I may win the yet to be offered award for the world’s slowest restoration – 75-003 and I have been together for nearly seventeen years. The contingencies of life have intervened to stretch out what I thought at first would be about a 5 year restoration. Apart from thoroughly enjoying the restoration process, this uber- slow effort has allowed me to benefit from many other restorers ideas and efforts. Examining the many Stearmans at fly- ins produced solutions to almost all my restoration questions. Despite this, I have never seen a baggage compartment system that I really liked for a 450 conversion with the oil tank in the baggage compartment. And every restorer has grappled with the placement of the electrical boxes and radios, trading off ease of installation and simplicity for ergonomics and aesthetics. Below is a description of my solutions to both problems.
THE BAGGAGE COMPARTMENT
By the time you shoehorn the oil tank and all the related plumbing into what was the baggage compartment, there isn’t much of it left. And after a multi- day cross country trip in a friend’s airplane, I realized that the stock baggage compartment is pretty minimal to start with. I wanted a baggage compartment that would maximize the use of the remaining space and also ensure that no matter what was placed in it, the elevator pushrod would be immune from interference. Additionally, access to the aft fuselage had to be preserved for future inspection or repair. I ended up solving all the above issues by designing a sheet metal baggage compartment held together with Dzus fasteners and piano hinge. An additional space for light articles was created by constructing a shelf resting on top of the upper longerons, aft of the stock baggage compartment. A small bulkhead, hammerformed over wooden form blocks, prevents articles from migrating back to the tail. All panels were formed from 0.032” 2024T-3 aluminum, but any other grade of aluminum would suffice. Care must be exercised when beading or dimpling the countersunk Dzus fasteners in the T-3 material to prevent cracking. Using 5052H32 or 3003H14 alloy would alleviate this problem.
Fig.1 shows the front, bottom, and rear of the baggage compartment cleco’ed together. A piece of piano hinge connects the front to the bottom and the bottom to the rear of the “box.” The dimensions of the pieces are as follows, all dimensions are to the bend lines and do not include the extra material required for edge flanges:
- Front: 24 ½” wide + flanges, X 16 ¼” deep.
- Bottom: 24 ½” width front edge + flanges, 22 ½” width rear edge + flanges, 13 ½” long.
- Rear: 22 ½” + flanges, X 16 ¼” deep.
- Sides: 13 ½” X 16 ¼”.
- Rear shelf: Front edge 22 ½” + flanges, Rear edge 18 ½” + flanges, Length 26 ½” + flanges.
The separate left and right side panels contain the Dzus fasteners, and the bent up flanges on the sides and bottom contain the Dzus springs. Since my airplane will have removable metal side panels allowing access to the Dzus fasteners from the outside, I chose to construct the box with the Dzus fasteners going inward. For a stock fabric covered airplane, orienting the Dzus fasteners outward will allow for the removal of the baggage compartment from within. Using flush Dzus fasteners will minimize the chance of articles in the baggage compartment snagging on the fasteners. The entire assembly is attached to the airframe with stock Stearman tube clamps. Tack welding an AN anchor nut to a standard Stearman steel tube clamp allows blind installation and removal of the screw fasteners with only moderate difficulty if later required.
Fig.2 shows the complete baggage compartment trial fitted to the airplane. A piece of ¾” angle aluminum, notched around the fuselage tubing, is riveted to the upper forward edge of the baggage compartment to provide additional rigidity to the upper forward panel edge. It is probably not really required and bending the edge over 90 degrees would work just as well. One frustrating issue that I was that of did encounter was that of panel distortion due to adding stiffening beads rolled into the panels to prevent them from “oil canning” in flight. (see photo 1) This distortion made assembly difficult. Riveting 3/8” or ½” bent up flanges to the outside of the panels instead of rolling beads into the panel would work just as well without introducing distorting stresses into the panels.
Fig.3 shows the completed installation including the “shelf” and the aft bulkhead. The bulknead was hammerformed from soft aluminum over wooden formblocks and attached to the shelf by anchor nuts and screws. I am in the process of obtaining several STC’s for the all the modifications on my project (Now that is definitely NOT an enjoyable part of the restoration) and consequently having the modifications approved by an aeronautical engineer. If anyone would like to copy this installation, I can make the engineering data available to facilitate either Form 337 or LSTC approval.
RADIO & ELECTRICAL BOX INSTALLATION
With real estate in short supply in a Stearman cockpit, the issue of where to put all the modern, and now required electrical and avionics equipment caused me many an hour of worried contemplation.
If a panel installed on the right hand side of the cockpit intrudes more than a few inches inside the fuselage truss, then full right aileron deflection is near impossible to obtain. Installing radios sideways to make the panel narrower, apart from looking a little unconventional, makes them hard to see and operate. Additionally, my years of flying larger commercial aircraft made me appreciate separate electrical busses as well as separate volt and amp meters. All this in turn required extra panel space for all the breakers and switches – more than could be accommodated in any sort of installation installed behind the front seat. Lastly, I wanted the carb heat control a little closer so that it could be utilized without unlocking or loosening the shoulder harness. The solution was to separate the electrical distribution panel from the radios, and make an electrical panel as shown in Fig.4, incorporating a bracket for the carb heat control.
The finished panel is 5 1/2“ wide and 33“ long and constructed in 2 separate pieces screwed together. The circular opening surrounds the vertical tube under the rear instrument panel. Aluminum angle brackets riveted to the underside of the panel attach to stock Stearman tube clamps on the vertical and diagonal fuselage members. SRA member Carl Williamson made a beautiful custom sized “Flight Data” case to hold the radios that attaches to the rear of the front seat slide tubes as per the stock installation. See Fig.5. As an added bonus, the cover closes to conceal the radios when parked, giving the airplane a really authentic 1930’s feel.
The final problem to solve was how to label everything to look like something the factory might have done back in the day. Stick on lettering or plastic tags were not going to cut it. At one point I was even considering CNC engraving. The breakthrough came when realized that powdercoating goes on at about 500 degrees and a laser beam is about 5000! I am not a fan of powder coating tube structures but I did have my instrument panels powdercoated in a wrinkle black finish. On a lark I took a scrap piece down to the local engraving shop – you know the place, the ones that do trophy’s and laser etch the “Hi my name is Bob” type nameplates. They tried it and the laser vaporized the powder coat, exposing bare aluminum underneath. The edges of the lettering is sharp and to the touch, the surface of the lettering feels recessed below the powder coat (see Fig.6). I made up a very detailed full size drawing in Fig.7 of what I wanted engraved where. The charge was about $250, most of which was set up time, including removing the side off the machine to accommodate the long piece. The only downside to this process is that you need to be sure of what goes where, as changing your mind later will require re-powdercoating the panel.
There are many ways to accomplish the same thing with any area of a custom restoration. I have noticed that a major effort of the project, especially in the non-stock custom areas of the restoration, is that stuff starts competing for real estate. These two ideas are just how I ended up solving two of the common problem areas where there was not enough space to install everything that I wanted to install. I hope that they are useful or inspirational to someone else, and many thanks to all those who have so generously shared their ideas with me. Hope to see you with ‘003 at Galesburgh this decade.