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Mfezi

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About Mfezi

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    Pretoria, South Africa

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  1. I always loved the Harvard. Our Air Force (SAAF) used them as trainers until 1995. Just before their retirement, they did a 55 aircraft fly-past - something you won't easily forget. Photo credit to John Miller: http://www.theharvard.co.za/the-saaf I have had the pleasure of flying along for aerobatics in the Pilatus PC-7 MkII a few times - the aircraft that replaced the Harvard in the SAAF - great modern aircraft but not quite the classic that the Harvard was.
  2. Gabor, I just want to thank you for these very professional detail presentations - they are actually useful references in themselves! Really looking forward to the kit.
  3. Fantastic attention to detail. I know this kit won't be cheap, but at the slow rate at which I complete models, it looks like it will be very well worth it!
  4. I just want to say - that is a beautiful build. Almost makes me want to go out and pick up one of these kits for myself...
  5. Thanks, Ben. We are actually namesakes (I'm also Ben). Unfortunately, my post wasn't really informative in relation to how a wing works - I'll leave it to the textbooks (or that NASA site mentioned above is a pretty good intro without trying to explain everything in one shot). I just wanted to give a bit of insight into the difference of studying something through the basics from the ground up, vs a quick explanation and how a quick explanation is sometimes not really possible. I've seen both approaches due to my studies and work on the one hand, and also doing private flying, gliding and microlight flying on the other, each of which included study material on "aerodynamics" that I personally felt was not just inadequate, it was usually wrong. As I said, I think Anderson's contribution to the Scientific American article was based on his frustration with the difficulty of explaining a fairly complex idea in sufficient detail in a few paragraphs and sketches while still keeping the physics correct. I'm sure engineers and scientists in other fields have the same frustration, and when they can't quickly explain how it works in two sentences, the interpretation is sometimes that the "scientists don't understand it either". Above someone mentioned that all wings create lift by pushing air down. This is of course not wrong at all - it is exactly what happens. However, there is a bit of a chicken and egg thing going on, because is the air being pushed down because of the lift, or is the lift produced because the air is pushed down? And when you look closely, you will see that the air in front of the wing actually flows upwards relative to the wing and so does the air on the outboard side of the tip vortices. And the word "push" is misleading, because a lot of the air affected by the wing is actually above the wing, and not below it. So, how does air relatively far above the wing end up being accelerated downwards? And since air is usually considered a continuous medium (it is virtually impossible to keep track of individual molecules), which "packet" of air are we talking about? If you are satisfied by the one-liner explanation, it is fine, but personally I feel there needs to be a bit more in the explanation, because there is a lot more that actually happens around that wing. As engineers, our job is to manipulate the physics to do something for us (produce lift) in the most efficient way possible - so the one-liner explanation is of little use for that. For a pilot, it may or may not be enough: Does it explain the shape of the wing, the relation between angle of attack and lift, the relation between drag and lift, and what happens when the wing stalls - all concepts that I think he needs to understand? And this is still just aerodynamics - flight mechanics is just as important and that is an entirely separate discipline again. As I said, I think the title of the Scientific American article is not completely wrong, especially if you add "in a few paragraphs", but the subtitle is completely out of place and it missed the point of what Anderson tried to convey.
  6. Perhaps a more serious post in relation to the original article. John Anderson is a highly respected aerodynamacist - I have several of his textbooks on my shelf. His book "Modern Compressible Flow with a Historical Perspective" is regarded by myself and many of my peers as a classic. The problem here lies more in how Scientific American presented what he said. I studied aerospace engineering and my Ph.D. was in applied aerodynamics, yet I cannot recall once walking into a lecture where the prof said: "Right, today we will discuss how a wing produces lift". It is a workup through basic gas dynamics, more advanced general gas dynamics, potential flow, viscous flow, wing theory, boundary layer theory, compressible flow, transonic aerodynamics, etc. At undergraduate level these topics are covered as modules over two or three courses but at graduate level, each one is explored separately in its own full-blown semester course - sometimes more than one semester course, in fact. In my case my understanding was further filled in by many hours, days, nights, weekends, summer vacations, etc. spent in the wind tunnel. When you discuss a specific application of aerodynamics in class - let's say 2D flow over an airfoil, most students already have such a solid background that the relations between pressure and velocity, shear forces, streamlines, vorticity, etc., are second nature - or at the very least should just require a bit of a review. They just have to apply their knowledge to the specific application in front of them and there is no reason to invent a simplified explanation for the physics. At least, this is how we did it in the United States where I studied, but I suspect the approach is very similar at all universities around the world that teach aeronautical engineering. That approach is in stark contrast to how popular science magazines, books and pilot manuals explain aerodynamics. When I did my PPL, there was literally about two pages about "how a wing produces lift". So, this material naturally needs to be simplified to a point that someone would supposedly understand it after looking at a picture and reading a paragraph. Most resulting explanations then end up being not just simplified, but often wrong and counter to the actual physics at play. Some of those theories are used so often that we eventually gave them names: "Bernoulli theory" (very little relation to the actual work done by the real Bernoulli who is one of the fathers of modern aerodynamics), "skipping stone-" or "bullet theory", "equal transit-time theory", etc. The excellent NASA website posted by SouthWestForrests above explore some of these so-called theories a little and they are also mentioned a bit further down in the Scientific American article. It is these oversimplified and incorrect explanations that John Anderson tried to highlight - but the journalist misinterpreted it to the point where he seems to suggest that even scientists and engineers don't understand how it works. That is not the problem - the problem is that they have a hard time explaining it in a few sentences, something that I also have difficulty doing without immediately going off in tangents about some of the underlying physics. The main title of the article itself, therefore, is perhaps not completely wrong. It should probably have read something like "No one can explain in a few sentences why planes stay in the air". If that is what he meant to convey (and I think that is what John Anderson had in mind) - then he does have a point. The subtitle: "Do recent explanations solve the mysteries of aerodynamic lift?" is completely out of place, however. There is no "mystery of aerodynamic lift" that needed "recent explanations". The journalist should have stopped after the main title.
  7. Wow. Sorry this happened to you, Yufei. The only upside is that it demonstrates how sought after your endorsements are. Nevertheless, this makes choosing between the Kittyhawk and GWH Su-27 a no-brainer for me.
  8. It was the two comments together that appeared that he didn't read the links, which people took time to provide (just as it took me time to find the picture to show him what it was). Habu apparently interpreted it the same way as I did - so it wasn't only me. However, I didn't simply shoot him down in my response - I gave him an explanation of how these drones were used in the same post. It appears that it is the word "silly" that got you and him worked up. Or maybe it was because I told him to read the links? Either way, it seems my post was interpreted both by you and by him in a very, very different way than I thought I wrote it. I'll step back from this discussion. I've already been told my inputs are unwanted and will be ignored - I'll respect his wishes.
  9. Agreed, Peter. The only thing that would probably help is if you can find a build review of the particular boxing of the kit and where the reviewer had actually used the kit decals - but it would require some luck to find exactly that. In the case of my P-47, I did actually research the kit, but all I could find was a bunch of in-box reviews that all stated that the decals looked good, which obviously is of no help in this case.
  10. Really great results on that MiG! Yes, unfortunately it appears hit and miss, and I guess I've just always had the ones that refuse to react to the decal solvents (including Micro Set/Sol). Clearly it is worth doing a test if the sheet offers a spare scheme that you can sacrifice. However, as I said, I would still tend to go for aftermarket if I had something available. Many Academy kits now come with Cartograf decals - those are fantastic and I wouldn't hesitate using them at all.
  11. Peter, this is unfortunately a recurring problem with Academy decals. I built their 1/72nd scale P-47D "Eileen" boxing recently: The decals look beautiful on the sheet, so I really wanted them to work despite having had the same issue with Academy decals previously. There are two main problems with their decals: 1) A problem with adhesion 2) They don't soften properly with most decal solutions The two solvents I tried were Micro Sol and Mr Softer. Between those two solvents, I have always had good results with literally every other brand of decals that I have used in the past. But on the Academy decals neither of them appeared to have much of an affect. I also tried a hot, wet cloth to press down on the decals, hoping the heat would soften them somewhat, which helped a little but not much. My solution in the end was to apply the decals that go onto relatively flat surfaces, such as the national markings and the fuselage art, by brushing on a bit of Future and then applying the decal onto it as if it was a decal setting solution. I also used hot water to wet the decal initially. This worked relatively well, since the future tends to shrink and suck down the decal, while it also solves the adhesion problem. However, this still doesn't help with decals going over compound surfaces that require proper softening. For those decals meant for compound surfaces, such as the invasion stripes under the fuselage and the checker nose of my P-47, I was forced to mask and paint in the end. The result was terrific, but man was it a lot of work to mask off those nose checkers. This probably doesn't help you at this stage, but since that P-47 was not my first Academy model and I have had this issue before, I have now decided that in future I will avoid using Academy decals completely unless it says on the box that they were printed by Cartograf.
  12. Understood. My humble apologies. Clearly I misinterpreted this as a question and made the stupid mistake of searching for and posting a picture to show you what it was: "What is the plane this Chinese Ji 5 just shot down? It is on my 1/72 DML Ji 5 (Mig 17F) kit. Don't think I have ever seen anything quite like it. jon" You are absolutely free to ignore me, and I promise I will try to remember not to respond to any of your posts in future, but I still think Rob's site has some wonderful information if you want to secretly take a peek anyway. I guess it really is time for that beer now.
  13. Ah, the internet. You try to help someone, give a bit of background info that literally directly addresses the question he asked initially, and someone tells you to "lighten up" - as if there was some parallel discussion going on that I didn't notice. I suppose it was because I asked him to actually read the fantastic links provided - especially that great site developed by Rob. Well, considering I was already in a pretty positive mood when I wrote my response, I'll go "lighten up" a little more and have a beer (while I work a bit on one of my models).
  14. Jon, I don't understand - two people have posted links to the history of these drones and how they were used for reconnaissance missions, yet you respond with these silly one-liners. In the context of your box art, they were used over China during the Vietnam war, among various other places and time frames. A number of them were shot down in the process, others crashed, but many also returned with valuable intelligence at the time. Why don't you read the links and find out a bit more about its history? Rob's site is very interesting and detailed, and there is also a lot of info in the two Wikipedia articles posted. You were apparently unfamiliar with the type - one of the great things about building models is that it gives you the opportunity to learn more about the fascinating histories behind what we build. Here is such an opportunity.
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