Friday, March 8, 2013

The Never Ending Saga of Building The Paratows Winch.

The project as you know, started in 2010 when I decided to design and build my own hydraulic winch. After 3 years of work and many modifications it is finally approaching perfection. I also went down to Discover Paragliding in Astoria Oregon in 2012 and earned my Tow Tech rating.

In the previous article I had mentioned a problem of the winch dumping all pressure when running at speed. After many tests I finally decided to mount my helmet camera to the winch to figure out what was going on back there. I don't know why this was not thought of before, but the issue presented itself loud and clear. The one way bearing that would drive the hydraulic pump during payout and free spin during rewind was failing. So I made it stronger. I went out with a few friends and did some towing and found that the winch is the smoothest payout any of us have ever felt. It provides amazing consistency and there is no jerking on the line due to line digs or rapid pressure changes. We had finally achieved success. Or so we thought. After about 20 tows the bearing failed again. Time for another redesign.

The pump drive system was redesigned and this time I installed a super strong bearing that carried a heavy price tag of $600. The tracking head also left a lot to be desired so that was redesigned and is working great now. I got the crew together once again to go out and prove it's operation. We did 7 tows and finally had no failures. Finally we had success right? Not really. The next time we went out for some towing fun I decided it was time for a torture test. We towed 10 times that day but we did the last 4 tows in rapid succession with no breaks for the winch. Everything worked great except now I had a heat issue. The pressure control valve would get so hot I could barely touch it. It was time for an oil cooler.

Since installing the oil cooler I have not had the heat issues anymore and have about anther 50 tows on the winch that have been failure free. As a precaution I have added a fan to the cooler for those hot summer days. After all these modifications there are still a few more I would like to do as the money comes available. These modifications are for operator ease and do not affect the pay out or safety in any way. So as it sits right now, the winch is in full operation for days of flying fun.

Now it is time for the towing stories and the rules of towing.

During my Tow Tech training I was told over and over again that weird stuff can and will happen and to be ready for anything. Even though strange things do happen at times, I firmly believe that tow launching is safer, faster, and more efficient than foot launching at a traditional site. We have the ability to tow right into the heart of thermal activity with a loaded wing that is highly resistant to collapses. During the launch and initial flight phase we don't have the issues with an unloaded wing that may collapse 10 feet off the ground and cause injury. Entering a thermal on tow has a mild impact on the glider when compared to free flight due to the pitch stability created by the speed assist on the tow bridle and the roll stability of a wing on tow. I will admit that there is a tow tolerance that must be built just like the bump tolerance we have learned. Thermal entry is not scary or dangerous, it is just a little different feeling than we are used to. The wing is pitched back slightly on tow and when you initially hit a thermal it pitches back a little further. The speed assist kicks in and it parks right back in it's slightly pitched back position. When you exit the thermal, instead of getting the surge that puts the wing in front of you, it will move directly overhead then pitch back again to it's speed assisted tow position.

I have had great experiences towing. I have also had great experiences being towed by my own winch. We have done light pressure tows, middle, and max pressure tows where I was hitting climb rates of 1,000 feet per minute! We have done thermal tows and simple sled ride tows. On those light lift days it is a great feeling to get towed up to the top of the lift and be able to boat around for an hour or so. (kiowapilot2000 on youtube to see some of the tows) This leads me to the simple rules of towing.

The most common issue I run into is that pilots have a tendency to “jump” into their harness before they are actually flying. That is the first rule. “Stay out of your harness just like a normal launch and be prepared to run again if needed.”

Pilots tend to inflate the glider and try to run the second I begin pulling away in the truck. At the beginning of a tow I will drive away, there will be a light tug on the line as the spool begins to spin. At this point I will begin adding pressure to the system. When you feel like it is a solid pull and you have to brace to hold against it then that is the time to inflate and run. The second rule. “wait for a solid pull, then run.”
There was one tow where the pilot flew right, then left, then further right, further left and further right again until they were pointing away from the winch. This is dangerous due to the possibility of a lockout where the glider will turn and dive into the ground. I dropped the pressure, slowed down the truck which allowed the pilot to regain control of their glider. This leads to the third rule. “Even though your on tow, you still have to fly your glider and stay behind the truck.”

The fourth rule. “if at any time your uncomfortable or want off the line, Pin off.”

The fifth rule. “have fun!”

Another interesting learning point was with an XC pilot. If you use a flight deck make sure that the clips that attach it to your harness are facing with the opening oriented in and not out. We had a tow where the pilot had the clips oriented out and did a reverse launch. What happened is one side of the tow bridle clipped into the flight deck and the pilot after launching was flying sideways in a hard weight shift to the left. The situation was corrected with an immediate drop in pressure which righted the pilot and allowed a safe landing.

The above cases are not the norm. 99% of the tows will be a non event as long as the pilot and tow operator do their part. We have had many great tows with some in excess of 3,000 feet AGL! If it is your first time towing with me it is okay, I tend to error on the side of caution when it comes to people I have not towed before and run the pressure to the pilots comfort level. I have a smooth system and the ability to watch you from your inflation until you pin off at the top of the tow. So come on out and play with Paratows. It will be a great time for all and I promise that the Paratows winch will provide the smoothest payout you have ever felt. Fly high and fly safe.

Chris Whitmus

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