Kite Designing and Kite making
Contents
1. http kitesurfingschool org kite htm Like an airplane wing a kite can fly due to various forces acting on it The main differences are that an airplane has thrust while a kite has line tension and an airplane is balanced by its weight around its C enter of Gravity CoG while a kite is balanced by its effective tow points which can be adjusted automatically by the kite or manually by the kiter and its weight at CoG Let take a quick look at all the force and torque players e Wind Generated Forces Lift This is the vertical force upward perpendicular to the wind that provide lift to the kite The Lift of the kite is proportional to the Lift Coefficient Cl of the airfoil which varies dependent on the angle of attack AoA of the kite From 0 to around 20 degrees most dominant AoA range for kiting Cl increases as AoA increases After the peak in around 15 to 20 degrees Cl will decrease More info about Lift can be found at http www grc nasa gov WWW Wright airplane lifteg html Drag or profile Drag is the horizontal force in the same direction as the wind that drags the kite rearward Similar to Lift the Drag force is proportional to the Drag Coefficient Cd which varies dependent on the AoA Cd normally increases as AoA increases More info about drag can be found at http www grc nasa gov WWW Wright airplane drageq html Lift Drag L D ratio The L D ratio shows how Lift changes as compare to Drag The faster Lift increases2. 2 26m Too bad mine is 2 195m Windsurfing is dying for this reason And us when A fact the Wipika riders Franz Olry and Christopher Tasti which actually win some events don t want to use too high AR kites because they are so fast and unstable that they can t make the kind of tricks they do with more stable kites They don t want a 20 kite quiver They want simplicity Same for Lou Wainman Mauricio Abreu and some other ones If you see them using high AR kites it s because competition pushes in this way not because they prefer except in light winds To resume if we go too quickly we ll burn our wings All the people involved in kiteboarding should take care with that R amp D AGREEMENT WITH NAISH Any kind of commercial strategical agreement was never made Both companies are completely independent free of mutual contract Both are Legaignoux licensees with same contract terms 4 LINE KITES Wipika supplies the Classic kites since July 1997 with an additional webbing so that all the Classic can be 22 of 24 6 13 2007 4 00 PM Kite Designing and Kite making 23 of 24 http kitesurfingschool org kite htm settled with 4 lines That means that we believe to the 4 line use since a long while but 99 of the customers didn t want to hear about it last year There are several ways to settle your Classic as a 4 line kite I ll come back on this matter in another message Very soon the Classic kites will be sold with a second w
3. http zeroprestige org Kite Sewing Methodologies Alex Stelios has released complete instruction how to sew and make one of his almost production kite at http www geocities com reystos ikaros_rev2 index html The page include a whole complete instruction set as well as the plan for the Ikaros kite version 2 For some reason the files are not there anymore you may want ask Alex directly Another place to learn the method to sew your own inflatable kite is the Zeroprestige archive at http web archive org web http zeroprestige org The FoilMaker manual at http www foilmaker co uk has a small section on sewing foil 9 of 24 6 13 2007 4 00 PM Kite Designing and Kite making http kitesurfingschool org kite htm Kite Making Discussion Groups The two most popular discussion groups for kite making are e Foildesign group at http groups yahoo com group Foildesign e Inflatodesign group at http groups yahoo com group Inflatodesign Join these two groups ask questions play with the software sew a kite and you will find that kite making is not a mysterious art anymore Pseudo Surfplan User Manual Version 5 02 Surfplan designed and written by David Aberdeen is a very easy to use piece of software but since it currently doesn t have a user manual its rich set of parameters could be too overwhelming to a new kite designer or even to a foil designer Since Surfplan is mostly used to design LEI kites in this Pseu
4. kitesurfingschool org kite htm Tip Chord Ratio The length of the tip chord as a percentage of the center chord less for more stability more for more depower more radical control Most designers would set this parameter from 25 to 50 if you set this number to 0 then you are designing a 2 line LEI Num Cells Panels Ribs in version 4 4 and older Number of the kite panels Less for ease of sewing more for smoother canopy most designers would set this parameter from 14 to 22 for LEI and 22 to 32 for foils or Arcs depending on the kite size Rib Spacing How and where to place the ribs where the two panels are sewn together Equal Spacing Place the ribs at equal distance along the span of the kite this is the default option Proportional to Chord longer chord sections have ribs further apart Constant Area Place ribs such that each kite panel has the same area Manually Spacing Manually place the rib Select this option and then click Edit Spacing to place the ribs manually Statistics This table shows all the current statistical information of the kite Flat Area Flat Wingspan Flat Aspect Ratio Projected Area Projected Wingspan Project Aspect Ratio Adjusted Area Flat Area 1 36 This number was invented by Bruno and used by many LEI kite manufacturers as kite size in the past mainly to compare a flat size LEI with an average flat size foil a 1 36 m2 flat size LEI is equal a 1 m2 average flat size foil
5. T lower sides Centre side Tip side I Rolled TE seam wingtip pE a i Top fi 0 Winatips 110 Bottom fi 0 Top 10 LE f10 Bottom 10 TE 10 Intersegment 10 Intersegment fi 0 r Bladders Bladders Ends Reset all to fio All seam allowances measured in mm OK Cancel C aw These are the seam allowances for sewing purposes and normally default at 10mm for all the seams It s best to use the default values in the beginning and change them after you have made 1 or 2 kite s to suit your preferences 15 Sled Lines Surfplan allows 4 line connection points 6 if you count the default connection points at 0 and 100 of Wingtip chord on each Wingtip that can be used for either front lines or back lines Sled Line Attachment Points xi In flight Aod Analysis z Vertical At window fee Front 0 power down 1 219 E 781 es 664 COP mid power E jE 41 182 Rear 100 power up mss fi 6518 64569 5 0 552 44 448 Line z aashman 110 0 085 5 085 points 90 10 265 15 265 35 10 892 15 892 7 Mark Sled line attachment points OK Cancel Line Attachment Points Specify the connection points in percentage of chord and click Apply to view the updated In flight AoA Analysis of these 4 connection points plus the default at 0 and 100 of the Wingtip Mark Sled Line Attachment Points Select to have Surfplan marked the line attachment points on the kite 19 of 24 6 13 2007 4 00 PM Kite Desi
6. the kite will rotate and change the effective tow point to match that of the CoPg the kite line will point straight to the CoPg For a full control sled the kite can readjust the tow point automatically or the kiter can do it manually While the kite is flying the CoP is changing and the kite balances its tow point correspondingly to keep longitudinal balance Balancing the tow point will change the kite AoA to the wind more drastically 3 of 24 6 13 2007 4 00 PM Kite Designing and Kite making 4 of 24 http kitesurfingschool org kite htm Summary with sled depending on the shape of the kite For example for a typical AR 5 sled with a kite angle of 50 degrees read the Sphere theory for kite angle decrease the tow point 1 of chord is equal to increase the AoA 0 5 degree and vice and versa So for a sled using a traditional airfoil LEI during the flight path the wind direction changes and the AoA increases the CoP will decrease and the the kite will rotate itself to increase the AoA further In this case the kite amplifies the AoA increase so the kite designer has to make sure that at all places along its path the kite will not luff nor stall due to this additional automatic adjustment from the kite This phenomenon from sled kite using traditional airfoil for LEI only as Arc uses mostly reflex airfoil due to concern about wingtip or shoulder collapsing makes it an excellent performer as it accelerates the
7. 5 5 5 Inflatable Arc 3 4 5 6 7 Inflatable and Arc have spherical shape a natural stable form therefore their ARs are normally higher than foil s Airfoil Profile Airfoil has lift but also drag A profile with the highest lift when stationary will give the strongest pull when stationary at the wind window AoA around 5 degrees A profile with highest lift drag ratio will accelerate faster and will generate strongest pull when flying across the power zone A high lift airfoil is sometime labelled a tractor airfoil as it will pull like a tractor at the wind window A high lift drag airfoil is labelled a speed airfoil as it flies very fast across the power zone and generate tremendous amount of pull while doing so A speed airfoil may generate a lot of pull at the wind window but may not be necessary as much as a tractor airfoil The following table show the recommended lift and lift drag ratio ranges Very Low Low Moderate High Very High Lift Coefficient 5 7 1 1 14 T at AoA 5 0 5 0 0 9 Tractor Lift Drag 40 50 70 90 110 Speed Please note that these Lift Drag ratios are the calculated ratio and not included Induced Drag In reality the real world L D ratios are reduced by a factor of 6 or 7 It s best to use an airfoil design program such as DesignFoil at http www dreesecode com if you want to buy the software after using the demo version you can get an excel
8. Also if you are interested in flat LEI kite design read Bruno s Flat LEI patent application at http www freepatentsonline com 20050230556 pdf and the Flat LEI section Airfoil Database Most kite design or foil design software come with some airfoil database however should you want more there are other airfoil databases and one of the most extensive airfoil databases is UIUC Airfoil Coordinates Database Kite Design Software The most popular kite design software for inflatable kite is currently SurfPlan Surf stands for Surface SurfPlan is currently available for download at hittp www surfplan com au SurfPlan currently does not have any official user manual however Kitesurfingschool org has a Pseudo Surfplan User Manual for LEI kite designers at the end of this page 6 13 2007 4 00 PM Kite Designing and Kite making http kitesurfingschool org kite htm Foil designers may want to use FoilMaker which was around before Surfplan and is very popular among the foil enthusiasts FoilMaker can be downloaded at hitp www foilmaker co uk FoilMaker has its complete user manual and the web site also offer some kite design samples Also Stelios Alexandrakis has released his Sledmaker software to the Open Source Community at htip www geocities com reystos sledmaker Use Sledmaker if you want to add features that are not available on Surfplan nor Foilmaker IKDesign is a newer generation kite design software which is rather int
9. Lift during the growth phase AoA from 0 to around 20 and decelerates the Lift loss during the decline phase AoA from 20 and above For AoA from minus 5 to 20 AoA increases during flight path gt CoP moves frontward gt Tow point follows CoP frontward gt AoA further increases gt Even more Lift For AoA from 20 and above AoA increases during flight path gt CoP moves rearward gt Tow point follows CoP rearward gt AoA decreases gt Hang on to the Lift as long as possible This effect is called Sled Boosting effect and is the reason why many kiters feel that they can jump easier and higher with LEI and LEI won the battle over foil in the early days of kitesurfing For sled using reflex airfoil such as Arc or LEI using reflex airfoil the Sled Boosting effect is reverse which means that it would protect the kite from exposing itself to very large or very small AoA This mean that for Arc the kite will try to retain within a range AoA with excellent L D ratio So this type of kite will be fast and leverage power from speed instead of lift like the case of LEI Furthermore with a 4 line sled the kiter can adjust the effective tow point adjusting the length of the front line and back line when the AoA become too little or too much This is what depower really mean for a 4 line sled At any CoP position a kiter can adjust the front line and back line such that the kite will fly a certain degrees of AoA smaller or larg
10. can be found at http naca larc nasa gov reports 1921 naca report 93 naca report 93 pdf Both the AC Moment and the CoP mathematical models are useful and can be used in different situations in the wing and kite design process For some reasons airplane designers are more comfortable with the AC Moment model this is one of the main reasons why airplanes have tail wing to counter balance the Moment of the main wing and kite designers are more comfortable with the CoP model it is easier to deal with 1 force than with a force and a moment In any event from these 2 models one can approximately determine the position of the CoP mathematically as CoP position AC Cm Cl The exact equation is CoP position AC Cm Cl Cos AoA Cd sin AoA So at any AoA once Cl Cd and Cm are known normally measured in the wind tunnel at quarter chord point we can determine the position of CoP at 0 25 Cm Cl of chord from the leading edge Please note the minus sign if Cm is negative the CoP is on the rear side of the quarter chord point traditional airfoils normally used in LEI and if Cm is positive the CoP is on the front side of the quarter chord point reflex airfoil normally used in Arc Why is CoP so important to a kite designer CoP is important to the kite designer because it is the location of the kite that the effective tow point has to be at or the bridle system has to support during the flight of the kite Since CoP of the kite is ch
11. compare to Drag or the slower Lift decreases compare to Drag the higher the L D ratio From 0 to around 20 degrees the most dominant AoA range for kiting the L D ratio is inverse proportional to AoA low AoA means high L D and high AoA means low L D Induced Drag Induced Drag is the drag occurred when a physical wing or kite is flying The total Drag of the kite is sum of the profile Drag and the induced Drag Induced Drag is proportional to square of Cl Lift Coefficient inverse proportional to the Aspect Ratio AR of the kite and also inverse proportional to the shape of the kite Induced Drag is minimum for an elliptical planfo rm Moment or Torque this is the rotational force that either flips the kite over its nose for traditional airfoil negative moment or over its tail for reflex airfoil positive moment The point along the chord where Moment force is constant for all AoAs is called the Aerodynamic Center History and experiments have shown that for most subsonic airfoils the quarter chord point at 25 of chord from the leading edge has a fairly constant Moment for AoAs from 5 to 20 degrees the range of AoA most important for airplanes and kites and most if not ALL modern data are measured using the quarter chord point as the AC Moment is proportional to Moment Coefficient Cm and the chord of the airfoil More info about AC and Moment can be found at http www grc nasa gov WWW Wright airplane ac html and http ww
12. effect is one of the main reason why a LEI kite jumps higher and easier to jump 4 The Lift Weight and Drag of the kite determine the wind window and the AoA of the kite at the wind window Important Kite Design Parameters The most easy to manipulate and highly visible kite parameters are Aspect Ratio AR Airfoil Profile and built in Angle of Attack AoA of the kite Aspect Ratio 6 13 2007 4 00 PM Kite Designing and Kite making 5 of 24 http kitesurfingschool org kite htm e Aspect Ratio is approximately Span Chord of the kite or more exactly Span Span Area Since AR determines the shape of the kite it is the most visible kite design parameter that the user will see Higher AR kites have less induced drag upwash and tip vortex effects than Lower AR kites of the same characteristics Induced drag is inverse proportional to AR So when stationary at the wind window a low AR kite can generate the same amount of pull as a higher AR kite of the same characteristics but as soon as we need to move the kite for more power for jumping or underpowered situation a higher AR kite can accelerate faster therefore get more power sooner than a low AR kite As a rule of thumb a higher AR kite has a larger Power Window the difference between min power and max power and a lower AR kite has a smaller Power Window Following are the recommended AR ranges Kite Type Very Low AR Low AR Moderate AR High AR Very High AR Foil 2 5 3 4
13. group of people who are gifted with tremendous amount of aerodynamic knowledge skilful in drafting sewing and other handy works Not anymore With the help of modern kite design fundamentals kite design software database of airfoils sample kite designs almost all kiters can make their own kite Let s take a look at all those elements one by one and see where we are with the art of kite making Kite Design Fundamentals Flat LEI Airfoil Database Kite Design Software Kite Design Samples Kitesurfingschool org Kite Design Sample Database Kite Sewing Methodologies Kite Making Discussion Groups Pseudo Surfplan User Manual LEI Sphere Theory Bruno s Post on Kitesurf Group Peter Lynn s Myths on Kitesurf Group OMNOOAWDY i ks gt Kite Design Fundamentals Kites especially sled kites are very complex aerodynamic devices as complex as if not more than airplane wings If you are not familiar with airfoil profile wing and the associated terminology read http www dreesecode com other aflprimer pdf or some other airfoil primer introduction before continuing Now let s take a quick look specifically at those that applies for kites Forces and Torques on a Kite Read this now if you are ready otherwise just read the summary or you can skip the whole thing now and read it later 6 13 2007 4 00 PM Kite Designing and Kite making 2 of 24 Links Feedback Contact Us Latest Modifications
14. have released a very interesting concept about designing LE kites using the sphere theory You can read more about the theory at http www geocities com reystos wipika timostelios htm it is also beneficial to read Bruno s patent and Bruno s Post on the Kitesurf Group Also check the Sphere Theory folder in the Files section of the Inflatodesign group http groups yahoo com group Inflatodesign files for more information One of the stumbling blocks for a new kite designer is the If change this parameter what else should change question The advantage of Stelios and Timo s theory is that once you understand and use it all of the following Surplan s kite design parameters are inter related and can be easily tuned Aspect Ratio AR Wingtip Center Chord Ratio Profile Alignment Point PAP Center AoA at vertical Wingtip AoA at vertical Center Profile Thickness in of chord Wingtip Profile Thickness in of chord LE tube size in of chord etc You normally select the AR the Wingtip Center Chord Ratio and the PAP around 42 as per Bruno s patent requirement for a 2 line LEI or for a 4 line LEI in mid power front line and back line lengths are equal of the kite and then calculate the rest using the Sphere Theory Click here to use the Sphere Theory spread sheet which is based on some formula sheets and spread sheet that Stelios has posted in the Files section of the InflatoDesign group Click here for the Surfplan
15. kite with aspect ratio 6 and with 100 double skin photos on Wipika web site and a short video soon With it we waterskied with 6 to 12 knots of wind and during the 1886 International Brest Speed Week we were clocked at 14 5 knots average speed during a 500m run while the best world class windsurfers reached 10 knots This is registered We also made kites with 20 30 40 60 80 100 double skin what was already described in the 1984 patent and kites made of clear mylar with scrim Probably you will see this kind of improvement in the next months or years who invented inflated struts without inner tube a competitor No in the past we used 2 different construction methods for inflated struts airtight fabric and mylar fabric with inner tube These ways are described in the original patent who invented 4 line straight bar with both front lines meeting at a main line going to the harness and with the bar sliding along the main line a competitor No we own a patent on this device since 1995 first used this device for buggying and won some races thanks to it Seasmik uses without any license the exact device we described so we ll have to sue them who invented 4 line inflated kite A competitor No the above patent also describes how to settle inflated kites with 4 lines by cutting the edges for example there are other ways always used cut tip kites with the 4 line straight bar explained all thes
16. sle file for a 4 line LEI kite designed based on the Sphere Theory A few notes to the Sphere Theory 20 of 24 6 13 2007 4 00 PM Kite Designing and Kite making http kitesurfingschool org kite htm e Bruno actually specified 0 degree built in AoA in his diagram The chord line is passing thr ough the base of the leading edge tube and the base of the trailing edge The AoA of the original Sphere the ory thus can be used to determine the diameter of the tube In Surfplan the chord line is passing through the center of the leading edge tube and the base of the trailing edge The Surfplan AoA is therefore 1 2 of the original Sphere Theory AoA e All the parameters obtained from the Sphere Theory may not be the most optimum parameters for modern LEI kites however they are reasonable and should work Please note that the Sphere Theory was based on a 2 line LEI and the PAP at 42 Bruno may have picked this number 42 from the Hitchhiker Guide to the Galaxy as traditional airfoils CoP range is from 30 to 55 and any number central to that range should work Should Bruno select the CoP range of 30 to 46 then the PAP should be 38 in his patent even though 42 should also work This original design was necessary for a designer in the early pre CAD days to design a kite with a generic airfoil which can be balanced and steered using only 2 lines attached at the wingtips 2 lines and no bridle this is the minimalist s dream With a modern k
17. the AoA in percentage of the chord A free body normally rotate around its Center of Gravity CoG so for inflatable this value should be around 40 In Flight AoA Analysis This table shows the analysis of the AoA of the kite in flight this table only shows the front line connection points at 0 and back line connection points at 100 the chord of wingtips For other connection points check the Sled Lines menu Vertical At 90 degrees overhead Powered Down The AoA of the profile when the kite is fully depowered no tension on back lines m CoP Mid power The AoA of the profile when the kite in mid power front lines and 6 13 2007 4 00 PM Kite Designing and Kite making http kitesurfingschool org kite htm back lines length are equal This value is calculated by Surfplan and normally the result is close to the built in AoA Center value specified in AoA Settings if the Profile Alignment Points are set close to the CoP of the Adjust AoA Analysis Parameters menu default at 33 Powered Up The AoA of the profile when the kite is fully powered up no tension on front lines Most kite designer would make sure that this number is positive and between 5 to 15 larger number for more empower and possibility of reverse relaunch if it is larger than the stall angle of the airfoil around 20 or higher At Window At the Wind Window overhead normally at 85 degrees overhead Powered Down The AoA of the profile when the kite i
18. wings ie three dimensional airfoils are more powerful than cambered single skin wings Wrong Cambered single skin wings will generally have higher lift coefficients than fully shaped 3 dimensional wings because they can work at higher angles of attack without stalling 3 D forms will be more luff resistant and can have higher L D but they won t be more powerful Tanstafl There ain t no such thing as a free lunch The fundamental design conflict is between one and two above Traction kites require high angle of attack to have desirable power for size characteristics but low angle of attack for good upwind performance Some kitesurfing tips Early this year we added an extra valve near the wingtips on Arcs to speed their inflation and to make them more resistant to tip collapse in the case that inflation leaks develop We aren t sure that this was necessary but added them just in case Being near the tips the disadvantage of these extra valves is that th ey can ingest water during relaunching If this is a problem for you just seal them off internally with double sided tape they can then easily be reopened if ever necessary Thank you to Nick Grant for this If you re going to break things it is not a good idea to do so when against wind and tide and far from land In Tahiti last week Mike Holland broke a line in such circumstances and was unable to re rig and relaunch so spent one day of his South Pacific holiday swimming in Thank you Mike fo
19. 3 351 sqm Num cells panels fi 6 Projected Span 2 941 m m Rib spacing Projected AR 2 582 Adjusted Area Flat 1 36 3 955 sqm Equal spacing z Leading edge 5 591 m Trailing edge 5 526 m m Kite Shape Elliptical z Percent square fo Front curvature fo Rear curvature fo I Scalloped TE Amount fi J Curved LE for single skin hybrids only I Planar LE I Manual offsets EditLE _ Edit TE Aod Settings Centre Tip In flight AoA Analysis Effective Profile Alignment point f33 f33 33 Aad 3 3 degrees Vertical At Window towpoint Powered Down 219 jm 23664 CoP mid power E je DEA Powered Up E EE fea5e3 Aaa rotation point chord 2922 Adjust Aad Analysis Parameters DK Cancel L aw Flat Wingspan The span of the kite in meters Center Chord The center chord of the kite in meters Calc size Click on this button to calculate the Wingspan and Center Chord using the total Surface Area and Aspect Ratio and the other already defined parameters Most kite designers would finalize these parameters at the end to have an even kite size or aspect ratio number a Flat Area Total surface area when flat or in other words the size of the kite Aspect Ratio Aspect Ratio of the kite Wingspan Wingspan Area Most kite designers would set this parameter from 4 to 7 6 13 2007 4 00 PM Kite Designing and Kite making 12 of 24 http
20. Kite Designing and Kite making 1 of 24 2 Ice Palms Internet Services Dan Tranh amp Dan Bau Beautiful exotic musical instruments DanTranh com Kitesurfing Search Contents Introduction Home FAQ Myths Equipment Tuning Safety Techniques e Basic How To e Jumping e Landing e Tricks e Light Air e Heavy Air e Speed e Finless e Tips e Log e Rules Snow Land Boat amp Night KiteSnowboarding KiteSkiing KiteTelemarking KiteSnowblading KiteSkating KiteLandBoarding KiteBoating Night Kiting Buy Design Build amp Repair Used Equipment Kite Designing Making Flat LEI Bow Kites Board Building Bar Making Bladder Repair Teaching amp Schools e Teaching e KTM Teaching Methodology e School Lists More Info Search Discussion RSS Feed Blogs Glossary Historic Gallery http kitesurfingschool org kite htm Kites Buggies Gear HQ Flexifoil Peter Lynn Mystic Life is better when it blows www coastalwindsports com Kiteworld The Online Kite store Kites Kitebuggys Kitesurfing www kiteworld co uk Windsurfing holidays The beginners paradise Lake Garda Stickl Sportcamp amp Hotel since 1976 www stickl com become a kiteboarder learn kiteboarding in paradise with our proffesional team www cuttlebone net Kite Designing Kite Making Last Update 05 07 2007 08 10 03 In the early days kite designing and making was an art exclusive to a small
21. Leading Edge Length Trailing Edge Length Kite Shape Elliptical Use ellipse as the base shape of the kite this is the default option and most designers would select this option Also an elliptical shape generate minimum induced drag Percent Square 0 for no effect default 100 for fully square or rectangle shape Front Curvature 0 for constant curving from center to tip default 100 for keeping the center of the LE straight and curve more near the tip Rear Curvature similar to Front Curvature but for the Trailing Edge Rectangular The kite has a rectangle shape Triangular Use triangle as the base shape of the kite Percent Square 0 for no effect 100 for fully square or rectangle shape Scalloped TE Select if you want the trailing edge scalloped between 2 inflatable struts Amount The amount to scallop in percentage of chord The default is 1 This is used mainly to reduce the flapping of the trailing edge Curved LE Not used for LEI kite this is mainly used for single skin kite to smoothly curve the LE panels for the fibreglass rod Planar LE Make the Leading Edge of the kite stay in a 2 dimensional plane Manual Offsets Select this to manually change the shape of the Leading and Trailing Edge of the kite Edit LE Edit the shape of the LE Edit TE Edit the shape of the TE AOA Settings For some very good discussion of the LEI s AoA and Profile Alignment Point settings read LE Sphere Theory
22. Profile Alignment Point To change the forward rearward sweep of the kite Center The amount to move the center of the kite forward positive number or rearward negative number in percentage of the center chord most LEI kite designers would set this from 20 to 40 The default value is 33 For a 2 line LEI Bruno has recommended that this alignment point should be around 42 with 0 degree built in center AoA please note that 0 degree AoA according to Bruno is a couple degrees AoA according to Surfplan Note that for Arc kites designers normally set this value closer to the leading edge than Inflatable Arc normally uses reflex airfoil such that the CoP is near the leading edge of the profile Tip The amount to move the tip of the kite forward or rearward in percentage of the wingtip chord most kite designers would set this similar to the Center Profile Alignment Point The default value is the same as Center Profile Alignment Point at 33 For simplicity this value should be 0 AOA The built in Angle of Attack of the profiles Center The built in AoA of the center of the kite most kite designers would set this from 0 to 5 degrees The default value is 3 degrees Tip The AoA of the tip of the kite most kite designers would set this from 0 to 5 degrees and equal or larger than the Center AoA The default value is 3 degrees AOA Rotation Point Chord The center point where the profile will rotate around when it changes
23. Wind Kite Type Ming 6 15 Knots 12 27 Knots 27 Knots oe Size 46 m2 10 m2 amp Larger 8 16 m2 5 10 m2 8 m2 5 m2 amp Smaller Moderate AR Low AR Very Low AR School Stable High Lift Low Lift Very Low Lift Low Lift Slow High Lift Drag Moderate Low Lift Drag Very Low Lift Drag Moderate AoA Low AoA Moderate Low AoA Moderate AR Moderate Low AR Low AR Bye Wee Very High Lift High Lift Moderate Lift Gusty Wind High Lift Drag Moderate Lift Drag Low Lift Drag High AoA High AR High Lift Very High Lift Drag High AoA All Around High Very High AoA Moderate AR Moderate Lift High Moderate Lift Drag Low AoA Moderate High AoA Moderate Low AR Low Lift Moderate Low Lift Drag Moderate AoA Very High AR Speed High High Lift Jump Freestyle Very High Lift Drag Moderate Low AoA High AR Moderate Lift High Lift Drag Low Very Low AoA Other Kite Design Fundamentals Moderate AR Low Lift Moderate Low Lift Drag Low AoA e Center profile should be selected for optimum lift and optimum lift drag ratio optimum as according to the type of kite requirements specified in the tables above e Wingtip profile should be selected for maximum luff resistance e g reflex profile e For sled kites Inflatable or Arc in spherical form A sled kite has similar projected surface of around 63 2 pi or 2 3 14159 of the flat surface regardless any other parame
24. all Flexifoil kite probably one of the pre cursors to Arc Flat LEI A Flat LEI has similar structure with a classic LEI except for the following differences e A flatter canopy design however most still have a deep canopy curve compared to regular foil to take advantage of the Sled Boosting effect e A bridle system consisting of a simple but somewhat elaborated bridle system for the front lines and a very simple bridle system for the back lines The front bridle system has multiple connection points to the leading edge to support the leading therefore Flat LEls are also referred to as Support Leading Edge SLE kites The canopy is more or less equivalent to the center part of the classic LEI canopy around 3 4 of the classic LEI canopy and the bridle system is equivalent to the sides of the classic LEI canopy about 1 4 or 1 8 of the canopy on each side 7 of 24 6 13 2007 4 00 PM Kite Designing and Kite making 8 of 24 http kitesurfingschool org kite htm One of the more popular commercial Flat LEIs Besides for the differences above a Flat LEI design should be somewhat similar to a classic LE I in theory It is then just a matter of properly design the canopy and the towing points via the new bridle systems Unfortunately current version of Surfplan does not provide full calculation and analysis of the tow points of the bridle for Flat LEI So in the mean time you have to design a flat LEI with some manual processes
25. anging during flight the effective tow point of 6 13 2007 4 00 PM Kite Designing and Kite making http kitesurfingschool org kite htm the kite has to change accordingly either support statically via bridle line tensions change automatically via a spherical shape or change manually via the back and front lines of a spherical shape e Gravity Force The kite weight is centered at its Center of Gravity The Lift of the kite must be larger than the weight of the kite for it to fly A kite is an unbalanced device and won t be able to fly by itself unless 1 It has a thrusters system that pushes it forward to counter balance the Drag force and some mechanism to counter balance the Moment e g tail plane For airplane without tail plane it needs to use reflex profile and place its CoG in front of the main wing This is the simple model for an air plane 2 Has a tether line placed at an appropriate location to counter react the Drag force and the Moment This is the model for a kite e Line Tension The line tension is the main force component of the kite that act similar to the thrust force of an airplane While the thrust force is an active force Line tension is a static force The effe ctive tow point is a location along the chord line that the line tension acts on A tow point can be a single fixed tow point a bridled tow point a dynamic sled tow point or a full control sled tow point e Single fixed tow point the tet
26. atio Wrong The strongest determinant of L D is angle of attack Low angles of attack yield high L D in an inverse relationship profile and aspect ratio have comparatively little effect Myth Two That the Lift Coefficient power for size of a kite is primarily determined by it s profile and aspect ratio Wrong Angle of attack is again by far the strongest determinant of pull for area and by close to a direct linear relationship in the range that matters for kites Myth Three That high aspect ratio equates to high performance Correct in theory but misleading for kites in practice Aspect ratio defined as span squared divided by area is a strong determinant of induced drag the dominant form of drag at low speeds for efficient airfoils but kites are not efficient airfoils by any definition so aspect ratio determined induced drag is not the major drag component for kites It would be possible to make a square wing A R 1 0 that is more efficient than the highest aspect ratio high performance kite currently available but making it useable as a kite would be another matter Myth Four That Thin sections are better than fat sections Wrong Unless your kite is to fly at something approaching the speed of sound anyway Sections as fat as 16 maximum thickness as a proportion of chord lose nothing by L D or lift coeff to thinner sections up to 300km nhr or so and are less prone to stalling and luffing Myth Five That double skin
27. center AoA has a smaller wind window but generate more pull at wind window and hard to luff a Tractor kite may have higher built in AoA around 3 to 5 degrees for more pull at wind window An all around kite may have a built in AoA of 2 to 3 degrees Due to the upwash and the wing vortex phenomena the built in wingtip AoA of a kite can be 1 or 2 degrees higher than the center AoA The upwash effect reduces the AoA of the wingtip a bit so add 1 or 2 degrees to the wingtip AoA to counter balance that effect For inflatable and Arc due to their geometry the wingtip AoA varies much different than the center AoA and therefore the built in wingtip AoA can be designed independent from the center AoA and the designer should add 1 or 2 degrees to the desired built in AoA to counter balance the up wash and the tip vortex effects Very Low AoA Low AoA Moderate AoA High AoA Range in 0 1 TE 3 degrees The following tables provide the summary of the AR Airfoil AoA parameters Low High AR Small POWER Window Large POWER Window Lift at wind window Weak pull at wind window Strong Pull at Wind Window Lift Drag Ratio Slow Fast Built in AoA Large WIND Window Small AoA at wind window less pull Luff Easily Small WIND Window High AoA at wind window more pull Hard to Luff Slower Faster and their uses in different types of kite z P Light Wind Moderate Wind Strong
28. do Surfp lan User Manual version 4 5 recently updated to version 5 02 we provide the descriptions of all the design parameters for LEI kites in Surfplan we will skip most of the foil related portion such as bridle etc The descriptions of the parameters are placed in the same order as they appear in the EDIT menus of Surfplan General Size and Shape Wingtip Shape Profile ILE Tube Canopy Bridle Skin Tension Ribs 10 D ribs and Mini ribs 11 Advanced 12 Calculation Data 13 Bladders 14 Seam Allowances 15 Sled Lines 16 Colors CHONAARWNS L 1 General 10 of 24 6 13 2007 4 00 PM Kite Designing and Kite making 11 of 24 http kitesurfingschool org kite htm General Parameters Kite name Hung s Second kite Designer Hung Vu Revision 5 02 Comments Story Kite Name Any name you want to give to the kite Designer Your name Revision Revision number of the design new in version 5 02 Comments Story Anything you want to say here 2 Size and Shape This is one of the most complex Surfplan s parameter menus you need to fill in so relax read and play around to understand the parameters properly before designing your own kites Kite Sizing x Statistic Value Flat wingspan 6 3 metes pic i Flat Area 5 378 sqm size Centre chord 11 25 metres Fist wingspan 5500 m Tip Chord ratio 35 Flat Aspect Ratio 5 625 ip Chord ratio 2 Projected Area
29. e designer can have the flexibility of a batten wingtip an appropriate profile wing tip or simply just Dacron material early 4 line LEI such as Naish ARS Elbow joined the LE and the front of the wingtips are joined as an elbow Most modern designers would select this option for convenience Curved LE The LE is curved all the way to the back of the wingtip there is no clear distinction between the LE and the wingtip Curved Under The wingtip is straight however the LE is curved new selection in version 5 02 Scalloped The wing tip is scalloped 13 of 24 6 13 2007 4 00 PM Kite Designing and Kite making http kitesurfingschool org kite htm Angled Wingtips Select this field and enter the angle of the wingtip positive for upward rearward and negative for downward forward 4 Profile Besides Size and Shape menu this is one of the more complex parameter menus in Surfplan One canno design a profile with Surfplan but can import a profile and change some parameters x Centre Wingtips Profile Type F Smooth Profiles Profile N baa Te Single skin rofile Name JO40 AZ No profile s en C Double skin at wingtip Pionie depti R Pap B alas Inflatable Inflatable LE strut Segmented x Import Export Import Export Tube size fg 11 2cm 3 3ScmI Zot centre Seam angle 45 Sail angle 45 degrees Upper limit is 57 77 Morph Profile Auto by Distance by Cho
30. e infringers and already stopped a few ones Something interesting to be known is that have no obligation starting legal action immediately that means that can start even when they will have invested a lot of energy and money in their product This is to explain that it is probably more risky for them to infringe that what they generally think NEW LICENSEES SOON Yes we are open to give other licenses but to companies which are able to bring something to the market not to companies with short term view or which sole way to get market shares is to discount their kites In 2000 2001 a few high image companies will enter the market WHO INVENTED who invented kiteboarding several people did it on their side without knowing that other pe ople previously made something close Ourselves we started in 1984 with windsurf boards because we were surfers and windsurfers but not waterskiers We built several boards for that purpose As our kites were very unstable at that time we mainly used waterskis because the waterstart was easier but the patent talks about windsurfing board type too We also tested any kind of boats and many other things that you can t even imagine and a patent drawing shows a guy on two 40cm water skates photos in the History page of www wipika com We made and sailed them It was fun m sure that we ll soon see advanced pilots trying this kind of skates who invented high AR inflated kite In 1985 we made a 17m
31. e things to Don Montague in 1998 Why didn t we apply these improvements earlier There are 2 main reasons Firstly when you settle a company and you have no money especially in France you have to work 80 hours a week to have it working properly So had no time for R amp D It s why in 1999 looked for people to take care of Wipika and get myself more time in R amp D also moved in early 2000 to Dominican Republic which is really a perfect place for R amp D Secondly the market was not ready for more evolved kites In the early ages we made very efficient kites then we understood that we had to make simple stable and safe In 1998 100 of the users were beginners there are not so many markets like this one In 1999 still 90 were beginners but the 10 other percents were starting to ask for more efficient kites so we prepared the Free Air AR3 3 range and started sales in early 2000 But because of Naish AR5 our new range is already old fashioned if you believe a few ones My main concern is safety and when hear that some beginners directly purchase ARS kites I m scared Firstly they are more difficult to relaunch but above all they are fast That makes them dangerous for beginners in the state of the market almost no schools nor well informed retailers We are starting a competition to efficiency just like windsurfing manufacturers did Remember Hey guy how many cambers do you have Only six and your board what size
32. ebbing like the Free Air to simplify transformation Classic and Free Air will also receive long velcros to fold the tips Many new Wipika items will be available in the next weeks and months including an interesting 4 line bar We ll keep you informed You are welcome to use abstracts of this message for public use as long as it is in good faith Please don t expect that I ll react to the messages which could follow mine I m still too busy to do it Sorry Thank you for your time and Best winds to all of you Bruno Peter Lynn s Myths on Kitesurf Group Peter Lynn s Myths posted on the Kitesurf group by lan Young at http sports groups yahoo com group kitesurf message 1 7055 When Peter released these myths it created many controversial debates and one of the reasons was that it s not clear what Peter meant by angle of attack Note that Peter talked about kite design here so the angle of attack he referred to probably meant the built in AoA and or the dominant AoA from 0 to 20 degrees and not all the AoAs of the kite when it flies From lan Young lt lanYoung iinet net au gt Date Thu Aug 3 2000 7 34 pm Subject Peter Lynn s Six Aerodynamic Myths of Kite Traction Food for thought from Peter Lynn for those of you who don t get his newsletter The Six Aerodynamic Myths of Kite Traction Myth One That the upwind performance that is lift drag ratio of kites is primarily a function of profile and aspect r
33. ension on front lines a Adjust AoA Analysis Parameters click this button to change the parameters used for the In flight AoA Analysis It is best to use some profile design and analysis tool to figure out these values for the center and wingtip profiles and enter them here or just use the default values CoP Center of Pressure of the kite in percentage of chord This should be the CoP of the kite when it is flying at the wind window AoA around 5 degrees see the Wind Window parameter Most designers would leave this number at the default value of 33 which is 33 due to a bug 7 if they don t know the CoP of the kite at wind window Normaly LEI uses traditional airfoils with the CoP at 5 degree AoA around 38 and Arc uses reflex airfoil with the CoP at 5 degree AoA near the leading edge around 5 Wind Window The angle of the kite relative to the ground when it is stabilizing straight overhead most designers would leave this number at the default value of 85 degrees or AoA of 5 degrees If you are designing a speed kite you may want to push the envelop a bit and try 87 or 89 degrees 3 Wingtip Shape To select the shape of the wingtips Wingtip options x Wintps Shape j Straight id 1 Straight Elbow joined Curved LE Scalloped I Angled wingtips ange degrees fi ve rearward ve forward OK Cancel Shape Straight This is the default value The advantage of this option is that th
34. er than the case of a 2 line sled kite The kite will fly properly once it reaches longitudinal balance and will continue to adjust its longitudinal balance automatically or the kiter can help manually during the flight The kite will stop flying when its thrust force is equal the sum of all the drag forces Profile Drag and Induced Drag So the wind window and the AoA of the kite at the wind window is determined by the kite itself the airfoil characteristics The built in effective tow point should be selected accordingly to be as close as the wind window CoP as possible via bridle setting for bridle kite and via Profile Attachment Points for sled kite Akite has Lift and Drag similar to an airplane 2 CoP of akite varies dependent on AoA CoP is closer to AC 25 of chord from leading edge for large AoA and farther from AC for small AoA For traditional foils CoP is normally around 27 AoA around 20 degrees to 55 AoA around 0 of chord from leading edge For reflex airfoil Arc the CoP is normally frontward from 0 to 25 of chord 3 The tow point of the kite should either statically bridled kite or dynamically sled kites support the range of variation of the CoP when the kite is flying across the wind window In the case of sled kite it is automatic By following the CoP automatically a sled kite using a traditional airfoil such as LEI amplifies the acceleration of Lift and sustain the peak This Sled Boosting
35. eresting especially for Bow Flat Inflatable kite design IKDesign is at http perso orange fr ikdesign Kite Design Samples It s better to make your first kite using an existing kite design sample The best place for inflatable kite design samples was at zeroprestige org however the site is no longer in operation Fortunately the archive is still available at http web archive org web http zeroprestige org In the beginning it s wise to play with only a few somewhat harmless parameters and once you feel more comfortable with the software read the Pseudo Surfplan User Manual and play with more complex parameters such as kite shape profile shape rib shape leading edge and trailing edge shape etc For foils there are kite design samples at the FoilMaker site http www foilmaker co uk KitesurfingSchool Org Kite Design Sample Database So go design your kites make them or have them made for you test them send us your designs and photos and comments for the KitesurfingSchool Org Kite Design Sample Database for future readers Theory amp R amp D Kites e LEI 2 line kite designed based on the Sphere Theory e LEI 4 line kite designed based on the Sphere Theory Built amp Tested Kites e Ikaros Version 2 at hitp www geocities com reystos ikaros_rev2 index html For some reason the files are not there anymore you may want ask Alex directly e Zeroprestige and other contributors kites at http web archive org web
36. ft coefficients to compensate for the unequal lift characteristics between the Ce nter and the Wingtip profiles at the appropriate AoA s It is best to use some profile design and anal ysis tool to figure out these values of the center and wingtip profiles and enter them here or just use the default values Center Lift coefficient for the Center profile normally set to 1 Tip Lift coefficient for the Wingtip profile relative to the Center default value is 1 the same as Center lift coefficient Normally the tip profile is flatter and it is not flying as well as the center portion so the lift coefficient for the wing tip should be set to 90 or so Flying Line Length Specify the line length in meters the default is 30m however to save space the modern line length is 25m or even 20m Handle Separation Or bar length the default value is 0 3m probably reflecting the fact that the front lines are connected together while the back lines are normally 5m apart 12 Calculation Data Calculation parameters ceea E i i g 90 degrees directly vertical eee Default is 85 degrees Cmca Note that these settings do not change the kite design in any way They are used to calculate the in flight characteristics of the design specifically the in flight centre Aad Parameters should be set to realistic guess of what the parameters will be not what you would like them to be The CoP should never be adjusted to get the desired AoA but ins
37. gning and Kite making http kitesurfingschool org kite htm 16 Colors Select the colors for the kite Colours x r Colour Schemes tip to centre Upper RWRWRW Lower LE R Ribs fe Unspecified schemes default to upper Bridle fb M LEGEND RRed PPurple Adjust colour G Green p Pink Custom1 z B Blue 0 Orange W White g Grey ee bBlack C Cyan Y Yellow 1 Custom gt 2 Custom gt ae Red Green Blue Upper skin picture s Surfplan kitesurfingschool bmp Browse Lower skin picture l Browse OK Cancel Apply Upper Enter the color code characters shown on the screen for each panel from the Wingtip to Center Lower LE Specify the color code for the LE or Lower skin for double skin foil or Arc Ribs Enter the color code characters for the inflatable struts Bridle Specify the color code for the bridle lines Lines Specify the color code for the flying lines new feature in version 5 02 Adjust Color Use the Red Green and Blue sliders to create the 2 custom color code 1 and 2 besides the pre coded colors Upper Skin Picture Specify the file containing the bit map image of the picture to use for the canopy Lower Skin Picture Only used for foil and Arc not applicable for LEI Mapping Select how the picture is mapped on to the kite there are 3 options Baseline Profile TE and Square This is a new feature in version 5 02 LEI Sphere Theory Stelios Alexandrakis and Timo Elias
38. han the weight of the kite the left over Lift will create line tension to generate pull and also thrust this thrust force T is equal to L W Tan AoA when the kite is fully balance due to the inclination of the line to move the kite forward only if this thrust is larger than the sum of Profile Drag and Induced Drag 2 Using the AC and Moment model the line tension and the weight of the kite has to balance the Moment of the kite about its AC or quarter chord point Normally when a kite is flying especially a traction kite lift is much higher than weight and the Moment about the AC is higher than the torque created by the weight of the kite The effective tow point should be rearward of the AC 25 of chord for traditional airfoil which has negative Moment and frontward of the AC for reflex airfoil which has positive Moment 3 Using the CoP model the difference of the Lift force at CoP and the kite weight at CoG is a force L1 slightly less than Lift and very close to CoP since Lift is normally much larger than Weight otherwise we won t feel any force on the line Let s call this spot CoPg If CoP is frontward of CoG CoPg is slightly rearward of CoP and if CoP is rearward of CoG CoPg is frontward of CoP The kite is balance longitudinally when the effective tow point is around the CoPg For a bridle system the CoPg should be within the range supported by the bridle system For a dynamic sled tow point system 2 line LEI
39. her line is connected directly to the kite This is almost never used in a traction kite there is however a kite patent on fixed tow point at http v3 espacenet com textdoc DB EPODOC amp IDX WO00158755 amp F 0 amp RPN WO9005663 Bridled tow point the effective tow point is determine by a bridle system consisting of multiple connections to the kite While the built in effective tow point is the most optimum location f or a bridle system to counter react the lift from the kite the bridle system can accommodate some variation around the built in effective tow point during flight by automatically adjusting the tension on various parts of the bridle lines Dynamic sled tow point Using a spherical form a sled intrinsically has a dynamic tow point configuration for the kite more for the central part less for the wingtip where the effective tow point can varies quite a range dynamically while the kite is flying this is the case of an original 2 line LEI as described in Bruno s LEI patent Full control sled tow point Using a spherical form and a system of front lines and back lines a 4 line sled has a dynamic fully controllable configuration where the effective tow point are dynamically readjusted during the fly and also be fully manipulated by the kiter this is the case of a 4 line sled LEI or Arc When a kite is balanced on the sky all the forces and torques acting on it must be equal This means 1 The Lift of the kite has to be larger t
40. ite design software modern airfoil database and 4 line LEI the designer and kiter have much more control therefore the answer of the universe 42 is no longer required So use the sphere theory as a guide to design your parameters Be adventurous with a 4 line LEI the possibilities are limitless Bruno s Post on Kitesurf Group In the message hitp sports groups yahoo com group kitesurf message 17096 posted on the Kitesurf group Bruno mentioned that one can design a new LEI kite by simply changing the AR parameter This message was the catalyst for Stelios to develop the Sphere Theory for designing LEI kites From Bruno Legaignoux lt design wipika com gt Date Thu Aug 3 2000 2 44 am Subject Bruno Legaignoux s message Hi I m Bruno Legaignoux For those which don t know my name we are with my brother Dominique the inventors of the inflated kite in the shape of a gore This message is to try to put the numerous rumours off My brother and were sailors French Junior champions cruising boat skippers sailing instructors surfers windsurfers etc We tried to develop very efficient sails and boats and finally we became interested in kites when seeing Jacob s Ladder a catamaran pulled by Flexifoils although we never flied a dual line kite It was in 1984 After a few researches we understood that no water relaunchable kite existed so it became obvious to us that we had to create one You can see some old photos at www wipi
41. ka com Pages chapitre1 html After one year of work we were sailing with water skis and demonstrating the device during the 1985 Brest International Speed Week We also applied for a patent The project was to find one or several licensees within 2 years but windsurfing was at its acme and no windsurf company was interested We never stopped believing in this sport so we had 10 years of VERY HARD time continuing the project without money looking for new markets for licensees then creating our own company and producing in France in 1993 94 at a too high cost please don t cry Then Windsurfing declined and Kiteboarding time came am proud to see that we were the main actors of kiteboarding birth but for sure we were not alone For example Cory Roeseler with the Kiteski device or Andreas Kuhn with a paraglider and a kind of wakeboard helped too with international media exposure In 1995 96 we went in very serious talks with Neil Pryde Finally they renounced but they accepted to produce small quantities for us and we started selling these kites in July 1997 under Wipika brand mark Then we found another manufacturer in Asia In 1998 Don Montague and Robby Naish came to us asking for a license As it was our original goal we agreed and told them that both of us needed a software to be able to make new designs quickly came to Hawaii and gave all my knowledge to Don Montague and their programmers One year later the program was working We
42. l team Effective www kiteworld co uk www windspirit direct com www cuttlebone net www FaceLiftStylus com Disclaimer The owners webmasters authors and contributors of this site make no representation nor warranty regarding errors missing of and correctness of the information contained in this web site Use the information contained herein at your own risk The owners webmasters authors and contributors are not responsible for any loss or accident to you or to other third parties including loss of business loss of sale equipment or property damage injury or death resulting from you or other third parties using the information contained herein 24 of 24 6 13 2007 4 00 PM
43. lent educational discount by mentioned that you are a reader of Kitesurfingschool org to design analyze and select the airfoil profile to use for the kite for kiting purposes the Reynolds number is around 1 000 000 to 2 000 000 Some kite designers being shy from the complexity of airfoil design and analysis uses the rule of thumb method of changing the profile thickness camber for changing the lift and lift drag characteristics of a profile This method is not accurate but maybe acceptable for kites As a general rule of thumb increase the profile thickness camber to increase lift at wind window and decrease a profile thickness c amber to increase the speed of the kite The following table show the range of profile thickness camber used for most kites Foil and Arc Inflatable Thin Profile Speed 14 or less Thin Profile Speed 8 9 Moderate Profile 15 Moderate Profile 10 Thick Profile 16 Thick Profile 11 Thicker Profile 17 Thicker Profile 12 Thickest Profile Tractor 18 or more Thickest Profile Tractor 13 14 Built in AoA A kite get more lift with a higher Angle of Attacked AoA to the wind more surface projected to the wind and also from 0 to 16 degrees of AoA the Lift Coefficient of an airfoil normally increase to an optimum value Each kite has a neutral built in AoA for the center of the kite and the wing tip when it is at the wind window straight over head with front lines and back lines of e
44. lues are 9 for both Center and Wingtips At Chord The location of the maximum profile depth in percentage of chord Most designers would set this value between 18 and 33 depending on the profile The default values are 25 for both Center and Wingtips Import Click this button to load an existing profile Export Click this button to save your profile for use in another kite designs Tube Size The LE tube size in percentage of chord Surfplan will automatically calculate and display the tube size in cm Most designers would select tube size between 6 and 12 of chord The default values are 9 for both Center and Wingtip tube sizes Seam Angle Specify the seam spot of the LE tube The seam location is marked by a red marker The default value is 45 degrees Sail Angle Specify the spot where the canopy is sewn onto the LE tube marked by a red marker The value has to be between 0 and the Upper Limit display next to the parameter which is dependent on the LE Tube Size The default value is 45 degrees View Rib Select the rib to view its profile The ribs are numbered from 1 at the Wingtip The ribs which have inflatable struts are marked with a after the number Morph Profile Specify how the profile along the wingspan will change from the Center profile to Wingtip profile There is no need to do anything here if the Center profile is identical to the Wingtip even when the No Profile at Wingtip option is selected ma Auto Morph fr
45. nose strut for ease of sewing Round Tail Struts Select for round tails at the strut ends Tail Angle Enter the tail angle of the ends of the struts good for reducing drag and turbulence at the strut ends Round nose Struts Select to have all the struts with round nose plumbing type of connection between the struts and LE This makes the LE and strut connections more rigid and more aerodynamic This field has no effect if each strut s nose shape has been defined in Irib Nose Shape field Upper LE Point degrees Specify the upper location in degrees to connect the struts Center and Wingtip to the LE The default value for Center strut is 80 and for Wingtip strut is 50 Lower LE Point degrees Specify the lower location in degrees to connect the struts Center and Wingtip to the LE The default value for Center strut is 0 and for Wingtip strut is 30 Center Diameter Chord Specify the maximum diameter of the strut in percentage of chord The default value is 7 for both center and wingtip strut Most designers would set this value such that the size of the strut is close within 10 differences to the size of the LE at that location TE Diameter Chord Specify the TE diameter of the strut in percentage of chord The default value is 2 for center strut and 5 for wingtip strut Surfplan will calculate display the size in cm automatically Most designers would try to keep this value larger than 2 5cm or 3cm for practical purposes t
46. o be able to insert the bladder into the strut In version 5 02 you can enter a specific value in mm instead of of chord Number of Segments Specify the number of segments to use in the Center and Wingtip struts default 5 for center and 3 for wingtip Seam Positions Specify the seam positions of the strut segments Automatic Calculate the seam position automatically using the Equal Angle Equal Spacing slider Manual Calculate the seam position semi automatically using the Equal Angle Equal Spacing slider and the Seam Limit location specified in percentage of the length of the strut chord Reflex auto Similar to automatic however use the reflex profile algorithm for reflex profile 10 D ribs and Mini ribs D ribs and Mini ribs are not applicable for LEI 17 of 24 6 13 2007 4 00 PM Kite Designing and Kite making http kitesurfingschool org kite htm ci x ie Ene Cancel C 1 3Cell ee D flares aw Height 70 Arched Dib Drib length Full lenath I Mark upper skin with drib limits I Minitibs Lengthfan z 11 Advanced CIT x Lift coefficients These lift co etficients can be used to add an effect for unequal profiles Centre fl at centre and wingtip This affects A zz the sled canopy calculations and to Tip j a smaller extent the bridle calculations for bridled foils Flying line length 20 metres lt 0 for infinite handle separation o3 metres Lift Coefficients Specify the li
47. ol org kite htm Skin Tension Most LEI designer would leave this field at the default value of None Disable 9 Ribs This is another important and complex Surfplan menu for LEI kites OOOO hh hmm 3 Cente m Winatips Use Ribs 107010701 All Upper LE point degrees feo 50 Lower LE point degrees fo 30 Rib type Centre diameter chord z cm 8 75 g cm 3 063 Segmented inflatable TE diameter chord 2 em 2 5 E cm 2 188 Nr of segments 5 E J Seams undemeath IV Round tail struts Seam positions Tail angle fo Irib nose shape a Method fAutomatic I Round nose struts Equal Equal angles SREE View Rib 9 centre OK Cancel Use Ribs Enter a series of 0 s and 1 s from Wingtip to Center to specify where you want to have inflatable struts 1 s The default is a string of 101010101 or 1 inflatable strut for every 2 ribs Rib Type Select the default value Segmented Inflatable for LEI kites Seams Underneath To specify the non default location for seams default is not selected to have a smoother canopy Irib Nose Shape To specify the nose shape of each individual inflatable strut inflatable rib either round 0 or regular 1 Enter a string of O s and 1 s to individually select the nose type of each strut from Wingtip to Center of the kite Select round nose strut plumbing type of connection betwe en the struts and LE for more rigidity and regular
48. om the Center profile to Wingtip profile automatically most designer would 14 of 24 6 13 2007 4 00 PM Kite Designing and Kite making http kitesurfingschool org kite htm select this default option By Distance Chord Use this slider button to select how the morphing should be dependent on by distance and or by chord The default value is By Chord 100 Keep Center Profile of Span Use this slider to specify how far to retain the Center Profile from the center of the kite The default value is 0 Keep Tip Profile Enter the number of ribs from the wing tip to retain the wingtip profile Morphing Graph A graph in the table shows the result of the morphing function as specified by the above parameters Manual Select this and click on the Change button to change the graph of the morphing function 5 ILE Tube LE Strut This option was in the Profile Screen in versions prior to 5 02 Segmented LE This is the default Armed LE Using the Armed method for making the LE strut Armed Limit The number of panels from the tip not to use the Armed method Canopy Shape xj FEM modelled canopy for sled foils Manual canopy for bridled foils Flat Curved 6 Canopy Detailed canopy for bridled foils Change OK Cancel C aw FEM Modelled Canopy for sled foils Select this default option for LEI If you are using some old sample kite designs make sure you select this option for Surfplan
49. qual length The range of the built in AoA is normally from 0 to 5 degrees Note that the wind window angle is around 85 degrees such that the in flight AoA of the center profile at the wind window is the sum of the built in AoA and 5 degrees or 90 85 Note that changing the built in AoA of the kite may also change the wind window angle such that the two will amplify each other to have a double AoA effect E g changing the built in AoA from 2 to 0 may make the wind window angle change from 85 to 86 therefore the in flight AoA of the kite at wind window is now 4 degrees instead of 7 It is interesting to read Peter Lynn s Myth 1 and 2 in which he stated that the Lift or pull of the kite at wind window is proportional to the AoA of the kite and the L D of a kite is inverse proportional to the AoA of a kite AoA here means AoA within the dominant AoA range of 0 to around 20 degrees which is directly influenced by the built in AoA of the kite 6 13 2007 4 00 PM Kite Designing and Kite making 6 of 24 http kitesurfingschool org kite htm A kite with a lower built in center AoA has a larger wind window but can over fly amp luff easily and does not pull much at wind window a Speed kite should have a lower built in AoA around 0 degrees These type of kites must have instantaneous AoA control for the kiter to prevent luffing and also for the kiter to sheet in to get more power at wind window if needed A kite with higher built in
50. r this tip When you are using our wrist leash velcro d to the bar end so that it doesn t get twisted up in spins lash it on with knitting wool in addition to the velcro so that it doesn t come off prematurely but will still release when required just like wool ties on a yacht spinnaker Thank the sheep for this one 6 13 2007 4 00 PM Kite Designing and Kite making http kitesurfingschool org kite htm New things this month Nothing Which is the first time ever except that there is something but I m just not talking about it until we hear back from our travelling testers It was what Mike was testing in Tahiti when he had a line break and the long swim And a little gossip to round off Andy Reid windsurfer kitesurfer boardmaker and with Justin our kite test rig operator finishes his BEng this year and goes to work at Team New Zealand for the next defence of the America s Cup Our loss their gain congratulations Andy Peter Lynn Ashburton New Zealand July 31 2000 Cheers lan Young Copyright 1998 2007 by KitesurfingSchool Org All Rights Reserved You are visitor number 6016777 Oprahs Home Facelift Kit Kiteworld Online Wind Spirit Store become a kiteboarder The Technique Seen On Oprahs The Online Kite store Kites Free Shipping US CAN Starboard learn kiteboarding in paradise with show Non Surgical Tool Safe amp Kitebuggys Kitesurfing Ezzy Quatro Chinook J P Neil Pryde our proffesiona
51. rd C Manual Kaa 3 p centre profile f View Rib Change of span p fs centre x Keep tip profile fi nr of ribs OK Cancel Apply Profile Type Single Skin for single skin kites Double Skin For foil or Arc Inflatable Select this option for LEI Smooth Profiles Surfplan will smooth out the profile automatically if this option is selected default is not selected No Profile at Wingtip This is the default A flat profile or no profile has a CoP at 25 A traditional cambered profiles used in LEI normally has CoP at 30 to 50 A reflex profile used in Arc has CoP from 0 to 23 Some designers believes that the closer the wing tip CoP to the front line attachment point the lighter the bar pressure Some other designers thinks it s the cente r CoP or the combination of center and wing tip CoPs LE Strut In version 5 02 this option has been moved to the ILE Tube screen Segmented LE This is the default Armed LE Using the Armed method for making the LE strut Armed Limit The number of panels from the tip not to use the Armed method Center and Wingtips Profile tables Profile Name The name of the profiles which have been loaded for the Center and the Wingtips appropriately The default profiles are DA2 for both Center and Wingtips Profile Depth The maximum depth thickness of the profile in percentage of chord most designers would set these values between 8 and 14 The default va
52. s fully depowered no tension on back lines CoP Mid power The AoA of the profile when the kite in mid power front lines and back lines length are equal This value is calculated by Surfplan and the result is close to the sum of the AoA Center value and the difference between 90 degrees and the Wind Window degrees specified in the Adjust AoA Analysis Parameters menu if the Profile Alignment Points are set close to the CoP of the Adjust AoA Analysis Parameters menu default at 33 Powered Up The AoA of the profile when the kite is fully powered up no tension on front lines Most kite designer would make sure that this number is positive and between 5 to 20 larger number for more empower and possibility of reverse relaunch if it is larger than the stall angle of the airfoil around 25 or higher Effective Tow Point This show the effective tow point in percentage of chord when the kite Powered Down No tension on back lines CoP Mid Power Front lines and back lines length are equal For LEI Bruno has recommended that this number should be around 42 actually Bruno s recommendation is for a 2 line LEI as one cannot change the effective tow point in that case Note that coincidently the default values of Surfplan 4 5 will yield a value of 41 182 for this field Note that for Arc this value should be much smaller around 5 to 10 as Arc normally uses reflex airfoil which has the CoP more forward Powered Up No t
53. shared it With it everybody can make a new good kite in 30 seconds just changing one parameter For example change AR 2 5 the default value with 8 and you will appear as a genius designer WHY PATENT PROTECTION Some people hate this way think that when you are a well organized company in a market where products evolve very quickly patent is just a waste of money and energy But if you are a small independent inventor you have no chance against large companies if you don t protect your ideas they won t even give you just credit for that Who on this list is against intellectual property music literature etc Our motivation was kept during the hard years because of the patent INFRINGERS Seen by my side there are only 3 kinds of kites e the ones which are far from ours like ram air kites delta kites etc 21 of 24 6 13 2007 4 00 PM Kite Designing and Kite making http kitesurfingschool org kite htm e the ones which are very close to ours if they got a license contract like Naish they are licensees if not they are infringing copies whether or not there are patented improvements on e there are kites designed with a sole goal to use our concept but escaping the patent by modifying the kite after studying the patent and looking for weak points in it In this case it is more difficult for me to get the justice admitting the infringement but I ll try each time think can win Obviously beat th
54. tead the CoP should be set to the best guess and the Profile Alignment and Ao4 coning can be played with to get the desired settings This is the same as Adjust AoA Analysis Parameters in the Size and Shape menu These parameters are used for the In flight AoA Analysis It is best to use some profile design and analysis too to figure out these values for the center profile and enter them here or just use the default values CoP Center of Pressure of the kite in percentage of chord This should be the CoP of the kite when it is flying at the wind window AoA around 5 degrees see the Wind Window parameter Most designers would leave this number at the default value of 33 which is 33 due to a bug 7 if they don t know the CoP of the kite at wind window Normaly LEI uses traditional airfoils with the CoP at 5 degree AoA around 38 and Arc uses reflex airfoil with the CoP at 5 degree AoA near the leading edge around 5 Wind Window The angle of the kite relative to the ground when it is stabilizing straight overhead most designers would leave this number at the default value of 85 degrees 18 of 24 6 13 2007 4 00 PM Kite Designing and Kite making http kitesurfingschool org kite htm or AoA of 5 degrees 13 Bladders This feature is not available in the demo version available to the public 14 Seam Allowances Seam Allowances f xj Note Vent seams are LE based on LE of upper E and lower skins and
55. ters of the kite AR Tip Center chord ratio etc If the wingtips are wide enough effective tow points of the back lines are larger than 80 of center chord one can reverse relaunch an inflatable or Arc by pulling on the back lines For LEI using traditional airfoil if the wingtip are wide enough and the effective tow point of the front lines is so forward normally less than 15 of chord that it reduces the AoA drastically the kite 6 13 2007 4 00 PM Kite Designing and Kite making http kitesurfingschool org kite htm will not fly on the front lines alone 100 depower More Kite Design Info LEI Sphere Theory e Arc Kite design at http foildesign org Sled_Kites please note that this page only discuss Arc which use mainly reflex airfoils due to problem with shoulder collapsing some of its comments is specific to Arc and not applicable to LEI e Some fundamental foil design at http www aerospaceweb org question airfoils q0035 shtml You can also find some links for very good program for foil design and analysis there Bruno Legaignoux s Inflatable patent at http www inflatablekite com Bruno Legaignoux s 4 Line Inflatable patent at http www inflatablekite com Bruno Legaignoux s Reverse Relaunch Bridle patent at http www inflatablekite com Bruno s Post on Kitesurf Group Peter Lynn s Arc patent Peter Lynn s Guerrilla patent Peter Lynn s Myths on Kitesurf Group Jalbert s ram air kite the original that started it
56. to update the canopy of the old designs Manual Canopy for bridled foils Select this if you design a bridle foil Detailed Canopy for bridled foils Select this if you design a bridle foil more manipulation than the Manual Canopy option Circular Curve Select this to make your kite canopy shaped in a circular curve of a certain Arc Degrees This is a new option in version 5 02 Arc Degrees Select the depth of your circular curve 180 degrees for a half of a circle 7 Bridle Select None sled and ignore the rest for LEI kite 15 of 24 6 13 2007 4 00 PM Kite Designing and Kite making http kitesurfingschool org kite htm 8 Skin Tension Certain kite material will stretch on pressure This menu provide a mean to specify how much skin tension how stretchy certain part of the kite may be exposed to and therefore take the anticipated stretch into account to compensate for the ultimate outcome Skin Tension fom vent of 0 chord Inflatable Strut Tension set the tension stretch anticipation on the LE and rib struts LE Factor Set to 1 for no tension and higher value for more tension and more stretch anticipation Most designers would set this to the default value of 1 2 Rib Factor Most designer would set this between 1 no stretch anticipation the default value and 1 2 same pressure and tension as the LE 16 of 24 6 13 2007 4 00 PM Kite Designing and Kite making http kitesurfingscho
57. w grc nasa gov WWW Wright airplane cp htm There are TWO MATHEMATICAL MODELS used by designers to consider how the Lift Drag forces and the Moment act on the airplane or kite The AC and Moment model In this model the Lift Drag forces and the Moment are considered acting at the AC The Moment if negative will flip the kite over the nose around the AC traditional airfoil and if positive will flip the kite over the tail around the AC reflex airfoil The Center of Pressure CoP model In this model there is only Lift and Drag forces acting at a single point on the chord line called the Center of Pressure CoP Since the CoP is not necessary at the same location as the AC the Lift and Drag forces the sum of Lift and Drag forces component that are perpendicular to the chord line let s call it Fcop will generate a torque around the AC Since the torque around the AC is constant the CoP is close to the AC when the force Fcop is high large AoA and the CoP is far from the AC when the force is small small AoA For traditional airfoil the Moment is negative therefore the CoP moves along the rearward side of AC from 25 of chord to the rear For reflex airfoil the Moment is positive therefore the CoP moves along the frontward side of AC from 25 of chord to front Since the Moment is constant it moves either along the front side or rear side of the AC dependent on the airfoil type and will NEVER cross the AC Some CoP chart
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