Quote:
Originally Posted by sendler
Thanks for the replies. My question stems from discussions of whether streamlining the front or the back of a motorcycle will make the most improvement if you were only to do one or the other. And, is it worth the trouble to run the tail at full length or will a Kamm truncation to 60% of the ideal length be only a marginal loss. The hemisphere in front of a cone was just my way of over-simplifying the shape so it would be still useful for analysis but also very easy to draw.
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The fuselage example above is much too long to for our discussion of Kamm truncation since most of the length along the sides is nearly straight. By the time you get to 60% of the length, you have made a long round nosed bullet with almost no angle remaining and haven't satisfied the other rule of thumb for Kamm which is to end with a width that is no more than half of the max width of the airfoil. The angle of my tail I have started to build is about 10.5* per side, 18 inches at the front, truncated to 8 inches at the back by 28 inches long.
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That it only takes 4% of the width for the radius of a round over on the front of my tail to harbor attachment is good news as that is only .75 inches which should be very easy to exceed with a pool noodle cut in half.
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Kamm's 50% frontal area wake body truncation was a concession to 'practicality' and had nothing to do with ideal streamlining.He knew they were still leaving 50 % or more of the drag on all the K-cars.