REPAIRING HEADLINERS

As if working on your side panelslast month wasn’t tedious enough,we now move on to headliners. I’m

amazed at how a company that had it soright could, in one year, get it so wrong.I’m referring to the headliner designchange introduced by Beech in the early1970s. I wonder if they consulted withthe mythical "sky is falling" characterChicken Little. Or maybe they took theline in The Graduate about getting intoplastic a little too seriously.

OLD HEADLINERS All kidding aside, we need to talk

about this large two-piece, semi-rigid,very temperature-sensitive headlinerused by Beech for about a decade.

Almost everyone who owns anaffected Bonanza, Baron, or even anoccasional Duke has experienced some(if not all) of the following problemsassociated with these unstable headliners:

1. Being nonthermal-setting, thematerial becomes quite soft in hotweather and over time will sag and pullaway from its mounting points, andassume a very distorted shape.

2. Twenty years of thermal activityresults in shrinkage, often causing a

pronounced gap between the forwardand aft sections of the two headlinerpanels.

3. In the first year this new headlin-er design was used, the window framesin the airplanes did not cover the edgesof the headliner where it met the topedges of the windshield and pilot andcopilot windows. When the materialdeforms and shrinks, it pulls away fromthese places, creating unsightly gapsand irregular edges.

4. Age also creates a cracking prob-lem, a result of the material becomingquite rigid and brittle as the plasticizersgas off.

5. As this headliner material loses itsshape, it puts stress on the adjoining non-thermal-setting plastic window trim,causing it to also deform. You've all seenthose wavy edges of the upper windowtrim where it meets the headliner in these’70s airplanes.

In all fairness to Beech, these prob-lems were not foreseeable at that time.Materials manufacturing companiesprobably didn’t know how time wouldaffect their products. Cost and weightdemands were bearing down hard on allaircraft manufacturers. It’s easy for usto analyze and second-guess things;after all, hindsight is 20/20.

As with many situations, time,skill, intuition and money can do morethan just fix problems; some things canactually be made better than new. Sograb your tools and let’s get started.

The first step is to get the headlinerpanels back to their designed or originalshape. What is bad about this headlinermaterial is also good. Being nonther-

mal-setting, heat can be used to makethe plastic foam-type material soft andsupple, allowing it to be remolded backto its original shape. The challenge hereis controlling that shape, and that meansmaking a mold or form.

Wood formers and plywood assem-bled into an arc shape identical to thecabin top works great. With the panelplaced on the wood form, heat isapplied with heat guns until the materi-al becomes soft. Then a sheet of .040"aluminum is form-pressed against theback side of the material, holding itevenly and firmly in place as the mate-rial cools and assumes its proper shape.

This process is repeated a section ata time until the entire panel is complete-ly reformed to be as it was when new.

Rolled-edge headliners—The very firstgeneration of headliners made from thismaterial are particularly challengingdue to the headliner material rolling intothe edge of the windows as mentionedearlier.

Beech quickly realized the prob-lems this caused, and redesigned thewindow frames to go completely aroundthe upper windshield and window areas.

For those of you with this rolled-edge headliner, four extra steps must beadded to the reforming process:

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INTERIORSTHE INSIDE STORY

PART IXBY DENNIS WOLTER

AIR MOD, CINCINNATI, OHIO

Typical distortion caused by years of thermal cycles.

Reshaping the headliner panel on a wood form.

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First, the formed edges of the pan-els are often cracked or torn and must berepaired with the polyfix and fine meshfiberglass process described in our sidepanel article last month.

Second, the edge must be heatedand reformed to meet the contour of thewindow or windshield edge.

Third, since some shrinkage hasprobably occurred, there is often anunclosable gap still existing at the upperwindshield edge. Here a 5/8" diameterwindlace cord covered with headlinermaterial and tapered at the outer cornersworks well to aesthetically fill this gap.

Fourth, secure the edges at the topof the pilot’s window and by the cabindoor with two or three upholsteryscrews. This properly secured materialwill no longer be affected by futureheating and cooling cycles. Waves andgaps are history!

Making certain headliner stays inshape—With the headliner back to itsdesigned shape, it's time to make certainit will not deform in the future. Toensure this, we bond .020" 2024 T-3aluminum to the back surface of theheadliner panels. For proper shape, it’simportant to place the headliner panelon the wood form while the aluminumpanels are bonded in place.

A little trick: On some airplanes, akink can develop where the air ventnozzles pull the headliner firmly up intoplace. We use a small cutting wheel tocut slits in the rigid aluminum backing.This allows just enough flexibility tominimize this kinking. Be careful tomake very shallow cuts into the alu-minum only.

If the headliner was not in too bada shape to begin with, this process willleave the finished side looking perfect.All you need to do is prep and spray it

with the new interior color, or stretchand bond a headliner material on theundamaged surface.

If light kinking has occurred, a lit-tle heat may bring the surface back to apresentable condition. If that doesn’t dothe trick, light filling can be done withtraditional flexible auto body fillers.However, this will modify the texturedsurface of the headliner, making sometype of covering process a necessity.

If severe surface damage hasoccurred, such as gouges or deep cracks,a very thin 1/8" layer of insulate or ure-thane foam must be bonded to the head-liner. This will present a smooth soft sur-face that will hide all the imperfectionson the old surface. Due to the thicknessof the foam, it will be necessary toremove some of the original foam back-ing so you can reinstall the thread-mounted air vent outlets. A router bit ona moto tool works great for this task!

Typical cracking at the edge of an earliest generation plastic headliner.

Aluminum backing bonded to the reformed headliner panel.

Cutting the kink-eliminating slits in the bulging aluminum.

One-eighth inch foam padding applied to a headliner with a badly damaged fin-ish surface.

Fixing the gap between headliners—Fabricate a 3-foot piece of windlacecord with two parallel stitches about3/32" apart. Bond this to a 2" by 30"strip of .025" 2024 T-3 aluminum tocreate a standing bead of finished cord-ing that can be slid in place to fill thegap. This cording material will expandand contract with temperature changesto create a pleasant-looking and perma-nent fill piece, eliminating the unsightlygap between the two large headlinerpanels. Sometimes you luck out. We’vebeen using these techniques for 30 yearsand no failures to date!

CURRENT HEADLINERSSo much for Round One. It's time

to move on to the last and current gen-eration of headliners. This design is thebetter designed and constructed of thetwo types of plastic-material-basedheadliners. Not only is the headlinermade of a more stable (though some-what delicate) material, the air system isfar more efficient in terms of the vol-ume of air it can move.

That said, Beech did take someshortcuts that resulted in a few prob-lems. First, the dropped-center designof the headliner creates two concaveshapes that present the potential for anybonded finish material to pull awayfrom the headliner as the material agesand begins to shrink.

The second problem is that Beechused a finish material that was bondedto a urethane foam backing that tends tobreak down when exposed to tempera-

ture changes and unfriendly chemicalsin the atmosphere.

In as few as three years, some ofthese headliner coverings will begin tofall down, leaving behind a mess ofblack degraded foam that has the con-sistency of warm bubble gum. Add tothis a tenacious layer of gooey adhesiveoriginally used to bond the material tothe headliner, and you have about a six-to eight-hour clean-up job involvinglots of lacquer thinner, rags, scrapers,abrasive pads and patience.

The third big issue with these head-liners is the way Beech rather poorlysecured the threaded rings that hold thevent nozzles and light fixtures to theheadliner. By design, these rings wereintended to be structurally secured to

the headliner with plates and screws,evidenced by the fact that they containmounting flanges and holes. But to savetime during assembly at the factory,Beech chose to glue them in place witha crudely applied bead of RTV siliconsealer—bathtub caulk, no less!

If a nozzle or light were removedfor repair, and the delicate adhesivefailed when reinstallation was attempt-ed, a person would have to remove theheadliner, disassemble and resecure themounting ring, install the nozzle orlight, and then reassemble and reinstallthe headliner—six to eight hours for anexperienced technician.

The real fix—In case you haven’tnoticed, I love making things better than

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Gap-filling windlace strip.

Typical mess caused by the bad backing foam.

Poorly secured light and vent mounting rings. Note the broken switch retainer.

when they were new. Get out your rub-ber gloves and a charcoal paint mask.With the headliner face down on aworkbench, remove the back side airduct access panels, the air outlet noz-zles, lights and switches. Then turn theheadliner face up and lift off the vinylfinish skin.

Before applying any lacquer thinner,you’ll need to scrape off as much of thatdegraded foam mess as possible. A 11⁄2"wide thin putty knife seems to be the toolof choice for this. Now you’re down tothe obnoxious adhesive I mentioned.

Brush on generous amounts of lac-quer thinner and also place thinner-soaked rags on, one section at a time. Letthe concoction soak for five to ten min-utes. You can move ahead and apply yoursoaked rags to the next area, and whilethey’re in place, go back to the previous-ly soaked section and start scraping.

We use about a 6" piece of .040"aircraft aluminum to doggedly scrapeaway the now somewhat-softened adhe-sive from the surface of the headliner.Hint: Use an old cardboard box as arepository for the old foam and adhesivebecause you’ll never get that gunk outof your garbage can.

Once most of the adhesive isremoved, you can use an abrasive padand more lacquer thinner to removemost of what’s left. (I plan to buy stock

in some lacquer thinner company.)Finish up with rags and thinner, and theworst is behind you.

Be sure to get all, and I do meanALL, of this stuff off. Even the smallestamount of this awful material will be areal mess on the new headliner cover.(If you like doing this job, give me a call– you’re hired!)

It’s likely that you will uncover somecracks and creases in the headliner struc-tural material, since it’s the same com-posite material as the late-style side pan-els discussed last month. Use the cyanideacrylite repair method as required.

Light & vent mounting rings—Now it’stime to properly secure the light andvent mounting rings. The vent rings arethe easiest to do since they have mount-ing flanges and holes at their outeredges. An 8-32 countersunk screw andself-locking nut, two holes and you’redone.

The lights require the fabrication ofa .050" 2024 T-3 aluminum mountingplate with an 8-32 sized hole at eachcorner and a precisely sized hole in thecenter that will seat against the flangeon the light's mounting ring.

You will notice that the lights havea clear plastic air seal bonnet that issecured to the threaded light mountingring with RTV silicon sealer.

It is important to also seal the outeredge of the new mounting plate. If youdon’t, air can leak behind the new head-liner and cause it to blow up like a bal-loon when in flight. I get two or threecalls a year on this problem. If you’re notsure, seal it.

Push switches—One final mechanicalissue is the way the push switches wereoriginally installed. Most often the plas-tic mounting tubes are not reusable. Ashort piece of the correct diameter rub-ber hose and a small screw clamp willsecurely hold a pesky switch in place. Ifa switch needs to be removed in thefuture, just remove the adjacent air ventand loosen the screw clamp through thenow open vent hole for easy access tothe switch.

RECOVERING THE HEADLINERIt’s finally time to actually pad and

recover the headliner. To eliminate thechallenge of keeping bonded finishmaterials secured in a concave shape,we upholster the headliner in threelengthwise sections, foaming and cover-ing the dropped center part first. We thenbond a 1" wide full-length strip of .040"2024 T-3 aluminum to the back side ofthe long edge of the outer cover material.

We secure the strip to the concavepart of the headliner with about 60 #6 x

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Scraping off the old glue residue. Properly secured light and vent outlet mounting rings. Note the low-tech, but effective, switch and mountingcomponents.

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1⁄2" countersunk PK screws. We bond alayer of 1⁄2" foam to the headliner at theinner edge of the 1" retaining strips.Trim the foam and the outer edge andstretch the finish material outward, andvoila, you have a beautiful blind-seam,structurally secure headliner that willnever come loose in the negative curvearea and never drop down.

Cut the holes for and install thelights, switches and vent nozzles. Grindoff the standing points of the PK screws

and you’re finished! The whole processtakes about 20 hours, but the results areworth it.

I get several calls a year from frus-trated owners, some with three- or four-year-old airplanes and some with fairlynew aftermarket interiors, who areexperiencing the pulling away or sag-ging headliner problems. It just rein-forces the adage that you’ll only have todo the job once if you take the time todo it right.

NEXT MONTH we move down to car-pets. It’s far less complex than whatwe’ve just gone through. I think we’re allready for some easier reading. Fly safe!

Dennis Wolter is an A&P, IA and a 3,000-hour instru-ment pilot who started Air Mod in 1973 to bringinnovative design and high-quality renovations tothe general aviation market. Dennis has a degree inindustrial design from the University of Cincinnati.

Inside curve retaining strips. Finished seam along inside curve of both sides of headliner.

As you peer in at the bottompart of your engine compart-ment, you can identify the throt-tle body assembly (yellowarrow) wherein the fuel mixtureand MP controls are located. Anintegral part of this assembly isthe removable fuel strainer (asshown in the inset photo - greenarrows).

Can you tell what is wrongwith the installation of the fuelstrainer?

See page 9529for the answer.

By Adrian Eichhorn,Alexandria,VA & Ron Timmermans, Fort Worth,TX