I'm doing some digging to learn a bit about wind behaviour due to terrain/obstructions etc in hopes to gain some enlightenment on my first official
loftings on the weekend. It was not a fun feeling given the tight spot we were in. True to the "rules" we shouldn't have been flying there really
because we barely had 2 line lengths downwind at the tight end of the space but when it's all you got what else can you do?
I'm hoping it's just a matter of the direction the wind was blowing which meant it came along and over a shallow ravine, then up and over some trees
into the field. Based on the curved arc in these diagrams I wonder if the movement of the air actually has an upward flow which is what the kite got
into (Psycho 3)? I've flown this thing in all kinds of conditions and many much stronger gusts than this and never got lofted. Our winds were zero
(literally) gusting to MAYBE 15-20km/h on the rarest of gusts.
Both times I was hardly moving, actually the big loft I was near dead stopped as I was transitioning to head back around. The kite was not sent at
all, just hanging out at 12:00 waiting to come around and up I went like I was a piece of lint. No yank, just up, up and away. Not sure how high, felt
like a mile of course but when you only have about 50 yards to badthings even 2 feet off the ground is not a good place to be.
Can someone help head scratch this one? I'm sure it's just a matter of bad luck in wind direction, no?
I assure you - it was nothing to do with this:
kitedelight - 24-6-2012 at 10:38 PM
your third pic is the only option, sorry.
lofting in 20kph gusts? The wind MUST have been stronger where the kites were flying, did you notice that throughout the session at all?
how far were you guys from the trees?
Not sure I can help anymore than asking these few more questions and leave it to more terrain knowledgeable folk.revpaul - 24-6-2012 at 11:00 PM
Kelly was parked about 30' behind me and my little fella was sitting on my lap on the landsailer (we were parked[waiting on a gust] pointed nose away
from Kelly).
Spencer looked back over his shoulder and shouted "Look guys, Kelly is flying!!".
I had thought I heard Kelly and Derek talking about jumping a little earlier so I simply figured Kelly was performing as per as I turned around to see
the (not bad) landing.
Paulstetson05 - 24-6-2012 at 11:24 PM
Besides the idea of the updraft (I think thermal) the only other idea I can add is how as wind goes over something it can sort of compress.
Paragliders use it all the time. The wind encounters the base at 4mph, in the middle at 4mph and top at 4mph but adds to the air from the base as it
travels over . When it reaches the top all the wind energy has added up to maybe 12mph like the pic with the trees. The energy has to go somewhere.
Add in a gust from 4 to 8 and suddenly you could have 24mph.
The problem with turbulence is you never know which way it will go. Its all fun if you have landed ok but it is often my cue to change something or
quit. Which might be why I progress slowly.Kamikuza - 24-6-2012 at 11:30 PM
"Rotors" is a word I've heard a lot at other forum ... yet to get around to a thorough research on them though ...beachrights - 25-6-2012 at 06:27 AM
Bladerunner - 25-6-2012 at 06:32 AM
It is the Psycho's fault .
I would sell it off real cheap ! snowspider - 25-6-2012 at 06:53 AM
Was it a hot sunny day, if so you may very well have caught a thermal lifting off. My understanding about lift from terrain is that it developes in
front of and somewhat above the obstuction. You guys flying behind a terrain obstuction will see downward rolling air (rotors) , trees and buildings
where the wind is moving over and arround,will give you a mix of everything ugly. If your lines are long enough you can fly above the lower turbulence
but maybe it boiled up into what seconds befor had been clean air. The curved line in the drawings is not so much showing lift ,its more indicating
the likely boarder between the two wind conditions.macboy - 25-6-2012 at 09:08 AM
It was a pretty nice hot day, yes. The loftings both happened in nearly the same area of the field. The bigger one was maybe 15 feet closer tot he
trees/ravine edge. Probably about 75 feet away?
Kami - rotors (I believe) are relatively localized to the obstructions and are much like the back of a pickup truck on the highway. THat swirling
turbulent area rotors the winds around.John Holgate - 25-6-2012 at 02:48 PM
If you've ever sat and watched how the water behaves in a stream or river where it flows around rocks, forms little eddies and can come back upstream
behind obstacles....wind is the same. You could have copped a bit of thermal or a bit of rotor. If the wind rolls downwards over an obstacle, then
at some point, it must travel upwards too. The fact it was happening in a particular spot leads me to think of a rotor/turbulence. I get all sorts
of weird things happening around home - particularly on the other side of my small dam - the turbulence coming off a 9ft high dam wall makes it a real
struggle to fly on the other side.
The best analogy for thermals is a Lava lamp - sun heats up a particular spot of land due to color/slope/material etc which in turns heats up the air
above it....eventually a large 'blister' of warm air rises up from the ground - just like a lava lamp and depending on the humidity levels and a few
other things that don't quite come to mind (!) eventually condenses and forms a cloud. Although you can certainly have thermals with no clouds above
them. And if a thermal has enough oomph to allow 500kg of Glider and pilots to easily gain altitude, I'd say it would be a fair bet it can lift 80kg
of pilot and kite!
A few years ago, what we call a willy-willy - same thing as a dust devil - actually came off the sea in an on-shore sea-breeze and slammed a couple of
our buggiers at Kingston. Just goes to show how tricky and hard to predict the wind can be. Throw in the turbulence from obstacles on land, varying
drag from the surface of the earth and chuck in a few thermals along the way and it can be a real mess!Kamikuza - 25-6-2012 at 06:32 PM
2 years back, in the middle of a city, some kind of weather event picked up a large and heavy marque and dumped it on the kids in the sports festival
at the wife's school ... broken limbs etc. Made the evening news. Just a regular summer day ...!
Be careful out there! And pay up your insurance :ozero gee - 25-6-2012 at 06:39 PM
I usually avoid kiting on land inland during the heat of the day when convection is at it's worst and aggrevated by turbulence from obstructions. I
have seen too many injuries to guys riding in those conditions.
