*


All times are UTC + 1 hour



Post new topic Reply to topic
 [ 25 posts ]  Go to page Previous  1, 2, 3  Next
Author Message
 Post subject: Re: difference in the strength of cold/dry vs warm/humid win
PostPosted: Thu Jan 17, 2013 4:59 pm 
Offline
Very Frequent Poster
User avatar

Joined: Fri Jul 16, 2010 6:27 am
Posts: 2051
Location: Ford Lake, Michigan
Bille wrote:
I Really notice that difference whenever i go from Mohave
to the coast in San Diego !

A 25 in the Dry Mohave desert, isn't anywhere Near as strong
as that coastal air with the same wind strength. I remember Mohave
being about 640ft above sea level, so it isn't really an altitude thing.

Bille


640 feet means about 1027mbar so it's about 1% less powerful than sea level wind purely from altitude. The dry air is about 0.05% more powerful than the moist coastal air. With a 20F difference in temperature that's about 1.5% less powerful warm air.

We can feel the dry air very easily so we like to think it affects the kite but it's everything else that's more important.


Top
Profile
 Post subject: Re: difference in the strength of cold/dry vs warm/humid win
PostPosted: Thu Jan 17, 2013 5:34 pm 
Offline
Very Frequent Poster
User avatar

Joined: Sun Sep 04, 2011 5:37 pm
Posts: 1527
edt wrote:
...

We can feel the dry air very easily so we like to think it affects the kite but it's everything else that's more important.


So it's mostly physiological then ?

One thing for Sure though , the SD crowd gets a Good laugh when
i show up with my Full wetsuit in the middle of summer !
i like it best when it's a hundred deg + & the water is Way warm .

Bille


Top
Profile
 Post subject: Re: difference in the strength of cold/dry vs warm/humid win
PostPosted: Thu Jan 17, 2013 5:41 pm 
Offline
Very Frequent Poster

Joined: Fri Oct 30, 2009 9:13 pm
Posts: 926
Like someone else said currents play a large role in power or perceived power. Strong currents can make or break a location. Here in the Houston area Galveston East beach is the main surf spot the problem with it is the strong current that is created from the jetty and shipping channel. Current will normally be with wind so as a personal rule I won't even attempt to kite there unless the forecast is over 20kts.

All so we get lots of pressure bubbles that pushes the wind up higher than our kites. This is because the island really is just a sand bar and until the bay gets hot the wind is really light on the beach. Usually 10kts lighter.

One last thing I will bring up is changing wind directions. Not only will the wind lull and gust it can shift direction. If it is real shifty and changing its angle a lot you could find your self going down wind even though you feel powered. This is really hard to notice and get in sync with. Just the other day I was out and about to pack up when I figured out that it was just shifting. Changed up my tacks with the wind and found myself shooting upwind even though the wind was light and I only really had enough to power to stay upwind with the tide going out.


Top
Profile
 Post subject: Re: difference in the strength of cold/dry vs warm/humid win
PostPosted: Thu Jan 17, 2013 6:19 pm 
Offline
Medium Poster

Joined: Sat Nov 17, 2012 7:39 pm
Posts: 101
Location: CA, HI
http://www.gribble.org/cycling/air_density.html

for dummies: hot, high and wet = bad

If you are interested how much, then you should calculate your rho (lbs/cuf or kg/kuM) and multiply it with your kite size. Playing with some numbers shows you exactly how your kite (and its pull) is affected by temp, altitude and dew point.

peace


Top
Profile
 Post subject: Re: difference in the strength of cold/dry vs warm/humid win
PostPosted: Thu Jan 17, 2013 7:24 pm 
Offline
Very Frequent Poster
User avatar

Joined: Fri Jul 16, 2010 6:27 am
Posts: 2051
Location: Ford Lake, Michigan
Bille wrote:
So it's mostly physiological then ?


Bille


oh no. The difference you feel is quite real. The problem is that we can feel moisture in the air very easily but we find it very difficult to tell when we are up or down 800 feet in altitude. So we think it's the dry air when it really is the altitude. Or maybe it will be a dry day and the wind gradient is very even, so it's 15mph on the ground and 15mph 20 meters up in the air, but on a moist day the wind gradient might be 15mph on the ground and 25mph 20 meters up in the air. So we think it's the dry air but it's really the wind gradient / altitude / temperature / current etc.

But the difference is definitely real.


Top
Profile
 Post subject: Re: difference in the strength of cold/dry vs warm/humid win
PostPosted: Thu Jan 17, 2013 7:38 pm 
Offline
Frequent Poster
User avatar

Joined: Tue Sep 04, 2012 3:21 pm
Posts: 209
Location: Canada
Does anyone have a Temp X Windspeed = Force chart for this? Because that would come in handy...


Top
Profile
 Post subject: Re: difference in the strength of cold/dry vs warm/humid win
PostPosted: Thu Jan 17, 2013 7:50 pm 
Offline
Very Frequent Poster
User avatar

Joined: Fri Jul 16, 2010 6:27 am
Posts: 2051
Location: Ford Lake, Michigan
shawn13 wrote:
Does anyone have a Temp X Windspeed = Force chart for this? Because that would come in handy...


pressure is proportional to temperature measured in K. 20c (68F) is 293K. So going from 20c to 10C (50F) is 10/293 about 3% stronger wind. You dont really need a chart just be able to do division.


Top
Profile
 Post subject: Re: difference in the strength of cold/dry vs warm/humid win
PostPosted: Thu Jan 17, 2013 8:38 pm 
Offline
Very Frequent Poster
User avatar

Joined: Wed Oct 16, 2002 1:00 am
Posts: 5359
Location: Denmark
Would just point to a 10 year old thread: http://www.kiteforum.com/viewtopic.php?f=1&t=5159

The image links were "old" (meaning, our national phone company has closed these sites), but I've replaced with new worlking pictures/links today 8)

If anyone find a "dead" link from me anywhere, any posting - please let me know, as I have all the data, and can easily be replaced.

Dont know if it can be used - but the very same topic :thumb:

Another thread, similar: http://www.kiteforum.com/viewtopic.php?f=1&t=2312432

:D Peter


Top
Profile
 Post subject: Re: difference in the strength of cold/dry vs warm/humid win
PostPosted: Thu Jan 17, 2013 9:37 pm 
Offline
Frequent Poster
User avatar

Joined: Tue Sep 04, 2012 3:21 pm
Posts: 209
Location: Canada
I was actually looking for something like this:

http://localkitespots.com/boost.htm


Top
Profile
 Post subject: Re: difference in the strength of cold/dry vs warm/humid win
PostPosted: Thu Jan 17, 2013 9:46 pm 
Offline
Very Frequent Poster
User avatar

Joined: Wed Oct 16, 2002 1:00 am
Posts: 5359
Location: Denmark
shawn13 wrote:
I was actually looking for something like this:

http://localkitespots.com/boost.htm


Exactly - thats why I linked to this (the very same) :thumb:

But if easier, a direct link:

Image

:D PF


Top
Profile
Display posts from previous:  Sort by  
Post new topic Reply to topic
 [ 25 posts ]  Go to page Previous  1, 2, 3  Next

All times are UTC + 1 hour


Who is online

Users browsing this forum: fourperf, kazama-fury, marlboroughman, TheRussian and 18 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group