LettersFromFlyoverCountry

LettersFromFlyoverCountry

Well Known Member
When you're mating wings, and you want to check that the fuselage is level fore and aft, where'sthe best place to do that, at least on an airplane where the top skins are already on.

I used to set a level on the longeron after of F-705, but that's inaccessible now. what about the floor beneath the seats?

For side to side level, I use the center spar, because putting it across the longerons could be inaccurate because one could actually be slightly higher than the other.
 
The cockpit side rails are the "leveling" point for the 2 seat RVs.

And you are correct in using the main spar carry-thru for side-to-side level.
 
It's interesting how this is a bit more difficult with the gear on and engine hung. On sawhorses, you get some more options for keeping it all level.

My fore-aft measured on the rails differs by .3 degrees.

Of course, all of this is made possible by the great edge distance mistake. Because I have one hole in the rear fork already drilled, it's going to be really close this time, too.

Such fun.
 
Mel,... does it matter if,...

Does fore and aft level really matter when mating the wings if the relative difference between the fuse and the wings is the same.

Meaning that if you lay a couple of pieces of angle accross the cockpit and then put a digital level on it,... and it indicates .6 degrees (example) and you set the wings to .6 degrees as well, you have 0 difference which is what the plans really call for with the 3 inch block and level set up?

Leveling the fuse and then going for 0 degrees on the wings with the block seems to be essentially the same thing?

Just curious since that eliminates having to put the plane on blocks to get the fuse level for mating the wings? If you mate the wings before gear and engine, getting the fuse to 0 is easy but if you mate later after it's on the gear, it is more of an issue. Just seems that it matters not as long as the final difference between the longerons and wing/block/level is 0.

Bill S
7a almost there
 
Yep!

BillSchlatterer said:
Does fore and aft level really matter when mating the wings if the relative difference between the fuse and the wings is the same.

Meaning that if you lay a couple of pieces of angle accross the cockpit and then put a digital level on it,... and it indicates .6 degrees (example) and you set the wings to .6 degrees as well, you have 0 difference which is what the plans really call for with the 3 inch block and level set up?

Leveling the fuse and then going for 0 degrees on the wings with the block seems to be essentially the same thing?

Just curious since that eliminates having to put the plane on blocks to get the fuse level for mating the wings? If you mate the wings before gear and engine, getting the fuse to 0 is easy but if you mate later after it's on the gear, it is more of an issue. Just seems that it matters not as long as the final difference between the longerons and wing/block/level is 0.
Bill S
7a almost there
Click to expand...
It's just a reference.
 
BillSchlatterer said:
Leveling the fuse and then going for 0 degrees on the wings with the block seems to be essentially the same thing?
Click to expand...

Unless I'm misunderstanding something, it's probably even simpler than you describe. Since the left wing was drilled for incidence back when it was on sawhorses, I figure I'll just take a reading on that wing, and make the right wing the same thing.

But now that I'm thinking of it, what would be the in-flight characterisitic of a set of wings that are off by, say, 1 degree?
 
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Bob Collins said:
But now that I'm thinking of it, what would be the in-flight characterisitic of a set of wings that are off by, say, 1 degree?
Click to expand...

It's much more important that both wings be the same.
If both wings are off by 1 degree, you will have slightly more drag as the wing will not properly match the horizontal stabilizer and thrust line.
 
2 x 6

Bob ,

On my 7A I used 2x6's under the mains and let air out of
the nose wheel and the fore aft level was perfect.
Then the side to side put shims under the low side and
I measured on the spar for the side to side.
Pretty easy to level if you do it this way.

Also you can use NASCAR air pressure if you want
from side to side to level it out instead of the shims.

Isn't this experimental stuff great.:D
 
What is NASCAR air pressure?

I spent about 2 1/2 hours on this tonight before calling it an evening. Having locked in the left wing a few years ago, my options are a little limited, and I just can't get the fore-aft reading on the left side skirt to match the right. (Explanation here). So I just don't trust what the level is telling me on the right side.

Because of my already-drilled rear spar hole in the rear fork (it's all related to the edge distance screw up a few years ago), I drew on the rear spar where the area of it that is within the 5/8" of the edge and it's going to be really close again (I'm waiting for a 5/16" to 1/8" bushing from McMasterCarr before I do anything serious).

No forward sweep, triangulation is perfect, but I can't get the right wing closer than within .1 degree of the left .

I'm getting close enough to the end of this project that I'm ready to pay someone to finish it. :D
 
Go for it!

Bob, If you have it within 0.1 degree, drill it. These airplanes are closer to tractors than watches. Many, many RVs have been built with bubble levels which could not achieve that kind of tolerance.
 
Why a .1 degree isn't,..

Bob, don't forget that a digital level rounds up and down so it is entirely possible that one side is actually .04 rounding down to .0 and the other side is .06 rounding up to .1 so you could be way less than a .1 off and not know it. That is unless your level reads out to 2 decimal places.

I also found that you have to keep the level pointing the same way when you move it side to side.

Think I got the decimal right :)

Bill S
7a almost there.
 
Bob Collins said:
I found that, too. Darndest thing.
Click to expand...

Bob,

If its any help or consolation, I found the wing to spar fitting so accurate all this leveling process was not necessary. The left to right angle of incidence was within a quarter degree and also in agreement with the longerons, no adjustment at the aft spar was necessary.

The airplane flies well except I need rudder trim for the wide speed range of the machine.
 
BillSchlatterer said:
Bob, don't forget that a digital level rounds up and down so it is entirely possible that one side is actually .04 rounding down to .0 and the other side is .06 rounding up to .1 so you could be way less than a .1 off and not know it. That is unless your level reads out to 2 decimal places.

I also found that you have to keep the level pointing the same way when you move it side to side.

Think I got the decimal right :)

Bill S
7a almost there.
Click to expand...

Most frustrating tool in the shop. Because it *can read* 0.0, we're always trying to make that happen. Even if it's beyond anal to do that :).

Thank GOD we don't have a real, honest-to-goodness machinist's level in the "aircraft manufacturing complex". LOL!
 
David-aviator said:
Bob,

If its any help or consolation, I found the wing to spar fitting so accurate all this leveling process was not necessary. The left to right angle of incidence was within a quarter degree and also in agreement with the longerons, no adjustment at the aft spar was necessary.

The airplane flies well except I need rudder trim for the wide speed range of the machine.
Click to expand...

I'm pretty much finding that too but these digital levels just taunt those of us with a little OCD. I swear, I spent two hours before work this morning just going from one side to the other and making the same measurement over and over and over again. Why? Because they were off by 0.1 degree.

Do you know what I learned today. I learned that if you slip one of those stainless steel 6" rulers under the back of a smart level, it will change the reading by 0.1 degree.

But there are now bigger fish to fry. Just for the heck of it, I checked the height of the right side of the HS above the ground, then checked the height of the left side of the HS above the ground, and it's about a 1/2" difference. Geez. I never liked that HS. Back when I was building in the garage and the thing was on sawhorses, all of these measurements and such added up. Badly made HS? twist in the fuse? Geez, who knows.

At this point, I'm warming to the idea of just finishing the darned thing, sticking 'er in the air, and seeing what happens.
 
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What Mel said....

Mel said:
...... These airplanes are closer to tractors than watches. Many, many RVs have been built with bubble levels which could not achieve that kind of tolerance.
Click to expand...

...and Bob, Ive seen RV's with one elevator with the entire counterweight above the stab while the other was level and the guy said it flies great! Others have the right stab an inch further back than the left...yeah. it flies great!

I've seen leaning vertical fins when viewed from the front...the guy said it flies great during aerobatics and anything else:) go figure..

Best,
 
Bob Collins said:
I'm pretty much finding that too but these digital But there are now bigger fish to fry. Just for the heck of it, I checked the height of the right side of the HS above the ground, then checked the height of the left side of the HS above the ground, and it's about a 1/2" difference.
Click to expand...


My HS was something like that, too. I did the math and ended up milling 0.005 or so off one of the shims to get it perfectly level. My hanger buddy, Vince, made fun of me for it. He was right to do so. :)
 
Bob Collins said:
Just for the heck of it, I checked the height of the right side of the HS above the ground, then checked the height of the left side of the HS above the ground, and it's about a 1/2" difference. Geez. I never liked that HS. Back when I was building in the garage and the thing was on sawhorses, all of these measurements and such added up. Badly made HS? twist in the fuse? Geez, who knows.
Click to expand...

Is the floor level? :)
 
Also keep in mind ...

..how many RVs (today with happy pilots!) were built over the years with nothing more than a bubble level for this process. some of our tools today are just TOO good at times.
I agree with someone above ... if you're within 0.1 degree ---- drill, baby, drill. :D
 
Beautiful!!!

Mel said:
Bob, If you have it within 0.1 degree, drill it. These airplanes are closer to tractors than watches.
Click to expand...

This is the truest statement regarding building a RV. It should a rule that you can't use a digital level.:p The rate of completions per year would increase dramatically if you only had to keep it between the lines of a bubble level.

If I remember someone checked a bubble level with a digital level and the difference between the lines was .4 degrees. Definitely in the ball park.

"Strive for Perfection, build for excellence."
 
Flying Scotsman said:
Thank GOD we don't have a real, honest-to-goodness machinist's level in the "aircraft manufacturing complex". LOL!
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I did have a machinists level in the hangar. Not only that, but also a hangar partner who happens to be a professional surveyor. Talk about OCD. But consider this: when we did the deed, we were experiencing 40 degree temperature swings from night to day (we did the final fit & drill late at night) at KDWA. Guess what happened to the measurements the next afternoon when we checked them?
 
don't keep me in suspense.....

What happened the next day after 40 degree temperature swing?
 
.3 degrees difference in the longerons? Can't get closer than .1 degree? Bob, I hate to say it, but you should start all over.

Seriously, I would guess you are using a digital protractor. You might do a calibration on it as turning it 180 degrees (the easiest way to work, side to side) often can show a slight error. Also, check the wings at multiple locations as there will be slight differences. As Mel said, use the average. I have been told that even .5 degrees will fly straight and true, but I wouldn't try it. Do your very best here. See you at OSH...

Bob Kelly
 
WenEng said:
What happened the next day after 40 degree temperature swing?
Click to expand...

Lots of big aluminum parts moving in different directions due to thermal expansion. Whereas the angular difference from side to side was unmeasurable the night before, it was like, oh, 0.15 degrees the next afternoon. I had to tell my OCD hangar partner to step away from the level :D
 
Bubbles... digital?

I used a laser level more than once. It works beautifully along the canopy rails (or rivet line), and even side to side on the engine mount bolts or firewall rivet lines.

Best investment I ever made too! (Borrowed it from my brother).

Don
 
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