Just a few comments. I didn't mean to oversimplify things earlier, but this was started on the
general forum.
Ted has said this in his previous writings, but he was not using the standard aeronautical definition of lift. He may have been describing the evil effect of the rate of change of pitching moment with angle of attack petering out at high lift.
I was talking about the lift curve slope and consequent actual lift force at some alpha for a given weight model, as I presumed Ted was. I think that for any given model, there can be too little mass and/or too steep a slope, making planes jumpy and devoid of enough inertia to deal well with gusts. With a constant theoretical slope for flapless planes, the flap progression ought to be the major determiner of that slope (right??). I also didn’t mention the possible role of span-wise a.c. position in encounters with
side gusts. I agree with what you have said.
Brett's comment about lift above was to emphasize the benefit of flap taping on consistency, rather than on max CL. I think you are on the right track regarding gust sensitivity, but I think you are looking at d CL / d alpha, rather than (d L / d alpha) / m. A good way to reduce gust sensitivity for a given turn radius capability is by having a high CL max and a hefty wing loading..
‘understand and agree. I tend to think of the two affects (slope of either curve and mass) separately, but see that your second expression is a nice overall measure. I thought that's what I said about consistency. Of course, I know that for level flight, the lift equals the plane's weight, regardless of the wing mechanisms. I do think though that for any particular model, there can be too much lift at other aoa’s (alphas), so that too little input is needed and there is too much gust sensitivity (increase in lift per change in air speed relative to weight – which is what I think you’ve said). ‘guess I’m being redundant, but...for reasons akin to what you’ve posted, I’d then diminish the flap deflection or area – or add that mass - to deal with gusts. Elevator/flap ratios enter here. The post from the member who did not seal flaps because of gust sensitivity seemed to suggest that gusts were creating too much sudden extra lift; I took him to mean that he’d left the flaps unsealed to prevent the plane's reacting too much. So I’d have chosen those more potent and consistent sealed flaps, but with less deflection or area.
That's what the clown on the left thought about the airplane he is holding in the picture. He didn't understand the problem he was having, and more elevator made it a lot worse.
I meant more stabilizer area and tail arm, with the appropriate % elevator area. In other words, “stab/elevator” was intended to mean taken together as “horizontal tail (area)”. FWIW, for the same tail, a longer tail arm
would actually require a tiny bit more elevator deflection to have the same effect in maneuvers, since the horizontal tail’s aoa increases with distance from the c.g. But, while increasing elevator deflection is the easiest thing to try, I’d expect increasing tail effect as a whole – stabilizing and lift producing - to be the better bet. Keeping the elevator to stab area ratio at a reasonable value seems prudent. That was just my initial take from what I’ve tried and read.
Without sealed elevator gaps, a 707 would be almost impossible to fly. There is a heap of stunt score available to whoever figures out a frictionless way to seal stunt flaps hinged behind their leading edge.
That fortunately doesn’t appear to be so true of our models. Perhaps I’m just not understanding what was meant, but to me, a slotted flap is a
slotted flap. When extended/deflected, it has to be open, or there’s no slot. So do you folks mean sealed just at or near neutral? If not, I’m not seeing how deflecting a sealed flap's leading edge above the t.e. surface could help. If it’s better for it to be sealed at zero deflection, that’s fine, but I still cannot imagine anyone wanting to tape a slot on a model, or having the controls even work then.
If I’ve still missed the boat, I’m always willing to learn, but I sense that this part of the discussion has really exceeded the tolerance of some of its general contributors, who like us to play out on the south 40. - SK
Topic: Sealed hinge lines? Are we absolutely sure about this??? (Read 11571 times)