Wie wird die Mooney so leise wie ein Mercedes? Folgend ist ein kurze Anleitung, wie eine neue Lärmschutzdämmung in eine M20C eingebaut wurde. Sehr ähnlich wird es wohl auch für die M20A-M20F realsierbar sein.

Removal of the seats and interior panels is a straight-forward but rather time-consuming job if care is exercised in avoiding damage to the plastic pieces. Once the interior is down to the old styrofoam sections and endless strips of aluminum tape, the process of stripping, cleaning and preparing can begin. To the left is a photo of 29Q's interior after removing upholstery and Royalite. This is also an excellent time to complete Mooney Service Bulletin 208, which involves checking the steel fuselage tubes for any indication of corrosion and examining insulation for signs of moisture damage. A treatment of anti-corrosive chemical (we used ACF-50, another alternative is CorrosionX) is recommended both on the exterior and on the inside of the steel tubes even if no corrosion is detected.

To the right is the cockpit ceiling with the factory fiberglass insulation mostly pulled away. Many applications of acetone were necessary to strip off the remnants of adhesive and the hanging strands of old insulation. Low temperatures or not, good ventilation is a necessity during this part of the job; wearing a respirator might not be a bad idea if using any chemicals stronger than acetone. The ceiling vent structure is visible in this photo. Russell Stalling of South West Texas Aviation pointed out the necessity of checking the water drain system on the vent. Russell suggested pouring water through the roof vent and ensuring that the fluid flows freely through the drain. If it doesn't, disassembly of the vent structure is necessary as the steel tubes along the roof may well have suffered corrosion damage. Again, copious quantities of tape must be removed during this part of the job and replaced before any new insulation is added.

After all the old styrofoam and tape is stripped and new tape has been applied--the '65 series used Aluminum tape, other Mooneys have duct tape on the seams--it's time to begin cutting and fitting the insulation underlayment. In the photo to the left, the inspection panels in the rear seat floor are open. Access to various control rods may be gained through these eight openings as is access to the backside of the main spar and the front part of the stub spar, a prime area for corrosion particularly in many of the older planes. The ModWorks insulation kit begins with a layer of 1/8" foil-backed closed-cell self-adhesive foam, the same material that is used for wrapping aluminum ducts in a home heating system. An FAA lab burn test gives this material a "Zero" for burn and spread. The application is--again--time consuming but not difficult. The material cuts easily and applies simply. It should not be in contact with the steel fuselage tubes but must abut all wiring harnesses and vacuum tubes as closely as possibly.
This material coats the entire ceiling, side walls, floor, baggage compartment and hat rack before the next layer of material is ready to be applied. Extra care to insure that new seam tape fits closely around the access holes for wiring and vacuum tubing will result in a more effective finished product; however, make certain that all lines are readily accessible after the insulation is applied. Also necessary is ensuring that any screw holes necessary to attach interior panels must be accessable. Discovering that all the holes have been covered with insulation adds significant frustration to the job.
After the ceiling, sides of the fuselage, baggage compartment and hat rack area have been covered with 1/8" insulation, the process of adding layers of thicker material can begin. According the the rather simple instructions provided with the super-soundproofing kit, the ceiling and floor is covered with 1/2" material and the walls are done in 1". This material is also burn-tested; it's a closed-cell foil-faced sound deadening layer with self-adhesive covered with kraft paper. It does not cut as easily as did the 1/8" layer and care must be taken not to allow the bats to fold over and stick to themselves when applying. The key is to use several smaller pieces rather than attempting to fit one big section. Also--quite apparent as you're working--begin with the ceiling and work your way down, leaving the floor for last.
Again, a space should be left between the steel fuselage tubes and the sound deadening material; access to all wires, tubes and screw holes must be maintained or the job will be significantly more complicated when time comes to install the Royalite panels. These panels, of course, should be repaired (if necessary and chaces are repairs will be needed) while out of the plane. Various kits are available through sources in Trade-A-Plane; standard epoxy kits also work well. The panels are thin and often exhibit cracking, particularly in stress areas such as around the arm rests. Doublers and be added to these areas quite simply or fiberglass cloth can be used to strenthen the material. A variety of dyes are also available to cover any imperfections in the panels. Once rather chinzy, most of the dyes are now quite effective. Suggestion is to stay fairly close to the original color; application is much easier this way. Also, several thin coats of dye works much better than a couple of thick coats replete with runs and pooling.
One of our interior photos show the 1/8" material on the floor and the walls finished with 1" sound deadening. Some of the more difficult areas to work with are in the foot wells where stripping is time-consuming, application of new tape is difficult and the cutting and fitting of new insulation will probably cause practicing Catholics to make an extra trip or two to the confession booth. One rapidly learns that the multitude of rivits and bolt heads that extend from almost every surface are guaranteed to abrade flesh on an almost constant basis. Refitting of the interior panels was quite straight-forward, particularly since we had marked the installation holes along the fuselage sides and already obtained slightly longer upholstery screws to make up for the added thickness of the insulation. Warning: if the holes in the side strips are pulled away or enlarged, don't drill new holes after putting Royalite side panels in place. The possibily of drilling through the side of the plane is an ever-present danger.
In fact, the use of a drill anywhere on the plane should only be contemplated after studying the possibility of damaging wires, vacuum lines or aluminum skin. Drills pass through aluminum very quickly and can cause expensive problems. Fitting of the Royalite in 29Q was quite simple. Only one or two places required trimming the panels despite the added thickness of the new insulation. We did discover that reinstallation of the front seats was somewhat hampered by the addition of insulation under the carpeting. There's no interference with seat movement but placement on the rails required some additional effort. Also, in the older Mooney's with Johnson bar gear, one should be sure not to add insulation on the portion of the floor where the bar clips into place with gear retracted. Space between the carpet and the bar handle can be uncomfortably tight.
We'll add some photos of the completed interior soon; the job of installing the super-soundproofing was not difficult but it was tedious. Finished result was all that we had hoped for; our interior now rivals that of a Lexus. Well, not quite, but it is much more quiet than the original condition and, more noticably, the level of vibration has been lowered significantly. Other benefits include having cleaned the carpet and having scraped and vacuumed three decades worth of dirt from the interior. New tape seals the inside of the aircraft much more effectively and the sound level with headset on is very comfortable. Our panels sparkle with new dye and seem much less flimsy when backed by the thick layers of insulation. Last point: a reweigh after completing the annual indicated total addition of weight to be slightly more than thirty pounds with almost no measurable chance in CG. All in all, a worthwhile project.
Any Mooney owners contemplating installation of the new insulation who wish to ask additional questions may feel free to contact us...mailto:bhazlett@lavida.com...and we'll offer at least encouragement if not useful information.