SonexBuilders.net

Hey guys, I wanted to get some advice on my Sonex. Last week I installed new landing gear and updated bolts. I used saw horses to rest the wings, and tail, and a engine lift on the motor mount. I had the saw horses to keep from damaging myself or the plane. The sawhorses were padded and directly under the spar. They did exactly what they were supposed to, because when I lowered the lift, it came down slightly faster than anticipated and the wings rested on the Sawhorses. This wasn't a violent maneauver and was slow. It just came down further than I wanted. When the wing came to rest I saw the skin move slightly on the inboard wing and heard it settle, but didn't see any dramatic flex of the wings. I lifted the plane up and inspected for deformation and rivets. I wouldn't imagine this caused any damage, i know stress tests are done in a similar way, but now im worried i damaged something internal. Should I inspect the plane and fly it, or should I consult outside and prepare to tear into my wings and have them replaced?

How far out on the wings were the sawhorses positioned?

About mid span by tie down hooks

buffmaintainer wrote:About mid span by tie down hooks

And how much weight do you think was on the wing? I imagine half the weight of the plane at most on each wing, probably less since you were also supporting the tail/engine? If so I'd say you're (very) far inside the envelope in terms of the spar handling the load through to the fuselage. My main concern would be at the contact points of the sawhorses to the wing, but even then the worst I could imagine is skin dimpling and/or a crushed rib, but only if contact was other than at the spar itself. I think you're close enough to the inspection plate to take a peek inside the wing around the point(s) of contact.

At max (6g) the wings are lifting well over a Ton worth of fuselage. I just can't imagine 350lbs mid-span on the main spar being remotely close to exceeding limits at the wing root. I might think differently if it happened near the wingtips due to the leverage/ flexing of the wing.

There's no discernable damage whatsoever. The wing never got a chance to flatten enough to even damage the skin or spar since the airfoil is symmetrical and im 100 percent confident the only contact point was the spar and the skin underneath. Ive spent hours going over the airframe and haven't seen anything indicating damage. I'll pull the panels and borescope just to be safe. I was reading Peter Ansons page where he took his sonex to 6Gs on a turbulence event and it smacked so hard that it put marks on the bottom of the spar tunnel. I did the calculations and my number came out to what you said. I figured the wings would have seen nowhere near 6gs of loading with the airplane empty. It didn't even have fuel in it. Ill double check and report back of I see anything.

Note that wings are meant to take loads spread out along the spar, not necessarily point-loads. You cannot simply talk about a wing’s G-rating and multiply that by the gross weight and say that such a load (or a specific fraction of that load) would be OK to apply at a certain point.

This is not to say that these wings were likely damaged. I just want people to understand the object they’re building and how it is intended to function. :-)

—Noel