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Quad design questions


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3 hours ago, p23brian said:

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

Pretty much, along with the bend in the LE, forms my concept of a "belly". 

The earliest versions of a Rev were often described as 2 sides fighting for control. This was caused by the center "V" being too steep, (not enough fabric between the halves). Cured in the "B" series, the center panel is larger overall, making the halves more cohesive. Effectively making the "belly" bigger!

PS: just a flier here, no scientist, no formal education on flying, I just enjoy them and do my best to explain them!

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Agreed, There is NO substitute for time with the handles.

Pretty much, along with the bend in the LE, forms my concept of a "belly".  The earliest versions of a Rev were often described as 2 sides fighting for control. This was caused by the center "V"

I would suggest actual fly time. Let your kite be an extention of your thoughts, feelings, expression to music, etc. Watch John's video tutorials (and others too). Fly with purpose. Hell, fly all wil

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1 hour ago, Wayne Dowler said:

Pretty much, along with the bend in the LE, forms my concept of a "belly". 

The earliest versions of a Rev were often described as 2 sides fighting for control. This was caused by the center "V" being too steep, (not enough fabric between the halves). Cured in the "B" series, the center panel is larger overall, making the halves more cohesive. Effectively making the "belly" bigger!

PS: just a flier here, no scientist, no formal education on flying, I just enjoy them and do my best to explain them!

This all matches with what I've been teaching.

Thats also why the flex and return in our spars is so important.

And to confirm / summarize some, the Rev quad platform (and all its variants) basically has dynamic camber in the wing, changing based on how flexible the leading edge is and how much pressure is being applied / released from the sail.

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I would suggest actual fly time. Let your kite be an extention of your thoughts, feelings, expression to music, etc. Watch John's video tutorials (and others too). Fly with purpose. Hell, fly all willy-nilly. It's your line time. Enjoy it.

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8 hours 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!


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Foil is definitely a vague term as we have used it here. Airfoil? Parafoil? French sword? Aluminum wrap? I'm guessing we're interchanging airfoil with parafoil, and that is causing some confusion.

The airfoils of an airplane, a sailboat and a kite, although related in some respects are radically different in form and function. They are three different animals with a few similarities, but different enough in design and motion that one would never be mistaken for the others. Once you start getting into things such as laminar and turbulent airflow, ideal camber and aspect ratio, the preferences/requirments for each type of airfoil will vary radically.

The Rev kite, if described in boat sail terminology, would be akin to having the jib, main and spinnaker sewn together as a unit. If you get directly underneath a Rev flying in a relatively strong wind, say a standard sail in 10-15mph wind, and look at the shapes and angles the sail assumes in different positions and transitions you will see how much and often it changes, and why comparing one to the other may be like comparing "apples to avocados".

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Foil is definitely a vague term as we have used it here. Airfoil? Parafoil? French sword? Aluminum wrap? I'm guessing we're interchanging airfoil with parafoil, and that is causing some confusion.
The airfoils of an airplane, a sailboat and a kite, although related in some respects are radically different in form and function. They are three different animals with a few similarities, but different enough in design and motion that one would never be mistaken for the others. Once you start getting into things such as laminar and turbulent airflow, ideal camber and aspect ratio, the preferences/requirments for each type of airfoil will vary radically.
The Rev kite, if described in boat sail terminology, would be akin to having the jib, main and spinnaker sewn together as a unit. If you get directly underneath a Rev flying in a relatively strong wind, say a standard sail in 10-15mph wind, and look at the shapes and angles the sail assumes in different positions and transitions you will see how much and often it changes, and why comparing one to the other may be like comparing "apples to avocados".


This is exactly what I was getting at. All 3 are airfoils. They all generate lift based on pressure difference between the two sides of the foil until the AoA is too large for laminar flow to remain attached all the way to the trailing edge. The shape a quad kite takes when it's under load is a pretty unusual shape for an airfoil. Obviously it works because the kites fly. More like comparing different types of apples in my opinion.

Consider that as the wind increases the quad changes shape in a way that increases lift, magnifying the effect of the wind speed increase. Camber increases and max draft moves back. If there were a way to tweak the kite to overcome this the same kite would be able to fly in a wider wind speed range.

The analogy of a jib and main working in conjunction with each other is reasonable but a spinnaker is a different animal completely. On most boats the jib and main can be adjusted to increase or decrease draft, and move the max draft position forward or back. I can see where it would be cool to be able to do this with a kite. A conventional free flying spinnaker is a downwind sail and only works as a foil in a pretty limited way.

Thanks for the discussion!


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Just a quick reply. I'll read all of it in depth later.

Steve at Tappestry Kites used a broadseem in some variations of his Enigma dual line kite and found it very effective in making the sail more efficient.


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Ken McNeill is the original guy using a shaped sail in stunt kiting.  I had an AirFx probably a dozen or more years ago and it was a monster in low wind.  That sail had straight lined edges sewn to curves, so it was 3 dimensional (more like a half dome tent than a tarp)

I've seen some of his kites with faces on them, imagine trying to make that image line up across the cantenary cut!  He said the famous blues bros kite donated to an auction (2004) represented the building time, materials and efforts of 3 normal kites, taking panels apart, minor image adjustments, etc.  Harold Ames owns this kite now I think.

 

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11 hours ago, p23brian said:

More like comparing different types of apples in my opinion. emoji6.png

Consider that as the wind increases the quad changes shape in a way that increases lift, magnifying the effect of the wind speed increase. Camber increases and max draft moves back. If there were a way to tweak the kite to overcome this the same kite would be able to fly in a wider wind speed range.

The analogy of a jib and main working in conjunction with each other is reasonable but a spinnaker is a different animal completely. On most boats the jib and main can be adjusted to increase or decrease draft, and move the max draft position forward or back.

I like the analogy -- comparing different kinds of apples. 

Not only the wind speed, but every control input, changes the shape of the sail. The amount of pull created by increasing the angle of attack to near 90 degrees limits the wind speed range.

Yeah, I shouldn't have included a spinnaker. How much room for adjustment in the jib and main?

 

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[quote post="62089" How much room for adjustment in the jib and main?
 


Varies quite a bit between boats, but as a general rule you can increase tension on the leading edge to move the draft forward and reduce lift. You can also manipulate the position of the clew (rear corner of the sail) to reduce camber and subsequently reduces lift. In lower winds you do the reverse to increase lift. This is a bit of an over simplification but I think it conveys the basic idea. Higher performance boats have many different controls to fine tune sail shape while underway.


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19 hours ago, p23brian said:

[quote post="62089" How much room for adjustment in the jib and main?
 


Varies quite a bit between boats, but as a general rule you can increase tension on the leading edge to move the draft forward and reduce lift. You can also manipulate the position of the clew (rear corner of the sail) to reduce camber and subsequently reduces lift. In lower winds you do the reverse to increase lift. This is a bit of an over simplification but I think it conveys the basic idea. Higher performance boats have many different controls to fine tune sail shape while underway.


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In this pic the big white/yellow/blue sail is an asymmetrical spinnaker.  The wind is coming from right to left of the pic and our direction of travel is about 90 degrees to the wind.  In this case the sail is set for a fairly full shape.  To adjust, the lower right corner of the sail (the tack) can be moved higher or lower.  Higher gives the sail a fuller shape (more lift) and pulling it lower flattens it out and reduces the drive.  The lower left corner (clew) can be moved left/right to maintain the correct angle to the wind as the boat changes direction.  This sail is not flat.  If 3 people each grabbed a corner and backed up until all the edges were taut the center would be concave.  Sailmakers use CAD systems to design all the panels very precisely to form the right shape for the sail.  

We were sailing from Destin, FL toward Pensacola when this was taken.  The bridge in the background goes between Navarre to the left and Navarre Beach to the right.  Really nice beaches all along this area.

spin-web.jpg

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19 hours ago, p23brian said:

[quote post="62089" How much room for adjustment in the jib and main?
 


Varies quite a bit between boats, but as a general rule you can increase tension on the leading edge to move the draft forward and reduce lift. You can also manipulate the position of the clew (rear corner of the sail) to reduce camber and subsequently reduces lift. In lower winds you do the reverse to increase lift. This is a bit of an over simplification but I think it conveys the basic idea. Higher performance boats have many different controls to fine tune sail shape while underway.


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In this one we're sailing close hauled (as close to straight upwind as possible before the sails lose lift.  Like a kite at the  top center of the window just before it slows down).  The genoa and main definitely work together in this case.  This horizontal lines on the sails are draft stripes that make it easier to see how much camber is in it.

On a side note, I've seen mention here on the forum of "insignia tape".  This stuff, whether in tape for or sheet form, is what's used to put the numbers and insignia on sails, thus the origin of the name.  If you need to buy some in whatever colors suit your fancy sailrite.com is a good place to look.

This pic was taken in the Gulf of Mexico just offshore from Pensacola Pass

HPIM2126.JPG

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Powerfoils are also a ton of fun.BUT you can get overpowered very quickly if you fail to realize that the wing shape creates lift that is lifting away from you.. The faster the kite goes through the window the harder it pulls.. AND no spars to break..

FoilsRFun.jpg

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Powerfoils are also a ton of fun.BUT you can get overpowered very quickly if you fail to realize that the wing shape creates lift that is lifting away from you.. The faster the kite goes through the window the harder it pulls.. AND no spars to break..
FoilsRFun.jpg


I've got one. Not that big though. Mine is a Prism Snapshot 1.9.


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2 hours ago, riffclown said:

You'd be blown away at how much fun a small foil can be...Symphony 2.2.4

Does the 4.5 on that kite indicate 4.5 sq meters?  For comparison the white/blue/yellow spinnaker in my pic is about 35 sq meters.  You really can't hold the sheet by hand if the wind is much over 5 mph.  The sheet goes through a ratcheting turning block onto a #8 winch to control it in any more than that.

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Yes, it's a 4.5 square Meter kite. The Symphony and your Snapshot by comparison are what is known as Sport Size which indicates a rough span of the kite and not necessarily in meters or meters square.. 

A good example of this is in this attached image.. The Smaller kite on top is a Sport Size 2.2 while the bottom kite is a 2 Square Meter Power Foil by the same manufacturer..

The Second Image shows the same 2sq Meter kite on top of a 4 sq Meter kite of same line.. 4m Square kite is very close in size to the Flexifoil Bullet in my other post..

Third Picture is an 8 square Meter kite used as a buggy engine at the Wright Memorial..

FWIW, even the smallest of these kites (the Symphony) can be used as a buggy engine.. In the right conditions any of these kites will turn you into Superman... for half a sec.. followed by a firm taste of reality..

Image2-2.2.jpg

CrossFire 2&4.jpg

8MToxic.PNG

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Yes, it's a 4.5 square Meter kite. The Symphony and your Snapshot by comparison are what is known as Sport Size which indicates a rough span of the kite and not necessarily in meters or meters square.. 
A good example of this is in this attached image.. The Smaller kite on top is a Sport Size 2.2 while the bottom kite is a 2 Square Meter Power Foil by the same manufacturer..
The Second Image shows the same 2sq Meter kite on top of a 4 sq Meter kite of same line.. 4m Square kite is very close in size to the Flexifoil Bullet in my other post..
Third Picture is an 8 square Meter kite used as a buggy engine at the Wright Memorial..
FWIW, even the smallest of these kites (the Symphony) can be used as a buggy engine.. In the right conditions any of these kites will turn you into Superman... for half a sec.. followed by a firm taste of reality..
Image2-2.2.jpg
CrossFire 2&4.jpg
8MToxic.PNG


Sounds like you'd have to be super careful with those big ones. I know how hard my snapshot pulls when the wind picks up. Anything much bigger Than that could really take you for a ride.


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@kevmort

Beautiful foil. I Like the HQ Beamers a LOT.. Great kites with a lot of stability.. IMO, The Beamer is a great kite for static flying because the flying window is larger for them and they are by design more forgiving. They are also among the ideal kites to learn traction kiting on. The Crossfires can accelerate well beyond their flying window and will just collapse. It's not a defect but a function of the design. Crossfires are more dependent on what we call apparent wind and like to stay moving forward no matter what. But that also allows them to power up quickly and take advantage of the upwind better from the Buggy perspective..  The reason I went with Crossfires was the higher aspect ratio which in my opinion improves upwind performance in a buggy AND the Crossfires have the Angle of Attack Adjustments (AAA) built into the bridle.. The Crossfires really begin to shine when the NON-Kite end of the lines is in motion.. I had a 5M HQ Toxic until recently.. I ended up selling it because I preferred the Crossfire 4M and Flexifoil 4.5 which were very close in size.

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