Wing Assembly - Plumb bob at wing / fuselage attachment bolt holes

[sjt]

If you build on a table the holes just end up as indicated above.

If you built in a vertical jig , then the only difference is that you could not use a level like this:
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You could just slightly rotate wing in stand so that plumb bob appears to be co-linear. It would not be co-linear you just could not tell with the naked eye.
But you would not find the spars to be level as shown above.



Even though I built on a table, I could have mounted the wing such that a plumb bob would would "look" like it was concentric, But, then I could not have used the level as in the picture. The angle would be whatever it needed to be.


When a wing is riveted on a table it is not going to ever move when you put it in a vertical jig. - Except it could be skewed long way.

In the picture below you can make out a wood shim I use to skew the wing the long way
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Even when I used a plumb bob it was just to make sure the wing was not skewed the long way. I expected it to be off a 1/2 inch - I made a washer that was the correct diameter to use the plumb bob in the short direction.

[jaredyates]

If someone would like to write up a version of this for the Beartracks I think it would be a useful resource that we could point back to.

[Frank]

Screen Shot 2025-12-03 at 11.09.47 AM.png It's worth pointing out that building "horizontally on a table" and building "vertically in a jig" are not mutually exclusive!

It makes sense to attach center ribs to front and rear spars horizontally on the table, for support and accuracy.
The spars are well supported, clamped in place, and center rib attachments easily accessed.

It makes sense to then move this structure to the vertical jig, attach nose and rear ribs and prepare for skinning.
The wing structure is locked into place, straight plumb and level, and won't be moved again until the skin is on.

This is what I did and I thank Stan for his ideas and photos.
Also, this Bearhawk factory video demonstrates the two-step process.

https://www.youtube.com/watch?v=MZWF5GHO2is

[sjt]

n3uw (John Snap) made a table that I thought was a great idea.

I expanded on his idea and made a larger monstrosity :

m1.jpg
My son wrecked my car so as punishment I made him weld up a 100 1/2 inch nut plates that I used to cover the surface:

m2.jpg


I will never be able to pick up or move it but it is nice to use for building.

I laid out all the lines for the the wing in pencil on the top surface.

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I glued up a bunch of right angle brackets (thru away the ones that were not 90 degrees)
24.jpg I used the nutplates that cost one car to affix them to the table.

Other then a table saw I use a lot of rubber bands:

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