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szicree

Well Known Member
Several months ago I fit the wings to the fuse and drilled the rear spar. Today I rechecked all the measurements and found that one wing is 0.1 degree too high, and the other is 0.1 degree too low. The only fix I can think of is to find a way to drill the rear spar attach slightly oversize while shifting the hole a bit. I figure each hole would have to move about 3/64 inch. Obviously this is a delicate operation and could easily make the situation worse. Is a 0.2 degree difference between wings significant? Will I only be able to fly in circles? Boy this really sucks right now. :(
 
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I wouldn't mess with it... just my opinion, though. there's a chance of making things worse and it's a fairly critical area... Also, doesn't Vans say something like "if it's within 1/4" it's good..." I believe their tolerances are far bigger than 0.1 deg. Remember, setting wing incidence was done before this kind of accuracy was possible and those planes fly fine too. :)
 
Steve,

I think this is one where I'd consult Van's (and it is very rare that I say that)....fairly critical area, and I'd at least want their opinion to back up any others you'd get here.

Paul
 
I agree

Steve,
Are you absolutely sure of the difference? How did you measure the incidence this time? Radomir has a very good point. Leave it alone 'til you talk to Van's. .1 degree sure is small.

Regards,
 
Geez, I know we strive for perfection but .1 degree - 3/64ths of an inch. If that ends up being critical I may have to start over. :D
 
Many, many airplanes, including RVs, have been built over the years with a "bubble" level. There is no way you can achieve 0.1 degree accuracy with a bubble. While it never hurts to check with the designer, I can assure you that this kind of accuracy is not necessary on this type of aircraft.
 
Symetry

Steve - talk to VANS but I would not worry. The good news about a single engined aeroplane is that there is NO symetry about it since the prop is rotating in one direction with a resultant cork screw airflow at least on the inner part of the wing. It will probably make it the best coordinated -4 ever!

I would also add that mine is sitting there with pilot holes in the rear spars ready to be drilled. I cant get the same set of readings off the level two days in a row! they are always + or - 0.1 deg.

Dont loose sleep!
 
I sure do appreciate all the quick responses. I've been out in the yard checking and rechecking (mostly sobbing really). I'm using a smart level and the mysterious 2.8 inch block. As near as I can tell it really is off by 0.1 degree on each side. Unfortunately, the left wing has too much and the left too little, so that I guess I'll only be able to fly at airports with a right-hand pattern :p . The thing that bothers me the most is that this is exactly the same method I used when I originally mated them and I must've checked it a gazillion times. I'm very puzzled to see that it is now different :confused: .

I was hoping that there was some specific allowable difference, but I guess only Van's will know. I've also measured everything in terms of edge distances and I think redrilling is out of the question.

Any additional ideas about this would be greatly appreciated and probably prevent some serious drinking.
 
Steve,

My Smart Level is cool, but I wouldn't bet my life on a tenth of a degree with it. Pick it up and shake it, turn it around and measure the other way, it will easily vary that much. There was a time when incidence was set with a bubble level. :)

I wouldn't sweat it.
 
How many different places on each wing have you measured the incidence at? I found that on my wings, depending on exactly where I put the level, I could get very small differences. I ended up going with the average.

Personally, I wouldn't try to fix this now. The only way to fix it without compromising the strength would be to replace the rear spar, which is a huge job. Messing around trying to redrill the holes in the existing spar might allow you to get the incidence sorted out, but with less strength than needed.

You can trim the aircraft laterally after you get flying by tweaking the flap angles on each wing, playing with the vertical location of the ailerons, and tweaking the aileron trailing edges. It is possible you might have a bit more roll off at the stall than some other RVs. If the stall proves too scary, then I would add an AOA system with aural stall warning.
 
Check the whole plane for level first.

We thought we were off slightly and could not figure how this could have happened. We then checked the plane for level and found that one of the shims had moved while we were drilling and pushing around. Re-leveled the plane and ...whooalla. Wings were properly set (again).

Now if that does not work, then.......
go place a bubble level on your wing and see if the bubble looks the same on both wings. (It will).

I bet it will be acceptable to the eye and fly straight and fast.

Pat Garboden
Ozark, MO
RV9-A 942WG (reserved) O-235 w/slider
RV9-A 942PT (reserved) O-320 w/tip up
 
This happened to me also, my buddy used his $200 8foot carpenters level and I used my $30 stanley and when I cheked mine with a digital meter it was off .1 degree also and his was perfect. I lost countless hours of sleep over it. We flew them for the 1st time together and he complained of a heavy wing, mine flew hands off! and has ever since. Bottom line- don't worry at all, it will be fine and fast. Mike Redd -7 425 hrs
 
please let us know what vans says

0.1 of a degree seems pretty doggone good to me. And wouldn't it only matter at the stall? The wing with the higher incidence would stall a gazillionth of a second before the other perhaps but I think there are easy fixes to this. Good Luck to you sir and I am hoping that your .1 of a degree is irrevelant.
 
I've had my smart level for over 10 years and have used it on several plane projects along side a decent quality bubble level. One thing is guaranteed - the last 0.1 degree on a smart level will drive you crazy. You did fine and don't worry about it any more. Now finish the plane and fly it. :)
 
Steve
Don't sweat it, You checked it before you drilled it, Right!!
Now throw the digital level away and move on.
I think the only good use of the digital level, is for setting control surface deflection. Otherwise we all probably get to anal about getting everything perfect.
I can't believe how straight my first RV4 flew with twisted ailerons, kinked trailing edges on elevators, and a trim tab that should have been rebuilt.
I figured I'd fly it and then see if I needed to fix it. I never did because it flew so well.
Put the bubble between the lines and drill!!

Jon
RV4 Started 1983 Completed 1990
RV4 started 1994 completed 1996
RV6A started 1998 completed 2004
RV8 Started March 2006 Completed Nov. 2006
 
azrv6 said:
. One thing is guaranteed - the last 0.1 degree on a smart level will drive you crazy.)
Click to expand...

LOL this is so true ... as I was setting my incidence I suddenly found myself at 0.0 degrees, then I gave the smart level a surprised look and it clicked over to 0.1. This happened more than once.
 
jthocker said:
Jon
RV4 Started 1983 Completed 1990
RV4 started 1994 completed 1996
RV6A started 1998 completed 2004
RV8 Started March 2006 Completed Nov. 2006
Click to expand...

This is the kinda stuff that makes the rest of us crazy! Do you ever sleep? Trust fund instead of a job?? Extra arms and legs??? Seriously, that is quite an impressive resume you've got there and I sure do appreciate the words of encouragement. I guess deep down it's hard to believe that all this metal will really fly, let alone in a straight line.
 
What accuracy?

Steve,
I have to have my two bobs (Aussie for 20c) worth here.

Firstly, your smart level, like mine, reads to 0.1 of a degree. That means it is only accurate to 0.05 of a degree;
1/. When the angle being measure goes up from 0.049 to 0.051 the indication will change from 0.0 (Rounded down) to 0.1 (Rounded up).
2/. Similarly, when the angle being measure goes down from 0.151 to 0.149 the indication will change from 0.2 to 0.1
So all you really know is that the angle is 0.1 plus or minus 0.05. It could be 0.05?.

Secondly, as Kevin H. mentioned, how many places on the span did you measure. I have QB wings and the variation of ONE wing across the span was 0.1. The other had no variation.

Thirdly, when I first flew I had a prominent roll to the left. After checking I found that the right aileron was sitting 2/32" (as they say at Vans. Not 1/16"). So, I slotted the aileron attach holes 2/32" and the roll was removed. So there is plenty of capability to sort out any roll during test flying.

So, if I were you, I would open a beer and stand back and admire how beautiful your RV looks with the wings on and congratulate yourself of progress.

Good luck,
Pete.
 
Level accuracy

szicree said:
Several months ago I fit the wings to the fuse and drilled the rear spar. Today I rechecked all the measurements and found that one wing is 0.1 degree too high, and the other is 0.1 degree too low. The only fix I can think of is to find a way to drill the rear spar attach slightly oversize while shifting the hole a bit. I figure each hole would have to move about 3/64 inch. Obviously this is a delicate operation and could easily make the situation worse. Is a 0.2 degree difference between wings significant? Will I only be able to fly in circles? Boy this really sucks right now. :(
Click to expand...

Steve, I can tell you for a fact that the digital read-out on the electronic levels is often not as accurate as the built in visual oil "bubble". I've used several of them including the SmartTool and tested them against each other for accuracy. I have found that the digital electronic readouts are not accurate to within 0.1 of a degree. They "increment" in 0.1 degree...but they are not "accurate" to 0.1 degree.

Don't even dream of re-drilling the rear spar. Very high chance of stuffing it. And then the nightmare will really start. It could mean not just replacing the doubler plate on the wing but you could end up having to replace the fuselage centre double fork.......oh the horror, the horror.
 
Steve
No trust fund, I just have taken advantage of living in my airlines Hub city.
Over 20 years I've probably bid a reserve schedule for 3/4's of the time. So I haven't minded being on call, as long as I have a project.

Good luck on your RV4, you're gonna love the visibility.

Jon (I only fly 8's now)
RV8,DC8
 
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