Release Site) –– (this is my personally preferred position) used with or without the nose line, this release position eliminates any potential unthreading problems. It does come with one risk, that of the 1/4" rapid link being blown back at your face, but that's not a problem if the bridle material is of sufficient strength to prevent bungee action.

Here are a couple of other options for keel releasing:

1 – route the pull string along the harness shoulder lines to either your chest or directly to your hand.

2 – route the pull string through the downtube. A friend just did this on his glider, custom making a couple of rollers at the top and bottom of the tube so there is no binding. He terminated the end at the base tube with a loop of plastic tube so he could hold it easily.

One thought might be to run the string inside a plastic tube. This will likely cause more drag on the string and make it harder to pull. so if tubing is to be used, keep the total length and bends short as possible.

IMPORTANT: make sure the direction of pull is perpendicular to the weaklink so you don't cut the bridle material and that it doesn't hang up anywhere.

COSTS:

Linknife — $20 each + shipping.
Club/dealer discounts available.

Bridles (aero or static), including Linknife,
rapid links and setup instructions — $50 each

ORDERING:

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US orders (Linknife single-order only)

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Other than US orders (Linknife only) drop me an email with your specifics for quantity and shipping method desired.

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Quantity orders of 10 or more Linknifes @ $15.00 each (add $10 shipping/insurance to US addresses for each 10 ordered)

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Bridles are made from red 900-pound heat set and stretched braided dacron with woven and hand-sewn loops in the ends. Kits include: Linknife release with extra O-ring, main 1:1 or 2:1 bridle, waist or shoulder bridle and connecting rapid links. Kits do not include the static tow waist bridle release mechanism (such as sailboat shackle) or release pull string as there are too many optional ways of setting this up. Custom bridles are available; please call or write with your specifications.

Static Line Tow Bridle (Hewett Center of Mass 2:1), or V-line (1:1 keel-to-pilot) Aerotow Bridle @ $50 each (plus $5.00 for ship/pkg) to US addresses. (Please add a note specifying which bridle you are ordering.)

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or send check to:
Birren Design Company
502 Shadywood Lane
Elk Grove, Illinois 60007
P: 847/640-0171
F: 847/640-0208
E: Email

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.

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——————— AEROTOWING SETUP ———————

for chest-only or with main V-bridle

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AEROTOWING SETUP
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