This webpage just had to be an archive of my DS theories.
Jo Grini, jo(at)grini.no - www.jojoen.no
1st thought |
My 2nd | My 3rd |
My 4th | My 5th
YES Jojo goes 229mph with his Kobra DS
More airfoils from Dirk Flug with comments:
New DS record
New airfoils from Dirk Flug with comments:
News from diary 8.july
My 2nd thought:
DAY .. 28.
February - 2004
- DS theory
Just a theory from a "non engineer":
DS (Dynamic Soaring) what is that ? Lately I have been using some brains on why and how this is happening. My latest "lightbulb" in my head came after looking at a trick on the tv. Moving air has less pressure and will actually be able to create a lift that can move pretty big objects and offcourse air upwards. I have made a movie for you - too understand how and why I think we can fly under the "shear layer" as we call it. There is also a great computer study of a slope in France made by Julien Giraud on the internet. look here. Video of my experiment is HERE (1,4mb .wmv). Backup server HERE
My 3rd thought:
DAY .. 10. March - 2004
So the next "issue" of my "DS theories" comes here. I had a long talk with an airline pilot that knows a lot about windshears and microburst's. The theory about DS "accelaration" is therefore explained easy like this: The mass of your model hitting headwind increases the airspeed that will be outlined if you continue flying in the headwind. But since our DS plane turns immediately into a new headwind (circling) the airspeed increases yet another time. Everytime we hit the headwind the speed increases. BUT Many times have I been flying below the "shearlayer" of wind coming over the hill and there it can be both rotors or almost no moving air at all. I can continue flying well below the "shearlayer" faster and faster. It might be that we are thinking to easy on our headwinds and what that is a shearlayer. Any change in wind will be a shearlayer and change of winds are seen all the time on the backside of a slope. Maybe by just flying thru a rotor will accelarate your plane ? I dont know yet. So anyhow we know that rotoring winds are happening on the backside of a slope but why ? The answers I have got from many is that it "just happens" because of the wind is not able to follow the terrain and will make a rotor because of this. I belive or have been thinking that a rotor happens because of the venturieffect. This effect will be made by the strong wind coming over the slope that makes the air becoming high velocity and low pressure compared to the air below. I say this because we can fly DS behind a treeline or on a seaslope when the wind is from land. Then the air is not compressed but moves freely over the slope. Again I am not an engineer so this is just practical thinking from my side.
My 4th thought
DAY .. 15. March - 2004
One of the
first things I take from these emails is that Andreas thinks that (on the
lifting egg theory):
But we know that the wind will not follow the
terrain above a certain windspeed and drop in height. And since I have seen
these "vortex'es" behind my slope I am curious to use them.
My 5th thought
|DS videos (all copyright Jo Grini,
Arranged with "apx" fastest first
News from diary 8.july
Here you have the video and the frame by frame pictures
Some attached pictures:
This is a follow-up on the glider king post.
I'm attaching a presentation that I gave at the University of New Mexico and also at San Jose State University, where I met
I suspect that you may not be interested in all the math, but at least it shows a picture of the glider I built
specifically for DS. In 1971, Prof. Robert C. Lasiewski was my thesis adviser at UCLA. Sadly he died shortly after we had
formulated a research program to study DS in albatross. As part of that study, the plan was to try to DS with an
RC glider. Both of us were trying to become RC fliers but we never became good enough to execute DS manoevers close
to a flat terrain. There were just too many crashes.
I was fortunate to find another thesis adviser at UCLA: Julian Cole He was not a zoologist, but an applied mathematician
who had a very open mind for interesting subjects (like DS).
The thesis is available from University Microfilms. See http://www.calstatela.edu/library/buydiss.htm
I have not gotten around to create a pdf of my thesis, although I scanned each page.
I'm still very fascinated by "gust soaring."
There is an ultralight full size glider pilot who appears to have mastered the art of gust soaring.
His name is Gary Osoba. See http://www.ipns.com/cole/Content/Published_Documents/Soaring0101.pdf
He uses the term "microlift" which amounts to the same thing as gust soaring. It is no accident that his ultralight glider is so well adapted
to gust soaring. My thesis predicted that also; but please check my math!
I really like your website and after all these years I still hope to do DS my self. This time not over flat terrain, but behind a tall mountain ridge.
Attached presentation of DS by Ferdinand Hendriks (1mb) Download HERE
The Crrcsim is great fro practicing F3F in the french version.