Butt Rib install problem

[Flyboy66]

According to the KF manual, the #1 rib is supposed to be placed 35 1/2" inboard of the #3 rib (center to center, no wing sweep). When I do this, the butt rib, if it would fit, would cover 1/2 of the rear spar pin, and forward spar pin.



I am inclined to move the #1 rib outboard just enough the the butt rib will clear the pins with just enough room to get a socket on the rear pin. The problem with that is that the fuel tanks might be 1/4" wider than the gap that it is supposed to fit into if I do this. My right tank is 34.5" wide at it widest, and the left is 34.125 at its widest. The edge trim job on the fuel tanks isn't strait, and I would like to trim off a little of the edge of the tanks (maybe 1/8th inch each side) to allow the #1 rib to be moved outboard enough to accommodate the Butt Rib.


I measured #3 rib location on both wings and it appears to be correct, so I dont understand why #1 rib cant be placed where it is supposed to be and not have the Butt Rib over the spar pins.

[avidflyer]

Not sure if I'm following you completely, but the spacing has to be right for the flaperon hinges to have something to rivet to. JImChuk

[aviator79]

I would take pictures and contact the factory on this one before you do anything you can't easily undo. As JimChuk said, the spacing is not arbitrary, and an 1/8" off on the rib position may prevent you from being able to rivet the flaperon brackets to the ribs. The hinges have some float, but my #1 and butt ribs were done at the factory and it still took some work to get the flaperon hinges to all align at the same time.

[Flyboy66]

Jim,

I am at the dentist office and don’t have my manual with me.

I believe I am supposed to install rib #1 thirty five and a half inches (center to center) inboard of Rib3, Then I am supposed to locate the Butt Rib inboard of that with a 1/16th inch gap between the two ribs. The problem with that is the butt rib cap strip would have to cover about 1/2 of the spar pin head that holds the wing spar on the spar lugs. So, it is impossible to slide the butt rib where it needs to go without cutting a notch in the cap strip and possibly the Butt Rib webbing.

Is that clear now? If not I can try to take a picture and email it to you.

[jmodguy]

Do NOT move the #1 rib position from the plans. This rib supports a hinge point. I sanded a notch in my butt rib with a dremel tool. This makes the rear spar bolt easy to insert. It will eventually be covered by the skylight.

[Flyboy66]

Do NOT move the #1 rib position from the plans. This rib supports a hinge point. I sanded a notch in my butt rib with a dremel tool. This makes the rear spar bolt easy to insert. It will eventually be covered by the skylight.

Do you have a picture of yours?

I would like to see how the Butt Ribs look installed, so anyone feel free to post a picture.

[Dave S]

Steve,


On our early S7 - I trimmed the capstrip by the rear spar to provide relief for the bolt. If I recall correctly, the front capstrip didn't interfere with the pin; however, my buttribs were made a few years ago and may have had a slightly different length on the capstrips.


The buttrib is not structural to the wing and a little trimming isn't a problem and won't affect the windscreen mounting. As others have mentioned - location of of the wing ribs is very critical.


Sorry, no photos over here of this.

[aviator79]

These are the best I have. I'd take some for you right now, but they are masked off for paint. I think trimming the butt ribs is the way to go.

[avidflyer]

I think I understand what your problem is now. First of all, the inboard rib on the wing (#1) should go where it's supposed to go so the flaperon hinges work out. No problem trimming off some of the butt rib cap strip ends so the bolts clear. Your windshield attaches to the butt rib, but if the last 1/2" of the cap strip isn't there, that should be no problem. JImChuk

[Flyboy66]

These are the best I have. I'd take some for you right now, but they are masked off for paint. I think trimming the butt ribs is the way to go.

I know this is a personal question, but do you have a problem? It appears that you might have a clamp addiction. Not being judgemental, just looking out for you.