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Old 01-11-2013, 07:38 PM   #67 (permalink)
ennored
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Large vehicle (RV) templating

OK, took care of the 5 posts with an intro over in the intro section. On to my questions!

I've read the Aero RV thread, and the "Dryden Van" paper. I wonder what a boattail would look like on my motorhome.

The aero template tool to the rescue:



Hmmm, looks like it would need to be long, VERY long. 1.78 times the height (132") is almost 20' long! That can't be, the Dryden van tail is only 3 1/2 feet. The Aero RV is like 4'. Hmmm, maybe the template is misleading. How much would a 4' tail actually taper in? Some math (from another thread) says that at the 20% point (4' of the 20' tail) it'd be at 7.5° and in about 5.5". Yup, template DOES look right.

Thought more about the Dryden Van, and templated it:



Well lookie there, it doesn't fit! Those dummies at NASA....

I didn't see a nice shot of the Aero RV to template, but by eye from the pictures that are here says it doesn't fit either.

More thinking. Find more examples.... I've known about the "TrailerTail" product for a while. Armed with the new knowledge on templates and such, looked again at it. Interesting. Flat sides (not curved), 4' long. Tapered in at 15° (yields about 12" "in").

That's where I'm at. In my head are the template, and a few actual large vehicles that have about a 12" taper (Dryden van is like 11" by my calculations).

Is there something to large vehicles that "confuses" the template? Maybe there's a length factor not captured? Or is it simply the boattails I've found are not optimum? TrailerTail and Aero RV, maybe, but the Dryden Van? Maybe it's the shape and 22° that are really important?

I welcome the experts' thoughts. Cool thing for my motorhome is I have a separate fiberglass rear cap that is a bit over a foot long now. Something that adds 2 or 3 feet is actually reasonable. A 3 sided, hollow centered tail could actually be done quite neatly.

(Also of note, I have a email in to a former aero engineer I know that is now at Navistar, the folks that did the Monaco Vesta. I hope to have some answers from him I can share here soon.)

Last edited by ennored; 01-15-2013 at 09:54 AM..
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