Looking for best way to level airplane.

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poormansairforce

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I am afraid to say anything anymore, so just silent picture…

View attachment 112097
My reply wasn't directed at you, just this thread in general and all in good humor.

You've got it. You only need 1 template and it doesn't even need to be an airfoil. It just needs to sit on the wing in the same position with identical reference marks across the front and back. Doesn't matter where, they are just for reference. Clamp the tube to the template edge and let the water settle and take your measurements at the wall mark and the template and do the math.

Make sure to measure on a vertical line and to the same location/corner of your template to allow for the dihedral tilting your template. The clamp should be weak enough so it doesn't collapse the tube completely. A couple of finish nails spaced correctly would work as well. Your template could be as simple as a 5' 2x4 screwed to a 6" 2x4 forming an L. The small leg points down and aligns with the rear edge of the wing right in front of the aileron. Measure to the top of the 5' 2x4 in all locations. Have fun!
 
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FinnFlyer

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My takeaway from Bill's long post is that having one end of the tube fixed on the wall is not useful. As you move the tube around the volume containing the water will change. Yes, water will always be at same height at both ends, but height relative to floor will change. Example, hold tube at one wingtip so water is level with that wingtip. Make a mark on the wall at water level. Move free end of tube to other wingtip so water is level with that wingtip. Now go look at the wall. Is the change in water level relative to the mark because wingtips are not level or because the tube was moved (volume containing the water changed)?

Note that Eugene's method (fixing end of tube on a wall) is different from the Egyptian method because the trough around the pyramid did not have a fixed point.

Maybe would work if you also mark the free end of the tube? I wouldn't trust it though.

When I leveled the wings on my RV-4 I used two tubes. Wingtip to wingtip and front/back of fuselage. Change in temperature, moving the tubes slightly, evaporation overnight, and water level changed and needed to recheck water level at all four ends.

Finn
 

Aerowerx

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.... the volume containing the water will change.......

Now go look at the wall. Is the change in water level relative to the mark because wingtips are not level or because the tube was moved (volume containing the water changed)?
The volume of water is constant (neglecting the minuscule evaporation).

One fundamental point that I haven't seen mentioned...

Is at least part of the tube resting on the floor at all times? If the entire length of tube is off the floor then, yes, the level relative to the mark will change. But if any part of the tube is on the floor then the level at the mark on the wall will not change.
 

Eugene

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Does it? Now move the tube back to the other wing.

(Perhaps I'm missing something here. Please enlighten me.)

Finn
Yes I did go back-and-forth many times from one wing to another. I also make sure that fuselage is still level at several different points from left to right. As far as I can tell my mission is accomplished here. And I am ready to start working on the struts.
 

Eugene

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The volume of water is constant (neglecting the minuscule evaporation).

One fundamental point that I haven't seen mentioned...

Is at least part of the tube resting on the floor at all times? If the entire length of tube is off the floor then, yes, the level relative to the mark will change. But if any part of the tube is on the floor then the level at the mark on the wall will not change.
I was trying to make sure that all of my tube is resting on the floor with two risers left and right vertical as possible
 

poormansairforce

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Does it? Now move the tube back to the other wing.

(Perhaps I'm missing something here. Please enlighten me.)

Finn
Yes, if you drop more tube onto the floor then the water level at the wall drops as well. This is why I mentioned measuring both points and subtracting the difference! Then you don't need to fuss forever with getting the water to the mark on a wall that you cannot see from 15' away! So, yes, you are still using the "Egyptian" method because water is still level (at least it was the last time I checked). We're not inventing anything new here no matter how many engineers weigh in on it.
 
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Eugene

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Well….
You could just use your iPhone.
Yes, I made a conclusion the difference between laser level and water level really really minimal. I was simply driving myself crazy in attempt of achieving perfection. That's my nature. Part of it was that laser line at the distance was not very sharp.
 
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BJC

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.Part of it was that laser line at the distance was not very sharp.
That is a big part of the challenges of high accuracy with most home shop laser levels. I experimented with shooting the laser through a pin hole to make the beam smaller, but it got to be a PITA. I use a water level to match two elevations. +/- 1/64" is realistic accuracy, which is much better than anything needed for an airframe.


BJC
 

dog

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Yes, I made a conclusion the difference between laser level and water level really really minimal. I was simply driving myself crazy in attempt of achieving perfection. That's my nature. Part of it was that laser line at the distance was not very sharp.
Thank you for the crazy,now I know more about
water levels and didnt have to do the crazy personaly on water levels ,instead using it on
trying to understand adhesive bonding of dissimilar materials.
I had wondered about the laser fuzzing, and once when building a bench for a metal band saw I leveled it with a laser and the fuzz was throwing me off ,so I set the laser just a bit lower until the laser fuzz would just kiss spots
along the top of the bench,could stand back in
the darkend room and see just a glint all along the bench top.
I realy like the idea of a water level with one fixed reference end and the free end to check
against,if the occasion required it would be possible to add any number of additional tubes.
 

wsimpso1

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Let's say you have the two ends of the tube even with each other, and the water level is 3 inches below the ends. If you lift one end up 1 inch the water will be 4 inches below that end, and only 2 inches below the other end. But the water level on/near both ends of the tube will be even with each other. The volume of water won't change.
Yes, the amount of liquid in the tube won't change. No the liquid will not be where you say - it will change to being 2-1/2" below the top of the fixed end of the tube. Let's try to imagine an example system. We have a back drop with a ruler marked from 0" to 12" and a tube with one open end at 10", the tube hangs down from there, turns around so the low spot is at 0" and then goes back up to an open end at 10". 10" down one side, 10" back up the other side 20" of tube. OK, there is some tube involved in making the turn, but it will be the same both at the beginning and after we move some stuff around. We fill the tube with fluid until the level on both sides is at 7".

Now we leave one end fixed and move the other end up one inch. The tube did not change length, so now the low spot of the tube is at 1/2" instead of at 0". We now have 9-1/2" of tube on the fixed side and 10-1/2" of tube on the moved side, so we still have 20" of tube. And we still have liquid 7" high starting at the bottom of the tube. But since we moved the bottom from 0" to 1/2", the liquid is now at 7-1/2".

We can for a more general explanation. If you have a constant diameter tube of any length and any shape below the top 4" with both ends open and even at 10", fill with liquid to put the level on both sides at 7", then leave one end fixed and move the other end up 1", that is the same as removing 1" of length of hose from the portion filled with liquid. The fluid that filled that one inch length is still present in the tube. Since the two ends must end up at the same level, that extra 1" is distributed equally to both sides, raising them each from 7" to 7-1/2".

Don't believe me? Go get a chunk of transparent hose, anchor one end with the open end up, fill the hose most of the way, hold the free end open end up with the ends together and mark the level. Then move the free end up slowly a full inch, and when the system settles down, note how much the water level moved and see if what your said fits with your empirical data...

Now, place one end of the tube so that the water level is 6 inches (for example) below one wing tip. It does not mater where the end of the tube is, so long as it is above the water level so the water doesn't spill. Take the other end of the tube to near the other wing tip. If the water is not 6 inches below the second wing tip then the dihedral is not even. It does not mater where the ends of the tube are, just the level of the water.

The level of the water will be the same at both ends of the tube, with respect to the center of the earth. The length of tube above that level is irrelevant.


Isn't that true?
Nope, if you reduce the volume of the filled part of the tube and keep the liquid amount the same, you will put that displaced volume on above the previous top. If you add volume in the filled area, the volume added will be filled with fluid from the top. Moving the end of the tube IS changing volume in the filled part of the tube...

Bill
 
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wsimpso1

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I am afraid to say anything anymore, so just silent picture…

View attachment 112097
Yes, and you have to measure or confirm the height at both ends for every check that you run, which can run into a lot of checking both ends if you are iterating through the level fuselage - adjust dihedral - adjust washout cycle a few times. It still works, it just gets tiring...
 

wsimpso1

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My takeaway from Bill's long post is that having one end of the tube fixed on the wall is not useful. As you move the tube around the volume containing the water will change. Yes, water will always be at same height at both ends, but height relative to floor will change. Example, hold tube at one wingtip so water is level with that wingtip. Make a mark on the wall at water level. Move free end of tube to other wingtip so water is level with that wingtip. Now go look at the wall. Is the change in water level relative to the mark because wingtips are not level or because the tube was moved (volume containing the water changed)?

Note that Eugene's method (fixing end of tube on a wall) is different from the Egyptian method because the trough around the pyramid did not have a fixed point.

Maybe would work if you also mark the free end of the tube? I wouldn't trust it though.

When I leveled the wings on my RV-4 I used two tubes. Wingtip to wingtip and front/back of fuselage. Change in temperature, moving the tubes slightly, evaporation overnight, and water level changed and needed to recheck water level at all four ends.

Finn
I said that using a single tube can work but I expect it to try your patience because for every measurement, you have to confirm the fixed end.

I too like multiple tubes with a tube at each end of every comparison you are making.

Building an RV4, FinnFlyer was not adjusting washout, that was set back when he assembled each wing. Structural skins lock that in...

Billski
 

Pops

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Just like a Geodetic wing. No adjusting for washout. It's like a sheeted wing with lots of lighting holes. What you build is what you get.
 

FinnFlyer

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But if any part of the tube is on the floor then the level at the mark on the wall will not change.
That has not been my experience.

Even with most of the tube flat on the floor, if I moved one end of the tube up or down, the water level at the other end also moved.

In any case, Eugene did go back and looked at the wall each time and compensated for it. So that works.

Just wanted to warn against assuming that the water level at the fixed end would stay the same.

Finn
 
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