New guy from Delaware, needs help!!

Hello everyone, my name is Matt and I just joined the forum today in search of some advice. I am a mechanical engineer from Wilmington, DE and building an RV-8. I've been working on this project for a long time, but am really in full swing now. I hope to be finished by the end of the year.

I wanted to get on here and get some advice on a problem that has really been bothering me. I am dying to move forward, but I really want to get this right. I am in the process of rigging up the elevators. I already had to re-order and build a new left hand elevator because of a mistake I made and couldn't live with on the first one. I am at the step that involves drilling the holes in the control horns. I know the horns are rarely aligned perfectly, I have spoken to Vans and some friends about that. Thats not the problem I have. My problem is that when I clamp the ends of the elevators to the horiz stab as the instructions say, the trailing edges of my elevators are not aligned. Just by eyeballing it, they seem to be off about a 1/2 inch. I know that having the trailing edges aligned is the most important thing here, and I have done a few searches on this forum which leads me to believe that one of my elevators is twisted. My questions for you guys are: Can this be repaired? If it cant be repaired, is having the ends slightly off but having the trailing edge aligned ok? I also want to know if anyone has come up with a good way to align the trailing edges on an RV-8 other than clamping the ends in trail? I have seen that on other models some people clamp an angle across the two, but the tapered elevator on the RV-8 doesn't allow for that. Thanks in advance for the help everyone, hopefully you guys can help me move forward when I get home tonight.

Hi Matt. Welcome to the forum. Your problem is not all that uncommon. It boils down to your preference. Ideally, it is best to have the elevators aligned. If the tips are off slightly, it's not a big deal. Mostly cosmetic. On the other hand, if you prefer to have the tips aligned, the miss rig of the elevators will cause a little extra drag but nothing you will notice.

Matt,
I have a friend with a -6A that drilled the horns incorrectly to the push tube.
His elevators were off about the same as yours.
He said it flew just fine.
I later flew his plane and didn't notice anything either.
My .02
(BTW Welcome!)

Well I havent drilled the hole in the horns for the control rod yet, just the pivot hole, so the problem isn't with the alignment of the horns. I figured either way that it wouldn't cause any major flight problems and its mainly cosmetic, but I like having things perfect. I may try to fix one of the elevators if its possible, but I also want to find a good way to align the trailing edge on the elevator. The tapered elev is tough.

crawfish said:

but I also want to find a good way to align the trailing edge on the elevator. The tapered elev is tough.

Click to expand...

Laser. Great for aligning all kinds of things, particularly is they're rounded, tapered, or just don't lend themselves to easy measuring for whatever reason.

great idea! I'll have to try that. I read on here that I may be able to remove some of the twist in the elevator if I remove the end rib and work it from there?

Digital Level

Make a solid bar out of aluminum that will fit between the elevator horns. Drill a horizontal hole #30 to use as a drill guide.
clamp the brackets together loosely.... with the bar between horns

Get a digital level and average the trailing edges to get your best fit. Drill one hole in one horn. RE adjust the trailing edges. Clamp the 'tool' and use it to drill the other Horne. Enlarge with a reamer.

I also used a digital level to make sure the elevators were even, worked fine.

My right elevator has 3/8"+ of twist, making it high in the outboard end. I talked to one of the Kens at Vans about it. He said that's not a major problem. His words: "That much twist on one side will be aerodynamically insignificant".

how did you determine the amount of the twist?

If I had to choose, I'd level the trailing edges with one another and let them be out of alignment at the tips, if they even are out of alignment. Your horizontal stabilizer may have a little twist in it as well.

For alignment, go buy a lasar level that will shoot both a vertical and horizontal line at the same time. After building three airplanes without one, I bought one at Sears and have used it on my Rocket. I have used it for everything and I don't mount anything to the airframe without it. It has made a significant difference in getting parts consistently aligned with one another. So far I have used it to mount all the empennage parts, the gear, wheel pants, cowl, wings, flaps, and gear leg fairings.

Yep, laser and a digital level makes a lot of the jobs dead easy. Check one side for deflection, reset the level to 0 degrees and then check the other to compare. Checking the amount of up and down deflection on all of the control surfaces can be down in just a few minutes.

Low Tech Approach

I clamped a string onto the outb'd end of the L elevator with a cleco clamp and stretched it tight all the way across to the outb'd end of the R. Had the Spousal Unit hold the R end of the string whilst I measured the amount it was off.