It has finally sunk
in that weak link
material is cheap.
I anticipate that
your release will
be cheap (and
valuable) insurance.
– Brian Fogoros

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

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TESTIMONIALS
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See the Linknife Operation
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"In my opinion, the LINKNIFE is exceptionally brilliant! It seems to solve most of the problems associated with release systems without increasing the complexities. I cannot think of any major weaknesses or objections that you did not address. Please send me four Linknife releases as soon as possible.... They are still the best releases I know about. Some of my flying buddies are needing releases and I have run out of spares."
--Donnell Hewett
Towing pioneer, author of the 12 Skyting Criteria, inventor of towline tension sensing and designer of the Hewett Center-of-Mass bridle.

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I tested your Linknife on one of my students as a lockout release, and it worked well. He got the nose too high and it released him post haste. Rethinking the lockout bridle is on my agenda if I ever get any time at all.
--Dave Broyles

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Just got back from the USUSA meet. Boy, that was a blast. Met a guy from your area who demonstrated your tow release – I'm impressed! Please send me a couple.
--Ron Kenney

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As the proud owner of a Linknife I will be certain to protect myself against that unwanted 200' of tow line. The Linknife setup with a limiting line to the nose of the glider will cut me free of the tow line before I may have realized that it was given to me.
--Mike Sylvia

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If you tow, you gotta get this doohicky. Cheap and efficient. If you have a tow rig and there's those who show up to tow without their bridle, this rig is easy to set up and won't cost you an arm and a leg if somebody takes off with it.
--Mike Badley

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We didn't all use them, but I was one that did. When I had a release failure on tow behind a Moyes' tug, I went for it and it worked flawlessly!
--Jim Zeiset – Green Team, at the Hay Tow meet, Australia

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We've been using the 2 Linknives bought as a test. I have found that they indeed do work great as a primary release on our aerotow bridles. We are now using them as a cost effective release for visitors that don't have a release of their own. We use an equestrian panic release as the backup on the shoulder strap... haven't had to use it once so far. BTW, the pull pressure of the release *seems* to be lighter at the tug on those releases using the Linknife.
--Tim Shea – S&S Aviation Adventures, Santa Cruz, CA

I want to order a dozen Linknifes. We are hosting a tow training and are using them in the main release position at the keel, with the harness release and hooknife as a backup. We are going to use the Linknifes as our primary because we have found them to be reliable and cost effective. Great job!
--Tim Shea

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I've been using a Linknife for a couple of seasons now and I like it a lot. I used a mason style release (I built them for awhile) before the Linknife, and a 3-string ATOL style and a 3-ring ATOL style before that (I made those too. Now I don't bother, the Linknife works so well and is so cheap it's not worth it). They all have problems associated with them and I think are more prone to failure than the Linknife. Give it a shot, do your first tow with it in mellow conditions... have a spotter with a hook knife to give you extra confidence. Once you try it you probably won't go back.
--Doug Keller

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I started using the Linknife as my primary release, then was running out of weaklinks, so moved it onto the secondary weaklink so that the normal "pin out" of my release *usually* does the releasing, but the Linknife is there just in case. A pretty sweet setup.
--Brent Harsh

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When it comes to static line towing, NOTHING works better than the Linknife.
--Jeff Sinason

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I had a release failure on the last tow that I used a 2 string release. I've been using the Linknife ever since. With the old 2 string release I would get hit between the legs every time I had a weaklink failure. Now I haven't had to worry about getting hit since the Linknife is very light weight and doesn't use the steel tow rings.
--James Lintott

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I am gradually getting all the club members to use the Linknife and as you know, we train with them. They are GREAT!
--Gordon Marshall – Sky Sports Flying School, W.Australia

18 months and no failures!!! Have managed to convince 95% of the pilots here to use the Linknife.
--Gordon Marshal

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Thanks to all who wrote in telling of their experiences. Your comments are most gratifying and fulfilling. Thanks to God for the inspiration.

Have there been any problems? Sure, as with anything, stuff can go wrong. But problems have been quite rare – here are all that have been reported so far:

1997, Tim Shea said the rapid link was spreading the weaklink too wide and was wearing the sides of the slots. No premature releases or other troubles reported. (Changing to a 1/4" rapid link v/s wide shackle will cure this)
1999, One pilot attached his pull string to the Linknife with a split ring (keychain-type) that came off when attempting to release. He had been warned that could happen but ignored it.
1997, Another pilot had a line break which left him with a very short line, about 20 feet. When attempting to drop the line, it got tangled in the bridle. He rolled it all up and landed uneventfully.

By the way, I personally have over 800 cuts on the Linknife I use for my own towing and the amount of pull is still only 4-5 pounds, showing that the blades are not dulling after more than 10 years of use.

Linknife Tow Release photo

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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PRODUCT REVIEW – LINKNIFE
from Gordon Marshall
received Feb 12, 2000

I came home and listened to the messages on my answering machine:

#1 beep beep
#2 beep beep
(why don't they just say who it was?)

#3 "G'day 9000 feet 2 days ago, 9000' yesterday, 5000' after I knocked off work. See ya at spring thermaling. Oh yeah, got this great new thing called a Linknife, you may have seen it?"

#4 beep beep (9000ft! (I knew it was Phil from Newman) The Linknife arrived just in time for an aerotowing weekend. I used it with some apprehension during the tow, wondering if the thing would release on me but .... it didn't, well not until I yanked it half to death. The next tow (it's early in the season OK, not all of us get away 1st tow... or even the second) when I was feeling more confidant with the Linknife, I cut off the tow with but a mere hint of pressure from one finger. The following weekend saw the start of the club's annual spring thermaling week, and I was eager to show of my new toy.
"How does it work?"
"Where do you put the ring?"
"Pretty simple, eh?"
"How much?"

I normally pin off with my foot because the release is just there and also because I don't have to take my hand off the base bar when turning into a thermal on release. BUT, my hand was always poised in case of release failure. With the Linknife, I feel very confident of a clean cut away with the minimum amount of pressure required. The Linknife is an ingenious little tube that holds on to your weaklink during the tow. When you pull (just touch) the release cord, it cuts the weaklink away.

Advantages–
– No rings on the towline
– No heavy 3 ring release
– Very light, cheap & simple

Disadvantages:
– Blades will get blunt (eventually)
– So bloody light it wraps around your bridle (in groundhandling after a tow)
– Lose the occasional "O" ring retainer (@ 20c each), soooo doyaselfafava and buy two (I know what yer gonna say but it's easier to have two).

• • •

Doug Keller, discussing a tandem release problem:

The student said he noticed that the bridle had twisted 2 or 3 times from twisting in the tow rope so the release line was wrapped around it. This is why it didn't release the first time I pulled it.

When the glider was back on the tow truck I saw the hook knife on the downtube just inches from me the whole time and I realized I never even thought about it, just didn't have time. That's when I thought that if I had been using my own bridle with my Linknife release I would have had no problem, because the weak link can twist inside the release with no effect and those blades would have only had to touch that weaklink to cut it.

It's like having an automatic hook knife. I'll never do another tow without the Linknife. I've been promoting it with the local crowd since I started using it but you know how most pilots are about changing equipment that they already have that has worked for them so far.

I'll definitely be pushing harder now and have a good example of why the status quo isn't always best.

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TESTIMONIALS
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