...I do need the distance from the leading edge of the wings to the leading edge of the horizontal stabilizer (both sides to get an average)....
The ability to easily arrive at reasonably close estimates for stuff like this is one of the most powerful skills in the arsenal of any aeronautic practitioner, engineering or otherwise. Here's how I handled this:
1. I downloaded the RV_All package from vansaircraft.com:
http://vansaircraft.com/public/downloads.htm
Actually, it was already on my computer, but that's where I got it from.
2. I imported the .dxf into my favorite graphics and mechanical design program, CorelDraw! (long story).
3. I looked up the basic specs for the RV-9 on vansaircraft.com:
http://vansaircraft.com/public/rv-9spe.htm
Which gave a length of 20' 5". By inspection, that is 245".
4. I went to my design program, took the side-view of the RV-9 and re-scaled it to a length of 245".
5. I used the horizontal measurement tool in CorelDraw! to measure from the leading edge of the wing to the leading edge of the horizontal stabilizer, and got 130.3".
Thomas we measured the distance for you. Right side -
131 1/2 inches and left side
131 3/8 inches. The measurements were taken 1 foot from HS tips inboard on both sides on a hot day. My helper was holding vertically 6 foot level and we used construction metal tape measure by Stanley not FAA certified
Well, yeah, if you have the airplane handy and you want to do it the easy and exact way, that's what you'd do!
So, my estimate is 130.3/131.5=99.2% of the actual measured distance, for an error of a little less than 1%. I would argue that that makes it worth not having to get out of bed.
By the way, here's one reason why this works for the RV-9, RV-10, or RV-12, but it might not be entirely satisfactory for other RVs:
For a stability calculation, you would probably want to be working not with the raw locations of the leading edges of the surfaces in question, but rather with the leading edges of their Mean Aerodynamic Chords (MACs). Or perhaps with the 25% chord line of the MACs. Anyhow, with rectangular wings such as those used on RVs, the MAC is the same as the wing chord, so no big deal (give or take a fraction of an inch for dihedral-plus-incidence induced sweep, but that's splitting hairs). But for the tapered surfaces of many RV tailplanes, the MAC will not be the same as the root chord of the surface, it will be a bit less.
For a trapezoidal surface like an RV tailplane, MAC is a fairly simple calculation. I can't remember the formula offhand, but you can find it on the web. You can also download MAC calculators from many RC airplane websites.
Thanks, Bob K.
