Here's the latest on my own project.
I finally got through the lateral-directional stability and control numbers! Man, for one short section in Raymer (and every other book I've got), that sure does puff out to a fair amount of calculation! As it sits, my original tail-volume calculation was pretty darn close (enough that the difference really doesn't show on the drawing), but now I know I can hold the requisite crosswind with 20 degrees rudder and have enough aileron to keep the wings level. The ailerons actually got a touch bigger (spanwise), but that was the major change from that work. I think I want to go back and recheck these numbers again - I've never done this particular set before and it seems like I always mess up the first time. Stay tuned on that...
I redrew the rudder hinge line to it's 'real' appearance (the previous angled hinge line was for calculation convenience and would have resulted in a slight pitch-up with rudder deflection).
The beast has also grown a wing-root fillet (seen only on the plan view here). My aft fuselage shape is great for ease of construction (flat wrap conic), but would be prone to flow separation aft of the widest point of the fuselage. I'm not sure if the fillet is big enough - it's such a voodoo art. Anyone have any more-experienced opinions there? In the same vein, I reduced the wing incidence two degrees, matching it to the maximum L/D speed instead of minimum sink speed. This also brought the trailing edge up farther away from the fuselage bottom and should help with the separation issue. Wish I could wind-tunnel test this... :ermm: The downside is that my tail skid now touches just before the full-stall angle, but that's common on sailplanes - if a ham-fisted pilot lands a 1-26 at full-stall, the tail will touch down with the mainwheel still a few inches in the air, slamming down the nose.
Other than that, I've done a very early loft of the forward fuselage and changed the shape of the lower canopy edge as a result. The previous curved bottom edge was aesthetic, but not a realistic shape.
So that's about it for now. Onwards and upwards.
I finally got through the lateral-directional stability and control numbers! Man, for one short section in Raymer (and every other book I've got), that sure does puff out to a fair amount of calculation! As it sits, my original tail-volume calculation was pretty darn close (enough that the difference really doesn't show on the drawing), but now I know I can hold the requisite crosswind with 20 degrees rudder and have enough aileron to keep the wings level. The ailerons actually got a touch bigger (spanwise), but that was the major change from that work. I think I want to go back and recheck these numbers again - I've never done this particular set before and it seems like I always mess up the first time. Stay tuned on that...
I redrew the rudder hinge line to it's 'real' appearance (the previous angled hinge line was for calculation convenience and would have resulted in a slight pitch-up with rudder deflection).
The beast has also grown a wing-root fillet (seen only on the plan view here). My aft fuselage shape is great for ease of construction (flat wrap conic), but would be prone to flow separation aft of the widest point of the fuselage. I'm not sure if the fillet is big enough - it's such a voodoo art. Anyone have any more-experienced opinions there? In the same vein, I reduced the wing incidence two degrees, matching it to the maximum L/D speed instead of minimum sink speed. This also brought the trailing edge up farther away from the fuselage bottom and should help with the separation issue. Wish I could wind-tunnel test this... :ermm: The downside is that my tail skid now touches just before the full-stall angle, but that's common on sailplanes - if a ham-fisted pilot lands a 1-26 at full-stall, the tail will touch down with the mainwheel still a few inches in the air, slamming down the nose.
Other than that, I've done a very early loft of the forward fuselage and changed the shape of the lower canopy edge as a result. The previous curved bottom edge was aesthetic, but not a realistic shape.
So that's about it for now. Onwards and upwards.
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