Physics question of the day

bambam · Since 15 Mar 2005 760 Posts Hood River Photographer

Hey Hein,

Come on man, lift is an equation that deals with many variables... One of them is velocity, which is basically the apparent wind that the foil encounters... Stop making people scramble for those aeronautical textbooks that we all just happen to keep on the coffee table...

Portland Pete · Since 08 Mar 2005 145 Posts HR Stoked

Hein
I'll bite, Here is a guess at an FBD from the board's perspective.
The board is on an upwind tack going across the river.
Water Current adds partially to board speed vector since it is not directly
inline with the board's direction of travel.

So my answer is no, 10+4 does not equal 14.

The numbers in the picture dont exactly match the question posed by Hein
but the vector magnitudes and directions are close to scale.
Pete

Guest · Tue May 17, 05 2:05 am

fokiten · Since 04 Mar 2005 188 Posts Stoked

Regards,,

I think it's clear that we are capable of simple.

We are more or less a simple folk.

It's when we stop patting ourselves on the back and handing out awards that we find we don't really have a clue about how it all works.

You can pump down a vacuum jar and as you approach a total absents these virtual particles precipitate out of the nothing; they exist in pairs and annihilate each other when they collide.

near the event horizons of black holes where space itself gets shredded some percentage of these virtual pairs lose their partners and become real particles.

Yup something from nothing, they call it Hawking radiation.

And because of it Black holes glow white hot.

We've no clue....

We're a simple folk; the bother of ants under a billion billion stars...

fokiten the malignant, wink,,lol

Guest · Tue May 17, 05 8:04 am

Pete,

But, what if the relative velocity of the wind (speed with a directional vector) was directly opposite the direction of the current (relative boat speed)... Hmm, suddenly 10+4 does indeed add up to the full 14...

But this all is just theoretical since in real life the kiter is moving relative to the wind and steering the kite, and thus your relative windspeed at the kite becomes an angular component of all that crap anyway. So, why ask why anyway?

trevorsmith · Since 25 Apr 2005 501 Posts PDX Addicted

Here is some more technical info about a windsurfing board and wind..Lots of drawings for angle of wind to the sail etc. Maybe someday we will see a kiteboard site about apparent wind.

http://www.bluefinz.com/technique/apparentwind/apparentwind.asp#TrueWind

pkh · Since 27 Feb 2005 6548 Posts Couve / Hood Site Lackey

Great link Trevor... I wonder how many kiteboarders even think about apparent wind?

gabe · Since 16 May 2005 475 Posts Obsessed

Hein · Since 08 Mar 2005 1313 Posts Possessed

If I'm going back and forth across the river then I think some current is better than the equivalent in more wind. Can't deny that a powered kite and a bit of current is a sweet combination.

Maybe its due to the fact that the apparent wind phenonemom dilutes the power of more wind to a greater degree. Current seems like it has a more direct effect on the board. Maybe it acts at more advantageous angle. Since it seems that no current and all current are not as good as some wind and a smaller amount of current then there must be a sweet spot where the ratio of wind to current is ideal. Wonder what that is?

Can't believe no one has invoked the 2 shot rule on me for this thread.
-Hein

fokiten · Since 04 Mar 2005 188 Posts Stoked

Regards,

I'd suggest that there is no current for folks afloat, only for folks ashore.

Meaning wind is wind, be it apparent or God given.

You the rider cannot distinguish the difference, therefor the question becomes moot.

Example:

Einstien call his theory "equivalence" not relativity,,,

It's like this, one cannot distinguish between being accelerated at one "G" in a box in deepest gravity free space,and being in the same box in the presents of a (local) one G gavitational feild.

You can do all the tests, drop stuff,,,falls at the same acceleration,,,etc, etc. they are equivalent,,,in his theory,,but now after tests, also some stuff , in fact.

This is how he decided light must bend in the presents of a gavitational field,,,,

you see,,
The accelerated box would move as the beam traveled through it,,,Ahem,, appearing to bend!! and since they're equivalent in theory...bingo

Genius is pretty simple eh? amazing

Same thing for you,,you cannot measure current and wind separately it's equivalent/ or better said "all the same to you" you the dude in the river.

fokiten

Guest · Wed May 18, 05 12:24 am

Guest · Wed May 18, 05 6:50 am

Not wanting to fuc with you all but,

If you kite at lesser upwind angles (you say>"and thus be more powered") you'd actually be less powered,,Hey no biggy...

I think ya gorgies are current obsessed, when in fact in terns of being in the flow there is no current independent of you, and without a shore to measure your movement against no way to tell your moving,,,That's the problem with the wind is it natural wind? or apparent wind?? without a sationary refference complete with it's own wind meter, there is just no way to know.

Again, standing on shore in a one Knt. breeze is equivalent to bobbing in a one knt. current in no wind.

They are indentical or equivalent in thier effect on wind sensors.

No biggy

I'm currently done with this,,,
regards
fokiten

fokiten · Since 04 Mar 2005 188 Posts Stoked

Ok,,

I see what you ment,,,you can kite on a beam reach,,and still make ground to winward gratis the kindly current.

Point to consider, aside from hawking radiation there is no free lunch.

example:
Courtesy of this kindly current your beam reach will still feel identical to that upwind course you have forgone.

no gain, nothing whatsoever in fact your getting fucked by that current in nuken,,,you'd have to run down wind just to breck even,,,

sorry I'll shut up now

Carry on gentelmen
out

shastadogs2 · Since 28 Mar 2005 336 Posts Obsessed

all this talk about wind is interesting, but for me its kinda' like talking about love-i would much rather be hangin' out with my gal. . .

i was on kitebeaches.com the other day, thanks to the person who put up that link, its useful.

great site, thaks again to the folks that keep it going, and to nw kiters, the friendliest i've met yet. stay on the high roads bro's.
jimbo

gabe · Since 16 May 2005 475 Posts Obsessed

sorry to bring up such an old thread, but i had made many strong theoretical arguments about this topic, while people suggested that actual experiences might change some of my views--specifically that current has no effect on dragging to a board. now, months later, after kiting in a very wide range of currents, and bodydragging back to the board 100x more than any other kiter since i have been strapless, i feel that i have a very strong collection of data points.

and these confirm my theoretical understanding that there is zero current effect on a bodydragging situation (as long as you and the board are in the same current of course.) i believe this is a myth created by the fact that most people don't body drag often and when they do it's after a huge crash that disorients them and makes them swim to relaunch, and they blame the problem on "current." so next time, no excuses--just be more efficient body dragging, and relaunch the kite faster so you can keep the board in sight. of course, if you leave the magic carpet and enter the beach to ditch your ripped kite, the board will be long gone.

of course, i also still contend that 10kt wind + 4 kt current is equivalent to 14kt wind. but the former feels better because you can kite lower angles while still getting back to the launch--basically a downwinder. i realized something basic but kind of amazing: if you are in 2kts of current at rufus for example, and you kite for 3 hrs, you will have done a 6+ mile downwinder! in these terms, no wonder it feels so fun... makes you never want to kite still water again. that's a lot of ground to make up.

Wind Slither · Since 04 Mar 2005 2573 Posts The 503 METAL

What's interesting to me is the other day at SI, the current was coming in so strong with the wind that nobody could stay upwind, even though there was plenty of power. Nobody that is, except Tonski who was having no problem. She was taking her first ride on a new board.

You guessed it, a Hein. Shocked

West-bound this week folks....let's get 'em.

fokiten · Since 04 Mar 2005 188 Posts Stoked