Needs to be rib-stitched?

[Chubby_cubby]

Pre-flighting my Cubby, I noticed the fabric over my fuel tank was loose over the rib next to my tank.

The original builder did not rib-stitch the fabric to the wooden ribs, he glued the fabric to the ribs. My assumption was the glue had come loose; after pulling out the tank though, the rib came apart (see the pic) :-(.

Being a complete novice, I’m thinking the stitching not only holds the fabric to the ribs, but also binds the rib together, is that accurate?

 

[cubdriver2]

Being a complete novice, I’m thinking the stitching not only holds the fabric to the ribs, but also binds the rib together, is that accurate?

Bingo

Glenn

 

[55-PA18A]

What do the rest of your ribs look like?

 

[skywagon8a]

I hate to be the bearer of bad news.....that wing needs a very through looking over. If that joint came apart, what about the rest of the joints? It may be that just that one piece of wood split. What does the other wing look like? The rib stitching is only supposed to hold the fabric....nothing else.

 

[Chubby_cubby]

The rest of the ribs look fine… no issues in either wing.

 

[Chubby_cubby]

What do the rest of your ribs look like?

The rest of the ribs look fine.

 

[Skywalker]

Try to get a closer look at the side of the broken strip. Is the grain runout really as bad as it looks? Do all the ribs appear to be from the same wood?

 

[dgapilot]

Try to get a closer look at the side of the broken strip. Is the grain runout really as bad as it looks? Do all the ribs appear to be from the same wood?

Sure doesn't look like a 15 to 1 grain runout.

 

[Chubby_cubby]

No other rib (thus far) has separated.

I think to be safe - maybe I should consider adding some addition plywood glued to top and bottom of each rib? That may be more effective in binding the top and bottom together vs trying to go back and rib-stick the top to the bottom, since it appears the glue is stronger than the wood. Thoughts?

 

[skywagon8a]

Here is some reading material for wood repairs.

Repair of Wood Aircraft Components

aviation maintenance, aircraft engineering, MRO, FAA, EASA, aircraft systems, aviation training, safety, aerospace, aircraft repair, aviation career

www.aircraftsystemstech.com

Aircraft Wood and Structural Repair

Page topic: "Aircraft Wood and Structural Repair". Created by: Diane Cannon. Language: english.

www.readkong.com

What's that strip of unfinished spar next to the rib's vertical? Did the builder move the rib after varnishing the spar?

 

[Chubby_cubby]

Here is some reading material for wood repairs.

Repair of Wood Aircraft Components

aviation maintenance, aircraft engineering, MRO, FAA, EASA, aircraft systems, aviation training, safety, aerospace, aircraft repair, aviation career

www.aircraftsystemstech.com

Aircraft Wood and Structural Repair

Page topic: "Aircraft Wood and Structural Repair". Created by: Diane Cannon. Language: english.

www.readkong.com

What's that strip of unfinished spar next to the rib's vertical? Did the builder move the rib after varnishing the spar?

Unknown... that's the way it looked when I pulled the tank.

Thank you for the links! Something like this is exactly what I was thinking...

 

[Chubby_cubby]

Is there a 'best' place to order some Birch plywood?

 

[skywagon8a]

Here are a couple of sources. There may be others.

Aircraft Plywood (Aviation Grade Plywood) - Wicks Aircraft Parts

Aircraft plywood is produced by using glues of the thermosetting, synthetic resin type. The quality requirements for plywood to be used in aircraft are much more exacting than for industrial plywood in general. Aircraft plywood meets MIL-P-6070B. The mill specification requires that the plywood...

www.wicksaircraft.com

https://www.aircraftspruce.com/search/search.php?s=birch plywood

 

[Chubby_cubby]

Here are a couple of sources. There may be others.

Aircraft Plywood (Aviation Grade Plywood) - Wicks Aircraft Parts

Aircraft plywood is produced by using glues of the thermosetting, synthetic resin type. The quality requirements for plywood to be used in aircraft are much more exacting than for industrial plywood in general. Aircraft plywood meets MIL-P-6070B. The mill specification requires that the plywood...

www.wicksaircraft.com

https://www.aircraftspruce.com/search/search.php?s=birch plywood

Much appreciated

 

[skywagon8a]

By the way, the purpose of the tacks is to hold the plywood until the glue dries. They are not considered part of the structure. If you can clamp the parts until the glue dries, go for it.

 

[Chubby_cubby]

Quick update.

I replaced the small braces on partial rib that runs over the top of the tank and reinstalled everything. I haven’t flown it yet as I also needed to install a GDL-82 ADSB, new coax cables etc, while the plane was down.

I think what happened is the original builder didn’t wrap the wing fabric around the root rib; it was only glued up to the edge of that rib which allowed the fabric to, over time come up… when the fabric released at the root rib, that put pressure on the thin partial rib that runs over the top of the tank. Added to that, the nails in the brace for that partial rib split the wood grain, so it didn’t take much for it to come apart.

I’ve re-glued and taped the fabric on the root rib, with the tape wrapping around the root rib. I had implemented a similar repair on the other wing and it seems to hold.

I’ll update this thread after I take a few turns around the patch.

 

[stewartb]

In high lift situations, like at landing speeds, the lift is pulling the fabric up. Rib stitching holds it in place. Allowing it to balloon could alter the wing’s lift in ways you can’t control. Not good.

 

[Chubby_cubby]

I wanted to add a few additional pics of my ribs... The original builder did not rip-stitch the wings (he did stitch the horizontal stabilizers and elevators); instead for the wings he opted to glued wide strips (see pics) to the ribs - to then, glue the fabric to the strips - to give the fabric more surface area??? - seems to be holding well but....

Should I consider rib-stiching each rib 'now'... to update these wings?

 

[skywagon8a]

Once upon a time I was watching a Stearman sized biplane performing at the Sun N Fun flyin in Florida, when I noticed a piece of fabric flapping in the breeze near the upper left wing tip. A short time later that little piece became bigger. Then in another short period of time, all the fabric on the top of the upper wing had peeled back for the full wing span, standing up along the trialing edge. The plane quickly lost speed with the nose pitching up, followed by the pilot bailing out. Fortunately he was wearing a parachute. Do you wear a parachute when you fly?

Many years ago Steve Whitman (a famous old time race pilot) tried a new method of gluing the fabric on his wing. One day the fabric peeled off ending his and his wife's lives.

 

[Chubby_cubby]

Once upon a time I was watching a Stearman sized biplane performing at the Sun N Fun flyin in Florida, when I noticed a piece of fabric flapping in the breeze near the upper left wing tip. A short time later that little piece became bigger. Then in another short period of time, all the fabric on the top of the upper wing had peeled back for the full wing span, standing up along the trialing edge. The plane quickly lost speed with the nose pitching up, followed by the pilot bailing out. Fortunately he was wearing a parachute. Do you wear a parachute when you fly?

Many years ago Steve Whitman (a famous old time race pilot) tried a new method of gluing the fabric on his wing. One day the fabric peeled off ending his and his wife's lives.

So folks have rib-stitched wings in a similar situation as mine or they haven't....? Ok, to stitch over the wider strips glued to the top of each rib or not ok? Give me something productive if you have anything to offer...

 

[phdigger123]

Rib stitching will be time well spent that will give you many years of comfort as you fly.

 

[skywagon8a]

I would stitch that wing. Pay attention to whatever that flat section is so as to not make the stitching so tight as to bend or break it. Alternatively you could drill holes in that wide flat section for the stitching to be closer to the rib, though I don't think that is necessary.

 

[Chubby_cubby]

Thank you all for your input. To be explicit - you would stitch directly through the painted fabric.. then seal the stitches and repaint the wings? (they are both done in like fashion).

 

[skywagon8a]

Stitch directly through the current fabric. Look in AC 43.13-1B for the acceptable procedures. https://www.faa.gov/regulations_pol....cfm/go/document.information/documentID/99861 There are figures which will show you the process.

 

[stewartb]

If it were me? If the current fabric’s paint allows, I’d rib stitch and look at pre-painted Oratex tapes to cover the stitches. Or use Oratex strait edge tapes, mask, and paint in place. But having never used Oratex, maybe there’s a reason not to. I’d think it would work on a gloss polyurethane.

 

[Skywalker]

Hipec did some testing to prove that wide strips don't work any better than gluing to ribs. The fabric in the middle of a wide strip can't feel the tension. They made a test bay, top surface only, flipped it over and stood in it. (glued to ribs only) I built a wood wing for a fat ultralight (325 lbs) and used glue only on 1/4" ribs. Put 60 hours on it and quit while I was ahead.
I would drill. Tightening over a wide strip might twist it, trying to keep it flat on each and every stitch would take more time than just drilling.

 

[RaisedByWolves]

They fly pretty bad with one wing not rib stitched.

 

[Chubby_cubby]

Hipec did some testing to prove that wide strips don't work any better than gluing to ribs. The fabric in the middle of a wide strip can't feel the tension. They made a test bay, top surface only, flipped it over and stood in it. (glued to ribs only) I built a wood wing for a fat ultralight (325 lbs) and used glue only on 1/4" ribs. Put 60 hours on it and quit while I was ahead.
I would drill. Tightening over a wide strip might twist it, trying to keep it flat on each and every stitch would take more time than just drilling.

What do you mean by: ‘just drilling’?

 

[Skywalker]

Drill next to the rib so the stitching is conventional, right next to the rib.

 

[Chubby_cubby]

Drill next to the rib so the stitching is conventional, right next to the rib.

ok.. so get a bit the size of the stitching - not sure how I'll not hit a rib eventually - given the number of holes to drill where I can't see... probably should use a soldering iron first to cauterize the fabric hole?

Thanks for all your help by the way!