Looking for best way to level airplane.

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Aerowerx

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Seriously?!
Did you even read the post I was replying too??
"Take your clear tube and submerge many coils of it into a 5 gal bucket
of water ..."

You're telling me the laws of physics have changed and the level at the open end will not change as the ambient pressure changes?

Never mind. Don't see how Gregory's idea will work. A standard atmospheric pressure will support about 35' of water column, so unless you have a very deep basement to put the bucket in ... I doubt the alcohol will make that much of a difference.

Perhaps he omitted to mention taking the submerged end out of the bucket and fixing it at a suitable height?

Finn
He did not say that the bucket was hermetically sealed, like a barometer. Me, and I think most others, assumed that the bucket was open to the air.
 

Daleandee

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Only at HBA can there be so much discussion about how a water level works.


BJC
:wonder: True dat! I hadn't even looked at the thread until I seen it was FIVE pages and wondered what all the noise was about ...
 

Eugene

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Eugene,
The fixture should reference nicely on some fixed point on the foil, like the leading edge.

Billski
I was thinking about it some more. Only hard points on the wing I have is first 10% is leading edge, trailing edge, and wing tips about 6" wide. So, all they need to do is copy for 6 inches of trailing edge and for 6 inches of leading edge and connect them somehow. I am confused why do I have to make 4 sets of them? Why isn't one fixture not good enough to try in different places?
 

wsimpso1

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If you can figure out a way to do all this with less than four templates and four levels (eight ends), you go for it. You might even end up with six levels. Buy a bunch of really cheap plastic rulers to put behind each e

Me, I put a template on each root and tip, one level between root leading edges, one between tip leading edges, and one on each wingtip between leading and trailing edges. Then you can get the fuselage leveled, get dihedral close, get washout close and then iterate until it stops changing. And you can sight between template tops the check that roots are same tilt and tips are same tilt.
 

Geraldc

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Who would guess that this can be so complicated.
Anyone that follows this site.

To add to this.
I used a water level when I put an extension on a house before I took the outside wall away. Came out perfect.
Place I worked put a conveyor system up that had to line up with one on other side of a wall.With thousands of $ of equipment and engineers with big paychecks and egos there was a 4 inch difference in height when wall was removed.
 

Eugene

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If you can figure out a way - you go for it.
Our long discussion about "bucket system" did opened my eyes to the fact that one end of this tube could be fixed anyway and you will be walking around with another portable end of water tube.

I am planning to nail one fixed end to the wall and mark the level line. With another portable end I will be walking around airplane to compare the difference. So, only one end of the tube and only one fixture should work. I have a constant chord 1500 mm and constant NACA 4412 airfoil. So, no need for 4 or 6 same fixtures.

And yes, I will have to move my portable and up and down every time and look to the wall and make sure that my fixed end water level is on my fixed mark every time. That should work. I think.... And I can call it "Eugene's system".
 

TLAR

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So you drill a hole in the bucket, insert a tube bulkhead fitting, then attach tube.
Bucket height is a reference point.
Coiling a tube in a bucket is asking for air bubbles.
Place water in bucket with a little dish washing detergent added in.
No doubt you now have a accurate level
 

FinnFlyer

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He did not say that the bucket was hermetically sealed, like a barometer. Me, and I think most others, assumed that the bucket was open to the air.
I repent. See edit of post #77.
I guess I need to retake my basic physics classes :(

Finn
 

TLAR

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FinnFlyer
Sir no disrespect intended
I have years of experience building all kinds of projects for the Corps of Engineers, while employed by various contractors.
I don’t have any degrees, I have real world experience getting er done
 

Gregory Perkins

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So you drill a hole in the bucket, insert a tube bulkhead fitting, then attach tube.
Bucket height is a reference point.
Coiling a tube in a bucket is asking for air bubbles.
Place water in bucket with a little dish washing detergent added in.
No doubt you now have a accurate level
TLAR - Not trying to contradict but trying to help others avoid costly mistakes.
DO NOT use any kind of soap that could in any way form a bubble. If you find a soap that works better than alchohol let me know. There are many kinds of alchohols and any should work or any other water soluable solvent to break surface tension.

Coiling the tube is a much easier cheaper and faster way and more versatile than
bulkhead fittings which could work if you remember the reference is not the bucket height but is the water level in the bucket. The reason coiled tubing is more versatile
is you can put 500 feet in the bucket and only pull out how much you need.
Technique is key with eliminating bubbles. Take two feet of tube and push it down
to the bottom of the bucket as you coil it so that the AIR in the tube always pushes
up. With every new coil made you can see if you trapped a bubble and back up to fix it.
If there are remaining doubters, take 300 feet of tube to a lake that is 300 feet wide
and after filling the tube with water, hold the end of one end of the tube just exactly
level with the surface of the water. On the other bank, hold the other end of the tube
exactly level with the surface of the water. Now, lift both ends out of the water at
the same time exactly one foot. What happened to the water in the tube ?

Remember to add food color or equal so it is easy to see the water level in the tube.

Also remember the Egyptians used the same technique. They didnt have tubes.
They built gutters that were flooded with water around the entire pyramid.

Water levels always beat construction laser levels because they have a precision
accuracy quoted at something like a quarter inch per 100 feet etc. So at 1000
feet that is two and a half inches, ten thousand feet etc. . The water level can go for thousands of feet unless you have a giant solid iron meteror under the ground affecting gravity. Weird though not relevant, both ends of the Suez canal are
not the same re water level.
 

wsimpso1

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It looks to me like we need to review the physics of water levels, then we can get to practical reality.

If you have liquid of the same density throughout, and let it go static with only local atmospheric pressure above it, the liquid will be at the same height everywhere. Imagine a trough a hundred feet long, no wind, no flow into or out of the trough, the whole surface is at a constant height. Now add a clear plastic hose going from one end of the trough to the other, filled with water to just be even with the water in the trough at one end. Hold the tube steady and let the fluid settle down, and the other end will also be even with the liquid at its end. So far so good.

Now this chunk of tubing has a fixed amount of fluid in it. And we can know how much too. Pi/4*d^2*L, where r is inside radius of your tube, and L is length of tubing that is filled with water. No counting the amount not having liquid in it, just the part of the tube with liquid. So now you can know the height at one end if you also know the height at the other end. You gotta know the height at both ends. Why? Well, just hold both ends together in front of your eyes, note the fluid levels. Hold one end steady and slide the other end up a few inches. What happens to the absolute water level before you? It goes up by half the amount that you raised that one end. You just tried to decrease the volume of tube containing liquid, but since you still have the same amount of liquid as when you started, well, levels had to go somewhere. So, you must put a scale on both ends of the level and read them both. You can not just go walking around with one end fixed and the other in your hand. You must read height at both ends. You will probably need a way to fix the tubes at both ends you can set it up, and write down both readings every time you come back for that measurement.

Is there anything we can do about this? I know a way to reduce this effect. Coil the tubing in a larger container, then run one end out where you want to make the measurement. Let's say you have a 3/8" ID tube at one end and a 12" ID bucket at the other end, a 1" lift of the tube at one end will push 3/8^*1 = 0.11 in^3 of water back into the bucket. How much in a 12" bucket? About 0.001" change in the level in the bucket. This is just due to one end up or down and might be small enough that you will never worry over it. This works fine unless you start taking tubing out of the bucket or put some back in the bucket between measurements as was suggested. While a inch of tubing movement up or down is pretty small, if you start moving tube from the floor into the bucket, you raise the water level faster. Let's just say our 3/8" ID tube is 1/2" OD. Put a foot of tubing that size into the bucket from the floor and you just displaced 0.5^2*PI()/4*12" = 2.36in^3, which is 0.021" at the surface in the bucket... move 10' and it is 0.21". 48 feet moves water level a full inch. So, if you are going to use a bunch of tubing, you better have the same amount outside the bucket for all measurements OR you better take absolute level measurements each time you change anything. It gets to be a pain in the behind this way.

For airplane rigging, you have tip and root, leading and trailing edges on both wings. Eight spots that you have to visit after every little tweak. Why? because you WILL bump something... Let's follow the process. You set and confirm that the fuselage is leveled left-right and fore-aft. Then you measure the dihedral. Lower on one side than the other. So you get out the wrenches and make an adjustment to the length of the main strut. Now you are measuring dihedral at the leading edge because you can not read the water level inside the wing. So your main strut changes and your heights are a little different. If you think you have the dihedral corrected, you will want to check the fuselage is still level. Things like dismounting one end of a main strut tend to disturb things. Then you check dihedral again after resetting the fuselage, might take a couple cycles to get the fuselage straight and the dihedral about right and about the same on both sides.

Then you start adjusting the washout. This usually requires dismounting the drag strut, turning one or both rod ends some integer number of half turns and reinstalling it. Check the fuselage level, the dihedral, the washout. Make another adjustment to the dihedral, then to the washout, which requires a visit to all eight spots... And you keep repeating this until the numbers are all where you want them and are no longer changing. That is a lot of establishing zeros over and over or writing down the levels at each one...

Or you could just make four templates as identical as you can, stick little plastic rulers and a way to hold the end of the tubing on the front and back of each one, stick these marked templates on the root and tip or both wings, and hang tubes between the pertinent spots, then fill the tubes. By just taking a look at each of four miniscus at the root, you can see if the fuselage has been disturbed and can watch it as you fix it so you can see when you are back "ON" instead of making a bunch more measurement and adjust cycles.

Then you can make a washout adjustment and in four seconds you can check the fuselage and in another 10 seconds see how much the leading edge moved when you adjusted the trailing edge. Your measurement cycle for each adjustment goes from 10-15 minutes to less than a minute if you really disturbed nothing. You save even more time if you disturb something because you can watch the levels as you adjust things again.

You will still spend hours on it, but now, you will stop when it is as close to perfect as you can make it, instead of stopping when you get tired of playing with it.

There is one other improvement that might be possible. With water levels at leading and trailing edges, the heights you measure are couple together dihedral and washout, requiring quite a few cycles to get right. If you could get height measurements at the main and drag spars, it might require less iterations. If you can run the water levels to supports directly above or below the main and drag spars with rulers to give you how high the water is, this might work nicely. Or it might be sufficiently harder to get at to see and measure and thus make the task harder than just accepting the coupling of variables.

Make sense yet?

Bill
 

Aerowerx

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....
Hold one end steady and slide the other end up a few inches. What happens to the absolute water level before you? It goes up by half the amount that you raised that one end. You just tried to decrease the volume of tube containing liquid, but since you still have the same amount of liquid as when you started, well, levels had to go somewhere.
....
Huh?

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.

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?
 
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