Towing Guide

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Towing Guide

Indlægaf Jonni Laumann » lør mar 27, 2010 1:52 pm

Har snakket en del med Stuart ( han har mange års erfaring med både uddannelse af tow piloter, scootertow og så sælger han hydrauliske tow.

Her er nogle gode råd fra en expert!!!!!

90% of the pilots will fly with a white weak link with a red striker, especially over water. That's a 250 pound link. Oddly, if you tie it with a double grapevine knot it will break within 10% of that value. Statistically, from experience, they break at 264 pounds. The knot will reduce the breaking strength and the link will always break at the knot at around that value. If you are scooter towing, use the 200 pound link instead un less it's a super light pilot than drop down to the White/blue link.Don't waste the time sewing weak link-s, or splicing them.Ty a double grapevine knot.
-If Main Towline breaks I use AT LEAST a 24" overlap on each side of the splice
-Line to the drogue parachute, I use a 36 - 48" overlap
We use a 3/16” one on the apex of our drogue to attach a leader line, and an 1/8” one for the quick link to rotate on.
1/8" bridle - forbindelse til sprængstykke (weaklink)
image001.gif (4.87 KiB) Vist 6700 gange

The weaklink MUST be free to rotate. It has a working load of 485 pounds and a breaking load of 2425 pounds. If you follow the common practice of girth hitching the link to the line, every time the glider rocks the weaklink will roll around your tow bridle and quickly saw it through. The link prevents that. If you don’t use them, you should girth hitch a sacrificial link to the closure loop of your tow bridal so it can be replace easily.

If I saw a glider hanging back 80 degrees on tow I’d say we have a problem, a VERY BIG ONE. I no longer scooter tow, since hydraulic towing is so much easier and safer. Typically we launch a pilot with around 50 – 70 pounds of line tension. Normal climb tension is 100 – 130 pounds with maybe 140 – 160 pounds for a tandem.

The greatest hazard of towing is having a glider hang back on launch. It LOOKS inflated and if you really crank up the tow tension you will get it to climb, but the tow forces are enormous! It is essentially constant stalled (parachutage) and you are trying to drag it aloft like a barely flying sheet of plywood. It happens because the winch tech adds tension to try to force the glider to climb BEFORE the glider comes completely overhead. The end result is typically a weaklink break, close to the ground, with the glider in a very bad place. The pilot will either pendulum backwards and pound in on their butt if they are low, take a surge, swing forward and pound in on their face if they are higher, or take a full frontal collapse and pound in harder. None of these are very good options.

If you pay close attention, you’ll note you almost never break weaklinks when it is windy enough to reverse, but mostly during calm conditions when the tow tech tries to assist the pilot by adding extra line tension.

The solution is a tow assist style bridle. It makes sure that IF the glider hangs back it automatically gets a wee bit of trim to make it come completely overhead. As a bonus if the glider rocks back say to the right, that side of the glider sees a higher angle of attack and automatically adds speed on that side until the glider straightens out. It makes towing way, way, way, way easier for both the pilot and the tow tech. We almost never tow a novice pilot without a tow assist and never scooter tow without them. It is probably THE best safety feature for towing a paraglider and we incorporate it in most of our tow bridals.
tow assist style bridle - NORMAL

tow assist style bridle - ACCelerated

Assuming you have the same tow distance available you can either go really fast and tow with huge tensions, or you can go slow with lighter tensions. Either technique gets you to almost the same height. Efficiency is where its at. As for optimal efficiency, let’s say I jump on your back as we launch from a mountain side. Do you want to fly the same speed as normal, slower, or faster?

Towing adds the same additional weight and requires the same wee additional speed. If you check closely with a vario, you will find that you tow with a better climb rate with a wee bit of speed applied during the tow.

I often tow with full speed bar in a windy day. I have yet to come close to getting a collapse since the wing is loaded heavily and already at a fairly high angle of attack. A front tuck is highly unlikely on tow. (If you break a weaklink on full speedbar the resulting surge might give you one though)
Jonni Laumann
Indlæg: 177
Tilmeldt: tors okt 30, 2008 1:18 pm

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