Tony Bingelis •

(That Can Ease Builder Problems) I don't know how many RV-6s are under construction worldwide but it must be a considerable number. Locally, we have two already flying and at least 8 others that are well underway. With that in mind, it occurred to me that there may be plenty of other builders (regardless of the type of project they have under construction) who would also be interested in alternative ways of coping with construction difficulties. That being the case, I thought I could be serving a useful purpose by describing a few of the general interest activities and experiences I've had to cope with recently. At any rate, here is how I took care of a few of those problems. Let me know if you would have handled them differently.

AUTOMOTIVE

BRASS CRIMP (COMPRESSION) TYPE FITTINGS

TOP VIEW (AS INSTALLED) BRASS -J I SLEEVE———^n I INSERT LI

FIREWALL

THE AN FITTING MODIFICATION AN8I9 SLEEVE

Most builders are now installing their brake system with Nylaflow tubing and brass automotive compression type fittings. Many of these same builders also prefer to use a firewall mounted hydraulic reservoir instead of those small individual reservoir units furnished with the RV-6 kit. That's understandable because inspecting the fluid level and servicing the individual master brake cylinder reservoirs inside the cockpit can be a somewhat messy operation . . . there are plenty of oil stained carpets that give mute testimony to that effect. The convenient firewall mounted brake reservoir lends itself to easy installation using AN fittings and aluminum tubing up to and including the AN bulkhead fitting through the firewall. However, once through the firewall, how do you switch to the more popular Nylaflow tubing system? Figure 1 shows how easy this is to accomplish. Fit the bulkhead fitting with a short 2" length of aluminum tubing and then connect the tubing stub to an automotive "T" fitting with a brass compression sleeve and nut. Do not forget to insert a short section of brass tubing inside the Nylaflow tubing to beef up the connection.

AN88 NUT

EXPLODED VIEW

TO FIREWALL MOUNTED

BRAKE RESERVOIR

FIGURE 1.

ri BRAKE INSTALLATION MODIFICATION

DRILLING THE HEAT

TREATED GEAR LEGS

The heat treated steel rod landing gear leg design used in the RV-6 was conceived many years ago by Steve Wittman who originally installed it in his Wittman Tailwind. Since then, this type of gear has also been used in some Cessnas, RV-3s, -4s and -6s, Sidewinders, and quite a few other homebuilts. Because the solid steel gear legs are heat treated, they are especially difficult to drill in place on the airplane with a hand held electric drill. Since that is so, why not drill them in the drill press? It can be done easily and accurately that way . . . and without the attendant risk of ending up with a misaligned landing gear.

First, you must get the airplane up on a stand and in a level attitude, high enough that you can slip the gear legs into their tubular sockets. Because the gear leg sockets have already been jigged and welded together as part of the engine mount, the gear configuration in the RV designs has been automatically and precisely established. All that remains for you to do is: 1. Level the aircraft, 2. Align and immobilize both axles. 3. Drill the anchoring bolt hole through each gear socket and gear leg. The recommended alignment jigging requires that a straight length of angle iron (about 88" long) be clamped or taped to each axle. This will automatically align both axles with the zero deSPORT AVIATION 29

The gear alignment procedure is very simple because the gear mount sockets are an integral part of the factory built engine mount. All you need to do is slip the gear legs into their sockets and clamp a straight angle iron bar (A) to each axle (B) to ensure alignment. The attachment bolt holes can then be drilled.

grees toe-in recommended by the designer. Next, be sure each gear leg is fully inserted with its upper end flush in the engine mount socket. Then, carefully determine the best location for the bolt hole and punch mark it. Check one more time that the fuselage is level and that the axles are aligned. Drill the initial pilot hole with a 1/8" cobalt drill bit. Be sure to use a good lubricant to keep the drill bit and the work cool. Begin drilling with a variable speed electric drill using a slow rpm and sufficient pressure to keep the drill bit cutting. DO NOT ALLOW THE DRILL BIT TO SPIN WITHOUT CUTTING METAL, otherwise you will harden the metal even more and further drilling will

become almost impossible. This hand drilling is a slow tiresome process because you must keep adding the cutting oil to the bit and hole . . .

and, at the same time, give constant attention to holding the drill steady. In time the drill will work through the outer tubular socket and begin an even slower penetration of the gear leg. Keep drilling until you have drilled into the gear leg just enough to definitely establish the hole location. Then quit and remove the gear leg from the aircraft. Move it over to the drill press and devise a way to jig it level . . . somehow. This may require the use of a clamp or two and some kind of support at the axle end . . . if you don't have somebody to help you. Adjust the drill press table as necessary to get the drill bit positioned in the partially started hole. Rotate the gear leg so that the drill bit is aligned with the center of the leg. Then, tighten the drill vise to immobilize the gear leg. That hole can be drilled through the leg quickly and accurately in the drill

press. But don't rush it. Keep the drill speed slow and, that's right, use plenty of cutting oil. Next, remove the gear leg from the drill press and reinstall it in the aircraft. Realign it carefully with the angle iron cross bar (wiggling an awl in the drilled hole helps). Then, using that same 1/8" drill bit, run it into the hole you just drilled while the gear was in the drill press, and drill through the back wall of the gear socket. Now you have an aligned gear leg and a pilot hole all the way through the assembly. The next objective is to enlarge that initial 1 /8" pilot hole. Chuck a 3/16" bit in your electric hand drill and begin enlarging the hole by drilling through the outer socket and, once again, slightly into the gear leg. Remove the gear leg for the second time and jig it in the drill press so you can complete drilling through that hard leg with the larger bit. Be sure when you clamp the gear leg in the drill press this time that the 1/8" pilot hole is vertically aligned. You can verify the hole's alignment by slipping a spare 1/8" bit in the hole and sighting it against the 3/16" bit already chucked in the drill press. One of the photos shows how this was done. After the 3/16" bit is run through the gear leg, it's back to the airplane where you once again align the axle. Insert that larger 3/16" drill bit and again drill through the back wall. You will notice that enlarging a drilled hole is easier than attempting to drill an original starter hole. The final bolt hole size is 5/16" for the RV-6. This drilling method in hardened steel is far quicker, more accurate, and safer than trying to do all drilling with a hand held drill with the gear installed. Keep this in mind. Only a single bolt through the upper gear leg secures it in place and establishes the wheel alignment. An oversized or wallowed out hole can spell trouble. COPING WITH A STAINLESS STEEL FIREWALL

Attempting to drill the hardened steel landing gear legs installed on the airplane with a hand held drill is a very slow and difficult way to do it. It is better to do the heavy drilling with the gear jigged in your drill press. Note how the spare drill bit (A) is used

as a sight gage to align the gear for the second drilling. 30 MARCH 1990

Preparing the firewall installation will require the drilling of as many as 16 holes (see Figure 2). If you don't already know it, drilling that many holes in a stainless steel firewall is not easy. Drilling a small hole is not so bad. Simply make a punch mark with an automatic punch, and then you can drill through that point with a small (No. 30 or 40) drill bit without difficulty. But the problem develops when you attempt to enlarge your pilot holes enough to accept grommets. That stainless steel material is very hard and very difficult to drill into. And

VACUUM PRESSURE REGULATOR

AIR/OIL SEPARATOR

-i FUEL PRESSURE SENDER

OPENING FOR WIRING I VOLTAGE REGULATOR

BRAKE FLUID RESERVOIR

OVER-VOLTAGE REG.

3"——1 CABIN VENTILATION (PILOT)

ON. PRESSURE SENDER

MANIFOLD PRESSURE

(ANBJ3-3D ELBOW)

ENGINE MOUNT BOLTS (6)

CAIIN VENTILATION (PASS I

NOTEALL FIREWALL OPENINGS FOR WIRING AND ENGINE CONTROLS TO BE SEALED

CABIN HEAT VALVE (CESSNA IV))

WITH PROTECTIVE METAL SHIELDS.

LANDING GEAR SOCKET ORCNTATK3N

BRAKE LINE OPENING (RUS)

BRAKE LINE OPENING (LHS)

'••-, IV4~ ^—t— * ——--

- .. '

-

,k -t—t--,—-EXH,IAUST OUTLET POSITIONING

- '- '

FIGURE 2. RV-6 FIREWALL LAYOUT (TONY'S)

yet it is also very ductile. So ductile that the back side of a drilled hole will develop sharp jagged edges as the drill breaks through. Deburring the hole without messing up its symmetry can also be difficult. The best holes in stainless steel are those made with a Whitney punch or some other metal punching set up. Unfortunatley, the Whitney punch can be used only for punching out holes near the edges of the material. A hand held nibbler tool will also do an excellent job of cutting out very large holes in the thin steel. Holes like those needed to install 2" ducting, for example. I have not dared to use my expensive Unibit to enlarge any drilled hole in the stainless steel firewall. Instead, I enlarge the small initial hole with a larger bit. However, it is almost impossible to

the metal around the edges of the hole. All these hole enlarging "techniques" for stainless steel have one thing in common. They generate a lot of vibration. So much so I was appalled to see that the needle in my vacuum gauge

had dropped off and was lying in the bottom of the case. The gauge, of course, was ruined because it was a sealed type that cannot be opened. Based on that experience, I have learned to remove the instrument panel,

get a nice round hole everytime. Be-

sides, the backside of the poorly shaped hole is usually somewhat jagged as well. The remedy seems to be to drill a slightly undersized hole, round it out and deburr it up with a smooth-cut rattail file. Yes, you can file the stainless with a good file, but it isn't easy. I've had pretty good results enlarging holes in stainless with a tapered rotary file. However, it tends to stretch-form

The rugged firewall is shown pan.. a holes for the throttle, mixture and carburetor heat controls, as well as for one more bulkhead fitting, have yet to be

drilled.

SPORT AVIATION 31

Shown here is one landing gear socket and the lower part of the firewall. Notice how critical the placement of the gascolator (A) and the battery and starter solenoids (B and C) can be if you have to guess beforehand where to locate them.

The classical method for cutting large holes in sheet metal relies on closely spaced drill holes outlining the area to be cut out. As shown here, a cold chisel can be used to cut away the metal between the drilled holes. A smooth file is used to finish the job.

or at least the instruments already installed, BEFORE I attempt to enlarge

der tray measures about 1-5/8". The opening I cut for my 3 avionic units hap-

additional riveting.

Actually, you should already have your avionics selected before you cut the opening to accommodate the sets. As for cutting out the hole, you don't have many options. For example, you

drilled holes in the firewall, or do any CUTTING THAT LARGE RADIO STACK OPENING

If you choose to mount your radio(s) in the instrument panel, you will have to find some way to cut out that large opening. The radio trays are 6-1/4" wide so I make my opening slightly wider (6-5/ 16", actually). How much total space to allow vertically is another matter. For example, my radio tray is 2-5/8" high, the loran tray 2" high, and the transpon32 MARCH 1990

pens to measure 6-5/16" x 6-5/16".

Right - Most builders consider the designer-recommended narrow center console depicted in the plans to be ugly. Consequently, builders are going with a 3" to 4" wide console as is evident here. Leg interference with controls? Apparently it depends on where your knees will be positioned.

can't get at that inside area with your bandsaw. Nor can you cut the thick (.060" to .080") aluminum material with aviation tin snips . . . or for that matter with a hand held nibbler. The old reliable method is a bit slow, but it always works. This is illustrated in one of the photos. You merely drill a lot of closely spaced holes along the marked cut-out lines to develop a perforated pattern. These individual holes can then be connected using a cold chisel and a hammer. Do this chisel work while the panel is clamped in a vise, or positioned over the edge of a solid steel surface. Don't try to save a little work by drilling the holes too close to the marked lines. You might drill into the line and mess up what could have been a perfect job. Anyway, the relatively soft aluminum panel files easily and trimming the opening down to the marked lines won't take much time. MY RV-6 ASSEMBLY NOTES

One note reminds me to be sure the aileron push-pull tubes are in the wings before attaching the wings to the fuselage. You can't get them in afterwards. I also noted that I installed and rigged the wings, tail and control surfaces before I installed the landing gear and the engine. This made the structure lighter and easier to hoist and level for the initial assembly. After the rigging was completed, the wings and tail were removed for the last time. However, before beginning the disassembling, I obtained two coffee cans with plastic lids. One I labeled "Wing Hardware", and the other, 'Tail Hardware". As I removed each bolt, washer, spacer, nut, etc. used in that installation, I placed it in the appropriate can. When the job was finished, the lids were taped on the cans and set aside in a large cardboard box. This carbon is intended to accommodate most ev-

erything that will be needed at the airport for the final assembly of the airplane. ITLL BE FINISHED SOON, IF NOT LATER Visitors keep saying, "Wow, you're almost finished, aren't you?" Almost finished?

I can understand why they think that because I have already fitted and rigged the wings, tail surfaces, control surfaces, installed the engine and have the airplane standing on the gear. In addition, I had just received and installed a beautiful set of Alan Tolle's cross-over exhausts custom made for my RV-6, acquired all the radios I intend to install (a King KX175B 720 channel nav/com, an Apollo Super Bandit 618

loran, a King KT78 transponder and a blind encoder), ordered a Warnke custom built prop and have jammed my panel full of instruments. Does all that make me almost finished?

Some builders find their cabin bulkhead (rollover frame) is not quite as wide as it needs to be for their fuselage, and try to stretch it a bit. A screw jack or small hydraulic jack jigged as shown has been used successfully. Although the frame is extremely strong, it can be buckled by excessive pressure.

Not when I realize that I still don't

have the seat belts and shoulder harnesses, upholstery or paint supplies. Besides, I haven't even ordered a battery yet. SPEAKING OF ORDERING

There is another thing we builders must do at this stage of construction -

order our aircraft registration number

from the FAA in Oklahoma City. For a paltry $10 you can request a "special

Number". Here's what I asked for and why. My first choice was N7TX. The second, N69TX. The third, N187TX, and

my fourth choice, any two numbers ending in TX.

Why those particular numbers? Well, this is my 7th powered aircraft project,

I'm 69 years old, my EAA Chapter is 187 and you probably guessed that I

live in Texas. Besides, I've learned to say "Tango X-ray" over the radio real good. You'll have to admit that I did all I

could to make it easy for the FAA to find a number for me. Apparently that didn't

The cabin bulkhead is slanted and the ends (A) must be marked and trimmed at the correct angle to obtain the correct dimension (B) This is one way to do it using a carpenter's square and C clamps for jigging.

the driveway. Ever notice how lonely looking an empty hangar can be?

help them much because all they have been able to do so far was to cash my

The following books by Tony Bingelis are available from the EAA Aviation Foundation, EAA Aviation Center, Oshkosh, Wl 54903-

check. More than a month has passed

and I am still waiting.

3086, 1-800/843-3612, in Wl 1-800/2364800. Major credit cards accepted.

However, they are not holding me up because I still have a "few" other things to accomplish . . . simple tasks such as cutting and fitting the Plexiglas canopy,

- Sportplane Builder (Aircraft Construction Methods, 320 pages) - $17.95. - Firewall Forward (Engine Installation Methods, 304 pages) - S19.95. - Sportplane Construction Techniques

riveting the front fuselage deck, install-

ing the gear leg fairings and wheel pants, completing the wiring and, ah yes, paint-

ing the airplane.

As for the painting, who knows when that can be undertaken. It is a poor time of the year to be painting an airplane in

BOOKS BY TONY

If you wish to contact the author of this column for additional information, please

write to Tony Bingelis, 8509 Greenflint Ln., Austin, TX 78759.

(A Builder's Handbook, 350 pages) - $20.95.

Add $2.40 postage and handling for each

publication ordered . . . or order all three for $52.97 plus $6.95 postage and handling.

Wisconsin residents add 5% sales tax.

SPORT AVIATION 33