Power Kite Forum

Lift, speed and Angle of attack

BeamerBob - 6-9-2007 at 07:14 AM

Our discussion was off topic in the kite review section so I started this separate thread.

I guess I'm confused by what speed is being referred to. Speed through the window or speed capability in a buggy. I'm thinking they aren't necessarily the same. Comparing my beamer with a similar sized crossfire, the crossfire is faster through the window AND lifts more. That shouldn't be given what happens to my hand out the car window.

Quote:
Originally posted by tridude
Man thats way too difficult. Next time in the car, roll down your window, and stick your hand out. Hand paralell to the ground. Feel the air pass over and under your hand, fairly uniform, with some lift in the palm, low drag/lift= speed/decreased AOA. Now tweek your hand at a 45 degree angle (your pinky down and index finger up). Feel the pressure/drag= lift--increased AOA! As silly as that sounds that helped me alot when I first started on depower!

tridude - 6-9-2007 at 08:55 AM

The hand examlpe was for the speed of the sail in relation to its angle. Less angle more speed and vise versa.

tridude - 7-9-2007 at 04:59 AM

Yes due to aspect ratios the Crossie is faster than the Beamer.

SoMoney - 8-9-2007 at 11:14 AM

Thats to funny, I was just getting into this with the Pass the Blade post erlier...

Davinch posted the Flexifoil link to an AoA Bridle mod that will work for most ‘split-secondary’ bridle systems.
http://www.flexifoil.com/downloads/instruction_manuals/blade...

Really helps you visualize what a kite/wing looks like in the air, especially at zenith.

For instance if directly over head a low AoA would force the wing to dive (ie low lift) so it stands to reason that the kite would resist climbing and opt for a low in the window flight characteristic.

A High AoA would do terrible low in the flight window, wanting to fall backwards every chance it gets which explains there difficulty to launch, however when it gets higher in it's wind window, it would provide great LIFT!

I wish I could send flexifoil my Rad7 and say "DO IT".....

Pdxnebula - 8-9-2007 at 08:00 PM

Just by shortening the C row of bridles by about 1/4" on my RushII 250 after I
1st got it, gave it a good boost as far as pulling power & changing the AoA of
the kite... Then shortening the C bridle set by another 1/4" on both bridle
primaries like so http://www.geocities.com/nebula_43/Kites/MVC-114S.JPG
which is mearly a small plastic bead like those found in any craft store...

It pulls even more still... Not bad at all for 1/2" adjustment on a 2 line kite,
it flys like it wants to pull as a 4-line, & still plenty fast & climbs to a good
high peak just short of verticle say 85° degrees +/- 1 or 2 ° ...
If 1 doesnt mind learning a little bit of areodynamics, & being extra careful ...
All kinds of things are possible as far as tweaking the power & lift of your kite...

Or not...

Pablo - 8-9-2007 at 08:42 PM

Most 4 line kites will also gain a whole lot by simply shaping the foil with brake pressure. get it just right and the kite will power up big time, get it wrong and you have a ball of fabric.

SoMoney - 9-9-2007 at 08:46 PM

Quote:
Originally posted by Pdxnebula
Just by shortening the C row of bridles by about 1/4" on my RushII 250 after I 1st got it, gave it a good boost as far as pulling power & changing the AoA of the kite... Then shortening the C bridle set by another 1/4" on both bridle primaries like
this...[img] http://www.geocities.com/nebula_43/Kites/MVC-114S.JPG [/img]

It pulls even more still... Not bad at all for a 2 line kite, it flys like it wants to pull as a 4-line, & still plenty fast & climbs to a good high peak just short of verticle say 85° degrees +/- 1 or 2 ° ... If 1 doesnt mind learning a little bit of areodynamics, & being extra careful ... ANYTHING is possible as far as tweaking the power & lift of your kite...



Im new to bridal mods. I take it that Plastic ring dose the line shortening. Where do you get em? :evil:

SoMoney - 14-9-2007 at 10:46 AM

Took a close look at the Bridle lines on a Radsail Pro II.

http://i26.photobucket.com/albums/c138/JoeVolcano/POWER%20KI...
http://i26.photobucket.com/albums/c138/JoeVolcano/POWER%20KI...
http://i26.photobucket.com/albums/c138/JoeVolcano/POWER%20KI...

Where your modification appears to be change the AoA on a profoil, such a bead would only change the wing shape of a Radsail Pro II.

I would need to remove my B & C bridle lines, creat another set of bridles that attach to my main secondary lines (gray in picture), and add knots for an AoA adjustable RadSail. It's bridle setup is almost identical to a Blade's.

RadsailP7bridel.JPG - 199kB

Pdxnebula - 14-9-2007 at 11:00 AM

True, it does work on a split bridle setup best... & your referring to the ProFoil , where as, the picture of the bridle & the bead modification are on my RushII 250, & the ProFoil does'nt have the same type bridle as the Rush...

SoMoney - 14-9-2007 at 12:47 PM

Ahh thanks, this makes more sense now. For some reason I thought it was the Teds ProFoil.

I've also located a great screen shot of the Buster II's PKDS system whiich alters AoA if the kites split secondary lines.

BUSTER2-AOA-Negative.JPG - 55kB

Sthrasher38 - 17-9-2007 at 04:12 PM

The bead is a good idea my 220lb butt would most likley break it looks like it works. Tridude how do you like the 6.5 Blade?:borg:

SoMoney - 18-9-2007 at 12:02 PM

I'm going to need to pay more attention to how Flexifoil does things. After examining there bridle layout, its not a matter of adding beads to the three main bridle points on each side of the kite, its a matter of changing which kite bridles go to which main bridles.
Since the kite bridles are all brought together to a single point for line attachment. Currently Radsail for instance attaches kite bridle to main bridle from the standpoint of proximity, but it should make little difference if I shuffle there order to a Flexifoil setup.


Attached is Flexifoil Blade IV Bridle schematic, it makes this whole AoA mod make much more sense.

http://i26.photobucket.com/albums/c138/JoeVolcano/POWER%20KI...

http://i26.photobucket.com/albums/c138/JoeVolcano/POWER%20KI...

BladeIV4.9sqm.jpg - 50kB

Pdxnebula - 20-9-2007 at 11:56 PM

The beads wont break thier only taking the pressure to the back set of bridle lines the C set, & I've had NO problems with the beads, on my RushII 250 & its sporting 300lb lines...

Still trying to figure out how to go about changing the AoA on the Profoil now... Just 1-2° degrees...

Cornel - 21-9-2007 at 05:50 AM

I'm new at kiting and I enjoy your comments on modifications. I was thinking to try some on my Ace 7m.

I experienced the change in AOA by accident.
Some sand got trapped inside the kite and out of the blue the kite had extra lift.
So much that I was up in the air 5-6' one time and it scarred my bad.

Did any of you try to make a depower out of a fixed bridal?
Is that even possible?

My take on it is that if you have continuous adjustment of AOA and the shape of the wing then you could end up with a depower kite.
Let me know if I'm off in the left field.

BeamerBob - 21-9-2007 at 06:07 AM

That is really interesting. The sand pulled the trailing edge down to catch more wind even at the zenith, or especially at the zenith. So just throw a half handful of sand in each cell and up up and away!

Pablo - 21-9-2007 at 09:33 AM

Quote:
Originally posted by BeamerBob
That is really interesting. The sand pulled the trailing edge down to catch more wind even at the zenith, or especially at the zenith. So just throw a half handful of sand in each cell and up up and away!


Dunno how good of an idea putting sand inside a kite is, think of what sand paper's made of. Another option. if you look up at the kite while it's flying at zenith you'll see some strings coming off the back edge of the kite, they're hooked up to the bottom of your handles. If you pull nice and lightly on the bottom of the handles while the kite's got some power in it you'll see the rear do the same cupping thing that the sand does, but without damaging the kite, plus you can release it whenever you want.

Some beginner kites will simply go to safety, they are designed for beginners after all and it's what's needed, the more advanced kites will take nicely to shaping the kite, some brake will shape the foil, too much will collapse the kite and it goes to safety.

Mess around with your kites, don't be afraid to try something new.

BeamerBob - 21-9-2007 at 09:52 AM

OHHHH, so that's what those little strings are for? :saint:

SoMoney - 22-9-2007 at 12:16 PM

Raining.... No jumping today! :karate:


I couple days ago in light winds I did a C/B bridle mod to my Radsail PRO II 7.0. I used a plastic D-ring buckle that I sawed a crease into so I didn't need to untie anything.
http://i26.photobucket.com/albums/c138/JoeVolcano/POWER%20KI...
http://i26.photobucket.com/albums/c138/JoeVolcano/POWER%20KI...
The Mod pictured was insufficient for any noticeable increase in lift so I began wrapping my C/B lines around the buckles. The wind was around 2Bft and the C/B line mod did increase LIFT noticeably! I did see creases in the sail itself do to uneven looping though. After hearing a couple "TWANGS" from the flight lines settling in, I liked the improvement! However I did NOT like the TWANG the improvement created, so I removed the buckles, and decided its better to do this with dedicated main B/C bridles or replace the B/C bridles with shorter runs.

After closer examination of my Radsail pro bridles and comparing it to the Blade IV's I have determined that in order to do an AoA mod the right way I will need 10 more main bridle lines. Then I can detach my C/B lines and dedicate them for AOA. The project will probably cost more than just grabbing a Pansh ACE of similar size that was designed to produce greater lift. I considered criss crossing the B/C bridles to different mains which would in effect change the Angle of Attack, but im not to sure about that idea. While I'm sure some one using a cheaper kite will find this ring mod more than sufficient to increase lift, its a bit to hokey for my tastes.


RADSAIL PRO:
http://i26.photobucket.com/albums/c138/JoeVolcano/POWER%20KI...

BLADE IV:
http://i26.photobucket.com/albums/c138/JoeVolcano/POWER%20KI...

BeamerBob - 24-9-2007 at 11:56 AM

Now you guys have me wondering if something along these lines (no pun intended) would pick up the speed on my symphony. Mine is much slower than a newer model that a friend has. I imagine if I shortened my A or A-B bridles it would decrease pull but increase speed. I need to open it up again and see if there is a possibility here.

Pdxnebula - 24-9-2007 at 02:50 PM

Start with the A bridles & only shorten them by like ¼"- ½" at a time & check the results... The B bridles tend to be the pivoting point & the A-C bridles are the real ( "+" & "-" ) points that affect the AoA the most, depending on how many rows of bridle you have, 3-4... Just generalizing the fundamentals of AoA...

3 rows of bridle lines it would be A & C, 4 rows would be, AB & CD

I love Fiddlin :)

SoMoney - 24-9-2007 at 08:15 PM

What I liked about the plastic ring mod was that I could get an idea of just how much line shortening I'm going to need to increase lift on a Radsail Pro 7 with negligible impact on speed or performance.

For a Radsail PRO 7 AoA mod, I'll need to shorten my B & C bridles between 2 & 3in. Problem is the best way to do this....... Sewing up 20 custom bridle lengths isn't exactly a job anyone can do.

Pdxnebula - 24-9-2007 at 10:45 PM

Its still possible if you can find a way to shorten the larks head knots on the bridle... Thats all the beads do ... but its much easier to do, in the bundles of a split bridle setup...

art_lessing - 25-9-2007 at 02:21 PM

Hey has any body done any of these angle adjustmenst to a pansh legend..I like my 5.5 and am getting the 4.5 ...the 5.5 turns slow...I wouldn't mind a bit of a speed mod for both....

Dan

SoMoney - 30-9-2007 at 08:48 AM

Pdxnebula:
Radsail uses ZigZag stiched bridles and the loops are pretty small to larks them easily. Good point though. I may be able to whip up 10 primary bridle extensions and larks to that.... Hmmmmmm.......

art_lessing:
Besides switching to handles, increasing turn speed usually means more break line adjustment, or you may want to look into the
Crossover Bridle Mod:
http://youtube.com/watch?v=igYmXsycLJQ

art_lessing - 1-10-2007 at 10:09 PM

ok this is good...so which points exactly does the inside line hook to....I saw that the line goes from the power bridal begining and then a part inside somewhere and then to another point and then to the wingtip.....so which are the two insde points????

DQ

Pdxnebula - 1-10-2007 at 11:12 PM

I havent done anything to the ProFoil AoA so far, it flys fine without anything done to it but a couple knots being added to the "Handle flying-lines" for fine tuning the power & brakelines... Heres a site that tells a lot & its not to technical...

http://members.tripod.com/daniel_gagnon0/id255.htm

Some other cool stuff too, following the links on the page...

P.S. if the page reads weird, its because its translated from french...

Taper123 - 2-10-2007 at 08:23 AM

Quote:
Originally posted by Pdxnebula
The B bridles tend to be the pivoting point & the A-C bridles are the real ( "+" & "-" ) points that affect the AoA the most, depending on how many rows of bridle you have, 3-4... Just generalizing the fundamentals of AoA...



You can always combine the a and c lines into a single line, then have your b line attached with a prussik knot. Then just slide it to adjust the AoA and then pull it tight.

Sometimes I do that for bridles, other times I'll make little pig tails at each bridle point and larks head the bridle to that and move them as needed. Never messed with the bridles on any of my factory kites though... they've always flown like they were designed to. Aspect ratios and the style/design of the kite play a big part in how a kite performs...

Pdxnebula - 2-10-2007 at 01:30 PM

I always thoroughly checkout all of my kites factory or not, sometimes QC seems to have been skipped, like my (riptide) 72" quadline thunderfoil...

Pdxnebula - 7-11-2007 at 08:19 AM

A bit of info; (From reliable source) the A-B bridles on the "Buster" are the critical set of AOA lines on the kite & 5mm + - stretch on too many of those bridle lines will affect the kite, anything over/under will need to be adjusted or fixed...

Bladerunner - 7-11-2007 at 08:55 AM

Quote:
Originally posted by Pdxnebula
A bit of info; (From reliable source) the A-B bridles on the "Buster" are the critical set of AOA lines on the kite & 5mm + - stretch on too many of those bridle lines will affect the kite, anything over/under will need to be adjusted or fixed...


I would think this is a general rule for most fixed bridles ?

You Dawg ! Have you managed to stretch out the 9m already :wow:

Pdxnebula - 7-11-2007 at 09:04 AM

For most Bridles I would think so, depending on whether they're setup, ABC or AB-CD...

Naw just tweakin it AFTER I got it that way... It was somebody elses doughnuts that done it...

:lol:

Pablo - 7-11-2007 at 05:15 PM

Get it right, too many pies,

Ken, he's got the pumpkin from me. Seems towing me, betty, and a trailer buggy with an adult while the bridal's wet is a bad idea, give it a year of that and the bridal's stretched just a wee bit. I added it up, that kite's been dragging around 600-700lbs for over a year now, It's been my main tandem buggy engine.

Pdxnebula - 7-11-2007 at 05:25 PM

Ok, Pies:yes:

Hopefully, after the bridle tweak, it'll get a new shot of color & look like a pumpkin again too... Tweaked each & every, A bridle knot, "AT" the kite last night by about 1" shorter, (talk about some TIGHT knots) should bring it back closer to the range of the adjustment line, will see what it does, when I get some wind...

Update: Had the 9.0m² out today, but wasnt able to give it a good flight in the LIGHT winds I had at the Park (0-1-2-3-4mph) wind at most... Was able to keep it up for about 15min. at 1 point so I must have had a steady shifting 3-4 mph...

Flew to the top of the window several times & stayed there for 30sec. so shortening all the A Lines by 1" helped in lowering the wind range of the kite & was still stable (as long as theres ANY wind) Now for some STEADY 5+mph...