Kite Theory

Going into hibernation

2008-10-13T16:39:00.000-07:00

Thanks to all that have visted.

I seem to have lost interest, and life has gotten complicated for me.

So, I will not be adding any more here.

Hopefully you've found it useful, and perhaps gained some insights.
Or maybe you disagree with what I've posted.
Free advice is funny that way.

I'll leave this stuff here, in case someone else comes along from a search engine, and hopefully can make some sense out of it.

Peace and Good Winds.

CFU v2.3

2008-08-23T14:44:00.001-07:00

Well.. the weather at the end of last week kinda sucked, so I spent a little time sewing.

I made another sail, moved the spreaders down a little, and shortened the tail 1 inch because it was getting caught on the ground sometimes. I've changed the standoffs to be the same length instead of the outer being 1/2 longer to see what that does.

I've also added graphics trying out the ideas I talked about in the panels thread last month.

Hopefully, tomorrow will have some decent wind.

CFU

2008-08-15T19:42:00.000-07:00

Got out for about an hour after work.
Winds were light and unreliable, but I got a couple runs in.
Crap editing again. Maybe one of these days, I'll learn the eye candy.
Until then, you'll have to suffer with me.

I'm calling this kite CFU, since math kite seems to confuse folks, and math kite is more of general set of rules.

Anyway, I've been having fun with this one. Still need to lower the spreader and play with the standoffs a bit more, but I like it so far.

Sorry for the scarce postings.

2008-08-15T11:33:00.000-07:00

Weather has been spotty, and I haven't gotten alot of time to fly.

I've made it just a bit deeper, and I've been playing with the standoffs.
Right now, I have a longer outer, which I like, but I need to try even ones as well, since longer outer seems to have made waps snag prone. Or.. maybe it's just me.

Anyway, I'm going to have to make a new sail. That lower spreader is just too high now, making it get stuck in turtle too easily. I think it needs to come down 1/2".

The deeper sail has also toned down the tail lifting in cyniques making them simpler. I'm not sure I can get it to rise as much as I did with the winglets though.

I guess I'll just have to live in the middle if I want to have all the tricks at hand.

Anyway, I will say that I think this one is close to being very good.
Corners are snappy, and figures are quite decent as well, with the only criticism I think being that it will go back into turtle/snap lazy too quick, making 2 points landings and stabs very narrow window of opportunities.

I can live with that since the rest of the tricks come so easily on this one.

I'll try to get some video next time I get out to fly it.

Hmm.. well that last change..

2008-08-08T11:25:00.001-07:00

So.. that last build was educational.

Here's what I've learned:

1) The trick to getting good taz is thin tips and stable belly floats. If the tips have too much area, there's too much to pull through the air, and the rotation doesn't complete. Also, when you second pull in the taz, if there's too much lift on the wing, you just get pop-ups instead of spin.

2) There's a fine line between getting lifters and getting out. Apparently I've crossed that line. I can get incredible lifters on that last one, but it often does not want to come out of turtle. I think I've gone too far up. Even in cyniques, the second pop is starting to lift the tail into a 2 pop rollup rather than just reverse the spin. It's an odd feeling.

So the tip shape is a success, but the turtle stuff is too lifty. I'm trying a bit shorter spreaders to see if that will compensate, but I suspect I'm just going to have to lower the spreaders about 1/2".

I should know after this weekend.

1/3 sail with asym TE

2008-08-04T18:11:00.000-07:00

Got the new sail built.

Here's a front shot. You might notice that the lower spreader is higher ~14 inches to the spine. Also, the upper spreader is 1/2 lower, which I'm hoping will help spin crazy copters, and get me back to the rising cyniques. It was already giving quite nice lifters, but since I was thinning the tips, and a little in the tail, I thought I'd try to give it a bit more area below the spreaders to help with those.

I think the amount of area on the outer sail panel is deceptive with deeper kites.

Here's another angle.

The weather is supposed to clear tomorrow, and be good for a bit, so hopefully I'll get some good test time on it.

New Camera Came

2008-08-02T14:13:00.001-07:00

Got the new camera last night. It's a JVC everio hard drive camera.
So far, I like it alot.

Got out for a little bit this morning, and recorded about 10 min's of tricks on the kite I built for kiteforge sloppily snipped/globbed together into 3ish mins.

If your curios about how it flies, you can see the vid here

Worts were not removed, since I think that's as important to see as anything else.

Flew yesterday

2008-07-28T09:17:00.001-07:00

So.. I was going to try to do a video showing the same set of tricks on the different renditions I've talked about here.

But, the wind blew mr tripod over, and broke my camcorder :(.

I ordered a new one, but it's coming ups ground, so, I wont see it for a while.

Anyway, I took a bunch of stuff to the field yesterday and did a bunch of side by sides.

I still find myself liking the flight behavior of the 1/3 kites over the 1/4.

But one thing that kinda struck me, is that the same problems I have with the 1/3 winglet kite I have with the 1/4 with the straighter te cut.

I think my next build will be a 1/3 without a winglet but with that asym cut I talked about below.

I'm wondering if it's not so much that I am not getting good taz because the standoffs are too deep and lifting, but if the winglets are lifting too much and popping it up rather than spinning in taz.

It will be interesting, since I'm going to scale it a little bigger as well. The 1/4 before I was using a 33.5 inch spine, since that's what it works out to when I cut a 32.5 rod, and put the tail knock and T in. But I like the idea of a bit larger kite, so I'm going to do it with a 36" spine, which will mean a larger wingspan since I want to keep it all in scale.

You've probably noticed that I haven't been posting the non-winglet plans.

That's mostly because I am not satisfied with them yet. When I get closer to something I like, I'll do a round 2 on kiteforge.

So... that last change was interesting

2008-07-24T07:59:00.000-07:00

Well... straightening out the outer TE was interesting.

I've gained alot of precision, and alot of presence. Cyniques are better. Flips take more weight, but don't get stuck in flare. But I've completely lost taz. It just won't do it with out a bit of luck.

So.. Hmm. What to do.

Well.. next step is to try an asym curve.

When I straightened out the curve, I did it evenly, makeing the green line shallower.

To add area, you can either add nearer the standoffs (blue), or nearer the tip (green).

My suspicion is that I need the blue line, to get more spin while hopefully keeping some of stuff that improved with adding more area.

More area

2008-07-20T13:29:00.000-07:00

So here's the new sail compared to the old sail. The new one is on the left. The old one is on the right.

If you look at the trailing edge curve, you'll see that the new one(left) is straighter that should give me a bit more area.

I'm hoping that it will slow down the kite a bit, and make corners a little better without sacrificing as much stuff in the taz. To compensate for the loss of momentum that the extra area will create, I've used a little heavier P300 LE, which I think will help it carry the spin.

We'll have to see, since the weather here has been either rainy, or without much wind. I'm hoping to give it a go this evening when it is supposed to pick up a little. I tried to go out this morning, but didn't have enough wind to tell much.

Outer wing panel area

2008-07-14T12:09:00.001-07:00

So, when I went back to the 1/4, to get the shallower sail, I made that yellow kite below.

The yellow line represents that sail. You might have to click on it to see, since the colors overlap. The yellow wing area follows the red line on the left, and the blue line on the right of where the blue line cross.

I wanted more area in the wing to make lifters and reversing lazies better, so I did the kite currently on kiteforge, which shows the difference in red.

Now.. you can still do more area without the winglet, which I've shown in blue, and I think I'll build that next, when I get my box of parts from skyskark at the end of the week.

Now, if you notice, both the red, and the blue increase the area of the outer wing panel.

So, why am I going to try this?

Well.. winglets add the area at the tip, which causes drag at the tip since you have to pull more area through the wind. It makes it spin slower, which I think is a little slow right now. It also makes for more scallop in the wing's TE, which means that the extra drag from the wing is mostly only at the winglet.

The blue line I think will adjust things in a different way. It will still give me better cyniques, than the yellow line, but won't drag the taz's as much. It will also add that drag along more of the outer wing, which I think should improve the corners a bit. It will also give me a little more area closer to the standoffs, which I think might help drive a bit without having to spread the standoffs. I'm hoping the blue line will give me a little better tricks on the back than the yellow while gaining back some of the taz/doubles/spin tricks that got weaker with the winglets.

At least that's my current speculation, which I'll know after I build it.

Panels

2008-07-08T19:04:00.000-07:00

Back when we had mostly nylon sails, paneling actually served a purpose.

Because a seam requires an overlap, the seam was actually stronger than the rest of the sail.By aligning the seams with the stress lines, you could reduce stretch in the sail as it wears.

Now today, paneling is mostly for decorative purposes, since the sails are mostly polyester and streatch less... in theory.

But in practice, we are putting alot more stress on the sails than we used to because we are stretching the sails with standoffs under more tension, and then making things worse by wrapping yoyo's.

Lets take a look at this blank sail.

Wrinkles can tell you where your kite is under stress.

Here's some areas highlighted so you can see what I'm talking about.

The red area is where it's stressed by the standoffs, while the green is the part that's pulled in a yoyo as the lines wrap up, and the sail is re-pressured.

So, if I was going to make a sail with graphics to make the sail last longer, I would do it with that in mind.

I think Jeff Howard did something like that with the precisionist.

Maybe something like this

With the black panels either made of a heavier fabric, or mylar backed or something along those lines.

First round of Build a Kite finished

2008-07-07T08:21:00.001-07:00

Except for the yoyo block location, the initial go at kiteforge is complete.

If you have any questions about it, or something needs some clarification please add that to this thread.

Otherwise, I may start talking about other stuff.

Build a Kite in July has begun

2008-07-01T06:18:00.000-07:00

June was mostly design theory.

July will be mostly spent at kiteforge doing some documentation on my latest build.

I hope that by giving practical examples, the stuff you read here will make more sense.

Also, perhaps you may find a building tip there that you find useful. I don't claim to be a good sewer, so please bear with me.

I'm not sure how much I'll be writing here in July, since I expect that doing the images and write ups for kiteforge will take alot of my free time.

But I plan to do any discussions about that here so that kiteforge is mostly a clean journal.

So, pop over there to see how that's going, but stay tuned here for any discussion that might come up about that particular design.

Nose Weight

2008-06-24T11:58:00.001-07:00

So, what about nose weight.

It would seem that nose weight should work like tail weight.
But it doesn't really.

If you have them both, it slows down the flip.

Here's what I think happens. When you add nose weight, you have more mass you need to move, and it's at the perimeter of the flip, which means it takes a larger moment to spin. It also forces the tail weight to travel in a larger circle than without it.

It's similar to an ice skater spinning. When they draw their mass (legs,arms,etc) in, they spin faster, and move them out to slow down.

It is my opinion that nose weight is not a good thing, and I'd rather distribute that weight in the frame above the T in say, the upper leading edges or the upper spreader, than use a weight at the nose.

Tail Weight and Flipping.

2008-06-23T16:07:00.000-07:00

Newton says that a body in motion, tends to stay in motion, while a body at rest tends to stay at rest.

Here are some images of a kite in a flip and how tail weight affects it. The blue is a tail weight, and in a flip, the tail weight leads through the ass end of the kite.

Lets look at a regular yoyo first, which would take these in sequence clockwise. (A,B,C,D)

The force applied in the pop, is up (A). The tail weight rises (B), and then stalls out at (C) since that's as far as it can go. The bit of left over momentum and gravity make the kite glide nose up through D, and then the wind lifts the nose back to A.

Now, yo-fade works counter clockwise. (C,B,A,D,C,B). The force vector is down. Starting at C, the tail weight moves down through B, and then to A. The frame carries any left over flip through D, and back to C, and then fights the flip, completing to B because the tendency in C is to revert back to D, and not go to B.

What does that mean? Well. tail weight is good for yoyo's, but bad for yo-fades. If you want to complete the yofade, you really need the mass in the rest of the frame so that the inertia is carried in the whole flip, rather than just a lump of mass moving in one direction.

Also, so lets also look at D. This is the dreaded "dead" spot in flare when you add tail weight. Now, why does that happen? Well 2 things.

First the force is toward the right, so the weight has no reason to rise. The only thing that is going to do that is the scooping action of the wing tunnel, but that has to impart force on the blue dot in the up direction, but you only apply force in a horizontal direction. So, instead, it flies like a dart toward you, again leading by the ass because of the tail weight.

The flipping caused by tail weight is alot like throwing a dart. If you throw it forward, it will go straight. If you throw a dart backward, it will tumble, and then eventually fly with the weight forward. Just because it starts to flip when thrown backward, doesn't mean it continues to tumble.

Build a Kite in July

2008-06-20T09:07:00.000-07:00

One thing I learned in school, was that theory is all fine and dandy.

But it was the homework that drove the ideas home.

So, I've started a sister blog to discuss what I'm doing design wise.

June 08 has been mostly devoted to design theory here.

July 08 will be mostly devoted to how I construct a kite at kiteforge.blogspot.com

That site will be more of a journal on my part of what I'm doing with my designs. If you build one there, you can apply what I've talked about here to tweak/tune it so that hopefully you'll end up with a kite that suits you.

It will be a place you can go to build what I've built, and have a reference to what I'm talking about with theory in this blog.

Upper Spreader Length

2008-06-18T17:50:00.001-07:00

So, a common thing people like to do is to shorten the upper spreader.

But, I think most people don't understand what's happening when they do that.

Here's a mock up of what the frame does when the upper spreader changes.

Because the lower spreaders are not changing, the lower spreader connects act as a pivot point.

Most kites have a slight bow to the leading edge (blue).

When you shorten the upper spreader (red) the wingtips actually move out, and you increase the aspect ratio. The black line is a neutral/straight position.

Now, the sail is the same since it's the same kite. When you shorten the upper spreader, it makes the sail in the nose area deeper, which can increase tracking. You also increase the flip because you are pushing a sharper wedge into the wind, which has less resistance.

Balance Revisited

2008-06-17T15:24:00.000-07:00

So, apparently my explanation the first go around might have been a bit confusing to some, so I'm going to try to explain it with pictures.

Here's our hypothetical kite.

The red line is aproximately where the center line of pressure is, meaning that there's approximately equal pressure above and below that line.

The blue line is where lower spreaders would traditionally be placed, with the blue dots where the bridle would traditionally be attached. Since the red line is comfortably between the blue dots, the bridle is nice and stable if you need to pump the lines, stop a flip, or do a 90 turn.

Since the spreader is what is pulled in a turtle, the farther it is from the red, the more leverage you have with to pull it out of turtle, which is actually not good for turtle stability. If you put any kite in turtle, and release the lines, it will not come out of turtle no matter how "unstable" the turtle is. There's no such thing as "deep turtle", only resistence to coming out of turtle. .

The yellow line here is where I like to put the spreaders instead. That moves it closer to the center line of pressure, but not on it, or it will not want to come out of turtle.

But if you were to bridle it at the yellow, you would be close to that center of pressure, and when you half axel, or otherwise are re-pressuring the sail, it will bob.

So the idea is to place the spreader where it will help turtle stability, but place the bridle where it will help flying stability.

I suppose.... another way to do the spreaders is to curve it in a frown with the T at the red, and the LS connects at the blue dot. That would also achieve something similar, but I'd still suggest attaching the bridle to the spine at the blue dot. But, in general I try to avoid pre-stressing rods because it just brings them closer to failing. Inducing S curves in the spreaders seems to be particularly bad, I think because it really stresses the hoop strength of the rods. But I add this bit, since some folks.. seem to really like doing it, and it is a legitimate solution.

Quick correction to last post

2008-06-16T08:32:00.000-07:00

In checking notes the two kites in the last post are different.

Although they both used the 1/4, the newer one is not as deep, and the trailing edge is cut about 1/4 higher to compensate the flip.

Quick Mathkite update

2008-06-14T07:15:00.000-07:00

So, a while back, I said I was going to go back to the 1/4.

Here's a quick image of where that ended up.

There are things about it that I like, and things I dont quite like.
The lifter isn't quite as stable as I'd like, and the cynique's are hard to rise, and mostly just stay at the same height.

On the otherhand, the crazy copters and taz machines are really easy, and spins are nice and floaty :|

Next iteration I'm going to add some smallish winglets, and make the tips a little shorter. I think that will even out the lifter/cynique issues for me.

Normally I wouldnt suggest jumping so much from one iteration to the next, but for me, this isnt a big jump. I've previously built ALOT of proto's based on the 1/4 nose angle, so I'm pretty confident about how to build it. Most of my earlier work from 2 years ago was based on this angle, but I didnt start working with winglets until I moved the the 1/3, mostly because at the time I was unconvinced about what they did, and also hadn't wanted to worry about how to build/sew them. With that drawback passed though, I think I am partial to their feel now.

A couple years ago, I brought this to monterey. I used a fatter outer wing at the time, which worked, but needed alot of tail weight.

It's similar to this one, but cut a little thinner and not as deep.

Standoff locations

2008-06-12T11:51:00.000-07:00

This is what you'd roughly see looking at the kite in a pancake.

In the top part of this image the red and blue are where you might put in inside and outside standoffs respectively.

As you move toward the yellow, the kite will flip back in a snap lazy faster, and feel floaty-er in a spin.

As you move the outer toward the green, you'll feel more presence on the lines, and you'll turn snappier.

The bottom part of the image shows what the profile looks like as you move them apart. The blue line shows the profile with a single stand off, and the move toward the darker green shows moving the standoffs apart.

You'll notice that as you move them apart, they get shorter.

One of the reasons I am showing you this angle is because the area under a given line is also important. In the top picture, you can think of it as the purple area. The more area you have, the more air you scoop in reverse. The more air you scoop in reverse the easier it is to flip up into fade from flare. If you scoop alot, 2 pop half axels are easier. If you scoop less, they flip more by momentum than scooping, which makes taz machines easier.

Two separate standoffs per side will scoop more air than a single standoff. But if you go too far apart, the area also will get smaller.

Where you put these standoffs will also affect the angle of the spine in a spin. There's alot of variables there that I haven't quite gotten pin'd down, so I'm not going to write about it yet.

But it is here that you adjust the CoP. If you move the standoffs, you also need to adjust the bridle, since the AoA is dependant on the CoP.

1 pop yoyo's

2008-06-11T12:34:00.001-07:00

As a general rule of thumb, when you single pull yoyo a kite, it travels in a loop.

We talk about this in terms of flipping, but don't usually think about it from the side.

It does not travel in a circle, but in a spiral because the wind is always pushing it away from us.

This is basically what it looks like when it rolls up depending on how tight that loop is.

Now, why does that matter?

Well, it may seem like the red loop is the best thing to tune for, since it's faster and travels less, it requires less effort, and less slack to achieve. If you want a single flip that is easy and repeatable, then that may be the case.

But, if you want multiple roll ups, the red path is very hard to pump to get more roll ups. You only have the last 1/4 of the rotation to accelerate again, so the blue and green is actually easier to do multi's.

The red path is also very prone to flipping, which means it's also very prone to unflipping. If the loop is too tight, Wap-do-waps become very hard, since the pop to spin will unroll it rather than spin the kite, and you'll just get yo-flacs.

Winglets

2008-06-10T12:06:00.000-07:00

If you notice below, the yellow kite had winglets.

What do they do?

Well. for one they washout when the pressure is higher, they bleed back. That lever action presents less sail, as well as a deeper sail to the wind, and become a kind of rudder to help tracking. In lighter wind, they don't bend back as much, and give you a bit more sail area. It's sort of a variable sail area.

But, that's not why I use them. I use them because they add area to that outer wing panel I talked about below.

Here, you see that the green area creates area that is not possible without the winglet. It helps stabilize turtles, and gives a bit more area at the tips that helps you carve a turn. It also adds drag, which can be both good or bad. It does make it spin a bit slower in tricks, and it also changes the shape of flips. I'll go into the shape of a flip later, since I think it's something we dont usually think about.

That area being farther out, helps quite a bit in reversing lazies, as well as helping keep the tips flipped up for lifters.

Bridle depth and pitch

2008-06-09T13:47:00.000-07:00

So, in last month's bridle post, I mentioned a bit about depth.

I whip'd up a couple of images in case it was not clear.

So here we see what happens when the bridle is longer. The red dot is where the kite can swing when it flips. The closer to the sail that is, the more pitch the bridle can induce.

Here we see a std 3pt vs a turbo bridle. As you can see, the pitch point for the turbo is much closer to the sail, which is why they feel pitchy-er and less stable.

Sail Depth

2008-06-07T09:34:00.000-07:00

Sail depth is an interesting thing.

There's 2 ways to achieve it.

You can keep the frame geometry the same, and cut less trailing edge as described below, with blue being more cut out, and green being less.

This is the profile you'd see from the top of the kite looking along the spine.

The other way to do it is by keeping the sail the same, and changing the frame geometry, usually by changing the spreader length.

Here, you see that by shortening the spreaders, the depth increases.

What's the difference?

Well, it depends on if you're trying to fly or trick.

Cut the TE more: faster, less pull, less presence/feedback, faster flip, faster axels, faster flatspins, need more wind.
Cut the TE less: better precision, more drag, snappier corners, better drive, better at the edge, more flight control, need less wind.

Make the spreaders longer: faster, more pull/overspin, slower flip, more resistance to axels, faster/flatter flat spins happier in turtle, less stable fades, need less wind
Make the spreaders shorter: slower, less pull/overspin, faster flip, less resistance to axels, slower flatspins that are more nose up, faster to fall out of turtles, more stable fades,need more wind to fly.

So, for some things, making the sail deeper either way is the same, while for others, they are opposite.

Trailing edge pt2

2008-06-05T08:47:00.000-07:00

In pt1, I say that the outer standoff point is very important.

What happens when you move the trailing edge?

The farther toward blue, the more flip you'll get, and the less resistence you'll present to the air in tricks like axels, since The depth that moves through the wind will be less, so it will be faster.

But it will also mean that you have less sail presented to the wind. What that translates into, is presence on the lines. The farther toward the blue, the less presence you'll feel. That means less pull, and less feedback. It also means less drive.

So the depth of the cutout basically is a balance between drive, and flip. The only way to really figure this one out is trial and error. I've tried alot of different amounts. Start with a guess, and then move it 1/4" at a time. Sew it up, fly, see if you need to make another one.

Speaking of flip.. it will also change the shape of the flip. I'll try to talk about that next with a bit about depth of the sail, since they kinda go together.

The trailing edge

2008-06-04T17:18:00.000-07:00

So, if I always use the same 2 sets of bases, how do you decide on how to cut the trailing edge?

I look at the sail as somewhat independant areas that are governed by the planes they form in the sail. Those planes are determined by where the folds align and are based on where the outer standoff is placed.

So, in this image, the most important point is where the green and blue touch. That is where the outer standoff is going to go. That point is important enough that it will be it's own topic that I'll follow up on.

In looking at this image, there's a couple of things to think about. The larger blue is the smaller green gets and vice versa if you want to keep a smooth trailing edge line. Or, you can choose to not keep a smooth line, which I sometimes do, keeping the area around the standoffs straighter. Also, you can change those cutout shapes to affect those areas of the sail.

Making green small makes that outer panel larger, which is good for lazies, and fades. It also adds drag, which can help precision. But it will also make flips slower, and will also offer more resistence in spinning tricks.

Making blue small adds drag, and will slow down the forward speed. It will also slow flips. But it will amplify the effects of the inner standoff, to make it flip back in like, snap lazies.

Now, making them both small might seem like a good idea, but with all that drag, you'll need alot of tail weight to make it flip, which is going mean you'll need more wind to fly, even though you have more area to present to the wind.

Outer Wing Panel

2008-06-03T14:10:00.000-07:00

When a kite is assembled, it's 3D.

But, not all the planes of a kite are in play at a given time.
The outer wing panel is very important when it comes to tricks.

The blue section is what you spin on in a lazy susan.

A lazy is a function of resistence from area (blue) vs mass (the rest of the kite). There should be some kinda balance there, or it spins wonky, and ugly. The larger the blue area tends to be in relation to the rest makes lazies prettier and usually easier.

If you watch alot of lazies, especially multi's, you'll see it basically spinning on that panel.

What tends to happen, is that that panel is pulled into the wind, and the mass behind it comes towards you making it spin. If that area is small, there's less plane to ride, and it will sink more on each rotation. You get a slight lift on the pull when you pull that plane into the wind though, so if it's larger, you can gain more height. Rise or fall depends on if you get more or less rise pulling that into the wind than it falls after you pull.

If you can get the line closer to the spine when you spin, you can use more of the sail to lift the spin.

This panel is also the plane you ride on when you're in a fade.

mathkite proportions

2008-06-02T12:31:00.001-07:00

So, as I said last month, I always start with a 1X1.5 template.

As you see, the blue is taking the nose to the 1/3 on the right side, while the green shows the outline of the 1/4.

They both end up about the same aspect when it's assembled, but the green is not as deep of a sail. The extra depth in the 1/3 sail is taken up by the standoffs being longer.

This image is not very precise, so I wouldn't suggest building off of it, but hopefully it can put some of the things last month into perspective and perhaps clarify my text descriptions. If you'd like to try, more power to you.

I usually shoot for the upper spreader to cross at 3/4 and the lowers to cross at a little higher than 1/3, to raise the spreaders, and make the stuff on the back easier.

Updates, and new approach

2008-06-01T05:30:00.000-07:00

As I mentioned below, sometimes life keeps us from doing things we like.
But, I am trying to keep this blog moving.

At least this time, it's not a completely bad thing.

Today is my b-day, and this morning I some how feel older.

In any event I've been trying another design change in my kites.
I've gone back to the 1/4 to make a shallower sail.

I've been thinking.. perhaps the blog has been too plain, and esoteric.

So I'm going to try to make posts shorter, and hopefully a bit simpler to understand.

I'm also going to make an effort to use more pictures. I suspect my descriptions may be a bit difficult to follow, especially if the ideas I'm talking about are new to you.

Today, I'm going to try to fly the new kite, and hopefully will have some things to talk about and show in the next couple days.

Sticks

2008-05-29T17:59:00.000-07:00

So.. tonight I thought I'd write a bit about rods.

For the most part, the rods we use are not... for us.

The vast majority of rods are flawed arrows. Pretty much any straight rod is an arrow shaft, and it's probably got something wrong with it.

Archers shell out alot of money for their arrows, and the tolerances on them are very narrow, or they warp/shatter when they're shot, or on impact. The ones that don't make spec, can't be sold as arrows. Rather than throw them away, they are sold off to people like us, rc plane folks, etc.

So, what is a carbon rod? Well, it's burnt plastic that's glued together. Plastics are drawn into thin fibers, and then burnt to make carbon strands. That stuff is strong in one direction, but it's also limp. The epoxy keeps it in shape.

There's all sorts of voodoo, and science that goes into the fibers and epoxy ratio's and chemistry. If you're interested, you can read the wikipedia page, but I'm not going into it, because I'm not going to re-invent the wheel.

But I will talk abit about the rod construction.

For the most part, there's pultrude, and wrapped.

Pultrude is pushed through a die, like pasta. For the most part, the fibers are aligned because of that. So, stiffness is ok, but there's little hoop strength. If it's torqued or crimped, it will split lengthwise. It's not so much an issue of stiffness and weight, since high modulus rods are pretty nice. But they are still more fragile, and they do badly with impacts.

A wrapped rod improves on that by using fibers the long way, as well as radially. The crossed fibers end up stronger, like plywood is stronger than solid wood.

It used to be that lower end kites had pultrude, and higher end kites had wrapped. These days though, archers are heavily moving to straight wrapped rods, and so the price difference between pultrude and wrapped isn't that significant, unless it's the really low end kites, and they are using the really cheap chinese rods.

I don't see much reason to use a pultruded rod, except possibly for top spreaders, since they do not need much strength, and a thin light pultrude is perfect. Some folks also like them for spines, but... I'd still prefer a straight wrapped rod for that. I'll try to go into that discussion in another post.

So, in 90% of cases, wrapped is better than pultruded.

What about straight vs tapered wrapped rods?

Well.. where do they come from? That's a good question, that I haven't got a good answer for. Avia's I think were wound on military surplus mandrels meant for fiberglass antennae. The others, might come from fishing rods. I suppose some might even be made for kite rods?! Not sure, who knows. It comes down to the mandrel, which needs to be really precise, or it wont come out after it's wrapped. Having those made with the precision necessary.. is expensive, so they usually will also come from some other industry.

Well ....is taper better than straight? That's a trickier question than it might seem, since it depends on what you're trying to do.

Once again, we see the cliche balancing act.

As a general rule of thumb a P series rod is going to be more durable. They're hard to break, but they're more flexible. Tapers are stiffer for their weight.

Tapers also have an uneven mass distribution because of their shape, and the way we use them in kites. The weight is concentrated at the center of the leading edges, and the spreaders. That means there's less weight at the tips, which means less spin, which is good for precision since it cuts down oversteer, and less so for tricks, since it doesn't hold as much momentum. The uneven weight can be used to tune balance since the upper and lower LE can be cut asymmetrically to move that mass around to some extent.

Tapers are also stiffer in the middle than the ends. That's very efficient in a kite frame since, the tips and nose do not need as much support as the middles. Similarly with a spreader, the most support is needed at the T. Which shaves some weight that might not be needed.

It's similar to bridge design. Bridges must be stronger in the center than the ends because of torque/leverage. Arches, suspension bridges, etc are built that way.

So, how do you choose which is more appropriate?

Well.. I usually use mass as my deciding factor in the LE. If I need more mass at the tips, then I use a straight rod. If I don't then a taper. Now.. sometimes, I will use a taper in the ULE, and a straight rod in the LLE, to shift weight both down, and out so I can use less weight in the tail, and still get the same amount of flip. The Avia plugs are the same idea.

As for the spreaders, I almost always use tapers, because I like stiffer spreaders since they make the kite much more responsive in tricks and lines. Pultrude is lousy for spreaders. Straight wrapped.... is usually a corner cutting tactic.

Hope that wasn't too long.

Bridles: Getting a handle on things

2008-05-27T11:59:00.000-07:00

So, to recap, in flight a bridle controls how the wind hits the kite.

But, since we don't spend all our time flying, lets look at a couple things about bridles and how they relate to tricks.

In a nutshell, a "trick" pulls the kite out of flight or imparts spin while it's in some uninflated position, in which case, it's not so much an issue of Angle of Attack, as it is leverage.

Trick flying is all about leverage, and momentum.

Lets start with a stall, since so many things start from there.

A snapstall is executed like an exaggerated combo turn. This relies on side pulls to dump the wind off. The wider the tow points are, the easier this becomes to both initiate, and hold/balace for either a stationary stall, or a slide, which is simply a crooked stall.

As you'll see, this is also a balancing game. The wider the tow points, the easier it is to get leverage on the side, so things like snap stalls, and comete's, get easier. But it will then fight tight sharp turns, since as I discussed below, wider points make for wider turns.

So It's a fight between flying, and not flying? Well no. Because we see the same issue when it comes to a fade. When the kite is in fade, the leverage is also easier when the TP's are wider. But, spinning a fade requires you to hold a fade to some extent. There is a point where the TP's become too wide, which makes the contact point of the bridle in fade farther from the nose and closer to the center of pressure in the fade position. When it's too close, the fade becomes very unstable. You can of course still spin it when it's in a suitable position.

When you are in turtle though, the bridle is not the factor since it rests on the spreader. So for all things turtle, the leverage points are at the spreader. That's a bit wierd though since the bridle can slide around. Typically though, it's at the standoff fittings, either between them, or on the outside of the outer standoff.

Well, what about active bridles?

That gets interesting. A turbo can be a bit beneficial in regards to fades, because when the bridle legs are drawn up in a fade, the towpoints move in. That lets you get more horizontal leverage in flight, and narrow those points to help in fade.

That's great right? Well.. not always.

There's a dark side to active bridles for tricks, and it's why I dont tend to use them.

The more active a bridle is, the more play there is in the bridle legs. What I mean by that is that the bridle must streatch before a leg is taught. For instance, if you want to face plant for crazy copter, the angle between the uphaul and the turbo leg must straighten before you get the sharp pull on the ULE. The longer the turbo line, the more that's an issue.

Now, some kites have a much smaller window of opportunity to get that yank than others, and on those kites, an active bridle can make crazy copters, and yofades harder, and they're often not the easiest tricks to do anyway.

I notice that handicap most on tricks that require a sudden sharp pop, or have a narrow window of opportunity.

On the otherhand, a turbo can make snap lazies easier. When you tip it back, the angle it falls is in line with the pivot plane of the turbo, which can make flipping back easier. I don't usually need that though, since moving the inboard standoffs closer to the spine also makes it much easier/faster to go back into a snap turtle.

But, like all things, a good flier can compensate and make things work anyway.

Personally, I use static 3 point bridles though, since I prefer a faster response to pops for tricks. If I were flying US style comps though, I'd probably opt for a short turbo.

Bridles: The wind in your sails

2008-05-24T12:51:00.000-07:00

Ok. So, the main thing a bridle does, is hold your kite into the wind so that it will fly.
It does that by controlling the angle of attack or AoA.

Lets look at a standard 3 point bridle. The focus of that is the tow point, or where you connect your lines. It's determined by the geometry of the 3 basic bridle lines.

The Uphaul connects the upper leading edge to the tow point.
The Inhaul connects the spine to the tow point.
The Outhaul connects the lower leading edge to the tow point.

As a fair rule of thumb, you can think of tuning a bridle as moving the tow point up/down, and inboard/outboard.

Up/down is controlled by the uphaul. Most makers build the kites so this is adjustable. By making the uphaul longer or shorter, you can change the AoA. Now.. why they make this adjustable.. I don't really understand, since it is my opinion that there is an optimal AoA, and moving up or down is actually a bad thing. When you move the TP up from optimal, it may seem to fly in lighter wind, but will make turns wider, and less efficient. If you move it lower than optimal, you'll lose drive, but your turns will be faster/tighter, and possibly oversteer.

Inboard and outboard are not usually adjustable on most kites. When you move it inboard, you turn tighter and require less hand movement. When you move it outboard, your turns get wider, and require larger hand movements. Moving the tow points outward, will also make the center less supported, and the kite will bow away from you under pressure. That bow'd in bit makes your sail deeper in a line, which helps tracking, but can also really stress your spreaders and the T area.

So, once again we see that this is a balancing act. Too low, and it won't go, and might oversteer, to high, and it will feel mushy. Too far in and you don't have leverage for momentum maneuvers. Too far out, and you'll be turning wide.

Seems simple? Well.. we also have another axis that is less considered. That's the away from the kite and toward the kite. When your bridle is shorter, the frame is less supported, which can mean that flipping is easier. A short bridle will be twitchier than a longer bridle, which can help in tricks since it doesn't have to swing as far. On the other hand, a longer bridle is more stable and supported, and will feel smoother, and more controlled.

This was the entirety of our choices for a good long while in kiting. 3 lines per bridle, each with straight forward roles, and more or less easy to comprehend. As long as none of the lines formed an angle larger than 90 deg, you were in good shape. (obtuse angles will compress the frame in bad ways)

Then came the MEFM, with it's turbo bridle, which I personally think is a bit of genius. It allows a variable AoA depending on what you're doing.

What makes a turbo bridle work? Well.. this one took me longer to wrap my head around than I care to admit.

First, lets remember what happens when we move that AoA lower. It turns sharper, but can also induce oversteer and choke drive. Now... that sounds like a bad thing, except when you turn, that's exactly what you want, but you dont when you're flying around. By using a turbo leg that connects the tow point to the up/outhauls, a turn will lower the towpoint, and make a turn sharper. Evening the lines brings the tow point back to it's neutral AoA.

Also, because the turbo lets you shorten the distance between the kite and the point where it can rock (where the uphaul/outhaul meet) in relation to the inputs, without moving the tow point closer to the kite as well, you can still support the frame, while allowing the kite to pitch easier.

That's sounds great right? Well... if you want to fly around yes.

But these days, we don't just fly around do we?

Bridles.

2008-05-22T17:35:00.000-07:00

So, tonight I thought I'd talk a bit about bridles.

Since this is a pretty complex topic, I'm going to break this up into several posts.

A bridle does 2 things:
It holds the kite in the wind.
It pulls the kite out of the wind.

I'd like to talk about them separately, since they are somewhat opposing.

Kite Clique Link

2008-05-22T17:30:00.000-07:00

Frazer asked me to join at kite clique, and I agreed so that folks might find this info from a kite blog hub.

I've spent some time trying to figure out the wordpress interface, and it's got me beat. I tried, and I failed to understand how the images work without wrap arounds. Multiple images..I just couldnt make work right.

So I am taking the easy route and just using a link.

Some thoughts on fabric

2008-05-20T11:11:00.000-07:00

Icky's the best right?

Well.. why? I think people don't ask that question much. But perhaps they should.

It's accepted/expected as the defacto fabric for a "professional" dualline.

First of all.. we have to look at where our fabric comes from.

Almost all our materials in kite building come from other industries. We are way too tiny to really have anything made for us. It's a wonder we have fittings.

Fabric is almost all from the sailing industries. It's used to make sails for boats. That being said, there are no fabrics made for kites.

So, what makes a fabric?

Well, there's the type of plastic in the fibers which for us is either nylon or polyester. Nylons take a much stronger color to them, but tend to fade faster. They are more elastic than polyesters as well, and will absorb water more than polyesters.

Then there's the weave. Some use thicker, or thinner threads woven more tightly or more loosely. Think... bed sheets, where there's a weight and a density. The patterns in the weave vary depending on what they're trying to achieve. The scrim is a special pattern woven in to stop a tear. If you're a boat, and your sails tear, you're screwed out on the water.

Finally, there's a coating to the fabric. Sometimes it's only on one side, others both. Sometimes it's just on the surface, and sometimes it's impregnated. Usually it's clear so you dont see it.

That coating, is really important.

First, it keeps the fabric from streatching along the diagonal, called a bias. Second it dramatically affects the hand, or softness/texture of a fabric. Third it can affect if and how much water gets absorbed, and if it breathes at all, and finally it affects how snappy the final fabric feels.

Ok, so why is Icky good? Well.. it has some things going for it. It's polyester, so there's very low streatch. It has a polycarbonate coating, which is very snappy, and very non-streatch, and it's very light.

So, what's wrong with that? Well.. it depends on what you're trying to do. IMHO, Icky is great for ul's, and sul's, where a snappy fabric can be more reactive, and a lighter fabric helps keep the weight down.

In a vented, I would much prefer a nylon kite. When it's windy, the little bit of streatchyness helps you absorb bumps. You don't have to worry about weight, since it's windy. And a streatchy sail is less apt to explode. When you have sudden pressure changes, like a crash or something, a fabric that is not elastic, only has one choice, which is to breach. Also, very smooth fabrics have less drag, which will make the kite faster... which is bad in a vented.

So what about a std? The vast majority of kites are going to be here. So, what's bad about icky? Well.. first of all, everyone seems to want it. So supplies are short, and the price is high. The weight of the fabric in modern std's has pretty much become a moot point since we started strapping lead to the tail. We are not so much concerned about light and tight.

I'd honestly rather have a std built from a heavier fabric, like a 3/4oz or maybe even a 1 oz. There's going to be more fiber in that fabric, which means it should wear longer. Since most people fly standards most of the time, wouldn't it make sense to make that to last instead of trying to fight for every gram, and then put it back on there with lead, more reinforcements, etc?

There are quite a few fabrics out there that are good. The stuff L1 was using is nice and crispy, with very good/deep color fastness. There's also the Z finish poly at kitestudio, that seems to be decent, but is crippled in color choices. Toray is all but gone these days, which is ok with me since that coating sucked, and it wore out way too fast.

But, I guess the point is, there are alot of fabrics out there that would be great choices for kites. Most of them come from the same handfull of textile manufacturers in Japan, and it's really not a matter of cost to produce. Icky can't cost that much more than the Z finish fabrics, but it's like $14+/yrd, while the Z is 4.

Now, I'm not saying don't use Icky. I like Icky quite a bit. But I also know it is just one fabric among many.

Manufacturers use it because that's what people expect.

People often say that they know what they like. But what they almost always really mean is that they like what they know. I think that goes for alot of things in kites, and well.. I think people should broaden their perspectives so that they can make a more informed choice. In the end you might still like icky best, and I'm fine with that. For some things, I do really like icky, like rev's.

Why do I blog?

2008-05-19T16:38:00.000-07:00

Well... There's a couple of reasons.

I had a gripe here, but it's not constructive, so I'm removing it.

In a nutshell though, the reason I'm blogging is because it will let me share info, and put something that's hopefully positive out there, instead of griping. I don't want to be cranky. It affects my perspective of the world, and it should not.

My sister died recently of a sudden brain aneurysm. She was not old, and it was not her time. She had alot to be grumpy about, but she did not live her life that way. In a sense, I guess I'm trying to learn from her example. It's not easy, and it takes some self reminding more often than it should, but she was right, and I was not.

So, I'm going to try to live my life differently.

Trick tips

2008-05-18T18:31:00.000-07:00

In general, I'm going to talk about tricks when I talk about flying.

Precision figures are neither my passion nor my forte.
On the otherhand, I've spent alot of time with tricks.

I say precision figures because I dont think that tricks should be sloppy.
The things that make a precision figure good should also hold true for tricks.

I don't want to get preachy about it though, since part of the fun in learning trick flying is just winging it and having fun with it. I think it's important to keep that in mind. If you stop having fun with your flying, you'll stop flying.

So, what do you need to know about trick flying?

First of all, you need to stop thinking that there is some kinda voodoo to learning any trick. Anyone can do any trick under the right circumstances. The better you get at doing a particular trick, the less you need to rely on chance and the more you can control the kite in less than the right circumstances.

What exactly does that mean?

Well.. to be honest, sometimes learning a particular trick can be frustrating. That's often because you're not quite sure how to do something. I find it helpful in those circumstances to try a couple things. This is assuming you understand how to basically do a trick, but have not quite got it yet.

Things to try if a trick is eluding you:
----------------------------------------
1) Try doing it with your non-dominant hand. I think everyone has one side that is stronger than the other. For me it's my right side. Sometimes your timing is just off for a trick. By using your non-dominant hand, it might be easier to get a different timing that works better. Trying this really helped me learn Taz machines and getting it instead of a 2 pop half axel.

2) Try doing it in a variety of winds. Sometimes things work better in more wind, or less wind. When you go out to the field, you don't have control of the wind. But, you can often find a place that is more sheltered from the wind on a windy day. For instance, if your field has a line of trees, try your trick in the wind shadow. Light wind is often easier to trick in since you're closer to a stall. But, that's sometimes not true, and it works better if you have a bit more wind pressure. Until you get a good feel for a trick, try it in a variety in conditions. You may find that it is easier to learn a trick in a wind condition that is not typical of what you've been trying.

3) Try doing it in different parts of the wind window. Try the top, 3/4, 1/2, and closer to the ground, some tricks are easier depending on where it is. For instance, crazy copters seem easiest for me higher in the window and harder the lower I get, but waps seem easier to me if they are lower. I believe that is because of the angle of the string to the kite in relation to the angle the wind is hitting the kite when the spin is started. Another thing to try, is changing the side of the window you are trying something. For instance, if you're trying to learn a flatspin, those are often easier at the side of the window. But when learning, sometimes it's easier to learn it either against the wind, or with the wind. Say you're trying to do a left handed pop for a flat spin. It may be easier for you to learn either floating with the wind, or against it. If you pop left at the left side of the window, you will float into the wind. If you pop left at the right side of the window, you are flying into the drift. One direction might be easier for you.

4) Try it crooked. If it requires an entry that you fly into, try entering at a diagonal in both the up and down direction. One might make it easier depending on what it is. Also try entering crooked, so that one wing is slightly higher than the other. Again, I'll use the flatspin as an example. It's often easier to enter a flatspin at an angle, than flying straight down. It is also easier if you enter a little crooked, and pop the higher wing. On the otherhand, sometimes rotofades are easier, especially in reverses, if you pop the lower wing.

5) Try a different kite that perhaps you've seen performing the trick well in a video. Now.. this one I say with a grain of salt. I'm not much of an advocate of better flying through shopping. But the fact remains, that sometimes, some kites make learning a certain trick a bit easier, and once you learn a trick on a friendly kite, it becomes easier to transition it to other kites. Most kites these days are "polyvalent" meaning that they do all the tricks. But being in the middle often means that it is not built to do all tricks the easiest.

6) When you start to get a trick, do it repetedly right away. If you're not quite getting a trick, there's something that you're used to doing that is not quite right for that trick. When you start to get it, you've changed that, and you need to try to remember what it is you're doing differently. Repetition can help your muscles remember what it is, as well as what to tune to make the trick cleaner, and also what to tune to make it harder so that you can learn how to affect the trick in less than ideal conditions and still get it to work.

That's it for tonight.
Thanks for reading.

Thanks for all the Kind thoughts

2008-05-18T17:39:00.000-07:00

Greetings,

I'd like to thank all the people that have expressed kind thoughts in regards to my post about withdrawing from the GWTW forum.

Perhaps you're reading my blog for the first time because of it. I invite you to stop by as often as you like. If you find the info useful, please invite someone else to visit. I have no method of advertising, so I'm counting on people that are interested to pass it to others that might also be interested. I don't get anything for posting here, except the hope that I might be helping someone understand more about kites.

I'll try to keep posting here regularly so that you don't get bored. But, this is real life, and some days I might need to deal with life, and may not get around to posting something.

Thanks for reading.

A little bit about my kites

2008-05-16T17:15:00.000-07:00

My approach to kite design has been very straight forward.

I don't try any voodoo, and I try to keep it all very basic.

By starting with a very reproducible known, I can better gauge what changes create what effects.

So, I start pretty much all my designs with a 1.5 template. What I mean by that is that I start with a sheet of paper that is 1 unit high, and 1.5 units wide.

I don't use any camber on the leading edge, and the nose angle is determined by a slope that is drawn from a corner to a proportion on the opposite side.

The kite below is a 1.5x1/3rd.

Using a 36" spine makes for a simple example. (that one's not because I sized it for a 32.5" rod + knock). So, for that kite, I mark 12 inches from the lower right corner, and draw a line from the upper left corner to that mark.

I've been experimenting with 2 different nose angles. 1.5X1/3 and 1.5x1/4. The interesting part of that, is that the nose angle is one of the least important factors in the final kite. People historically get all worked up about high or low aspect blah blah.

I've come to the conclusion that the nose angle is really not that critical.

Now, that doesn't mean that it is meaningless, just that you'll spend 10% of the time messing with the nose angle, 10% on the bridle, 20% on spreader and standoff locations and lengths, and 60% on the trailing edge.

Ok, so typically I use the 1/3, or 1/4, find the 1/3 along the spine for the spreader location, and then let pythagoras figure out the spreader length and attachment point on the LE.

At 1/3, the sail is deep, which makes alot of things very stable, but the depth ends up needing more wind. At 1/4 the sail is more shallow, which makes things faster, and lighter, but also less stable.

These descriptions are painted very widely, but for the most part I think are accurate.

There are alot of ways to overcome problems with the choices mentioned, and that's where you're going to spend most of the time in a kite design.

If I need more flip, there are various things I try depending on the rest of it. Sometimes that's weight, sometimes its shortening the spreaders, sometimes that's moving the standoff's apart, sometimes it's making the standoffs longer, sometimes it's just more tail weight, or shortening the upper spreader.

It all depends on what I'm trying to get besides just flipping.

For instance, there's looping in the flip. If you watch the kite from the side during a rollup, some kites make a wide loop, and some kites flip more around the spreaders. It might seem like that doesn't matter since either way it flips. But that travel does matter because you want your kite to do more than just yoyo, and that travel affects other tricks, like wap's. If it's too narrow, the pull to spin the wap will just unroll it. If it's too wide, your entry becomes very long, and you need to move forward with it more or you'll choke it short.

There's alot of compromising to make a kite that tricks in the middle of everything. My current bane is balancing it for taz machines, which seem to not like the trailing edge I've used. I have thickness in the wingtips and at the standoffs to make cyniques almost childs play. It also lets me do lifters, but tuning those in has made taz's difficult as it wants to do more of a halfaxel, and finding that pitch where it will taz instead of 2 pop 1/2 axel is very narrow.

If I remove the wing flaps, and trim the tips a bit, it gets much easier to taz, but then I lose the lifter, which I can tune back in a little bit with the outer standoff.

Anyway, I'm almost to the point where I think I might go back to the 1/4 and work with a shallower sail. It might make balancing the tricks a bit easier, even though I think it makes things less stable.

More on lazies.

2008-05-15T13:01:00.000-07:00

Today I'd like to talk a bit more about lazy susan's and design.

I already talked a bit about turtle, but lazies are not that simple.

In a LS, of course you turtle and pop on line. It pulls the bridle which converts that pull at the point where it crosses the spreader. Also, it's important to keep the plane of the kite away from you so you dont lose height as much.

I think there are 2 kinds of lazies. They are not different enough to really be different, but it's something I think you need to look out for.

The difference IMO, is where the bridle is catching along the spreader. If it catches more toward the tail, you get a spin that is like the flapjack spin. If you catch it more toward the tip, it spins more on the outer wing.

Why does that matter?

Well.. if your catch is straight, you are pulling on almost an entire half of the kite. When you pop in say a Jacobs Ladder, it's more of this straight pop.

On the otherhand, if you popping from a snap lazy, k2000, etc, it's more of a wing spin. When I say wing spin, it's spining on the plane formed between the nose, outer standoff, and the tip. The larger that area is, the easier that is. These tend to be floaty since you pull that plane into the wind instead of just spinning and letting gravity work. It's kinda important if you want to gain height in lazies, and cyniques because that is how you do it.

So, when I look at a lazy, where it's catching on the wing has alot to do with the way it spins. (not if it spins). I think that's important to note because you can move that point after initiation by varying the pressure and timing. That's also how you can control the plane it's spinning at to keep the plane into the wind so you're not dropping.

Sorry today's blurb is short, but I have to get back to work.

Math Kite examples

2008-05-13T19:37:00.000-07:00

It appears that my text descriptions might not be clear to some folks so, here's a couple pics. This is what I've been flying lately. Yes the right yoyo stopper has slid down. This photo was taken when I was still figuring out where to put them. They were just clipped on, but have since been fastened .

Here's how I attach the inhauls. There are 2 orings glued on either side of the knot on the spine to keep it from moving around.
If you look carefully, you can see the lashing at the tail above. The back looks like this.

It's a loop of string that goes around the spine and then out the front, and then looped onto the knock on both sides.

lazies and tail weight.

2008-05-13T07:23:00.000-07:00

I think this trick was originally made popular by Prism, but I'm not certain about that.

Back in the day, you'd fly to the top, slack it, and then pull one side to spin it. It would kinda rotate, and then fall out. It was kinda lazy and it was not an instant trick.

Then, came the flapjack, which was so deliberate and violent, that it had instant moxy. Many many spreaders were sacrificed.

There's a couple really good lessons to learn here. First is that we are mostly sheep. For almost a decade, those were the only 2 ways people did that trick, I think mostly because we stopped thinking about what might be possible and for the most part put tricks into the "complete" pile.

Now.. why did that change? Well.. surely that is at least partly because of kite design, which I'll get into in a moment. But I think it is also partly because flightschool and way to fly, did not make it over the pond to france, and the internet kite video was not a huge influence yet. So... people over there were not flying with the notion that Dodd had figured it all out and was ready to sell them lessons.

Talent was involved for sure, but we had talent in the US as well. I think the French though... tend to make things work, rather than buy something that already works. More tinker, and not solely consumers.

There's a video on the net somewhere, of old school US/benson kites doing the "new school" french stuff, on K2's, outerspace, illusions, and eclipse. We were not limited by the equipment, but by imagination.

So, the french guys abandoned the idea of super cambered edges and stubby tails, and went back to basics. They figured out that tailweight would flip the kite faster, and inner standoffs closer to the tail would initiate turtles from a snap stall type input.

So, what can we learn from that? Well.. first lets look at tail weight. There's a couple ways to look at tail weight that seem diametrically opposed.

First is that it makes kites flip. That one is fairly well understood and accepted.

The second is that it makes it not flip. Huh? That's right, it makes it not flip.

Newton's law: Things in motion stay in motion, things at rest stay at rest.

So, when you flip the kite, the weight brings the ass around.

When it's not, it takes force to get it moving.

That's why kites with alot of tail weight get stuck in flare, and why tailweight can help taz machines. (I'll do a taz machine article later)

It can also help you keep from flipping out of the turtle when you pop it for the spin.

Now, in the below article I describe how the pop pulls the kite out of turtle.

But, when you pop it, the tail is higher than the spreader that you're pulling on for the spin. So the pull on the spreader wants to pop it down because it's on one side of the center of pressure from the rear. But, you're also pulling underneath the tail weight, which if it's fairly significant will want to make the tail go up. It is the same thing that makes a motorcycle do a wheelie.

If you had a kite that didnt want to multilazy well, alot of tail weight would probably help.

I'm going to stop here, and pick up lazy talk later.

Velcro

2008-05-12T09:12:00.000-07:00

Well... seems to me that most sport kites use a velcro tail strap.

I'm going to just go ahead and say it: I don't like velcro.

The original thought was that by using velcro, the spine would push out the tail in a crash, and thus keep it from going through the nose webbing.

Well.. having crashed alot of kites in my time, that theory is a load of bunk.
Very rarely does that thing let go, and really today, we don't want to go walk after a lawn dart to fix the tail.

So, what else can it be good for? Tension?
I dont really think so. I dont use velcro in my tails, and I dont have any problems maintaining the tension between the nose and the tail.

The only thing that it's arguably good for is holding tail weights (at least IMO). But there are so many other options that make that moot.

Velcro.. just seem very old school, and clunky to me. It's also more sewing, and a place where something can punch through. It also makes an angle where the bridle is apt to catch.

I guess the DS tail is probably the cleanest velcro tails are going to get, but why even use it?

I usually use a lashing that loops around the spine to keep it from moving left right, and through a knock to keep it from sliding around. That way, I just need to sew a dacron tab to the tail, and melt 2 holes. Clean, light, cheap, fast.

Balance

2008-05-12T09:11:00.000-07:00

Everyone pretty much knows that any sportkite is a compromise.
But I think there are "rules" that are not hard and fast.

Today, I'm going to talk about a couple that I think people should inspect more.

Center T location and bridle attachment. Why are those related?

Classically, the inhaul is tied at the center T, and the up and outhauls are tied to the spreader connectors.

So, what's wrong with that?

Well, I don't think that arrangement is really ideal.

Let's start with the spreader height.
- In the past, spreaders have been fairly low, and toward the tail. A kite frame is your basic A frame, and by using it low, you make a stronger triangle. When our sticks were fiberglass or pultruded, that was important.
- But, today our sticks are more resilient. Further, there has been much more emphasis on tricks relying on the turtle. The closer to the tail that the spreader is, the longer the lever is when you pull lines in the turtle. That means that the closer to the tail, the easier it is to pull it out of turtle.
- There's also another issue. Rod strength per length/weight. Lighter rods are usually more flexible and prone to breakage, so the lower the rod, the longer it must be, and consequently the thicker it needs to be to keep from breaking. But that also adds weight.

So.... you can save weight, and have a stiffer rod by moving the spreader higher, and thus shorter to maintain the same frame geometry. It will also make your turtles more stable. Sounds great right?

Well.. if you go too high, you can leave the tips too unsupported, and you may experience shudder in higher winds.

That brings me to bridle attachment. Almost all kites attach the bridle to the frame at the connectors. But, if you raise your spreader, you also raise your bridle closer to the center of pressure. That will make it unstable and you'll feel it bob when you pressure up, like after a half axel, a snap stall, or other hard pressure change.

So, your bridle is compromising your framing right?

Well... if you stick with the old rules.. yes.

Thing is.. you dont have to attach the bridle to the frame at the connectors.

On most of my kites, the inhauls attach to the spine a couple inches below the T. That allows me to allow a very stable turtle, and still avoid the bob.

So.. what about wing tip shudder? Well... that's a little more tricky. I usually try to design so that there's enough support, but sometimes you have a shape you want, that you dont want to alter. In that case, you can use an overhaul line. That's an extra line to the LE either below the LS or between the US, and LS. A kite shudders because it is not supported enough. Ideally, if you frame and bridle a kite right, the frame should not shudder, and will simply explode when you exceed the pressure.

I don't think many designers have really thought about these things, with the exception of Ramlal in the Transfers. The Opium had a psuedo overhaul to the tip, but that was supposed to help in fades. Everyone just removed it as kinda useless.

So, there's my blurb of the day regarding kite design, and being stuck thinking inside the box.