Oratex STC Press Release

[TR Dunn]

Piper didn't design the truss rib, truss ribs have been around since the early days of flight but they were made of 1/4" wooden sticks. Piper just shorten the amount of time to build one out of wood and glue by riveting aluminum together. Granted the aluminum truss rib is stronger then the fragile wooden stick built ribs but no where as strong as a press stamped out aluminum rib

Glenn

In reality the truss design was in use long before flight. It was merely adopted into the realm of flight due to its strength to weight ratio. By "design" I infer engineered the truss type of construction for the required forces. If you believe Piper merely riveted some pieces together and hoped for the best, you are misinformed. These ribs are indeed engineered, in the sense that, do I dare say it, math was employed to meet a strength criterion. The topic is TRUSS construction, I have referenced no other design. However, since you opened the door, one can easily engineer a truss rib stronger than your referenced "stamped out aluminum rib", if strength were the only design criterion. TR

 

[Steve Pierce]

We had stripped an original factory built Piper PA18A with a 180 HP engine installed. Piper had cotton fabric strips wraped arround the top and bottom caps of the ribs and the ribs were hold straight by means of bracing tape. If you want, I can send you photos next Monday. The actual aircraft fabric was attached to the wraped arround cotton fabric strips with lacing chord.

That is inner rib bracing tape. It runs longitudinally from the top of one rib to the bottom of the next rib. It keeps the ribs straight until you stitch them.

 

[Steve Pierce]

We had stripped an original factory built Piper PA18A with a 180 HP engine installed. Piper had cotton fabric strips wraped arround the top and bottom caps of the ribs and the ribs were hold straight by means of bracing tape. If you want, I can send you photos next Monday. The actual aircraft fabric was attached to the wraped arround cotton fabric strips with lacing chord.

Or are you talking about the reinforcing tape that runs over the top of the fabric over the rib cap and the stitching is done over it?

 

[Steve Pierce]

You are perfectly right with what you say if you use the arround the rib stitching method, but if you rib stitch arround the top and bottom cap separately, the corrugated sharp edges can damage the lacing cord. Therefore rib stitching arround the rib is the method preferred by Piper ribs, but this method is not intended to make the ribs stronger. Piper did an excellent design job with these ribs, well-engineered, but looking at the labour costs, quite expensive to make.

I think the idea is that the truss is carrying the load, not just the cap strip.

 

[Steve Pierce]

Here is a photo album Lars sent me of the Oratex covering process using the cap strips. Very smooth since there are no rib stitches or tapes.

Oratex STC Capstrip

13 new items added to shared album

photos.app.goo.gl

 

[Steve Pierce]

Rick Papp covered his Carbon Cub in red Oratex early on and had some color issues. Oratex stepped up and sent a crew to Rick's place and recovered his airplane. It has been at Oshkosh several years. Here are pictures of it.

Rick Papp's Carbon Cub

6 new items added to shared album

photos.app.goo.gl

 

[Siegfried Lanitz]

The attached photo depicts what Siegfried is referring to on an original Piper truss rib. Photo is of our '54 PA-18A wings with original Piper factory spars and ribs that we shall cover in Oratex. I believe the point Siegfried is making (please correct me if I am mistaken, Siegfried) is the rib lacing was not considered as a structural member when Piper engineered the truss style rib. Two things going on here; Structural design of the truss style rib and the method of fabric attachment. Piper engineers made a truss style rib to withstand the forces with designed margins. They then used lacing cord to attach the fabric as the best method available at the time to protect the integrity of their design. Objective is to prevent the fabric from deviating from the airfoil shape. How its attached with the cord is irrelevant on structural strength of the rib truss. Cord was the go-to process as it is cheap and light and does not compromise the integrity of the caps as if hardware such as screws or rivets are used in the fabric attachment process, the penetration of the cap must be accounted for in the engineering of the truss. TR

View attachment 105044

Your comment hits exactly the point. I couldn't have said it any better. And this answers the key question of this thread: No, the rib stitching around the rib is NOT done to prevent the truss design from falling apart. It is only an attachment integration for the aircraft fabric, besides the original Piper technology to wrap cotton around the top and bottom caps and to stitch the fabric onto this cotton wrap. This process is documented in the two attached photos. We took the photos of a Piper PA18A, which Piper had exported as a factory new aircraft to Austria and hichi now the world's first certified Piper with the LANITZ AVIATION DESIGN CHANGE: PIPER UNSTITCHED.

 

[Steve Pierce]

Your comment hits exactly the point. I couldn't have said it any better. And this answers the key question of this thread: No, the rib stitching around the rib is NOT done to prevent the truss design from falling apart. It is only an attachment integration for the aircraft fabric, besides the original Piper technology to wrap cotton around the top and bottom caps and to stitch the fabric onto this cotton wrap. This process is documented in the two attached photos. We took the photos of a Piper PA18A, which Piper had exported as a factory new aircraft to Austria and hichi now the world's first certified Piper with the LANITZ AVIATION DESIGN CHANGE: PIPER UNSTITCHED.

I have never seen Piper do that. I have rebuilt 5 Super Cubs that have never been recovered and worked on several other tube and fabric Pipers that had factory covering and I have never seen this before nor is it in any of the covering drawings.

 

[thaefeli]

Siegfried, thanks for posting.
My question is about recovering.
What happens when an event happens (ground loop, hangar door event, etc) and you need to remove the fabric for structural repair and recover?
I have used your fabric glue and it is very strong. I can see the wooden strips failing before either glue bond and you will have a real mess of separated wood strips to deal with?
Tom

 

[dgapilot]

Your comment hits exactly the point. I couldn't have said it any better. And this answers the key question of this thread: No, the rib stitching around the rib is NOT done to prevent the truss design from falling apart. It is only an attachment integration for the aircraft fabric, besides the original Piper technology to wrap cotton around the top and bottom caps and to stitch the fabric onto this cotton wrap. This process is documented in the two attached photos. We took the photos of a Piper PA18A, which Piper had exported as a factory new aircraft to Austria and hichi now the world's first certified Piper with the LANITZ AVIATION DESIGN CHANGE: PIPER UNSTITCHED.

I've recovered several tube and fabric Pipers and have never seen or heard of Piper wrapping the cap strips like your picture shows. The Piper drawings for covering don't show that either. I suspect the wings that you uncovered that were done that way had been recovered by someone after the aircraft left the Piper factory. The only place where the stitching goes around the cap strip is the lower ribs in the tank bay areas, other than that the stitching goes top to bottom (or bottom to top depending on where you want your knots).

 

[rv6ator]

We just finished our Javron which is covered in Oratex 6000. We used traditional rib stitching methods and are pleased with the results. Even with the rib stitching the complete covering job was relatively quick with no issues.

 

[55-PA18A]

There was a question asked earlier in this thread that I haven’t seen addressed. What do you do when you need to repair or recover a wing using this method? If the cap strip is glued to the rib and the fabric is glued to the cap strip using glue that is as permanent as claimed, what do you do?

Rib stitching a wing isn’t that difficult nor does it take all that long. You’ll need to rib stitch the horizontals, elevators, and rudder anyway.

 

[supercub83a]

Paint stripper will remove the glue. Maybe some other chemicals as well.

 

[skukum12]

FYI, Lanitz and crew are at Oshkosh as I type. Due to the extreme time consumption during events such as these, responses to forum questions will inevitably be delayed.

 

[Farmboy]

I expect Jake Papp’s SuperCub is now there with a fresh covering on it. And looking good.