Flying wire attachment methods

[b7gwap]

I had a question for anyone who owns, has built/designed, or knows about tube spars and how the flying and landing wires attach to these spars on part 103 aircraft, specifically two-spar designs à la Quicksilver etc, where there are compression struts joining the spars fore and aft. I've been studying Mike Sandlin's basic ultralight glider drawings, and noticed that on almost all of the designs he uses an AN4 bolt positioned vertically through the spars, with a tang, thimble and swage for the flying wires. From what I've picked up from Raymer and my statics and strengths class, removing material from the top and bottom of a beam is not ideal, that it would be better to drill this hole horizontally to put it nearer the neutral axis. I've been trying to get pictures or diagrams of other successful types that use similar construction techniques, but this is proving difficult. It looks like on some quicksilvers the bolts are installed this way, with the tangs fastened under the bolt head on the leading edge of the front tube, but I can't be sure. If this is so, couldn't this introduce a torsion load onto the spar, and a bending load across the joint between the compression strut and the saddle? Are bolts better in tension or shear? It seems like Mike'e designs haven't had any issues as designed, so maybe I'm overthinking this. Any thoughts?

 

[b7gwap]

 

[Dana]

 

[b7gwap]

 

[Dana]

 

[PTAirco]

 

[Matt G.]

 

[TJay]

 

[Joe Fisher]

 

[b7gwap]

 

[Matt G.]

 

[PTAirco]

 

[Matt G.]

 

[Dana]

 

[PTAirco]