N79FT A Skybolt Story

In "fuselage":

Fitting Lower Wings To The Fuse


On: Jun 17, 2014
In: 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 :)

Airplane!!!!

Airplane!!!!


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In "fuselage":

Lower Wing Fittings and Torque Tube


On: Jun 16, 2014
In: fuselage
Tags: CAD, fuselage, torque tube, control system, ailerons, elevator, lower wings, fittings

For starters, cleaned up the torque tube; added all the hardware (thanks cwilliamrose again for AN hardware models!) and proper mates. Was a nice warm-up, and came out real well.

Torque Tube, Cleaned Up with HW

Torque Tube, Cleaned Up with HW

After that, added the lower wing front fittings to the fuse. Piece of cake! :)

Lower wing front and gear rear fittings

Lower wing front and gear rear fittings

... and zoomed in.

... and zoomed in.

Notice on the above picture how they interfere with the tubes of the fuse truss (geometry penetrates one another). There are a couple ways to fix that; plans just call for 'trimming in place'. Note to self: figure out if the weld should only be around the bottom longeron; or if to weld the top of the fitting to the vertical too?

The cool thing about SW is that I can "cut" in place; add a bit of margin on the real pattern for the fitting, and make it to fit without constant trial and error.

And then, lower wing rear fitting.. that one is tricky due to the way it's dimensioned on the plans (it makes sense plan-wise, since it maintains clearances between longerons and spar butts, etc; so hole positioning takes metal thickness into the account). Can't believe it took me 2 hours and a few tries to figure out how to model this right. Learning curves be damned :)

Lower wing rear fitting

Lower wing rear fitting

Now, the reason for all that trouble is that getting the flat pattern out of that is just 1 mouse click!

Lower wing rear fitting

Lower wing rear fitting

I think this was a great day. :)


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In "fuselage":

Torque Tube Basics


On: Jun 15, 2014
In: fuselage
Tags: CAD, fuselage, torque tube, control system, ailerons, elevator

Started modeling just the very basics of the torque tube. The idea is to hang it on the fuse, attach the aileron pushrods to it, and check clearances in the wings (and finally get to start making them! :)).

Just a few screenshots today. Lots of time spent reading plans (haven't paid as much attention to Fuselage / Control Stick setup as I did to the wings).

Gladly, I had the truss model from way back when (I did it to learn SolidWorks Weldments feature).

Anyways, pretty pictures below.

Aileron Actuator Arm Sketch

Aileron Actuator Arm Sketch

... and model.

... and model.

Torque Tube Collar

Torque Tube Collar

Very basic model of the Torque Tube (but all I need right now, minus the aileron arms)

Very basic model of the Torque Tube (but all I need right now, minus the aileron arms)

Torque Tube on the Fuselage

Torque Tube on the Fuselage

And eyeball alignment check - fits!!! :)

And eyeball alignment check - fits!!! :)



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This construction log only shows how I did things during the construction of my Skybolt. These pages are for information and personal entertainment only and not to be construed as the only way, or even the perceived correct way of doing things. You are responsible for your own construction techniques.