Joggled Skin Repair Doubler

[hombre]

If you joggle an internal repair doubler up and over a stringer and pick up the existing stringer fasteners, are these fasteners ineffective?

Bruhn discusses joggled members, i.e. angles, and says a general rule of thumb is not to allow any axial load across the joggle. The required balancing load is not available except in the vertical leg and thus a loss of stiffness and strength results.

A joggled doubler obviously does not have a vertical leg, so the balancing load should be a moment that may be reacted by the fasteners. I cannot see in this instance how the row of fasteners across the joggle is completely ineffective as a colleague has told me.

Any thoughts?

 

[Sparweb]

It's as effective only as much as the deflections allow. A flat sheet stretches under load, and the rivets load up only enough to balance the forces and deflections simultaneously. A joggle present between two rivet rows would introduce a "large" deflection (large, that is, in proportion to all the other deflections). The rivets in the first row will be lightly loaded - just enough to make the deflection of the base sheet match the doubler's - and the second row would do all the work.


Steven Fahey, CET

 

[jetmaker]

Would not suggest a joggled doubler. Instead, use separate doublers to step over the padup.

jetmaker