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Old Sep 14, 2012, 09:59 PM
3 Sons - Legos and Lift
2motheus's Avatar
Grand Rapids, MI
Joined Apr 2004
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Quote:
Originally Posted by Andy Meysner View Post
Tried out a 28oz 2m plane with no problems.

However I'm wondering whether my technique near the apogee of the launch is wrong and I'm pulling back too much when the tension on the line starts to reduce. My launch heights are 300 ft with about a 25ft zoom. Is it better to stop pulling back when the tension reduces and allow the plane to 'kite' to gain more altitude near the end of the launch? Maybe even walk forward a bit to allow more line out like a kite? I thought perhaps I'm preventing a higher launch height by shortening the line too much.


Andy
Hi Andy,

Launches to 300' on a 500' layout should be a minimum, even with no wind.
As aeajr says, good tension at release should give you a confident start, then maintaining tension shouldn't require a lot of backward movement. If your plane is not rotating to a good angle and you're having to move back quickly to catch up to it, consider adjusting the tow hook and/or elevator.

I also agree that you shouldn't stay on the line until the tension is bleeding off. Make the dip and zoom while you still have good pull to convert airspeed to altitude.


Ray,

I launch a 3.6 meter Topaz regularly, and unlimited moldies when I get a chance. The heaviest plane I have launched might be Gordy Stahl's very weathered Pike "Imperfect" at the NATS.

Here's one way to think about it.
A certain amount of work is needed to get a particular plane to a given altitude, and wingspan is only one of the variables. It has more to do with weight and stall speed.
With a fixed amount of power (determined by puller and wind), you can pull up a light plane relatively quickly. A heavier plane requires more work to get to the same altitude, so you want to deliver the limited power over a longer period of time. Adjusting the camber for higher lift and lower airspeed allows you to raise the heavier plane to the same altitude with the available power. It just takes longer.
And as long as you stay above stall, you can kite back and forth to get more energy from any wind you have, sometimes even letting the line back out to maximize altitude.

Have a great weekend,
Tim
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Old Sep 15, 2012, 02:58 AM
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I forgot to mention letting line back out. . That works when you have enough breeze. As long as you maintain tension you can walk forward slowly and add line bac to increase the length of the launch line.
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Old Sep 15, 2012, 07:31 AM
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http://www.rcgroups.com/forums/showthread.php?t=1732320
I am running a survey for full house glider pilots. If you get a chance, stop by and provide your input.

thanks.
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Old Sep 15, 2012, 08:21 AM
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Andy Meysner's Avatar
Mississauga ON Canada
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Thanks Ed and Tim for all the feedback and advice. I'm looking forward to putting it into practice and refining the technique.

Andy
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Old Sep 16, 2012, 09:22 PM
3 Sons - Legos and Lift
2motheus's Avatar
Grand Rapids, MI
Joined Apr 2004
565 Posts
Camber testing

To illustrate my statements above I did some testing this afternoon with the 3.6m Topaz. Wind was 10 mph or lower. I did a series of launches alternating between cruise and launch camber. The results show how much more a cambered wing extracts energy from the wind. Not only are the cambered launches over 100 feet higher on average, but I moved back only 10 feet during the pull. I moved back about 25 feet for the non-cambered launches, so a lot more energy was coming from me than from the wind.

In the graph below there are 3 launches with no camber, and 4 higher ones with camber. The numbers on the graph show the altitude at the end of the zoom.

Note: I have not tuned the plane for cruise mode launches. I think some up elevator would have made the flat wing launch better.

Even though this was done with a light plane, the fact that I didn't have to move back much at all makes me confident that a heavier plane tuned properly would go up just fine.

I'm not sure I'm explaining this real well, so let me know if you have any questions.

Tim
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Old Sep 16, 2012, 09:25 PM
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Perfectly clear to me.
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Old Sep 19, 2012, 04:09 PM
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Tim,

Wow, what a difference! Can you explain please though what the exact differences in the wing configuration were. Did you just add some flap, and how much?

Thanks,
Andy
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Old Sep 19, 2012, 09:21 PM
3 Sons - Legos and Lift
2motheus's Avatar
Grand Rapids, MI
Joined Apr 2004
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Camber settings

I haven't been able to locate specs on the Topaz airfoil, but it looks kind of like the one on the Supra, from what I found on charlesriverrc.org. That's where I went for guidance.

For the higher cambered launches I lowered both the flaps and ailerons 12 degrees. This ended up being too squirrely, so I reduced the camber on the ailerons to something closer to 8 degrees. This tamed it down, but I'm sure there is more adjusting to do. I won't know for sure until I solve a rudder centering problem.

The lower launches were done with the flaps and ailerons in flat cruise mode. As I mentioned before, I think these launches could have been higher with a little elevator and/or tow hook tuning. In any case, having no camber option is what you would have with an RES plane.

I will post more results when I get a chance. It's definitely possible to get high launches with a non-cambered wing. You just need to get it tuned in. The purpose of these measurements was to show how cambering helps to increase lift and decrease the pull distance.

Tim
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Old Sep 19, 2012, 09:27 PM
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I believe the Topaz is an MH32, but it doesn't matter. Under launch under two, especially with launch camber set, the airfoil is not going to be in play.
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Old Sep 22, 2012, 11:16 PM
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I flew off the One Winch!

Hi Guys,
At this year's Nats, the One Winch was there doing demo launches. I had a chance to fly my Perfect, and a few other ships including a woodie....it worked fantastic!

Unlike a High Start or Bungee, you control the tow, so unlike those two, if theirs a problem you can back off the tension immediately.

It saves your shoulder, lower back and hip too versus pulling all that load each time against a strong high start.

Same as a winch...but a lot easier to hump out of the car to the set up area.

It saves a few miles a flying day of chasing a chute because the tow doesn't take much space in relationship to the height of the launch.

All the components are done very professionally, so looks nice and will last your life time.
Gordy
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Old Nov 02, 2012, 12:10 PM
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United States, VA, Richmond
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I've had my One Winch for about two weeks now. I've done about 30 launches on it.

I launched a scale 2.5M FlyFly Swift S-1 using a single hook at the base of the fuse. The hook wasn't even centered. No problems. Got it to about 200ft. I have shortened the line though to fit my field. The glider flies like poop but had no problems on the OneWinch
I'm really impressed, this glider is very heavy (lots of nose ballast for cg reasons) but it still lugged it up! I'm running the 4:1 ratio.

I'm going to try next with my TP model 3M Duo Discus I'm putting together now which is also a bit heavy. I'm hoping to get in the neighborhood of 400ft but that will likely take some nice headwind.

I have to hand it to Tim on getting 500+ft!!!!!
I think the OneWinch is easy to use, I was self-launching from my first launch with no misshaps. However, my launches are getting better so there is a learning curve, just not that steep.
Recommended!
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Old Nov 02, 2012, 01:45 PM
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United States, KY, La Grange
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Pete - timing is everything. I am about to start a new build of a 1/3 scale primary glider, but for now my only launch options are the club winch. That makes me nervous, especially launching a 4 meter wing which will be built to original factory plan specs with some reinforcement for good measure. I've been thinking about the One Winch as a better launch option due to the ability to control the ascent and 'feel' the glider as it climbs. Glad to see someone else launching scale ships with it.

One question, are you launching from a toss, or are you rolling the plane off of the deck as most recommend for winch launching a scale ship?

For that matter, has anyone used the One Winch for a roll-out type launch?

Dion
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Old Nov 02, 2012, 02:36 PM
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4 Meter wing? What is the target weight?

Is this for thermal soaring where you will want a high launch or to get the glider out into slope lift where a relatively low launch is needed but usually in restricted space?

Will you typically be launching into the wind (5 mph or more) or do you have a lot of calm days?

I have never done a rolling start with the OneWinch. I have launched my 3.4M Ventus 2C with a winch from a rolling start. It would be interesting to see how it would work with the OneWinch.

The unknown is how well you can get that inital burst of speed to get the glider airborne. From a hand throw your throw provides this. But from a standing start on the ground ... I wonder. Might not be an issue at all.

One thought is, if you did need a little help getting that inital burst would be to have a piece of bungee or hi-start tube attached to the aircraft end of the OneWinch to help get that inital burst that could be helpul to getting a scale ship off the ground. I don't know if it would be necessary or not but it would make an interesting launch. Sort of a OneWinch/Hi-start combo.

When we launched with a winch off the ground, one person would hold the tail whlie the pilot would tap up tension on the winch. When the tension built to a certain level we would release the glider and up it would go. We would usualy use a harness for ground launching with the hooks under the wings going to a center hook that would grab the winch ring. I guess you would do it the same way with the OneWinch.

Just not sure how easy it would be to get the inital burst you need to get airborne. That is why I thought of the bungee or a section of HI-start that you could tension up to help get the glider airborne. Walk back to stretch the rubber while someone holds the glider tail. When you hit that tension point, let go and walk back as normal with the OneWinch. You could probably do it all by yourself with a little practice.

Sounds like a fun project. Wish I could join in. I will be following any posts on this.
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Old Nov 02, 2012, 04:52 PM
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Okay I like this!
I was wondering if there were some other scale pilots out there!
ROG takeoff is possible with a runway and a helper to hold the plane. You walk back and get the tension about 60% of what you would do in a hand launch. Use a bridal setup and I bet you would get a nice take-off into a climb. Very scale!

I also think you could just toss it and really, really lay into the line and get it going. The problem with ROG as I'm sure you know is it's not great for your final altitude.

Nonetheless, I'm still scared to toss my Duo. So pretty right now. I would hate to have a misshap on maiden....
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Old Nov 02, 2012, 05:38 PM
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Thanks guys. Interesting idea with the bungee Ed, but I'd also be concerned that if the tension wasn't matched correctly on the winch line, you might actually do more harm with some built in slack. I do like Pete's idea of building up tension on the ground with a helper, just like with a regular winch.

There are two goals with this scale project - #1 is the build. It's all about the build, and not much more. I'm going for the 'museum quality, and oh by the way it flies too' approach. A distant #2 is flying it, or more like 'gliding' it. The primary 'gliders' of the 20's and 30's were being bungeed of of the top of a hill and the pilots would glide them down the slope. I don't think there was a lot of thermalling or even sloping involved, and my subject actually pre-dates the term 'sailplane'.

So if I get a 200 ft launch, then gracefully 'glide' back to Earth and land in one piece, I will be happy as a clam. I have plenty of other ships for the one hour thermal flights and spot landing contests.

Pete - any chance for some ROG video?
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