Over the last week I deburred the primary structure (front/rear spars and ribs) on both wings. Important stuff, but boring…so no pictures.

The only thing worthy of note is the process I used to re-torque the fiber-lock nuts that hold both tiedown plates to the spars – one of the steps in getting the wings ready for leading edge and skin riveting. Until recently, I think most builders just used a torque wrench to snug those nuts in place without regard for the drag exerted by the self-locking feature of the nut. Overcoming that extra drag “uses up” some of the force applied by the wrench, so it’s important to add that extra ‘drag torque’ to the torque specified for the nut. That ensures that the nut itself gets enough torque.

So how do you figure out what that drag torque is? It’s easy…just set your torque wrench to the lowest possible value (1-2 in-lbs on mine) and see if the wrench will turn the nut. If it doesn’t, add torque in 1 in-lb increments until the nut moves…that’s the drag torque. For the batch of AN365 fiber-lock nuts I was using, that worked out to be 4-5 in-lbs – but your settings may vary. Adding that 4-5 in-lbs to the normal 20-25 in-lbs for the nut gives the proper torque setting. Easy!