water level

[sjt]

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Syringe was from tractor supply - probably for a horse. Whatever it was used for I would have run the other way.
a2.jpga3.jpgThe plunger keeps it from spilling while moving.


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For me the attach holes have a 1/2 inch offset referenced from main spar attach hole with a vertical plumb bob.

[Chewie]

Very nice! I just had a tube and clear water, yours shows up much better.
My plumb bob is at the same spot as yours right now.

[sjt]

I put that black washer there to emphasize the offset. The washer has a 1/2 inch radius.

[sjt]

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When I made my brackets, I match drilled an array of holes that could be used for supporting a string. This is the wing tip.


And this is the Root end with a string in the matching hole.

I am not sure if there is a real value in the string since there does not seem to be any angular relationsionship.
b1.jpgc1.jpgThe water level is used to set the wing tip height. Extra shims were required.

d1.jpg ​​​​​​I do not know if this has value but I check the string distance to the flange using a lathe bit. I clamped the wing tip down to hold angular rotation.

[sjt]

My plumb bob was just a check. The wing was built and riveted together on a table. The Rear spar was moved up 1.34 inches. When I moved the wing to the stand it was confirmation that the 1.34 number for wood spacers would produce the 1/2 inch offset.

My wing stand had level supports, and the plumb bob thru the main spar attach could not be at any other location other then 1/2 away from rear spar attach point.

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[geraldmorrissey]

I have about a hundred questions for you guys. I'm a couple of months behind you so I would appreciate lots of pictures. Maybe some with a more macro image. I'm kind of lost in the detail.
Gerry
Patrol #30

[Chewie]

Gerry I could maybe do a YouTube walk around and talk through my thoughts, although that might raise more questions than answers!

[sjt]

patrol 284

In regards to the mylar template, the main spar and rear spar are parallel. There is also another line on the drawing. That line is perpendicular to the spars, possibly, that line might be considered the cord line.

If you were building on a table, the main spar and rear spar must be perpendicular to the table. It is reasonable to let the main spar support it weight on the table and lock it down perpendicular to the table. You also want the rear spar to be perpendicular to the table. But you do not want the rear spar to support it weight on the table. You want the rear spar to be perpendicular and spaced up off of the table. So, the question is how much should the rear spar be spaced up. The line that is common to both spar lines is what I called the "cord line". You want that line to be parallel with the table.

The only way to get those spar lines perpendicular to table , and the common "cord line " to be square with both spar lines is to raise the rear spar.

You made two parallel sides on all of the center rib blanks because the mylar drawing has main spar and rear parallel.




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In this picture I have placed my mylar on the table. The lines that are the spars are vertical and at right angles to the table. The "cord line" is parallel to the table. The only way that this would work out is if you have blocks of wood under the rear spar to set the angle of the "cord line " to be parallel with table surfce.

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In this picture, you can see a 1/4 drill rod that I have spaced up with blocks of metal. One end of the 1/4 drill rod is going thru the main spar attach point. The drill rod goes thru the main spar attach point at right angles to the spar. The rod is carefully checked to be parallel with the surface of the table which is also level.

Although you can not see the end of the drill rod, I think I put a conical shape on it, The drill rod does not go thru the rear attach hole. The drill rod is perpendicular to all spars, and thru the main spar attach.
You shoud be able to perceive that the drill rod point is about 1/2 inch away from the rear attach point. The same thing will happen with the plumb bob when I transfer it to the vertical stand.


If you build on a table the pointie drill rod is your check that the rear spar is spaced up.
If you build with a vertical stand, the plumb bob is your check.

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I did a cad work up to show what this will look like on the table. The plumb bob in one of the previous pictures, is just a visual confirmation. For me, everything is riveted on table. There is nothing for me to do once i move it to the vertical stand. It either is 1/2 inch away from the rear attach or I have did not use the correct wood blocks.








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[sjt]

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Level "cord line"




Main spar at right angles to table

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Rear spar at right angles to table but spaced up 1.34 inches. The cord line "pointie drill rod" will be 1/2 inch away from rear attach.





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[sjt]

sjt (stan austin tx) p284


One further way of looking at it:

My center ribs have parallel Main Spar and Rear spar sides.

The rear spar has to be at the height (~1.34 patrol) .

My center ribs only require small notches at cap strips. I would never cut them shorter (with the exception of rib 8 main spar splice).

The cleco side clamps force the rib top flange to smoothly transistion to rear spar top flange.


Everything is parallel, The main and rear spars are parallel and at perpendicular to table.
The Center rib has parallel sides. The is only one freedom of motion. The rear spar has to be moved to match the top airfoil .

For my patrol and mylar that turns out to be a bunch of 1.34 blocks.

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[sjt]

And as an artifact of having raised rear spar up 1.34 inches, the main spar and rear spar attach holes are not concentric.


That is way the attach holes are usually made undersize and have to be match drilled to fuselage at a later date.

The patrol wing specification has a 2 degree cord line.
The patrol fuselage has concentric main and rear spar attach fittings angled up 3 degrees.
When the wing is hung on airplane it will be angled (3 -2 =1) degrees down relative to fuselage.

The aluminum 2024 attach fittings have to be made to fit the 4130 fuselage by match drilling 2024 to the 4130 fuselage.

I believe what happens is you have a level fuselage. Then you set the wing cord at 2 degrees, and then you try to make the purple hole concentric with the green fuselage hole.
The fuselage holes are already concetric and angled at 3 degrees. If you did not angle the wing down 1 degree (relative) then the cord line would be 3 degrees and not the 2 degrees it is supposed to be.

If one were to look at the fuselage fittings square on you should see a non concentric 2024 purple fitting - that is before it is drilled.
After drilling main and rear spar everyting will be concentric. You could put a drill rod thru all attach holes and the wing would be able to pivot about fuselage fittings.

At that point you would start working on the strut to lock in the dihedaral. The patrol has a 1 degree dihedral.
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