I need to replace some rotten floorboards, and install new carpets. Any advice?
(Search strings: floorboard replacement, floor-board replacement, floor board replacement, carpet replacement, replace my floorboards, replace my carpet)
If you get wool carpet, my understanding is that it is automatically considered to be fire retardant, and requires no extra treatment. One simple option, though slightly more expensive than a local carpet purchase, is to order a carpet set from Airtex, with the correct paperwork: (http://www.airtexinteriors.com/). You can also make your new floorboards and take them to a good local marine or auto carpet/interior outfit, have them make and install new carpet, and then you can treat it. Do a BAC search on “carpet” to learn what you need to know about this option. Most of today’s replacement automotive carpet and upholstery actually meets a more stringent DOT flammability standard; but not household carpet and upholstery materials. If those are used, they should be treated, though it is debatable whether that is actually a ‘hard requirement’ for private aircraft service. But why use something other than aviation or automotive carpet, when you would be taking a huge gamble on toxic out-gassing, flammability, melting, etc.?
I have found that half the planes I’ve examined have had the correct original floorboard wood replaced with cheap regular CDX plywood that is two times too thick, and three times heavier, than is proper or required. If you get the right wood, 1/4″ is plenty thick enough. 3/16″ meets the original drawing specs, if you can locate some minimum 4-ply at a reasonable price. It is worth paying the extra for the marine grade or aircraft grade wood. It has more plies, and is far stronger, for any given size, than the more common cabinet or building supply wood. If the plane has thick builder’s plywood in it now, you’ll probably knock off thirty pounds by using the correct stuff. As far as the thickness goes, believe it or not, the original Beech design intent was based on puncture resistance to a 110-pound woman wearing high-heel shoes. Not exactly a criteria these days! Just for example, a premium grade 1/4″ plywood made to aircraft specs will have five plies. Marine grade 5-ply 3/8″ may be less expensive, but is naturally much heavier than the 5-ply 1/4″ aircraft wood.
As an interesting side note, Beech did not have special aircraft specifications for the floorboard wood in the Bonanza and Baron (and subsequently our Club planes); they used ‘commercial plywood’. But the term applied to high-grade, higher ply count quality plywood back then; not to the three-ply CDX builder’s junk commonly seen now, since it has escalated so much in price. If you just call Beech Tech Support and ask about the floorboard material, their notes will say ‘3-ply commercial plywood’. But if you actually examine original floorboards, you will find that they are nowhere close to being as poor a quality as today’s ‘commercial plywood’.
You can probably get some idea of what plywood to look for by browsing the Aircraft Spruce catalog, including the online catalog (http://www.aircraftspruce.com/menus/search.php).
One caveat: if you have items that are fastened to the wood alone (like a fire extinguisher bracket), using wood screws, these woods are all much too thin for that. You should install a flush Tee-nut from the back, so that a threaded screw can go into it from the top. A small dab of good epoxy will secure the Tee-nut to the clean new wood. Let me know if you aren’t familiar with Tee-nuts. A couple of patches of aluminum duct tape (the foil type; not the common gray fabric duct tape), placed over the head of the Tee nuts, will prevent the steel heads from rubbing against the aluminum floor structure. Make sure that any mounting screws don’t protrude past the Tee nuts, and into the aluminum floor structure!
Special note:
– While you are at it, this is a good time to deep-six any sheet-metal screws formerly used to retain the floor-boards to the floor skin. I recommend replacing them with proper anchor nuts and machine screws. Some people replace them with Tinnerman plates, and Type B sheet-metal screws. Either of these can be riveted in place beneath the floorboards, and will provide permanent fastener attachment (as long as the correct screws are used).
– Some people use Riv-Nuts for this purpose, primarily because they are easier to install. I always advise against them. They are expedient, but if they ever spin in their holes while you are trying to get the fastener out, you are in for some real fun. If you insist on using them, make certain that they are real BF Goodrich Riv-Nuts with the key on the underside of the head; not the cheaper aftermarket clones (such as NutSerts or no-name products). When you install Riv-Nuts, you put a small notch in the side of the hole, either with the proper cutter, or a miniature file. The key fits in the notch, making a real Riv-Nut much more resistant to spinning due to fastener torque.
You can look around locally at a premium cabinet shop supply, and see whether you can find any 4-ply or 5-ply plywood in 3/16″ or 1/4″. If you can’t find or afford 1/4″ that has four or five plies, I would move up to 5/16″ max. 3/8″ is really overkill, especially on weight. If it doesn’t have at least four plies, it probably won’t be stiff enough to distribute loads properly. Don’t give in to the temptation to use thick, cheap, heavy, soft plywood for your new floorboards.
For what it is worth, here are the original drawing specifications for the floor-board wood used in the 19/23/24/76:
***
Floorboards P/N 169-530004-205, -211, -223, -565, -571 are manufactured from commercial fir plywood sheet, grade A-B, minimum 3 ply, 0.187 thick (nominal 3/16″ thick).
***
Notes:
– Most original 19/23/24/76 floor-boards are found to be a quarter-inch thick, with four plies.
– The floorboards are not treated with a fire retardant, neither before nor after installation. This has been confirmed by both Beech Technical Support, and by the Plant 2 Floor Manager in Wichita (where the plywood is still being used in new Bonanzas and Barons).