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Originally Posted by Big Dave
Thanks Phil. I thought I was on the right track. I intend to use about 25% of my bed length in a curved transition to my 1-in-5 slope.
Interesting. Mair's boat-tail shape is exactly that used by manufacturers of sniper rifle bullets. They call them "boat-tail spitzers." Of course being supersonic, they use very pointed forward sections.
All this is axial slope. How should I curve it laterally? Or should I? As I recall, aircraft canopies are rounded in both axes.
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Big Dave,you'll want to integrate the forward edge of the cap to fit that of the trailing edge of the cab of course.And the cab has some "tumble home" angle to it,rather than just being a vertical wall.As the cap progresses rearward,you could start increasing the radius of the intersection between the top and sides and allowing the sides to kinda roll into a curved sidewall.I know pictures would be helpful.Sorry! Anyway,as you approach the end of the cap,your sides could be rolled into a continuous curvature over into the top.It would be like the boat shell on the T-100 is now.And like the "Aberdeen Projectile" boat tail you see on the supersonic bullets.It's alot harder to construct,due to the compound curves.A cedar-strip canoe is built with the compound curves and they take about 400-man hours to complete.Whew!!!!!!!!!!!! Lots of work.The air loves this stuff,but for the trouble,you may never see that much difference at the Diesel pump.You may just want to let the sides lay at the same angle but gently curve in at the same rate that the roofline is descending.On Darin's thread for his permanent boat tail we generated a ideal teardrop template.You scale your vehicle's height to where it will fit under the template at the point of max roof height,and the template defines the curve of ideal airflow.You can end it wherever you like,just like Kamm did,and have good attached flow,right up to the "chop".Check it out if you haven't seen it.You can use it for the sides as well.If you bring the sides in,you cut wake area a bit extra compared to straight sides,but is does cut down on cargo room.Everything is a compromise!