Toobuilder
Well Known Member
I've been working on the wheelpants and gear leg fairings lately and stumbled upon a curious outcome. As is seen quite often, the builder of my Rocket installed the wheel pants generally aligned with the ground rather than the direction of flight. Consequently, the wheelpants are in a negative angle of attack in flight. Since I need to rework these things anyway, I drilled new mounting holes and lowered the tail of one of the pants to allign with the direction of flight. I did some other work as well so I was not too suprised to see the ball off center in cruise (normally dead center with feet on the floor). Long story short, I did some extensive cleanup on the OTHER side and did some test flying this morning. My cleaned up side shows less drag as the ball is well off center now, but I figured I'd land, change the first pant back to "nose down" and see if it moved the ball any. It did. I was able to land, change the pant back and was up at 8000 feet again in just a few minutes. Once established in cruise, the ball came back to about half of its previous displacement from the flight minutes before. Rudder displacement to both sides showed the ball settle right back in position once released.
Conclusion: negative angle of attack provides LESS drag on this airplane. This is less than scientific, admittedly, but it is a repeatable in situ test. One needs to keep in mind however, that the wheel openings on this example are huge and are probably scooping a bunch of air with the nose "up" ( or more likely, the nose "down" position masks the scooping effect). I intend to close the gap significantly with future glass work, and then seal the remaining gap with baffle material or horse hair rubbing on the tire. I suspect that will change the outcome. Once I seal up the gap, I'll play with the angle of attack again and report back.
BTW, these are the standard Vans "pressure recovery" wheelpants.
Anyway, just thought some of you would find this interesting.
Conclusion: negative angle of attack provides LESS drag on this airplane. This is less than scientific, admittedly, but it is a repeatable in situ test. One needs to keep in mind however, that the wheel openings on this example are huge and are probably scooping a bunch of air with the nose "up" ( or more likely, the nose "down" position masks the scooping effect). I intend to close the gap significantly with future glass work, and then seal the remaining gap with baffle material or horse hair rubbing on the tire. I suspect that will change the outcome. Once I seal up the gap, I'll play with the angle of attack again and report back.
BTW, these are the standard Vans "pressure recovery" wheelpants.
Anyway, just thought some of you would find this interesting.
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