Originally Posted by ennored
I've posted in a couple threads about boattails, but not here, where I first was drawn to Ecomodder.
In the beginning of this thread you mention that you kind of just guessed a taper for your boattail. You say it's just over 4' long. Just how much does it taper in? Did you lay out the curved part, or simply eyeball it?
There is 18 inches of taper occurring on the first 24 inches of the 4'6" of each rib. I made a 'control' rib of that specification and pounded out each of the 28 ribs to match the control. The taper occurs in the first 24 inches of the length of the rib, instead of the whole length like I probably should have done it.
I did it that way because I was flying along in a J-3 Cub once a long time ago and watched some water vapor moving over the top of the curved wing surface and down the extended aileron as we turned, without separating, and that shape stuck in my mind. So I made my ribs like the Piper wing.
In retrospect that was pretty dumb, but it did still have a great effect on mileage. Once the front mods and the wheel pants are finished I'll do some more testing and maybe make the tail conform to the holy template, or not, depends on how it does and how much time I can spend on it. I have had zero time for months and it's making me crazy.