*


All times are UTC + 1 hour



Post new topic Reply to topic
 [ 45 posts ]  Go to page Previous  1, 2, 3, 4, 5  Next
Author Message
 Post subject: Re: Unexpected telltale results
PostPosted: Sun Aug 25, 2013 1:12 pm 
Offline
Medium Poster
User avatar

Joined: Tue Jul 15, 2008 1:40 pm
Posts: 199
El Rudo wrote:
lobodomar wrote:
Exactly. Even in the closed position, the vented canopy (net+outer ripstop) adds extra drag and weight.

BTW I own a 2011 OR razor, so had my share of first hand experience with the venturi system. It's a nice kite, but in my opinion the venturi is a marketing thing, something to stand out from the crowded kite market. Think about airplane slots: they are close to the LE, not to the TE like on OR kites. It's close to the LE that you need to energyze the boundary layer so that it keeps attached to the wing along the chord. Plus most of the lift is produced in the first half of the kite (center of pressure is usually at about 1/4 of the chord).

But of course OR didn't put the vent in the front, I doubt that a naturally vented (instead of mechanically open-close) slot would not screw up the kite's aerodynamics in a such a critical zone. They put it in the back, where it can do neither harm nor good.


The initial idea of the OR designers was to put the vents more towards the LE. Tell tale testing showed that they would be more effective towards the TE, to suck the flow back on to the canopy at higher AoA's, like Bille describes above. Airplane wings are designed to perform with AoA's differing only a few degrees. Kites fly with way bigger AoA variations depending on what you do with them.

The extra drag and weight you mention are there in deed, but we're talking a few grams and only very little drag.



Even if it's true that the vents manage to reestabilish a less turbulent flow between their location and the trailing edge, it really doesn't matter much if there is any separation between the vent and the front of the kite.

To be fair, because of interference of the leading edge tube, the center of pressure of kites is probably more than 25% of the chord like on regular airfoils. But still, most of the lift is generated before where the vents are located. I still think that OR placed them where neither much harm nor good can be done.


Top
Profile
 Post subject: Re: Unexpected telltale results
PostPosted: Sun Aug 25, 2013 1:25 pm 
Offline
Medium Poster
User avatar

Joined: Tue Jul 15, 2008 1:40 pm
Posts: 199
Kamikuza wrote:

I think it'd be a case of negatives outweighing the positives to do it closer to the LE on kites.



That's for sure :wink:

Kamikuza wrote:
No more of a marketing gimmick than diamond tips, no pulleys, sigma LE etc etc . . . ;)


I have no idea what diamond tips are, so they are probably a gimmick.
Pulleys were and in many cases still are a design necessity which is becoming somewhat less imperative as bridled kite design evolved.
I had and sometimes still have great times on my 2009 naish helix, fantastic high wind kite. Low end does suck big time, is a pig to fly in light winds - of course: it has much less canopy where it really matters for lift generation!


Top
Profile
 Post subject: Re: Unexpected telltale results
PostPosted: Sun Aug 25, 2013 1:46 pm 
Offline
Very Frequent Poster
User avatar

Joined: Fri Jan 09, 2009 4:49 am
Posts: 3610
Location: Japan
Point being about diamond tips etc that they've disappeared from the "gene pool" so were probably a gimmick. Using that line of thinking, the Cypher didn't have vents, and now it's gone . . . hmm :lol:


Top
Profile
 Post subject: Re: Unexpected telltale results
PostPosted: Sun Aug 25, 2013 2:32 pm 
Offline
Medium Poster
User avatar

Joined: Tue Oct 20, 2009 9:04 pm
Posts: 113
Location: Moncton NB Canada
Another thing: slots on aircraft wings are always, or almost always incorporated into a feature that drastically changes the shape of the airfoil (slat & flap extension). They are not useful for standard AOA changes, but for maintaining lift through drastic changes to the camber and speed of the aircraft. Again, if it were a concept that worked on kites, OR would stand out sugnificantly from other kites and other manufacturers would license their design. The fact of the matter is, i doubt anyone has flown an OR kite with the Venturi taped shut to see what difference there really is. Im guessing nothing noticable.


Top
Profile
 Post subject: Re: Unexpected telltale results
PostPosted: Sun Aug 25, 2013 3:18 pm 
Offline
Frequent Poster
User avatar

Joined: Mon Jun 25, 2007 8:15 pm
Posts: 296
@ Kamikuza, the Cypher has been replaced by the Prodigy, also without vents.
@ MikeYQM, the 2008 Rises with vents have almost exactly the same planform as the unvented 2007 Rise. Anyone who has flown both can tell you the difference. But you're right, have someone tape up the slots on an OR kite and go back to back with a vented kite can tell you all you need to know. You can do it in the same session, tape it up at home, ride it for a while, take off the tape and see what has changed. Do post your findings on here!

The fact that the industry hasn't been licensing this says more about the industry/market than the venturi's.
Kiteboarding as it has developed over the last years has an emphasis on easy and safe flying, proper wind range and versatility. Consensus is that there are not many bad kites out there for what most kiters do. Apart from course racing kiteboarding is not really competitive, most kiters don't care if they can ride super upwind or in some other way benefit from their kite superior aerodynamics, they mostly ride half wind tacks and are totally happy with a kite that allows them to do some tricks and jumps in a bit of a wind range. All together this leads to a kind of "we don't fix what's not broken" status quo, which is in a way regrettable.
cheers,
Rudo


That's exactly why I really like it when someone puts tell tales on it his kites and discusses it on here.


Last edited by El Rudo on Sun Aug 25, 2013 3:36 pm, edited 1 time in total.

Top
Profile
 Post subject: Re: Unexpected telltale results
PostPosted: Sun Aug 25, 2013 3:23 pm 
Offline
Medium Poster
User avatar

Joined: Tue Oct 20, 2009 9:04 pm
Posts: 113
Location: Moncton NB Canada
El Rudo, "almost the same" planform can mean huge differences, especially with bridle changes. And i dont fault the industry for not licensing this concept. Truly revolutionary changes have been widely licensed across the board: LEI kites, single point inflation etc. so why not the venturi if its as much of a game changer as it claims?


Top
Profile
 Post subject: Re: Unexpected telltale results
PostPosted: Sun Aug 25, 2013 3:42 pm 
Offline
Frequent Poster
User avatar

Joined: Mon Jun 25, 2007 8:15 pm
Posts: 296
MikeYQM wrote:
El Rudo, "almost the same" planform can mean huge differences, especially with bridle changes. And i dont fault the industry for not licensing this concept. Truly revolutionary changes have been widely licensed across the board: LEI kites, single point inflation etc. so why not the venturi if its as much of a game changer as it claims?


Sure, the planform itself means little. But, since you own a vented kite, and doubt whether it's effective, do the tape test and tell us what you find! I see a nice SSW for Moncton tomorrow afternoon so can we expect the results by Tuesday? :D


Top
Profile
 Post subject: Re: Unexpected telltale results
PostPosted: Sun Aug 25, 2013 4:21 pm 
Offline
Very Frequent Poster
User avatar

Joined: Sun Sep 04, 2011 5:37 pm
Posts: 1732
Slotted leading edges and vented flaps on airplane wings have bin
around since before WW-ll ; they have both Active and passive designs.
When done correctly they will add almost NO drag when closed, and Lots
of lift when open.

If the current designs used on modern kites aren't producing the desired
results, then they need to work More on there designs , because the concept
has already bin proven.
Or Maybe ---
the vents work Differently on a curved profile wing like our kites , than on a straight
wing like on an airplane ? Anyway, it's a Good problem that "Could" have
a different solution that hasn't bin thought of yet.

Bille


Top
Profile
 Post subject: Re: Unexpected telltale results
PostPosted: Sun Aug 25, 2013 7:03 pm 
Offline
Medium Poster
User avatar

Joined: Tue Oct 20, 2009 9:04 pm
Posts: 113
Location: Moncton NB Canada
I dont have a OR kite.


Top
Profile
 Post subject: Re: Unexpected telltale results
PostPosted: Sun Aug 25, 2013 7:41 pm 
Offline
Very Frequent Poster

Joined: Sun Jul 13, 2008 9:49 am
Posts: 1115
Location: shallow sea
El Rudo wrote:
tautologies wrote:
eree wrote:
oh, so that is why so many world cup races are won by the kiters riding ocean rodeo kites! :bravo:
impressive...

jesus dude whats up with the constant sarcasm?

I'll bite. The guys at Crissy can tell you that a few years back the OR Rise kite was a serious contender in their races. Or should I say, racers on OR gear (kites don't win races). The Rise was a medium AR kite never purposely designed for course racing. When others brands started designing specific racing kites with maxed out ARs that was over.
Designing competitive racing gear takes serious R&D efforts only a few brands can afford, for that juicy 0,1% chunk of the market most brands tend to leave it alone.
Kiters expect a kite to do everything, and everything unhooked. Most of us are flying compromises. James is spot on with his comment that adding venturis is only one way of balancing performance and ease of handling.
On the OR kites, the vents do work. Try one and you know it.

last time i checked, this is not a facebook, so i don't have to "like" every post here. i can say what i think. i hope you can use my thoughts as a feedback for improving your product.
i know ozone did with the name of the one of their kite.
i know lot of brands did withe bridle configuration for their kites.
http://www.kiteforum.com/viewtopic.php?f=1&t=2353406&hilit=airush+flow

stuff that works usually catches up by other brands. i didn't hear about venturi slots anywhere ever since. or slingshots splitstrut. or sigma segmented LE either, and the anti-stiction windows?
look at the nature, do any of the flying species have those slots or no central support structure (strut)?
natural world and kiteboarding speeds are quite comparable, you know.
(and "anti-stiction" - is that even a word?)

but look what happened to airush sector board! lot of followers. this board made lot of 17 sqm kites obsolete.


Top
Profile
Display posts from previous:  Sort by  
Post new topic Reply to topic
 [ 45 posts ]  Go to page Previous  1, 2, 3, 4, 5  Next

All times are UTC + 1 hour


Who is online

Users browsing this forum: Geronimo79, nafets and 30 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