[Mhead]

I am finishing up the stiffeners for my -7 rudder and they are somewhat bowed similiar to the ribs in the stabilizers. I am tempted to flute them to make them sit flat on the skin. I searched the forums and only found a lot of discussion about oil canning, etc. Should I flute, or just back rivet them making sure they are pressed flat to the skin?

 

[jsharkey]

I am finishing up the stiffeners for my -7 rudder and they are somewhat bowed similiar to the ribs in the stabilizers. I am tempted to flute them to make them sit flat on the skin. I searched the forums and only found a lot of discussion about oil canning, etc. Should I flute, or just back rivet them making sure they are pressed flat to the skin?

Back rivet pressed flat to the skin. Fluting is generally only used to straighten any out of plane bow induced when you you bend a flange on a curved edge. The rudder siffeners are straight so any bow should be minimal after you rivet them down to the skin.

 

[mgomez]

No fluting should be required

I didn't need to flute mine. The rudder is straight, and the stiffeners can be used as they are.

 

[N787R]

No fluting should be needed

Normally no flutting is needed.
When I did mine, I made a mistake in cutting the stiffners in the right way thinking that the hole positions are all the same.
But they are not. That made me think that I have to do fluting to get the stiffners match the holes.

But I realized my mistake and had to order new stiffners and do it the correct way.

B

 

[scard]

If they are coming out a little bowed after dimpling, make sure you are dimpling hard enough. Too light of a dimpled row of holes will clearly curve the piece.

 

[rwarre]

At the same stage

I am also working on rudder stiffeners for my 7A and found that when I match/drilled the holes the alignment was off maybe 1/32 or less. A slight pull to one side lined them up.

 

[DaX]

I only flute if a row of holes isn't straight. You can hold a steel rule up to the bottom of a line of holes to check. The worst part so far had to be the top rudder tip rib - mine is heavily fluted.

My stiffeners had a slight slight bend in them, but I put 3 clecos in each (one on each end and one in the middle), and started at the center between clecos and worked outward toward the clecos. I have nice flat rudder skins.

 

[Mhead]

I back riveted the stiffeners on both skins this morning without fluting and they came out nice and straight. Thanks for the comments.