Quad design questions

[p23brian]

Just pondering a few aspects of quad design over the past few rainy days and have a couple of questions.

1. Why are the two vertical spars on the back of the kite rather than the front? It would seem that if they were on the front (bridle side) the sail would take a more efficient foil shape when it fills with wind.

2. What are the characteristics of an expensive kite that differentiate it from an inexpensive one? My inexpensive Freilein Exodus seems more or less identical in design to the much more expensive kites. I've looked it over carefully and the level of workmanship seems extremely high. The panels are all cut perfectly. Every stitch on every seam is perfect. But I know many of you more experienced folks have purchased lots of more expensive kites. I'm curious about the differences and cost/benefit trade offs.

3. Have any quads ever been designed with any type of sail adjustability? Going back to my sailing experience, lots of people have different sails on their boat for different conditions just like folks with multiple kites. But at the same time, a given sail can be adjusted to increase or decrease draft (camber) and also move the position of maximum draft toward or away from the leading edge while the boat is underway. It probably wouldn't be practical to adjust the sail on a kite when it's flying but being able to do so on the ground would seem doable.

4. Somewhat related to #1 and #3, quad sails appear to be built as flat panels, in other words if 4 people tugged on the corners until the edges were all taut the sail would be flat with no sag in the middle. Sails for a boat are sewn to intentionally have a "belly" in them so they create lift. You can google broadseaming for a better description than I could provide. Essentially when 2 panels are sewn together one is cut so the edge is straight and the other is cut with an intentionally designed curve. When sewn together the sail takes a 3D shape. Has this ever been tried in kite design?

I'm just curious. Not trying to push any buttons or stir the pot intentionally. Looking forward to some interesting discussion.

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[Edmond Dragut]

for how long you fly quads ? 

you do not stir nothing you just show how inexperienced you are on kiting (any kind of kite) and your taste to compare things build for different functions. apples are apples and avocados avocados. functionality, maneuverability and design play the most important aspect on the play. 

sails for bots are build to catch the wind and keep it in sail, kites are sliding on wind.you cant compare a V6 gas engine with a V6 Diesel. compare kites with kites and sails boats with sails boats.

now Freiline comparative with Revolution, 20 years manufacturing difference,Rev invented Freiline copied on past 2-3 yeares .difference? if you will have a bit of experience and pay attention at different Rev models 1,5 , EXP, B-series, B-Pro, New York minute, Masterpiece you will see what? exactly, different sowing patterns. Because kites glide on wind different sowing patterns make the wind to slide differently

spars on front ? you want to catch the wind or glide on? a boat sail will not fly if you will try to converted on to a kite.That you will do punting the spars on front,you will create that "belly" what is not admitted in kiting. 

yes kites not just quads are having the adjustability features but in bridle because the sail is a flat surface

you see it any Revolution Reflex? yes Reflex is having a belly but in opposite side of wind,That make the sail to glide on wind no matter from where is blowing how long you are in around 140-150 degrees on the front 

Forth question you ask is the answer of the first, kites must be a flat surface and depending of design different kites have an angle between wings (see delta kites).

no questions about parafoil kites? single line,two lines,quads ? a parachute is a parafoil kite or a boat sail? in advance i answer for you, parachutes are boat sails not even close design to a parafoil kite. modern parachutes have some of the characteristics of parafoil kites give them the possibility to be flayed and steered left and right for more precision landing but any similarity is stooping there. all the best, happy more flying and how a friend will say "do not forget to breathe" 

 

 

[p23brian]

for how long you fly quads ?

About 3 weeks.


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[Wayne Dowler]

I'll attempt, might not get it all right:

1- Spars act like masts - the sail shape forms a pocket for the wind between them. Hopefully to keep it there as you fly. With the spars frontside, you would have no real resistance to losing the sail shape. To keep it "flat" and taut, you'd need to move the line attachment points out to the corners. Verticals too.

2- Quality is getting better on the less expensive kites. Wasn't always so. Andy has instituted strict QC standards on the Freilein kites, based on experience with other brands (both good and bad). Plus the more expensive allowed for choices in color combos - you could personalize them to be your creation.

3- Closest thing to adjust-ability I've seen is the many types within a model - ie - a std, mid, f/v, x/v, etc, all within a model - "B" Pro series comes to mind. Each has a specific wind range best suited for that particular type. And of course the interchangeability of the framing, to make your combo feel the way you want it to.

4- Your frame creates the "belly". Everyone had different tastes here, I like plenty of flex, some not as much. I fly race frames in conditions most put theirs away in, it all comes down to your comfort level.

Hope this either answers some questions or at least gets the discussion rolling .....!

PS: bought my first Rev in '97, 98 sometime!!

 

 

[Brettgrant99]

#1 - Foil is a very generic term.  What is an "efficient" shape?

#2 - The expensive kites paid for the initial development, the cheaper ones are basically copies.

#3 - Revs tend to not have many kites adjustments.  It seems like with quads, most people adjust the handles and the upper/lower line lengths.  A quad like the TC Ultra had quite a few more.  Many dual line stunt kites have lots of adjustments.  My Utopia has many different adjustments, more than many kites.  I could probably configure it over a 100 different ways (I've never bothered to count).

#4 - Many Blue Moon Kites were made with broadseaming.  These were dual line kites. 

I have many additional and expansive opinions, but I will keep them to myself at this time.

[Brettgrant99]

22 minutes ago, Wayne Dowler said:

I'll attempt, might not get it all right:

1- Spars act like masts - the sail shape forms a pocket for the wind between them. Hopefully to keep it there as you fly. With the spars frontside, you would have no real resistance to losing the sail shape. To keep it "flat" and taut, you'd need to move the line attachment points out to the corners. Verticals too.

2- Quality is getting better on the less expensive kites. Wasn't always so. Andy has instituted strict QC standards on the Freilein kites, based on experience with other brands (both good and bad). Plus the more expensive allowed for choices in color combos - you could personalize them to be your creation.

3- Closest thing to adjust-ability I've seen is the many types within a model - ie - a std, mid, f/v, x/v, etc, all within a model - "B" Pro series comes to mind. Each has a specific wind range best suited for that particular type. And of course the interchangeability of the framing, to make your combo feel the way you want it to.

4- Your frame creates the "belly". Everyone had different tastes here, I like plenty of flex, some not as much. I fly race frames in conditions most put theirs away in, it all comes down to your comfort level.

Hope this either answers some questions or at least gets the discussion rolling .....!

PS: bought my first Rev in '97, 98 sometime!!

 

 

Would you elaborate on point #1?  What do you mean "forms a pocket for the wind between them"?  If your background is sailing, I agree with the original poster that the spars in front make more sense.  However, the Rev was basically designed as a flat kite, so I agree that spars basically are there to hold the sail flat.

On point number 4, the question of "belly" really confuses me.  I got my first rev in 95 or 96.  I don't remember anyone talking about belly, even up in the early 2000's.  I got out of kiting for quite a while, and now it seems like all the talk is about frames.  Is there a discussion about what belly is?  With the flat sail of the Rev, the only way to create belly, as a sailor would think of it, in the sail would be by shortening the vertical spars.  If the vertical spars are really flexible, than they could create it.

[Edmond Dragut]

almost for sure Wayne speak about that "belly" formed between leading edge,spare and sowing of the trailing edge, there are not evident but the wind is create them by stretching the sail and bungee from caps.for that you make adjustments and tide the bungee after 2-3 flights  

[Wayne Dowler]

The style of flying I use, is trying to keep the wind as much as possible in the sail. Think of it as a ball (wind) and not dropping it as you fly around. PS: I fly a lot of team flying, lots of prescribed moves needing power instantly. Free flying alone is a whole nother universe! I do fly solo too. In that I'm OK with the kite being a little on the looser side of power, team means right now.

I sailed - the difference is that you are not driving another object. only the kite. Different animals. In kites, you're only trying to move the sail, not something else. While they are both "engines", the purpose for each is very different, therefore the different designs.

Belly? Watch someone else do the flying and get under the sail. Watch as it billows out in the middle to form a pocket (belly). We've learned to use that power to keep things flying in lots of conditions. Frames can increase or decrease that pocket, depending on stiffness. More flex = bigger belly - stiffer = less.

Times have changed a lot over the years. Much of the info from over a decade ago has been superseded by styles today. Not to say it isn't valid, just dated.

 

[p23brian]

#1 - Foil is a very generic term.  What is an "efficient" shape?

This link gives an overview of NACA foils and aircraft wing shapes. Same principles apply to kites. A little on the technical side but a kite does more or less the same thing as an aircraft wing.

https://en.m.wikipedia.org/wiki/NACA_airfoil#

Thanks for the replies!


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[Edmond Dragut]

great comparison, keep it up 

[Wayne Dowler]

Thinking about (belly) more - 

The pattern of the Rev is flat, but in flight, very much a shaped sail. As wind increases, so too does the amount of distortion from that flatness, Bunjis help with giving and limiting that allowance, but they do allow some movement. So too, do the frame members. If reshaping wasn't an intended objective - why not lash it all down, use something so stiff as to not deform in the LE? Lighter, more flexible frames give you more distortion from that original flat pattern. Stronger, heavier limit it! 

PS: there is no wrong or right! Just what YOU get out of your experience playing on the wind! Info is always welcomed, but flying, in the end, is what it is all about!

[riffclown]

For price points, more expensive doesn't necessarily mean better and as you've noted, Less expensive doesn't necessarily mean cheaper.  The Freilein kites are sewn better and to more exacting standards than any of the current competition. It's almost too perfect. You will not find a stitch out of place on a Feilein Kite.. If you do, OSK would probably replace it for you.

Many of the advancements or modifications on the Freilein Kites are the results of OSK's feedback for Quads they sold through the years, repairs they've made to them  and the willingness to make changes to their own product based on consumer input. Those changes may not please everyone but I guarantee you that those changes were made due to consumer feedback.  I made a simple phone call about the bag and they changed the bag length to accommodate..

Adjust-ability, -- once you get proficient at your normal sails, you can tweak with framing choices, bridle mods (like French bridles) and venting options. Find what's best for you!!

-Rev was the original innovator and has a very strong following and some pretty extreme loyalists..

-Freilein is a relative newcomer that's capitalizing on the expiration of Rev's patent while making changes based on their own innovations. The lower price point has gotten a lot of attention from new and experienced pilots alike.

-Phoenix is a effort by a former Rev Masterpiece Designer and producer of the B-Series Pro to provide his (Bazzer) innovations to  the quad market.

There are others already on the market across the spectrum of price points and quality. There are also some very interesting designs in the "near ready for market" category.  EVERYONE has an opinion as to what is best. My opinion differs from others' but I know what I like. I won't force my opinions on you. You have to individually find your options and figure out what's best for YOU. There is no ultimate wisdom and no ultimate kite. YET.

 

 

 

 

 

[Brettgrant99]

2 minutes ago, p23brian said:

 

 

This link gives an overview of NACA foils and aircraft wing shapes. Same principles apply to kites. A little on the technical side but a kite does more or less the same thing as an aircraft wing.

https://en.m.wikipedia.org/wiki/NACA_airfoil#

Thanks for the replies!


Sent from my iPhone using KiteLife mobile app

 

So to give some of my background, I spent fifteen years as a rocket scientist :).  I did navigation and simulation.  I often had to deal with aerodynamicists, so I understand a bit about the field, but not everything.  I did ask them about aero models for stunt kites, and basically none exist.  I am sure that someone, somewhere has studied it, but the guys that I asked weren't aware of any.  Of course, they were more interested in airplanes and missiles and rockets.  Back to the point.

I highly, disagree with you assertion that the same principles apply to kites.  That is simply just too generic of a statement.  They do apply to some kites, some of the time.  I don't think that they apply to stunt kites while in the center of the "wind window".  At this location, the kite has an extreme angle of attack.  It isn't flying like the model of an airfoil described in clean, laminar flow.  Rather the kites is like a flat plate, perpendicular to the airflow.

The different NACA airfoil shapes are for use in particular situations.  Which one is most efficient?  Depends upon the situation.  I guess that was the basis of my question.  I assumed (a terrible word, so many issues with assumptions) a few things about your question.  Typically, when one talks about airfoils, they generally talk about the cross sections of an airfoil.  On a sailboat, the cross section that is typically spoken about and illustrated is the one that is roughly parallel to the boom.  I assumed that you were speaking about a vertical cross section, from your description.  After reading Wayne's response on what belly is, it is clear that he is talking about a horizontal cross section.  Here, vertical is in the direction of gravity, and horizontal is parallel to the flying field's surface.  I assumed that you were thinking of the nice, laminar flow style diagram that can be seen in many places that describe setting a sail properly.  With this in mind, I total agree that the spars being in the back, with that vertical cross section in mind, seem "funny", and that a smoother, laminar shape would be created by having the spars in front of the sail.  So I saw this as a question, why does the rev fly when the sail shape is not what I expect it to be from my sailing experience?  My response was to get you to think about the question.  In a kite, what is an efficient sail shape?  Are they the same for all kites?  Is a shape for a kite that is effective, the same as for an airplane or a boat?  Do a boat and an airplane and a kite all fly the same way?  I hope that you can look at my answer and at least think about it a little bit.  I don't mind more technical discussion.  My original question stands, "What is an efficient shape?".

For all of this talk, I do agree with Wayne (and I am sure that others will echo the same or similar advice):

50 minutes ago, Wayne Dowler said:

PS: there is no wrong or right! Just what YOU get out of your experience playing on the wind! Info is always welcomed, but flying, in the end, is what it is all about!

 

[Brettgrant99]

1 hour ago, Wayne Dowler said:

The style of flying I use, is trying to keep the wind as much as possible in the sail. Think of it as a ball (wind) and not dropping it as you fly around. PS: I fly a lot of team flying, lots of prescribed moves needing power instantly. Free flying alone is a whole nother universe! I do fly solo too. In that I'm OK with the kite being a little on the looser side of power, team means right now.

I sailed - the difference is that you are not driving another object. only the kite. Different animals. In kites, you're only trying to move the sail, not something else. While they are both "engines", the purpose for each is very different, therefore the different designs.

Belly? Watch someone else do the flying and get under the sail. Watch as it billows out in the middle to form a pocket (belly). We've learned to use that power to keep things flying in lots of conditions. Frames can increase or decrease that pocket, depending on stiffness. More flex = bigger belly - stiffer = less.

Times have changed a lot over the years. Much of the info from over a decade ago has been superseded by styles today. Not to say it isn't valid, just dated.

 

Thanks for your description, I can picture what you are saying now.  I don't think that I would have called it belly, but I don't have any other better term for it.  I'm not entirely convinced that the belly adds lift.  While I understand what you say about power, from a modeling standpoint, I am not sure of how "power" is defined (I am not asking you to define it, either) and how it relates to belly.  A more flexible frame would typically be lighter too.  And I am sure that windspeed plays a very important part, too.

[p23brian]

1 hour ago, Wayne Dowler said:

Thinking about (belly) more - 

The pattern of the Rev is flat, but in flight, very much a shaped sail. As wind increases, so too does the amount of distortion from that flatness, Bunjis help with giving and limiting that allowance, but they do allow some movement. So too, do the frame members. If reshaping wasn't an intended objective - why not lash it all down, use something so stiff as to not deform in the LE? Lighter, more flexible frames give you more distortion from that original flat pattern. Stronger, heavier limit it! 

PS: there is no wrong or right! Just what YOU get out of your experience playing on the wind! Info is always welcomed, but flying, in the end, is what it is all about!

Agreed.  The sail itself is flat, but the spars are flexible.  Under pressure they bend, allowing the sail to distort to a non-flat shape that generates lift.

I just like to understand the science as best I can so I can advance my flying skills without resorting to more random trial and error.  

Thanks for taking the time to reply!

[riffclown]

4 minutes ago, p23brian said:

I just like to understand the science as best I can so I can advance my flying skills without resorting to more random trial and error. 

As a subscriber you have access to the tutorials.. Take a preparatory look at @John Barresi's tutorial for sail loading..It explains loading the sail while maintaining a constant position.. The shape changes to store the "potential energy" allowing you alter the kites acceleration characteristics.  It's where the "belly" of the kite come into play most prominently. Even if you feel you aren't personally ready for the particular technique, it will help you understand the physics behind it better.

[p23brian]

When I used the term "belly" in #4 in my initial post I was referring to camber or draft.  A sail for a boat isn't a flat panel.  If you stretch it out so all the edges are taut it will sag in the middle due to the way the panels are sewn.  This is by design.  I was curious whether this had ever been applied to kites.  The sail on my Freilein is flat and from what I can tell from pics, the sails on Revs and other similar designs are also flat.  As has been mentioned previously, when a kite sail fills with wind and the spars bend the sail no longer stays flat.  Therefore it can generate lift.

[p23brian]

2 hours ago, Brettgrant99 said:

Would you elaborate on point #1?  What do you mean "forms a pocket for the wind between them"?  If your background is sailing, I agree with the original poster that the spars in front make more sense.  However, the Rev was basically designed as a flat kite, so I agree that spars basically are there to hold the sail flat.

On point number 4, the question of "belly" really confuses me.  I got my first rev in 95 or 96.  I don't remember anyone talking about belly, even up in the early 2000's.  I got out of kiting for quite a while, and now it seems like all the talk is about frames.  Is there a discussion about what belly is?  With the flat sail of the Rev, the only way to create belly, as a sailor would think of it, in the sail would be by shortening the vertical spars.  If the vertical spars are really flexible, than they could create it.

I think Wayne refers to the unsupported part of the trailing edge between the vertical spars forming the belly.

[p23brian]

57 minutes ago, Brettgrant99 said:

I highly, disagree with you assertion that the same principles apply to kites.  That is simply just too generic of a statement.  They do apply to some kites, some of the time.  I don't think that they apply to stunt kites while in the center of the "wind window".  At this location, the kite has an extreme angle of attack.  It isn't flying like the model of an airfoil described in clean, laminar flow.  Rather the kites is like a flat plate, perpendicular to the airflow.

I think we'll have to just agree to disagree on this if you don't think a kite is an airfoil.  I appreciate your participation in this thread though.

[p23brian]

4 hours ago, Edmond Dragut said:

for how long you fly quads ? 

you do not stir nothing you just show how inexperienced you are on kiting (any kind of kite) and your taste to compare things build for different functions. apples are apples and avocados avocados. functionality, maneuverability and design play the most important aspect on the play. 

sails for bots are build to catch the wind and keep it in sail, kites are sliding on wind.you cant compare a V6 gas engine with a V6 Diesel. compare kites with kites and sails boats with sails boats.

now Freiline comparative with Revolution, 20 years manufacturing difference,Rev invented Freiline copied on past 2-3 yeares .difference? if you will have a bit of experience and pay attention at different Rev models 1,5 , EXP, B-series, B-Pro, New York minute, Masterpiece you will see what? exactly, different sowing patterns. Because kites glide on wind different sowing patterns make the wind to slide differently

spars on front ? you want to catch the wind or glide on? a boat sail will not fly if you will try to converted on to a kite.That you will do punting the spars on front,you will create that "belly" what is not admitted in kiting. 

yes kites not just quads are having the adjustability features but in bridle because the sail is a flat surface

you see it any Revolution Reflex? yes Reflex is having a belly but in opposite side of wind,That make the sail to glide on wind no matter from where is blowing how long you are in around 140-150 degrees on the front 

Forth question you ask is the answer of the first, kites must be a flat surface and depending of design different kites have an angle between wings (see delta kites).

no questions about parafoil kites? single line,two lines,quads ? a parachute is a parafoil kite or a boat sail? in advance i answer for you, parachutes are boat sails not even close design to a parafoil kite. modern parachutes have some of the characteristics of parafoil kites give them the possibility to be flayed and steered left and right for more precision landing but any similarity is stooping there. all the best, happy more flying and how a friend will say "do not forget to breathe" 

 

 

Your reply sounds a little on the snarky side.  I will give you the benefit of the doubt and assume you didn't intend it that way.

I would be interested if you could explain this quote from your post.  This is part of what I was curious about:

"difference? if you will have a bit of experience and pay attention at different Rev models 1,5 , EXP, B-series, B-Pro, New York minute, Masterpiece you will see what? exactly, different sowing patterns. Because kites glide on wind different sowing patterns make the wind to slide differently"

If the kite is sewn so the sail is flat how do different sewing patterns cause the kite to "glide on wind" differently?  Let's assume a full sail with no venting.

Thank you for your reply.

[Edmond Dragut]

27 minutes ago, p23brian said:

Your reply sounds a little on the snarky side.  I will give you the benefit of the doubt and assume you didn't intend it that way.

I would be interested if you could explain this quote from your post.  This is part of what I was curious about:

"difference? if you will have a bit of experience and pay attention at different Rev models 1,5 , EXP, B-series, B-Pro, New York minute, Masterpiece you will see what? exactly, different sowing patterns. Because kites glide on wind different sowing patterns make the wind to slide differently"

If the kite is sewn so the sail is flat how do different sewing patterns cause the kite to "glide on wind" differently?  Let's assume a full sail with no venting.

Thank you for your reply.

check you PM, i will let the opinions to flow for your original question

[p23brian]

4 hours ago, Edmond Dragut said:

no questions about parafoil kites? single line,two lines,quads ? a parachute is a parafoil kite or a boat sail? in advance i answer for you, parachutes are boat sails not even close design to a parafoil kite. modern parachutes have some of the characteristics of parafoil kites give them the possibility to be flayed and steered left and right for more precision landing but any similarity is stooping there. all the best, happy more flying and how a friend will say "do not forget to breathe" 

 

 

I do own a small single line parafoil, a 2 line parafoil (Prism Snaphshot 1.9) and an old 2 line stunt kite (New Tech Cherry Bomb).  I'm new to quads and I'm interested in discussing them so I can learn to fly them quicker.  So far I'm happy with my progress.

[riffclown]

Some time back the question was asked in a thread concerning one piece sails about adding a seam to a one piece sail. Seams not only add a higher resistance to stretching but also allows to change the grain of the fabric so it handles tension differently.  My reply below should give you the physics of channeling via the seams in a kite.

... you'd have to add material as well to provide the strength and "stretch" resistance. If you're adding those things, you're also adding additional weight. Not necessarily a bad thing.. EVERYTHING in kiting is a matter of trade offs. Strength vs Weight. Design vs. Architecture, Materials vs. Cost. The key is finding the balance that meets your needs for any given set of conditions.. 

Also, the simple thread seam wouldn't provide the channeling of airflow across the sail itself. Those small areas of slight turbulent flow and air resistance on an otherwise laminar like flow structure provides the feel or touch that is so coveted. If you look at the B-Series sail design you can almost see the channeling of the actual air flow.

When you get into Vented  and Mesh Kites, it's also interesting to note if you look a something like a Shook Mesh, you can see the same channeling with the breaks between the sails providing an open air relief for the strip immediately preceding it.. That's one reason I prefer a mesh over a vented. You get a highly reduced pull without sacrificing the overall balance of the sail surface. The additional break points actually increase the feel of the kite over a normal vent pattern. Sorry, the engineer in me tries to get out sometimes. 

FWIW, I enjoy flying the one piece sails more than the SLE I have. I've only recently gotten my first B Series and I'm really looking forward to flying it.

 

 

[Brettgrant99]

46 minutes ago, p23brian said:

I think we'll have to just agree to disagree on this if you don't think a kite is an airfoil.  I appreciate your participation in this thread though.

I didn't say that I didn't think that a kite is an airfoil.  Sorry I wasn't clear enough. 

[SHBKF]

Dang!  Know Eye Deer.  But I will add that I realized early on that with a Revolution Sportwing you were essentially flying the kite by the bridle, a really long bridle.  After the thrill outweighed the seemingly high expense I did not give much thought to the design, just to thinking about how to fly the amazing kite.  When I look at a Rev style kite I see it as two conventional diamond kites, trimmed at the top & attached at the crossbow spars.  Just a couple thoughts from out here in the sticks.

Yeah, I have a few Revs, SHBKF                             old image showing the early part of the hoard..........