[79FT]: Building Things

Fitting Lower Wings To The Fuse

in search for missing bends

On: Jun 17, 2014
In: [Skybolt] Fuselage
Tags: CAD, fuselage, lower wings, fittings

Today, ended up messing around with putting the lower wing and the fuselage together...

Lower wings are set up at 1.5 degree incidence, 1.0 dihedral.

Started with that I realized that I mis-positioned the hole on the front spar and gear fitting. Simple fix :)

Next, came a lot of thinking and reading. Here's the problem.

The plans position fittings perpendicular to the longeron.

Fittings on the lower longeron

Fittings on the lower longeron

Holes are co-linear, and incidence is achieved because of the stagger in the attach holes on the spars. Airfoil chord, tilted up 1.5 degrees make these holes come together.

The problem is that spar sides then become non-coplanar with the fittings' faces; possibly introducing bad fit, play, misalignment, and whatever problems I can't think of.

Here's how the spars go 'into' the fittings. I circled the rear spar, since Ill use that for illustrating the problem.

Spars on fuse (rest of wing hidden from view not to obstruct

Spars on fuse (rest of wing hidden from view not to obstruct

Now, looking at it from the tip of the spar towards the fuselage, you can see the angle between the fitting and the spar. That's because of 1.5 degrees of incidence.

Angles don't match == no fit.

Angles don't match == no fit.

This problem caused about an hour and a half worth of research with no results...

Firebolt and Pitts plans explicitly state either bending, or welding fittings to longerons at correct angles. Not Skybolt though...

Ended up posting on the Forum. Let's see what the folks say....

On a more positive note; I can see an outline of an airplane in this now ;) Made some virtual, mental airplane noises :)



Don't forget to keep the blue side up.

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