The Aeroplane Speaks [2]
the Spars need not be so strong and so deep, which results in not so thick a Surface. That means the Chord can be proportionately decreased without adversely affecting the Camber. With the Chord decreased, the Span becomes relatively greater, and so produces a splendid Aspect Ratio, and an excellent proportion of Lift to Drift.''
``I don't deny that they have rather got me there,'' said the Drift, ``but all the same, don't forget my increase due to the drift of the Struts and their bracing wires.''
``Yes, I dare say,'' replied the Surface, ``but remember that my Spars are less deep than before, and consequently I am not so thick now, and shall for that reason also be able to go through the air with a less proportion of Drift to Lift.''
``Remember me also, please,'' croaked the Angle of Incidence. ``Since the Surface has now less weight to carry for its area, I may be set at a still lesser and finer Angle. That means less Drift again. We are certainly getting on splendidly! Show us how it looks now, Blackboard.'' And the Blackboard obligingly showed them as follows:
``Well, what do you think of that?'' they all cried to the Drift.
``You think you are very clever,'' sneered the Drift. ``But you are not helping Efficiency as much as you think. The suction effect on the top of the lower Surface will give a downward motion to the air above it and the result will be that the bottom of the top Surface will not secure as good a Reaction from the air as would otherwise be the case, and that means loss of Lift; and you can't help matters by increasing the gap between the surfaces because that means longer Struts and Wires, and that in itself would help me, not to speak of increasing the Weight. You see it's not quite so easy as you thought.''
At this moment a hiccough was heard, and a rather fast and rakish-looking chap, named Stagger, spoke up. ``How d'ye do, miss,'' he said politely to Efficiency, with a side glance out of his wicked old eye. ``I'm a bit of a knut, and without the slightest trouble I can easily minimize the disadvantage that old reprobate Drift has been frightening you with. I just stagger the top Surface a bit forward, and no longer is that suction effect dead under it. At the same time I'm sure the top Surface will kindly extend its Span for such distance as its Spars will support it without the aid of Struts. Such extension will be quite useful, as there will be no Surface at all underneath it to interfere with the Reaction above.'' And the Stagger leaned forward and picked up the Chalk, and this is the picture he drew:
Said the Blackboard, ``That's not half bad! It really begins to look something like the real thing, eh?''
``The real thing, is it?'' grumbled Drift. ``Just consider that contraption in the light of any one Principle, and I warrant you will not find one of them applied to perfection. The whole thing is nothing but a Compromise.'' And he glared fixedly at poor Efficiency.
``Oh, dear! Oh, dear!'' she cried. ``I'm always getting into trouble. What WILL the Designer say?''
``Never mind, my dear,'' said the Lift-Drift Ratio, consolingly. ``You are improving rapidly, and quite useful enough now to think of doing a job of work.''
``Well, that's good news,'' and Efficiency wiped her eyes with her Fabric and became almost cheerful. ``Suppose we think about finishing it now? There will have to be an Engine and Propeller, won't there? And a body to fix them in, and tanks for oil and petrol, and a tail, and,'' archly, ``one of those dashing young Pilots, what?''
``Well, we are getting within sight of those interesting Factors,'' said the Lift-Drift Ratio, ``but first of all we had better decide upon the Area of the Surfaces, their Angle of Incidence and Camber. If we are to ascend as quickly as possible the Aeroplane must be SLOW in order to secure the best possible Lift-Drift Ratio, for the drift of the struts wires, body, etc., increases approximately as the square of the speed, but it carries with it no lift as it does in the case of the Surface. The less speed then,
``I don't deny that they have rather got me there,'' said the Drift, ``but all the same, don't forget my increase due to the drift of the Struts and their bracing wires.''
``Yes, I dare say,'' replied the Surface, ``but remember that my Spars are less deep than before, and consequently I am not so thick now, and shall for that reason also be able to go through the air with a less proportion of Drift to Lift.''
``Remember me also, please,'' croaked the Angle of Incidence. ``Since the Surface has now less weight to carry for its area, I may be set at a still lesser and finer Angle. That means less Drift again. We are certainly getting on splendidly! Show us how it looks now, Blackboard.'' And the Blackboard obligingly showed them as follows:
``Well, what do you think of that?'' they all cried to the Drift.
``You think you are very clever,'' sneered the Drift. ``But you are not helping Efficiency as much as you think. The suction effect on the top of the lower Surface will give a downward motion to the air above it and the result will be that the bottom of the top Surface will not secure as good a Reaction from the air as would otherwise be the case, and that means loss of Lift; and you can't help matters by increasing the gap between the surfaces because that means longer Struts and Wires, and that in itself would help me, not to speak of increasing the Weight. You see it's not quite so easy as you thought.''
At this moment a hiccough was heard, and a rather fast and rakish-looking chap, named Stagger, spoke up. ``How d'ye do, miss,'' he said politely to Efficiency, with a side glance out of his wicked old eye. ``I'm a bit of a knut, and without the slightest trouble I can easily minimize the disadvantage that old reprobate Drift has been frightening you with. I just stagger the top Surface a bit forward, and no longer is that suction effect dead under it. At the same time I'm sure the top Surface will kindly extend its Span for such distance as its Spars will support it without the aid of Struts. Such extension will be quite useful, as there will be no Surface at all underneath it to interfere with the Reaction above.'' And the Stagger leaned forward and picked up the Chalk, and this is the picture he drew:
Said the Blackboard, ``That's not half bad! It really begins to look something like the real thing, eh?''
``The real thing, is it?'' grumbled Drift. ``Just consider that contraption in the light of any one Principle, and I warrant you will not find one of them applied to perfection. The whole thing is nothing but a Compromise.'' And he glared fixedly at poor Efficiency.
``Oh, dear! Oh, dear!'' she cried. ``I'm always getting into trouble. What WILL the Designer say?''
``Never mind, my dear,'' said the Lift-Drift Ratio, consolingly. ``You are improving rapidly, and quite useful enough now to think of doing a job of work.''
``Well, that's good news,'' and Efficiency wiped her eyes with her Fabric and became almost cheerful. ``Suppose we think about finishing it now? There will have to be an Engine and Propeller, won't there? And a body to fix them in, and tanks for oil and petrol, and a tail, and,'' archly, ``one of those dashing young Pilots, what?''
``Well, we are getting within sight of those interesting Factors,'' said the Lift-Drift Ratio, ``but first of all we had better decide upon the Area of the Surfaces, their Angle of Incidence and Camber. If we are to ascend as quickly as possible the Aeroplane must be SLOW in order to secure the best possible Lift-Drift Ratio, for the drift of the struts wires, body, etc., increases approximately as the square of the speed, but it carries with it no lift as it does in the case of the Surface. The less speed then,