1979 Decathlon Fabric Issues

H

Hoop4100

Member
Joined
Feb 11, 2025
Messages
5
Location
Aguadilla Puerto Rico
I need help with two fabric issues.

Issue 1

The belly skin is gone. while cleaning the aircraft for annual, I picked at some lose paint and an inspection hole fell out of the ground and took some of the nearby finishing tape with it. Pic enclosed. I want to replace the belly skin and have some ideas. has anybody done this.

Issue 2

The top of the wing white paint is chipping like crazy. The fabric seems to be in good enough shape. I plan to cut a sample out and test it for sure. But I’m considering whether it would be better to sand, silver and paint, or strip, clean, silver and pain. Pic also.

The fabric paint appear to be original. No log book entries about replacement. The owner has flown this airplane 300 hours over the past year and wants another year of two out of this fabric and 500 more hours. can I get it for him?!

Thank you for any advice!!

Dave
 

Attachments

  • IMG_9615.webp
    IMG_9615.webp
    141 KB · Views: 32
  • IMG_9613.webp
    IMG_9613.webp
    83.8 KB · Views: 32
Time for recover. problem is, if sunlight ever gets through those cracks and on the Dacron, it takes about three months for that Dacron to decompose into white powder.

On the belly - usually those cross pieces crack, and allow horrible vibration. Anchor them firmly, then recover. Use rib stitches, and wherever you make a fabric overlap, stitch with a curved needle.

Recovering is quick, compared to stripping and repainting. If there is no damage I can do a Cub wing in a weekend. Get yourself a battery powered pop rivet puller and you can shave almost a day off of what it tskes me.

Plus, look what you do to the value of the sircraft?
 
Identifying what covering system used on the Decathlon is the first step of repair. Once identified, you'll be using the correct fabric, glue, and topcoats.

Few manuals
Air-Tech https://airtechcoatings.com/wp-content/uploads/2018/08/AIR-TECH-Complete-Manual.pdf
Ceconite https://www.conaircraft.com/_files/ugd/d66f5e_9653c858211f4636b7d4fcbb4787e540.pdf
Stits/ Poly-Fiber https://www.conaircraft.com/_files/ugd/d66f5e_1ec5fa221f42471385a8ed2c97c69571.pdf
Stewart System (waterborne) https://stewartsystems.aero/wp-content/uploads/Rev-4-Procedure-Manual-July-2019-compressed-copy.pdf

Ceconite will have a blue or green tint on backside of fabric (viewed from within). Find a clean section.

Stits/ Poly-Fiber will have a pink tint on backside.

Cant speak to AirTech or Stewart system... although id say that looks like Ceconite.

If so, Section 6 in Ceconite manual would be a great reference for belly recover. A fabric to fabric glued seam is legal. Must be one inch overlap and over structure. Finishing tape over top of glued seam, then build stages of dope.

Id like to be optimistic and say spray rejuvenator on the tops of those wings, silver, then retopcoat... but I just did that to my ringwormed/cracked wings...and could not save them (similar looking wing). You would be time and money ahead to eat that recover.

thumbnail_IMG_4009.jpg
 
Last edited:
Bob Turner said:
Time for recover. problem is, if sunlight ever gets through those cracks and on the Dacron, it takes about three months for that Dacron to decompose into white powder.

On the belly - usually those cross pieces crack, and allow horrible vibration. Anchor them firmly, then recover. Use rib stitches, and wherever you make a fabric overlap, stitch with a curved needle.

Recovering is quick, compared to stripping and repainting. If there is no damage I can do a Cub wing in a weekend. Get yourself a battery powered pop rivet puller and you can shave almost a day off of what it tskes me.

Plus, look what you do to the value of the sircraft?
Click to expand...

that is fast work Bob..I assume you recovered the complete wing and you removed it from the airplane to do it?!

thank you..Dave
 
Chan Hughes said:
Identifying what covering system used on the Decathlon is the first step of repair. Once identified, you'll be using the correct fabric, glue, and topcoats.

Few manuals
Air-Tech https://airtechcoatings.com/wp-content/uploads/2018/08/AIR-TECH-Complete-Manual.pdf
Ceconite https://www.conaircraft.com/_files/ugd/d66f5e_9653c858211f4636b7d4fcbb4787e540.pdf
Stits/ Poly-Fiber https://www.conaircraft.com/_files/ugd/d66f5e_1ec5fa221f42471385a8ed2c97c69571.pdf
Stewart System (waterborne) https://stewartsystems.aero/wp-content/uploads/Rev-4-Procedure-Manual-July-2019-compressed-copy.pdf

Ceconite will have a blue or green tint on backside of fabric (viewed from within). Find a clean section.

Stits/ Poly-Fiber will have a pink tint on backside.

Cant speak to AirTech or Stewart system... although id say that looks like Ceconite.

If so, Section 6 in Ceconite manual would be a great reference for belly recover. A fabric to fabric glued seam is legal. Must be one inch overlap and over structure. Finishing tape over top of glued seam, then build stages of dope.

Id like to be optimistic and say spray rejuvenator on the tops of those wings, silver, then retopcoat... but I just did that to my ringwormed/cracked wings...and could not save them (similar looking wing). You would be time and money ahead to eat that recover.

View attachment 8160
Click to expand...

chan..so if it is Ceconite you would you cut back the fabric an inch or so longer from the fuselage tube on the bottom side corner and try and glue it to the tube first..then install the new fabric with a 1” minimum overlap onto the fuselage side and cover that with finishing tape?!
 
Bob Turner said:
A number of STC systems are approved for patches over anything. I believe Stewarts is one.
Click to expand...

yes it is..and there is some Stewart’s system stuff on the belly. Some repairs have been made and didn’t stick good enough. Probably because the lower skin is oily and didn’t get cleaned enough. Too bad I cannot install a metal belly like they use now. A much better idea!! Thank you
 
This is from my admittedly porous memory and I'll cheerfully accept correction if wrong; The Champion 7GCBA (Agricultural) was identical to the 7GCBC except for a metal belly and increased gross weight.

Would this possibly be a legal justification for a metal belly on other Citabrias?

Maybe this is a opportunity for an STC.
 
Well, if the rest of fuselage is showing similar flaking, poor adhesion of topcoat, and a saturated/contaminated base fabric...a recover is in store. If only the bottom is in poor shape, replacement of belly may be all you need. Ultimately the IA's call... as replacement of entire belly would be a major repair.

Appendix E in Ceconite manual deals with repairs
Appendix I in Stits/Poly fiber manual deals with repairs
(you need to know what is on the AC)

Lets say that decision is made and you only plan to replace belly, cutting out belly would be the start. 1/2 inch inboard of lower longerons along bottom. You would essentially glue new fabric to the old fabric with atleast 1 inch of overlap...New Super Seam glue for Ceconite system, Poly Tak for Stits/PolyFiber system. This overlap must be over structure (the L side and R side longerons). Finishing tape over top. Build dope layers.

The problem I foresee is stripping OLD fabric (colored dope) down to base fabric at the lower longerons (where you will be gluing old fabric to new).
Soaking that section with thinners, MEK, etc to get down to base fabric may loosen the glue joint of old fabric at the structure. No bueno.

I would recommend sanding old fabric in that section...not stripping. IF ceconite, can sand through colored butyrate and even into silver. Then glue new fabric direct to silver layer. I got this tip direct from an engineer at Consolidated Aircraft Coatings for making repairs. They hold the rights to Polyfiber, Ceconite, and Randolph coatings.

My recommendation is not gospel, take a lot of pics and share with other dope guys. Greg and Hualdo @ consolidated aircraft coatings are my go to.

Hope this helps!
 
Last edited:
Without checking I am going to guess that the metal belly has nothing to do with the gross weight increase, and that the increase is only for restricted category ag planes.

Yes - my "weekend" cover was a J3 wing, on sawhorses. Bare wing through first cost of silver. Rib stitching is eight hours. Pop rivets go faster.
 
A data point.....Stewarts does not require seems to be over structure. This would allow you to remove and replace the fabric area shown in the photograph in post #1. The Stewarts Manual is available free online. Below in italics is a cut/paste of "Glued Seams over open areas." text. Also, you may send Stewarts an email. I found they have good customer service. There is also a part of the manual caled "repairs" that Bob in post #4 referred to that calls out how to prep the existing fabric to receive the patch (repair fabric.)


Cemented overlap seams will have a glue width of at least 1”. This generally applies to areas such as glued seams on stabilizers, elevators, rudders, flaps, ailerons and longerons. Sewn seams are not necessary. Glued seams over open areas such as at transition of vertical fin to top of fuselage skin are permissible without a sewed seam. A minimum overlap seam of 1” is required with a minimum width of 2” finish tape centered over the edge of glued seam.
 
Without looking, I believe Stitts repairs can be done like that. Stitts did not approve open seams on the initial cover, but I assure you such seams are just as strong as Stewarts seams.
 
You must log in or register to reply here.
Back
Top