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Rib stich or rivet

George,

Just wait until you you decide "it's time to recover". After you have removed the fabric and the Martin Clips, you will see what people mean!

As an aside, I have heard Clyde Smith, Jr. comment several times about the use of Martin Clips/screws/rivet's to attach fabric to Piper wings. In attaching the fabric this way, all the stress of the suction on the top of the wing is transmitted only to the cap-strip of the ribs as opposed to the entire rib with rib stitching going completely under the the rib. Piper NEVER approved any method other than rib-stitching for the original Piper ribs.

John Scott
 
another small problem with pop rivets is reveled in time when the reinforcing tape compresses, it allows the rivet to get loose, then migrates through the finish tapes. Started seeing it on Citabria's in the 70's, especially in the prop blast area. The "pull" of the air over the wing in flight is up, and with nothing but the heads of the "pop" rivets holding the airfoil in shape has always kind of bothered me. At least, the rib stitching keeps the complete rib in play. I know Aeronca series with screws, or rivets, Cessna's with their clips, Taylorcrafts with their Martin Clips and various other aircraft makes have all worked. But they are all light and relatively slow airplanes. You do not see any thing but rib stitching on the heavy or fast stuff.
Running at least six needles keeping the run around time down, I can average 5 to 5.5 hrs. on a cub size wing by myself. With help sending the needles back, stitch both wings in under 8 hrs.
 
No cracks anywhere? Then they are as safe with rib stitches as they were with the Martin strips - perhaps a lot safer, because the entire rib is bearing the load as was pointed out a while back.

That said, I would reduce the price of any Cub I was buying by the cost of a new set of ribs, if they had holes every two and a half inches. And new ribs are heavier, so a pox on those who messed up the original ribs.
 
Last I checked CC, American Champion, and Aviat all pop rivet. If you have stamped ribs that is the way to go. Truss ribs, I would stitch.
 
There are two points here 1) dynamic loads on covering/ribs during flight and how those loads are transmitted and 2) integrity of ribs after installation of Martin Clips.

I asked Clyde the question at Sentimental Journey and acquired a copy of his article in Cub Clues #121. To me it comes down to this: An engineer told Clyde that " ... %70 of the lift on a wing is done by the upper curved surface ...". If that is accurate in ALL attitudes (angle of attack and air speeds) then anything but rib stitching would not work. But this gets into the classic Newton vs. Bernoulli argument.

http://hyperphysics.phy-astr.gsu.edu/hbase/fluids/angatt.html

The other issue is rib integrity. This is addressed in the article " ... inspect the rib thoroughly for signs of elongated holes or any cracks emanating from the holes, and if none are found and your IA approves the pre-cover inspection, then continue to use them." It goes on to not recommend using the wire system again.

I am pursing the issue because I want to be safe but at the same time not feel the covering is going to come off or my ribs will collapse next time I fly. When I recover I will use rib stitching and reuse my original Piper ribs provided they are in good shape. If they are not I'll buy two $1013 PA-ll rib kits from UNIVAR and be done with it.

Thanks for the responses.
 
George,

I think the problem will become self evident when you remove the fabric and attempt to remove the clips from the ribs. I think this is when the majority of damage is done to the ribs.

You may want to go ahead and invest in a new set of ribs at today's prices instead of waiting for the inevitable increase. You can always sell the new set if you think your ribs are re-usable. :eek: :lol:

John Scott
 
Scott: Good point and one that has recurred on this thread and others. I need to search someone out who has removed clips.
 
A small pair of dikes to cut the wires or a small pair of needle nose pliers will keep from further damaging the ribs while removing the wires.
 
George said:
There are two points here 1) dynamic loads on covering/ribs during flight and how those loads are transmitted and 2) integrity of ribs after installation of Martin Clips.

I asked Clyde the question at Sentimental Journey and acquired a copy of his article in Cub Clues #121. To me it comes down to this: An engineer told Clyde that " ... %70 of the lift on a wing is done by the upper curved surface ...". If that is accurate in ALL attitudes (angle of attack and air speeds) then anything but rib stitching would not work. But this gets into the classic Newton vs. Bernoulli argument.

http://hyperphysics.phy-astr.gsu.edu/hbase/fluids/angatt.html

The other issue is rib integrity. This is addressed in the article " ... inspect the rib thoroughly for signs of elongated holes or any cracks emanating from the holes, and if none are found and your IA approves the pre-cover inspection, then continue to use them." It goes on to not recommend using the wire system again.

I am pursing the issue because I want to be safe but at the same time not feel the covering is going to come off or my ribs will collapse next time I fly. When I recover I will use rib stitching and reuse my original Piper ribs provided they are in good shape. If they are not I'll buy two $1013 PA-ll rib kits from UNIVAR and be done with it.

Thanks for the responses.
Click to expand...

George-

I have had several people tell me the way to go is a univair butt rib, and Dakota Cub for the rest of the ribs,FYI.

If it were my PA-11 I would probably just put my current wings up for sale, and buy brand new wings and cover them. It all comes down to what you plan on paying yourself or your IA to clean everything up, dissasemble/reassemble, you may come out close to equal with a new set of wings. Cub rebuilding is quite an economics lesson....

Tim
 
Learn something every day! Steve - your point about pop rivets and reinforcing strip collapse is well taken. Now I know why all the pops in the slipstream on the super D have cracks in the finish around them.

On the other hand, reinforcing tapes look to me like they have taken a giant step backwards in terms of strength and the ability to hold a shape. Even with pre-punching, we get wrinkles around the pop rivets. What we need is an STC for rib stitching on the Decathlons. I wonder what it would take? They ought to simply make it legal. Opinion.
 
My Cub has Schneider stamped ribs and the flanges were dimpled to make the rivets flush under the fabric. I have drilled them out twice and the ribs are no worse for it. Makes for a smooth wing.
 
behindpropellers said:
George said:
....... If they are not I'll buy two $1013 PA-ll rib kits from UNIVAR and be done with it.

Thanks for the responses.
Click to expand...

George-

I have had several people tell me the way to go is a univair butt rib, and Dakota Cub for the rest of the ribs,FYI.

If it were my PA-11 I would probably just put my current wings up for sale, and buy brand new wings and cover them. It all comes down to what you plan on paying yourself or your IA to clean everything up, dissasemble/reassemble, you may come out close to equal with a new set of wings. Cub rebuilding is quite an economics lesson....

Tim
Click to expand...

Yeah, much, much easier. I bought a Univair rib set for my -11 during my rebuild and have been very, very happy. I used the wing rivets, after first making sure they were easy to remove. They are.
 
rib stitching is not that bad!!!

Just got done doing my first wing and my 11 yr. old son was my best helper!!!! we took about 20 min per rib and got the wing done in 1 after noon he is so proud of himself and so am I...
I would be a rib stitching fan...hope to be back in the air next summer?
 
Steve Pierce said:
This has been discussed before but I can't find it at the moment. The problem I have had with pop rivets and screws is the next cover job. I also like the look of nice straight hidden rib stitches. It has been proven that the Piper truss rib is stronger when rib stitched. The whole rib is carrying the balloning effect of the fabric rather than just the cap strip. Call me old fashion but I like original Piper ribs and rib stitching.
Click to expand...

In my two wings I have one stamped rib, the weird one in the center of the tank bay, and the fabric is riveted on. I'm going to be so glad to be finished with this airplane and really know what I have. Too much cheese ball work to fix! Anyway, am I understanding correctly that because the fabric is riveted on the rib is ruined for recover? Do I just dremel them off? I've never seen fabric rivets before.
 
This is indeed an old thread.

Most Cubs with 18 gal tanks have just a doubled up capstrip under the tank. Carefully drill the rivets out, inspect it real good, then stitch it on recover. The tank goes in after covering. The load on that rib is minimal, except for slipstream vibration. It should hold unless the holes have serious cracks emanating.

In the last 15 years I have changed the way I stitch. I personally think that Stitts lady who speaks of the island, palm tree, rabbit approach describes the only way to attach fabric. She is easy to look at, and her method is truly easy to follow.

Like the original Seine knot, you need to review each time you stitch, unless you do a wing every month.

I just finished a Stearman wing. I have done quite a few Cub wings, but never a Stearman. It is a giant task. Cover the bottom, stitch the two inboard ribs, then cover the top. Even then, there are some tricks I was unaware of. Even the aileron cove gets stitched.
 
frequent_flyer said:
Take a look at any CubCrafters aircraft. Not a single stitch but hundreds of fabric rivets. I assume it's a lot quicker. Don't know of any downside except offending the purists.
Click to expand...

I suspect it is a pain to remove the rivets when it is time to recover. The vero beach supercubs all had rivets installed.
 
Depending on the aircraft, not all aircraft have the option of rivet vs stitching. Is stitching or rivets of fabric both approved on all Cubs?

Marty57
 
Rivets are not approved on Piper original ribs, nor should they be.

They are fine on Aeroncae. I doubt they are approved on Dakota, although they are on the Univair Cub ribs. Different design.

I have not seen the Staggerwing video - will look on a better computer.
 
Slightly different. That looks like a variant of two half hitches. The Stitts knot is apparently a genuine Seine knot. Fewer steps, I think.
 
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