Plastic sheet/strip

Big Ed

N50247 - '79 Super D
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I've got a couple of spots where cables and control hardware are cutting thru the belly fabric from the inside. I'd like to cement a strip of thin plastic or poly to the inside of the fabric as a sacrificial surface at hotspots.

What kind of plastic are inspection rings made of? Is that material available in sheet form? Is there another suitable material that might be commonly available?
PXL_20210628_183355067.jpg
 

Big Ed

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Looks like inspection rings are typically made of cellulose acetate butyrate (CAB). ACS has sheets but they are large and expensive. Looking for other sources.
 

kubark42

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Delrin is a great low-friction, high-wear plastic. Any kind of HDPE is also good and low-friction. Neither of them glue very well, though.

You could also build a chafe guard by simply doubling up with some extra dacron. My understanding is that the goal is not to prevent wear so much as to slow wear down to the point that the chafe protection outlives the fabric elsewhere. At this point, anything light will do. Heck, you might even try a small scrap of formica, as the paper-based backside allows it to be glued and the kitchen-facing front-side is very, very high wearing.
 

Big Ed

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You could also build a chafe guard by simply doubling up with some extra dacron.
That is what I did as an interim measure over the weekend. Glued a double strip of Ceconite 101 heavy duty fabric to the backside. That should last at least a few months while I look for something better. After researching, I think CAB is probably the right material. Just need to find a decent source for small quantities. Maybe at Oshkosh?

At some point in the past, someone glued glass cloth to the inside for the same purpose. Not sure how long ago, but it was cut completely through on the rear area. Proper tensioning of the cables should help, BUT ... when I pulled the cables tight, it did not raise them up off the fabric. Am quite certain that pulling G's is going to press the cables hard against the fabric.

PXL_20210628_003611668.jpg

PXL_20210628_003611668 (1).jpg

The worst spot is directly under the torque tube casting. That makes direct contact with the fabric and cuts into it every time the torque tube is rolled.

torque tube casting.PNG
 

Hiperbiper

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Ed,
When tensioned properly the cables (if they are routed correctly) shouldn't ever come into contact with or abraid the belly fabric. At least I've never seen it. And I'd like to think as long as this airframe has been in production something like this would have been identified and fixed...
Chris
 

Big Ed

N50247 - '79 Super D
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Ed,
When tensioned properly the cables (if they are routed correctly) shouldn't ever come into contact with or abraid the belly fabric. At least I've never seen it. And I'd like to think as long as this airframe has been in production something like this would have been identified and fixed...
Chris
The cables are properly tensioned and routed. We checked both today.

Possibly the belly stringers are bowed in a bit between the tabs. It doesn't look that way, but I did not put a straight edge to it to check. Wouldn't be able to do much about it.
 

Joe

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Best solution cure what ever is causing them to touch the fabric. Plan B glue down a strip of leather, if you can get a good bond to the fabric.
 

Bob Turner

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Actually, I think the plastic is a good idea. Try a model train shop. It comes in sheets. And Super Seam will probably hold it forever.
Agree, though - better to build up the stringers so the fabric clears.
 

Big Ed

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So I got some insight from the factory on this during my visit. It is a common problem on the Bellanca aircraft. So much so that they sell a wooden spacer that slides under the center belly stringer to increase the distance between the fabric and cables. Here is the technical drawing:

PXL_20210728_155713709 (2).jpg
 

Bartman

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Interesting. Did they say what they've done to new planes to keep it from happening?

I've been working around that area the last couple of days, this thread keeps coming to mind so I'm checking and double checking as things are coming together.
 

Big Ed

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Interesting. Did they say what they've done to new planes to keep it from happening?

I've been working around that area the last couple of days, this thread keeps coming to mind so I'm checking and double checking as things are coming together.
He explained why it is not a problem now, but I don't recall what the explanation was. I think maybe the stringer tabs are longer to accommodate the larger pulleys they use now.

Yes, my fabric is original.
 

Bartman

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spoke to Dale about this today with questions about the belly stringers. like you said Ed, they make the standoffs longer now so the same stringers can be used and hold the fabric down away from the pulleys and cables. I've fitting my stringers and there is only about 1/8" between the cables and where the fabric will be just aft of the second pair of pulleys.