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Homebuilt Aircraft Interiors, Part 2 - Cockpit Conveniences and Refinements
By Tony Bingelis (originally published in EAA Sport Aviation, February 1985)
STRIPPED-DOWN austere interior, of course, enables you to have a lighter, more agile airplane. It does not, however, assure you of having the most comfortable or the safest airplane.
In an attempt to keep weight down, you might be tempted to deprive yourself of some small creature comforts that could add greater enjoyment to your flying, often with little or no weight penalty being incurred. Don't automatically rule out all cockpit refinements, not without good reason. Here are a few examples of what I have in mind. Each of these can be easily installed and are guaranteed to make your time aloft more enjoyable; a map pocket or map case, glove compartment, arm rests, headrest, heel scuff plates, sun shade or visor, bubble canopy screen or curtain, radio stack vent and handholds to name a few of the more popular items with most builders.
Of course, you may not want or be able to incorporate all of these, let's call them, refinements. However, do not rule any of them out until you have read a bit more about each. Let's start with Handholds.
It depends on your airplane design, naturally, but there can be no argument that almost any airplane should have some sort of an aid to help you get in and out of it.
A handhold mounted on the windshield bow (frame) or a hand grip built into the glareshield, particularly in aside-by-side two-seater, meets that need and is a genuine cockpit convenience.
Your handhold could take any of several simple forms depending primarily upon the type of structure to which it will be attached. Figure 1 illustrates a couple of options. The January 1985 issue of SPORT AVIATION, illustrates two more.
The dandiest convenience you can have in any biplane has to be one of those classic handholds built into the top wing cut-out. Without it, pulling yourself out of the cockpit invites the risk of damage to plane and pilot. The weight penalty? A few ounces.
Shall we go on?
It's Curtains For Bubble Canopies
A large bubble canopy, particularly on a two-seater, must certainly be the airborne equivalent of a sweat shop. The amount of solar heat it lets in must be intensified by the curvature of the large plastic bubble acting like a huge magnifying glass. Although that conclusion may not be scientifically accurate, I am willing to believe it. Boy, does it get hot in there!
Do you want quick relief? Mask and paint an opaque band approximately 12 inches wide down the center of your canopy bubble. Do this on the inside of the Plexiglas using white paint. White is the color to use to obtain the coolest cabin temperatures, however miniscule that difference might be.
Painting the canopy glass on the inside creates a better effect and also affords protection for the paint from external abuse and chipping. A quick-drying enamel is my choice for the job. Remember, lacquer thinners and other volatile liquids can, in time, cause Plexiglas to craze.
Another way to make shade in the cockpit is by installing curtains. Figure 2 should put you on the right track if you want to fabricate a simple installation for your airplane.
If your canopy frame tubing is less than 3/4" in diameter, you might feel that drilling those 3/16" mounting holes for the curtain rod installation will weaken the canopy frame too much. I don't think they would but, if you prefer, you can instead, epoxy small rectangular wood blocks butted up to the canopy frame. With the small holes drilled into the blocks instead of the canopy frame you can still obtain the needed support for the lightweight aluminum curtain rods (1/4" 2024 T3 aluminum tubing).
Select a plain, light colored, semi-sheer curtain material. It will effectively screen out the hot rays of the sun without creating that closed-in feeling.
What makes this installation, or a variation thereof, extra functional is that you will be able to push the curtain back to any intermediate position at will.
The weight penalty for this one should be less than a pound unless you have a very large canopy.
Radio Stack Cooling Vents
A single radio installed in your panel does not require any particular ventilation provision. It is a different matter, though, when you have two or three units installed one directly over the other in what pilots refer to as their "radio stack". Although aircraft radios are now transisterized they still do generate heat and do require some form of cooling to minimize long term deterioration of dielectrics and other component parts.
It is unlikely that many of us will have a large stack of radios so we need not concern ourselves with electric fans and similar cooling devices.
For the most part, all the cooling we need is what we can obtain from the flow of air through a vent or port located directly over the radio stack.
A vent acts very much like a chimney allowing the hot air to rise and leave the radio compartment area. The incoming air is cooler so the cooling cycle continues.
All that is needed for ventilating a couple of radios is a small vent located in the top of the glareshield (windshield deck) directly over the radios. Small individual louvers will also work as well.
The time to install a radio cooling vent or ventilating louvers is after you have overlaid your glareshield but before the windshield is permanently installed. Otherwise, access will be difficult because the windshield will interfere with your hole drilling and vent installation efforts.
Whatever the type of opening you provide for the ventilation air, the opening should be protected to keep foreign objects from falling into the radios below.
If, because of the number of radios stacked or because of an exceptionally hot climate, you need more cooling air consider installing ram air cooling. It is easy enough to do.
Install a short length of tubing clamping it vertically to one side of the radio installation. This will serve as a distributor for the ram air after you plug one end and connect the other with ducting to a ram air source. The ram air will then be ducted to the distributor tube and from there spewed out over the radios through strategically drilled holes. If you find this hard to visualize take a look at Figure 3 for instant clarification.
If more cooling is required, you could also install a similar distributor on the opposite side of the radio stack. A good source for the ram air would be an opening on the back engine baffle to which you could attach the ducting. It need not be larger than 5/8" or so in diameter.
Map Pocket? Map Case?
Call it what you will, every airplane should have at least one. A place to stow your navigation charts, log book and pencil if nothing else. However, map pockets being what they are, seem to attract all kinds of stuff ranging from magazines to sandwiches and used drink cans. Yes sir, every airplane needs someplace to stow things where they are easily accessible to the pilot. Your cockpit will be a safer place, a more attractive and comfortable place, if that sort of clutter is hidden from view and secured.
If you want to see what a messy cockpit looks like take a look in any cockpit that has maps and papers wedged in behind tubular structure or poked under the seat.
A map pocket eliminates that eyesore because its gathered elastic opening does an excellent job of containing anything poked into it. Anyone who is tempted to do an impromptu acrobatic maneuver will be delighted with a map pocket's capacity and ability to keep everything inside where it belongs.
You could, of course, build a regular map case from metal or thin plywood complete with a lid and fastener. That's how they used to be. One of this type would be all right in a biplane or in any airplane with a welded steel tube or metal fuselage where it could be secured to the diagonals or uprights. Somehow a map case, per se, might look a bit out of place in a well furbished interior. Besides, it is difficult to retrieve small objects from the bottom of a hard walled map case unless you have small hands.
One of the photos shows how effectively map pockets can be located. Note that one is on the door (actually each door) and the other behind the seat in this BD-4. These locations seem to be made to order to map pockets.
A Glove Compartment For Me?
What? No gloves? Well, wouldn't it be a handy place to stow your aircraft log book and papers, extra glasses (for sun or seeing), note pad and pencils and even navigational sectionals? The location on the instrument panel is always easily accessible.
The instrument panel in a two-seater (side-by-side) is made to order for the installation of a glove compartment. Unless your airplane is to be highly instrumented and loaded with radios there will always be a lot of unused blank panel areas. Besides, you won't have to spread out the instruments in order to fill out the panel.
Tailor the size of the glove compartment opening to the space available. It should be at least 6 inches wide and about 12 inches deep. A sectional chart is smaller than that so any number of them could also be accommodated.
You don't need to fabricate a heavy structure for a glove compartment. A thin plywood base and a cloth sleeve closed on one end would serve just as well. Here again the form that the interior takes will depend on the structure you have to work with.
Usually a glove compartment door will be hinged on the bottom with a piano hinge and secured with a Hartwell fastener or latch. This results in a nice flush installation. You can take this basic arrangement one step further and limit the door opening to 90° so as to provide you with a small table to use in flight. A place to put your coffee mug or soft drink while you attend to your other pilot duties.
Arm rests are welcome accessories in most any cockpit. An arm rest located between the seats can reduce the effort required to hold your arm extended to reach a center mounted throttle. This arm rest could be equally useful to the co-pilot. Add an arm rest on either side of the cockpit and you will really have it all. During a long flight it is very nice to be able to sort of raise yourself up on the elbows and shift your weight around to remove the numbing load from your you-know-what. Even a brief exercise such as that will help rest and refresh your body.
Although making and installing an arm rest is easy, it is a bit more difficult to locate one properly. To be sure you get yours in the best position, you should wait until your seats are installed so you can try various arrangements.
Heel Scuff Plates
These metal plates add a touch of elegance and are a very practical addition to any homebuilt regardless of whether or not a carpet is installed. The plates are intended to eliminate the wear and tear your heels impose on the floor.
Make the scuff plates of aluminum sheet about .040" thick and measuring about 4 inches by 6 inches. Locate them at the rudder pedals so that when your feet are positioned normally your heels will center on the aluminum heel scuff plates. Of course, you can make the plates larger or smaller to suit your personal requirements. Secure them through the carpet to the floor with small sheet metal screws, one in each corner. However, be sure that there are no wires, hydraulic lines or fuel lines in the area beneath. If the use of screws is out of the question, you may be able to immobilize the plates on the carpeting with Silicone adhesive or Pliobond.
Headrests are almost mandatory in many of the current crop of low profile plastic planes. The reclining seats in these "star wars" advanced concept designs can give you one sore neck without some sort of support.
Fortunately, fabricating and installing a headrest is no more difficult than an arm rest, particularly in this type of aircraft. More difficult is the installation of a headrest in an airplane fitted with conventional seats. Most of these seats are not very tall and the headrest has to project well above the seat back in order to be functional. This type of headrest is hardly worth the effort and you could well do without one.
Sunshades and Visors
You have them in your auto so why not in your airplane? A variety of shaded plastic visors are stocked by many automotive shops and discount stores. Look for a lightweight design without a frame. Figuring out how to mount it may be difficult without restricting its, degree of adjustment. Be sure to locate it where you can obtain the best windshield coverage and still be able to flip it up out of your way.
Satisfied with the installation? Now you can flip it down and fly off into the setting sun without squinting . . . just like in the movies.