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Hi Ted, You are completely right. Kite's and aerodynamics is a very interesting combination. I think in Mat's article and in my PDF-reply there are many relations between science and kite-reality, but unfortunately we can't copy all of the aerodynamics theory on kites. We must realize that there are many differences between kites and airplanes. Among others, think about the less rigid structure (deforming profiles, banana effect, etc.), the bridle- and flying lines (different stability situation, different pivotline, etc.), the velocity (influences on flow around the airfoil, stall, inner pressure in a foilkite, etc.), the arched shaped (foil-) kites (several consequences on all kinds of properties), etc. etc. Although there are many differences I'm convinced that there are a lot of similarities. I think it's impossible to give a complete answer on your questions in a few sentences. I try to do it the short way. Question 1: The stall at the edge of the window problem: It's difficult to say anything in general about this stalling-problem, because the reason for this problem will depend on the properties of the kite (profile shape, AR, AoA, planview, canopy curve, depower or fixed bridle, etc.) and also: is it really a stall where you are talking about? At the edge of the window also luffing is a good possibility. Especially with racekites it can be luffing. Controlling with the brakes can solve it or you can alter your bridlelines. But stalling is also possible. It can be caused by the slow speed of the airflow or a too high AoA. The slow speed can cause, among others, two main problems: 1. (tip-) Collapse because the inner pressure is to low or 2. The lift fails because lift needs enough velocity of the airflow. This will happen more with low or gusty winds (especially in turns) then with high winds. Many solutions are possible: 1. Improve your experience with your kite (especially in low winds and in turns). 2. Try to keep the speed of the airflow as high as possible and 3. Watch the AoA of the kite. If possible make the AoA not to big (careful with your brake-input). Jerry has written a lot of very good articles and replies on this forum. I can recommend you to read especially the long ones (do you have a week or two...:-)). About this 'edge of the window problem' he wrote this interesting reply: http://www.racekites.com/forum/forum_posts.asp?TID=3628&KW=beamer&PN=1. Question 2: The effects of altering the line length and drag on the angle of attack: Normally it's the other way around: the AoA has an influence on the total drag, but with kites the drag (and weight!) of the lines can have an influence on the AoA to. For example: heavy or long brakelines can have the same stalling-effect as a lot of sand in your kite located at the trailing edge. And almost every aspect of the performance of the kite has a relation with the AoA of the kite. So the AoA has a lot of influence on the kite's behavior. In theory: make the line as short and light as possible for your application. You can read a lot more about all the aspects of altering the linelenghts on this forum. Hi Mat, let me finish with a rectification... I wrote that with the theory of aerodynamics it's simply right or wrong. Well, after reading that again, I must admit that it's not always that simple. In science certainties are not always provable and also in aerodynamics not every theory is already a clear certainty, but sometimes it's all there is. With regards to my response it makes no difference, but in general It's wrong to say it's all black and white in aerodynamics. Cheers, Ad

Hi Jerry, The circulation theory (Prandtl, Kutta, Joukowski, Lanchester) and, as a spin-off, the lifting line theory of Prandtl are very important developments in the first two decades of the 20th century. These theories definitely not 'crept' into training programmes. They belong to the fundamentals of aerodynamics. The lifting line theory and equations of Prandtl are used for more than 80 years now and are still used in many areas of aerodynamics (including kitedesign, but maybe unconscious). So we are certainly not talking about the same theory I'm afraid. I agree with you that for those who have an interest in kites and aerodynamics, articles like those from Mat are very welcome. Problem with aerodynamics is that it's an exact science, with strict laws and mathematical equations. It's right or it's wrong. That's why writing about it isn't easy, but it's sure a lot of fun. The best proof of that is Mat's enthusiastic article and my struggle with your language to write these replies... :-) Cheers, Ad

Hi MatJ, thanks for the appreciation. For a better read I have uploaded my reply in a PDF-file here: http://rapidshare.com/files/70530662/Research_Report_Reply_PDF.pdf.html (1. Copy and paste this link 2. Scroll down 3. Select download: click on 'Free' 4. Scroll down 5. Take over the shown code 6. Click on: 'download'). Ad

Hi Grazzer, When I saw my reply after I had submit it, I regret it already. It looks very massive and it's almost unreadable, but I think more than 60% of the text is not mine, but are quotes. I see this report of MatJ as an important 'review'. I think a lot of people will read it now and in the future. They will take this as a good reference for 'how kites fly'. That's all right with me, because most of all the text is very good. But when I read a number of incorrect statements (the vision on the theories of Newton and Bernoulli, wrong equations, etc.), I thought it was better to write a reply. But maybe you're right, Grazzer. Perhaps I better did this by means of a private message. This reply cost me more than 5 minutes as you understand. Besides flying kites and designing and building them for a lot of years, writing about kites and aerodynamics is a passion of mine. This writing has never (and will never!) been used by me to hurt someone. Even thinking about the fact that people can see it the way you described ('potential slanging match') makes me feel sad. Ad

Sorry, the lay-out isn't very clarifying in this comment-section... A little manual for the above reply: All the quotes start with a number from 1 to 24. All my replies start with *** Cheers, Ad

Hi MatJ, I'm afraid that a lot of statements and assertions in this report aren't right. Here is first a summary of assertions (1-14) in your article about the theories of Newton and Bernoulli which aren't correct. 1. Quote MatJ: '...this model is not an accurate version of how it really works. If it was, the maximum lift could be obtained from an almost vertical surface, where the molecules were deflected as sharply downwards as possible. However experiments show us that this is not the case, which brings us on to the second major theory...' 2. Quote MatJ: '...The angle of attack of these kites tends to be fairly small

Review of the month? This is one of the 3 best reviews on Racekites.

The Pepper isn't made of Chikara. It is the new cloth Mirai. This cloth is coated on one side (Chikara is coated on both sides), but with a water repellant treatment. It's heavier than Chikara (+/- 48 g / m^2 instead of +/- 41 g/m^2). Ad

It's easy to find out if the modification is made. Check the points where the bridlelines are attached to the kite. Than compare the A/B - points with the C/D points. The C/D points are the points where the modification was made. HQ add a second knot on the end of the loop into the bridleline. Ad