Extra Top Inboard Wing Stiffeners

[acpilot]

I am planning to back rivet some extra wing stiffeners (extra J-Channel) under the wing top skins in the 2 cavities outside the wing walk On each wing. My thinking is they will provide some strength in case myself or someone else mistakenly step off the wing walk area. Hopefully will prevent a dent etc. Curious is any other builders have tried this, or is it just over kill.

 

[BobTurner]

I am planning to back rivet some extra wing stiffeners (extra J-Channel) under the wing top skins in the 2 cavities outside the wing walk On each wing. My thinking is they will provide some strength in case myself or someone else mistakenly step off the wing walk area. Hopefully will prevent a dent etc. Curious is any other builders have tried this, or is it just over kill.

My opinion - no data - is that the area outside the reinforced wing walk area is strong enough that an occasional mis-step there will not leave a dent. Just avoid making it a habit. I do, however, ban stiletto high heels from the wing, anywhere and everywhere.

 

[Ralph Inkster]

I agree with Bob. The more likely type of damage would be scuffing the paint beyond the wing walk area.
The real area of concern to deal with is the trailing edge/rear spar area, if passengers step there, there is potential of either bending the skin or over time causing a crack in between the rivets along the rear spar (I have delt with both!)

 

[acpilot]

Thanks for all the info. I did fabricate 2 stiffeners for each cavity adjacent to the wing walk area And will install them. Kinda over kill I guess but maybe will save me someday.

 

[RotaVR]

I agree with Bob. The more likely type of damage would be scuffing the paint beyond the wing walk area.
The real area of concern to deal with is the trailing edge/rear spar area, if passengers step there, there is potential of either bending the skin or over time causing a crack in between the rivets along the rear spar (I have delt with both!)

Ralph,
Other than stop drilling how did you deal with the skin crack between rivets along rear spar as mentioned above? I have almost the same on my -4 except just forward of the rear spar and just outboard of the wing walk reinforced area. Possibly caused by over 30 yrs of engress / egress? Thank You, Steve.

 

[Ralph Inkster]

Advised by Vans to replace that skin, which we did.

 

[dmn056]

Putting an unsupported stiffener in the middle of a large flat panel significantly changes it's vibration characteristics, and can cause cracks to develop near the ends of the stiffener. If you really want the stiffener there, you could look at tying its ends to the adjacent ribs.

 

[planenutz]

Of course if somebody DID stand on that area and they were sufficiently heavy enough to deflect the skin inwards, they would also bend and stretch your stiffeners. And that would cause a more permanent problem than the original skin just deflecting in and back out again.

Personally I think you've got a solution looking for a problem that doesn't exist. More weight, more complication. More build time. Potential downstream problems. So that would be a "no" from me.

Put a wing walk strip on the wing in the appropriate area and brief your passengers if you're concerned about it. The big black rubber strip seems a natural place to step for anyone with common sence and I've never had anyone take it upon themselves to wander off into the void. Ever.

 

[acpilot]

Thank you again for the feedback. I have already put them on the 1st cavity beside the wing walk doublers on the left wing. I saw a fellow builder online do it and thought it might be a good idea. My thought was that the tanks have many stiffeners like this so I couldn’t hurt, however, after reading the various concerns I will probably not do them on the right wing. I can’t close my wings until my Canada MD-RA inspection, so I will make a point to ask the inspector. I am not too concerned with structural integrity but will also email Vans with pictures and ask their opinion on it. Worst case gotta buy a new inboard top skin.