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Lower Wing Fittings vs. Incidence

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fidot

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Howdy, folks.

Doing some CAD trying to figure out lower wing to fuse attachment; and hitting a problem.

Lots of pictures below :)

Fittings drawn to plans have front and rear wing holes co-linear and concentric. Viewed from the firewall backwards:

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Also, the fittings are perpendicular to the longerons, and their centerline is parallel to the longeron:

attachment.php


This presents a problem with the incidence set. Spars, fittings, and plates will be at 1.5 degree (incidence) angle to the fittings. You can clearly see it here (this is the wing model mated to the fitting with most of the wing hidden for clarity. You're looking at the spar on the rear fitting only)

attachment.php


Obviously same problem on the front fitting.

This makes fittings' faces non-coplanar with the spars; *unless* those fittings are bent..

I have looked at Firebolt plans; and they bend the fittings.
Pitts has them attached at appropriate angles as well; so that fitting faces are coplanar.

Skybolt though has no mention of bending. Skybolt newsletters don't either; as doesn't a little supplement written by HFW.

How did you guys deal with this?

My thinking is:

- Weld front fittings at right angle
- Weld rear fitting at the tab that 'wraps' around lower longeron only
- Using spar stub clamped in between front fittings, bend just the tops of them 1.5 degrees back, ensuring that the gear leg attach holes' stay aligned with the lower longeron
- Using spar stub clamped between rear fitting tongues', bend it back 1.5 degrees
- Weld the rest of them ensuring proper angles
- Drill pilot holes
*** many years here ***
- Drill final holes with spars when fitting for initial rigging.

Ug.

Please pardon the images below; I don't seem to be able to figure out how to upload images and NOT have them show up at the bottom of the post; but just embed them into posts :(

1.JPG


2.jpg


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