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Don't know about the F-15C, but the F-18E has plenty enough thrust. A lot has to do with the ducting, too.
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Latest blog entry: Using acrylic floor gloss to coat foam
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Interestingly, re the 3d airfoils.. they have really changed heaps in recent times in our models.. Not so thick & round leading edges anymore - much thinner & sharp LE .. As you were saying flow detaches almost entirely in very high angles of attack & planform & aspect ration take over (does tail moment then come into it a fair bit too re lateral stability? guessing it does) - but anyway, I think designers must have found these thinner airfoils do fine with post-stall 3d as well as the sharper LE... that's both with & without aerodynamic washout devises like vortex generators on the outboard sections |
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Last edited by Natesh; Nov 30, 2015 at 10:43 AM.
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Well, there's one thing to very thin airfoils... They can function like thick ones at times.
Flow detaches too early but then re-attaches, causing a circulation bubble atop the leading edge. The more problematic ones are medium-thickness profiles, because these create the same bubble but it explodes suddenly, causing a total detachment of the flow over the wing with no warning. Thin airfoils instead, the bubble grows bigger with angle of attack causing vibrations so the pilot has a physical warning way before it reaches stall, at which point it detaches completely like the medium thickness foil. |
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Which may be the tell with this models foil design. Tip stall potential in the alpha for this swept wing where the foil goes from thick root to thinner medium tip foil may fit why it breaks loose very quickly with higher wing loading. May be an explanation for some unrecoverable stalled flat spins just at the right speed and wrong AoA for everything to suddenly go off.
Mind you this model still handles the prestall way better than most. Wing shape may be....... |
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"Back to airfoils, airfoils with more camber "
Jandro........How about an add on to your piece about stall progression on delta wing forms. The SU 35 is,after all, virtually a delta wing plane. I'd like to know why mine "waggles" at a particular sink rate as if it was stalling and recovering on alternate wing tips. If I don't throttle up or nose down it just starts to sink faster. |
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As in a flat drop or what's the flight condition? Cause a lot of things can trigger an oscillation.
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[QUOTE=locharrow;33325867How about an add on to your piece about stall progression on delta wing forms. The SU 35 is,after all, virtually a delta wing plane.
I'd like to know why mine "waggles" at a particular sink rate as if it was stalling and recovering on alternate wing tips. If I don't throttle up or nose down it just starts to sink faster. [/QUOTE] not really.. It's quite far from it IMO. Nothing close to even tailed deltas like the Pak FA & f-22.. those delta designs seem to be MUCH more controllable in high alpha (without flight control systems of course). |
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Do the Su35 is easy to control?
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The F4 progressed to move the tail stabilator back further though the engine and weight sits further forward mainly on the wings. Thus they had adverse yaw and roll and instead of having ailerons counter each other, one aileron went down on one side and a counter air brake popped up on the other side. This was because it still had the effects of a true delta wing effecting it's stability. There is the idea that the wings shape in a triangled delta is a delta wing but the definition goes further where the wing is placed relative to the overall weight distribution. Euro or Mirage where the engine is near the elevons vs and delta wing positioned further forward like with a F22 acting more like normal wings only with a lower AR just having the delta shape. But because it's far enough forward pitch must then be left to the separate tail stabs again positioned around the engines. The blend between both world's is the PakFa where it's delta form starts far enough forward but aft enough that the wings ailerons are far enough aft to be elevons or have enough of a pitch moment for them to be used with pitch at certain speeds. Tailed deltas the original definition of the type are prone to spin stalls because the delta wing tends to blank their air flow in pitch up. The Phantom, A4 and other similar designs like them were know for this. So I think the reason for the repeating comparisons and corrections of what a tailed delta is is because it's had varied definitions between laymen and aviation. |
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Last edited by Maxthrottle; Dec 01, 2015 at 02:01 AM.
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