New Butt Rib

[astjp2]

Re: New Butt Rib

Look at the rib, here is the website!

http://www.de-aircraft.com/partsgallery.html#03

[TimHicks]

Re: New Butt Rib

Tim,
Here is a picture of how an original pre-war wing was done that may help--From the picture of your built up rib you need to add more support for the section between the spars to keep it from warping when shrinking the fabric-but not the broom handles--ugh. Something you might check is to make sure the screws that go into the spars for the supports still tighten---if not a mixture of fiberglass resin and saw dust to fill the holes and screw into that works well.

Buell, Thanks for the excellent picture. It's great to see how it was originally done. I can see the u-channel braces. But my wing has been retrofit with a fuel tank. And I intend to keep the fuel tank. That precludes my using these braces between the spars (where the fuel tank is). Does that mean that I can't get a built-up rib to work with the fuel tank? I should just order two new stamped (box section) butt ribs from D&E?

[Hank Jarrett]

Re: New Butt Rib

Tim,
look again at Buell's picture. There is triangular piece of aluminum riveted to the top and bottom of the root rib to stiffen it against deflection towards the tank. If you have a built up rib you have to either use the U channels without the tank or the triangles with it. I can't see it but I imagine there is a spacer or aluminum channel under the triangles to keep them from deflecting towards the tank when the fabric tries to pull the root rib in. The fabric would prevent them from deflecting up but if you need the channel to stop down deflection it would work for up too.
I can't see any reason you couldn't use a post war double rib, IF your IA will sign it off. You may have to put a 337 in to make the modification. I would NOT use a post war rib unless he signs off on it. It isn't dangerous to make the change, but your plane would be out of conformity and that is all an insurance company would need to deny coverage, even if the rib had nothing to do with an accident.
I wish I could get to my 41 and look at the RH wing. It has a wing tank, but the root rib has a noticeable bow away from the fuselage, so I suspect it does NOT have the stiffener correct.
Hank

[TimHicks]

Re: New Butt Rib

Yeah, I think that this is what I'll do. If you'll look at my third post in this thread, you'll see that my right wing, the one with the built-up butt rib, has the sheet-aluminum stiffeners and the fuel tank. I'll attach a picture from another angle below.
I didn't notice any bow in either butt rib when there was fabric (there maybe was some, but not so pronounced that I noticed). I'll see if I can find a pic to demonstrate this.

So my current plan is to leave the right wing as it is (built-up rib with triangular aluminum strongbacks), and replace the stamped rib (not box section) that came out of the left wing with the new built-up rib from Mr Larsen and add the same type of strongbacks to that rib.

[astjp2]

Re: New Butt Rib

SNAP! thats what you will hear when you get the fabric tight!

[TimHicks]

Re: New Butt Rib

It sounds like you're speaking from experience, Tim.
Tell us, please, the specifics about what happened.

[astjp2]

Re: New Butt Rib

Yep, had both ribs go snap when tightening the fabric, I did have the reinforcements and they still broke. That is why I suggested using the D&E ribs. Tim

[Buell Powell]

Re: New Butt Rib

Tim,
As best I can remember on my 41-I have wood spacers taped between the vert cap strip supports on the ribs and compression struts to add some support also. Another thing I think helps is when you start heat shrinking the fabric-do the initial shrinking on both sides of the wing and covering over the ends of the butt ribs before the final setting @ pull everything evenly to keep from putting to much stress on one part of the rib at a time--especially the cap strips.