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Flat land Dynamic Soaring?

Old 01-12-2003, 11:53 PM
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BMatthews
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Default Flat land Dynamic Soaring?

Seeing the thread and vid about DS reminded me of one day a lot of years ago. I'd gone out to my local thermal field only to be greeted by gale force winds and a lot of sullen thermal flyers standing around. After chatting for a while one other guy and I decided to have a go at the wind since a high start was already out. This started one of the strangest flights I've ever had....

The model I was using was an original 2 meter span flat winged aileron "hack" model. It handled the wind quite well and it was a while before I realized that I had been airborne for about 10 minutes but had never gotten above the launch height. I'd crab back and forth across the wind at a good clip and whenever the wind tried to lift the windward wing I'd turn into it with an aggresive turn and pull back a little. This would zoom the model up anywhere from 15 to 50 feet and leave me still with good flying speed crabbing back the opposite way.

I played with these rotors climbing up and alternatley being pushed back down almost as fast for about 20 minutes. By that time my nerves were a wreck but I was laughing like a hyena. The other guy with the FAI Flamingo had done almost as well having been hit by one too many down pushes about 2 or 3 minutes before me.

I put up one more flight after my nerves had settled but I couldn't seem to get into the same groove (burnout?) and the flight was only about 8 or 10 minutes.

So has anyone else tackled stormy days like this?

I've often thought about a model just for this sort of flying but truth be told when you wake up to a cloudy, blustery day it just seems easier to turn over and stay warm and cozy than to venture out in that often cold blustery fall weather.
Old 01-13-2003, 04:34 PM
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Chillybee
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Default Flat land Dynamic Soaring?

I've had similar situations with my 2 meter glider but no ailerons were involved. On those really windy days, it would just sit there and not move forward at all. Crabbing from side to side took alot of skill since once the wing got under the wingtip, downwind it goes. I've wondered if I was getting lift from other objects on the ground or just hit some weak thermals near the ground. But at any rate, my flights had lasted about 15 minutes. Maybe it's my "too stubborn to go home attitude" that kept me trying it over and over again. However, I flew my 1st zagi (15 oz total weight)off of 50 foot high dirt mound saturday in 30mph winds and it really reminding me of the thermal ship. The only difference was that I could fly the zagi into the dirt and nothing happened.
Old 01-14-2003, 03:48 AM
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Default Flat land Dynamic Soaring?

Yeah, I figured out that it was the energy out of rotors and speed shift that kept me up. Wild way to fly.

Too bad you were doing it with a poly ship. The sharper response I had from having ailerons took away all concern about survival and let me concentrate on USING the shifts and rotors very positively. When a gust would roll the model to leeward I'd just crank the stick and the model would literally pivot upwards off the windward wingtip as though there was a big hand lifting the model from that wingtip. It was quite a sight.

Not that you didn't have fun I'm sure but it sounds like you were a bit busier keeping it on track than I was.

But I can't believe we're the only two that have done this....

HEY, WHAT ABOUT THE REST OF YOU GUYS....
Old 01-14-2003, 07:39 AM
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Default Dynamic soaring turkey vultures

On a very windy day in a very flat area near my house I saw 3 turkey vultures coming toward me, so I watched them, they were headed down wind and when they came to a line of tall trees, they made 2 or 3 DS passes behind the trees, picked up some energy and hedded on down wind... cool, now if only I could do that!
Old 01-14-2003, 08:12 AM
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Default Flat land Dynamic Soaring?

Why not try it. There's lots of stories about slope soaring off a line of trees. The only problem is that it's not a great move up for the air so it's not a lot of energy and it only goes to about twice the tree height. But if it was REALLY windy and you had the right sort of model then this dynamic thing might just work in that case.
Old 01-14-2003, 09:11 AM
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Ollie
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Default Flat land Dynamic Soaring?

Some people think that the stationary lift experienced on windy days over more or less flat ground is a form of wave lift. The air has many moods and many characteristics to the flow, some of which are rare.

One overcast day I flew for over eleven minutes at telephone pole height, in a light drizzle of rain, with very little wind, over flat ground and over an area larger than any low altitude thermal. Now what do you suppose that was? It only happened to me once but it was a memorable experience.

In the summer time here in southwest Florida there is often an easterly breeze in the morning. By sometime in the middle of the afternoon a cooler sea breese often sets in from the Gulf of Mexico. The colliding air mass of the seabreeze slips under the warmer air mass from the interior creating gentle lift over a wide area that lasts for an hour or two. We call it the afternoon balloon. Sometimes it is acompanied by a rain shower.
Old 01-14-2003, 08:34 PM
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Default Flat land Dynamic Soaring?

Ollie, I've seen this quite a few times when flying free flight. On VERY dew laden and soggy mornings and especially when foggy but without rain. The air near the ground just seems to be all upwards to about 100 feet or so (about your telephone pole height) and then tops out. Coupe d'Hiver's and P30's sent up in this stuff just hit that 100 foot mark and loiter at pretty much the same height or only loose 20 feet or so before the DT cuts in at 3 minutes. This sort of behaviour is very repeatable here in the Pacific North"wet" and is hardly an isolated incident. I also had a Gentle Lady morning where I got a 20 minute flight over a plowed field in dank cloudy DAMP conditions. Nothing I did in this case would get it higher but if I left the zone and came back it would oh so slowly work it's way back up to the same height.

I think it's the dew forming a very moisture heavy layer close to the ground. Something in that layer is lifting the models up but I have NO idea what it is since you can't feel a darn thing moving. Perhaps the mass of the moisure itself being absorbed into the upper air forms an upwelling of dense water vapour laden air that disapates as it gets higher? And that is what mimicks thermal lift? Just a guess.

I DO know that I don't trust anyone that says their model gets such and such a time in still early morning air. It's all false given the way the free flights stay up in dew and fog.
Old 01-14-2003, 09:14 PM
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lvspark
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Default Flat land Dynamic Soaring?

check this link here mpeg
Old 01-14-2003, 09:21 PM
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Default Flat land Dynamic Soaring?

and another that gives a better idea here

and one more here
Old 01-14-2003, 10:48 PM
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Default Awesome!

Well that's what those turkey vultures were doing... except not quite so FAST! Yahoo, I gotta try that!

CJS
Old 01-15-2003, 01:16 AM
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Default Flat land Dynamic Soaring?

Can we all have a big round of applause for lvspark?....... Take a bow there sparky.... you've eaned it.

Thanks for those vids. All the DS references I've seen before were related to using a slope. I had no idea that we could use a tree line or how. Now I think I see. That sure looks like fun...

So now I need a compact slope model with a bungee hook on the belly.... great.... another one on the list....

PS: That DS on the tree line reminds me of how we would dynamic soar (didn't call it that at the time, called it wind flying) with control line combat models after the engine died. The idea was when the engine started to burp it's last bits of fuel that you would start doing big long figure 8's from low to the ground and pulling up as the model gets to the 4 oclock and 8 oclock positions with the wind coming from 12 oclock and dead downwind being 6 oclock. Done right and adapting to suck the energy out of the wind you could fly till dark as long as you didn't vary at all. Those lines were very draggy ya know..

It just never occured to me that the principle is the same here... :stupid:

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