Dynamic Soaring in the ground boundary layer - RC Groups
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Jan 15, 2007, 09:27 PM
Registered User
MSelig's Avatar

Dynamic Soaring in the ground boundary layer

Here's a link to a movie from FS One that shows dynamic soaring on land.
I think this would be pretty hard to do in real from a chase vehicle....


From that link:
"The sailplane starts out near the ground and flies in orbits that extract
energy from the wind shear. At one point the sailplane ends up doing
orbits that cover about 500 ft of altitude from top-to-bottom. This
is something that could be done in real life with a pretty good wind.
The wind is blowing at 30 mph at 6 ft above the ground. Aloft the
winds get up to 75 mph. The atmospheric ground boundary layer is
about 500-ft thick and is typical of what could be found over open
grasslands. The sailplane has a wing span of 13 ft and a wing loading
of 2.5 lbs/sq-ft (26 pound total weight). This pretty much matches the
size and weight of a Wandering Albatross. The g-loads get pretty high
at certain points ... and I'd guess that's why real birds don't fly
quite like this one."

Last edited by MSelig; Jan 15, 2007 at 09:39 PM.
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Jan 15, 2007, 10:29 PM
Pilot of things.
bryanduke's Avatar
Looks good - we just need to get a real 13ft model to do that now. Winch launch then dive in?

NASA Dryden has a SODAR setup we could maybe use to help map the winds.

Jan 17, 2007, 01:11 PM
UN Earth peoples true enemy
treehog's Avatar

I can see a whole load of chase cars on the the great plains and they not after

I can see a whole load of chase cars on the the great plains and they not after tornados not just yet until one of them figures that the wildest wind sheer ever made
and the way to get the fastesst kick butt speeeeeeds

way to go

As a rough rule the bigger the plane the faster it will go and in the great plains where roads are straight and not full of cars a chase car could be worth the effort if it could result in exceeding the present 300mph mark so I can see a bucket load of chase cars
and 13 foot gliders god help the low flying crows

and if you go fast not being beside a hill to hit will keep costs down a bit

Also dont tell the airlines about this fuel saving sytem as we will all get airsick fast
as we wing it down wind for free

However there are lots of places this car chase or any chase DS system cant be done so I am pusuing that line of logic preferably sitting in a deck chair at a club and doing my DS there (dreams )

I have expermented a bit with trying to find DS from air tripped affectes on flatish terrain such as long distance turbulant tree line affects sine wave riding and down flowing air and needless to say most attempts have produced no noticeable results but a few did seem to have a kicker affect similar to hill DS

Are you able with that FS to repeat the glider project using a electric motor instead that would supply the missing energy required to make stationary DS affect posible

I suspect that a high pitch high speed propellor used in the dive mode would supply the correct amount of missing energy and you would not have chase of downwind after the craft and so save energy from car chase and energy as you sit in deck chair
lazy fly DS

I could be wrong the solution might be a short engine run low to the ground and go upwind and motor off then climb or mayby both methods work equaly well

As the Simulator can probably get results back faster than real life it would be interesting to know if electric assist DS is worth the effort in speed gains over normal F5b dive zoom flying

I suspect it will at the very least double the flying times in steady wind ideal conditions

I suspect it wil also result in that cheaper combos will return high speeds to top end F5b and top f5b will return speeds even faster again with smaller deeper pitch props

At this stage its only a vauge possibilty but if simulator confirmed that flat terrain DS elecrtic assist was useful and what metods were best that increase the possibilty that far down wind hill tripped up DS affects might be possible also

I opened a thread on a similar theme where you can see what I mean

If you cant run the electric version not to worry I will get around to making one of the freebee simulators do that but I am not much into the simulator stuff for DS yet only sims for the UAV stuff presently


Jan 18, 2007, 01:37 PM
Michael Allen
NASA has taken SODAR data on winter days when the temperature inversion was very stong and found strong wind shear. Summer wind gradients seem to be less because of mixing from convection.

NASA also has a 14-ft span autonomous motorglider based on the SBXC.

How high are the g-loads?
Jan 20, 2007, 08:49 PM
Registered User
lesterpk's Avatar
Joe Wurts did a demo and DS'd a hedge line on the edge of the field for a while down in NZ a few years back.
Jan 21, 2007, 07:59 AM
launch low, fly high

That goes back a few years! That was the Soarchamps in Christchurch, I think 1999. I remember that the hedge height was about 3 to 4 meters, and that the DS orbits that I was doing were a bit downwind from the hedge. Not a lot of energy, really just sustainment DS. The fun part was that the required flight path included the wing tip being on the order of a half meter from the ground on the lowest part of the orbit. Not for the faint of heart.

Originally Posted by lesterpk
Joe Wurts did a demo and DS'd a hedge line on the edge of the field for a while down in NZ a few years back.
Jan 21, 2007, 02:09 PM
Dave Reese's Avatar

Dr. Ferdinand Hendriks

Thats a pretty cool sim.

Dr. Hendriks wrote a paper about this back in 1972. He also built a glider to test his theories out but according to him he didn't have the thumbs required to fully test his theory.

>Dr. Ferdinand Hendriks wrote<
"In 1972, I attempted DS in shear flow over horizontal terrain using a radio controlled glider. Unfortunately, those attempts failed. In the mid-1990's, RC glider experts successfully performed DS in the concentrated wind shear layer of Parker Mtn, CA. Flying RC gliders in this thrilling manner has now become wildly popular among a growing group of RC gliding enthusiasts. Movie clips of DS in shear have been published widely on the WWW. The current world speed record of DS gliders stands at over 200 mph. While DS-ing in shear has been realized with unmanned, controlled gliders, DS-ing in turbulence has (to my knowledge) not. My mathematical model of gust soaring suggests that it requires very slow flight (light wing loading). Gust soaring should be the domain of flying animals with very low wing loading. Frigate birds, Kites, and even butterflies. With today's technology,
demonstration and development of a smart, gust soaring glider seems closer than ever." -Dr. Ferdinand Hendriks
Jan 22, 2007, 03:20 AM
Registered User
lesterpk's Avatar
Yep, that was a while ago. I wasn't there as I was living in Australia at the time but heard plenty about it. Soarchamps are a couple hours further south this year, Timaru, looks like a pretty decent bunch (6-8) from the NI heading down.
Made any plans for the Soarfest yet?
Jan 22, 2007, 09:16 AM
Throw Caution to the Wind
Lavawing's Avatar
I don't know if we'll every be fully DSing the ground boundary layer. But I know I want to see evidence of KOTH DSing in an outfit like that.
Jan 22, 2007, 06:19 PM
launch low, fly high
Originally Posted by lesterpk
Made any plans for the Soarfest yet?
We are planning on attending, and have made reservations for a place to stay at. See you there!
Jan 23, 2007, 01:37 AM
Registered User
terry.cx's Avatar
I've not flown much DS, but I sure have come back from enough downwind thermals when the wind was blowing. The difference between winds aloft and wind at ground level is certainly there but mostly the wind speed gradually decreases as you get lower. Mostly I dive down on the way back not only to increase my airspeed but to get lower where the wind wasn't blowing as hard. I can't recall when the wind speed dropped low enough to encourage me to pull up and circle. Like previously mentioned, I think you're going to need something to trip the boundry layer up wind someplace for this to work.
BTW, Michael I met you at least 15 years ago at a Valley Forge contest. The next day I bought a Prodigy that I still have.

Jan 23, 2007, 01:57 AM
Registered User
MSelig's Avatar
The g-load gets up to about 10 g's (requires mostly smooth flying to
keep it down this low). Here's a video that shows the g-load. Each
cycle gets higher speed, more altitude and more g's:

http://www.inertiasoft.com/videos/fs...ing640x480.mov (37 MB)

Below the g-load number is the max g's in the flight. It starts out near
1 g.

The 640x480 size shows all this data:

- g-load
- flight speed
- "wind sock"
- compass
- alpha and beta
- rate of climb
- altitude
- map
- stick input

I had to use the latest version of Apple's QuickTime (7.1, free) to have
the mov-file play properly. I think it uses the "latest and greatest"
codec from Apple.

I've not been able to fly this ground boundary layer DS from the ground
view (standing pilot). Also, flying from a camera stuck on the plane is
pretty hard/disorienting. So the only thing here that works for me is
this lagged camera view.

I've also put some other soaring videos there:

http://www.inertiasoft.com/videos/fs...ancaCrater.wmv (DS, 11 MB)
http://www.inertiasoft.com/videos/fs...gFullScale.wmv (aerotow, 28 MB)

I've got another video of flying in a full-scale Swift doing DS in an
inversion layer wind-shear low to ground. But it is a pretty big file
to post...

At some point these might get posted on the fsone site.


Terry - Valley Forge. Humm ... I seem to remember a contest back then
where a Terry put an E214-something up in a tree. Same contest/same
Terry??? I still have a Prodigy also, and Paul Carlson is still around
here selling model stuff.

BTW - This DS stuff in the ground BL requires a pretty hefty wind at
ground level, and it's also the type of wind shear (BL) that's found out
on the open planes (not many trees around). In the video above, the
wind compass shows that the wind speed increases smoothly w/ altitude.
And another trick to flying like this is the super high wing loading.

All consistent w/ Dr. Ferdinand Hendriks! I first got to read that back in 1984
when Herk Stokely gave me a copy.

Jan 23, 2007, 03:09 AM
Registered User
terry.cx's Avatar
Originally Posted by MSelig

Terry - Valley Forge. Humm ... I seem to remember a contest back then
where a Terry put an E214-something up in a tree. Same contest/same
Terry??? I still have a Prodigy also, and Paul Carlson is still around
here selling model stuff.
Not me, maybe Terry Luckenbaugh. I flew a Cumic Plus.

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