Tony Bingelis •

(That Can Ease Builder Problems)

I don't know how many RV-6s areunder construction worldwide but itmust be a considerable number. Lo-cally, we have two already flying and atleast 8 others that are well underway.

With that in mind, it occurred to methat there may be plenty of other build-ers (regardless of the type of projectthey have under construction) whowould also be interested in alternativeways of coping with construction dif-ficulties.

That being the case, I thought I couldbe serving a useful purpose by describ-ing a few of the general interest ac-tivities and experiences I've had to copewith recently.

At any rate, here is how I took careof a few of those problems. Let me knowif you would have handled them diffe-rently.

THE AN FITTING MODIFICATION

Most builders are now installing theirbrake system with Nylaflow tubing andbrass automotive compression type fit-tings. Many of these same builders alsoprefer to use a firewall mounted hy-draulic reservoir instead of those smallindividual reservoir units furnished withthe RV-6 kit.

That's understandable because in-specting the fluid level and servicing theindividual master brake cylinder reser-voirs inside the cockpit can be a some-what messy operation . . . there areplenty of oil stained carpets that givemute testimony to that effect.

The convenient firewall mountedbrake reservoir lends itself to easy in-stallation using AN fittings andaluminum tubing up to and including theAN bulkhead fitting through the firewall.However, once through the firewall,how do you switch to the more popularNylaflow tubing system?

Figure 1 shows how easy this is toaccomplish. Fit the bulkhead fitting witha short 2" length of aluminum tubingand then connect the tubing stub to anautomotive "T" fitting with a brass com-pression sleeve and nut. Do not forgetto insert a short section of brass tubinginside the Nylaflow tubing to beef upthe connection.

FIREWALL

AUTOMOTIVEBRASS CRIMP (COMPRESSION)TYPE FITTINGS

TOP VIEW(AS INSTALLED)

BRASS -J ISLEEVE———^n IINSERT LI

AN8I9 SLEEVE AN88 NUT

EXPLODED VIEW

TO FIREWALL MOUNTEDBRAKE RESERVOIR

FIGURE 1.

BRAKE INSTALLATION MODIFICATIONri

DRILLING THE HEATTREATED GEAR LEGS

The heat treated steel rod landinggear leg design used in the RV-6 wasconceived many years ago by SteveWittman who originally installed it in hisWittman Tailwind. Since then, this typeof gear has also been used in someCessnas, RV-3s, -4s and -6s, Sidewind-ers, and quite a few other homebuilts.

Because the solid steel gear legs areheat treated, they are especially difficultto drill in place on the airplane with ahand held electric drill. Since that is so,why not drill them in the drill press? Itcan be done easily and accurately thatway . . . and without the attendant riskof ending up with a misaligned landinggear.

First, you must get the airplane up ona stand and in a level attitude, highenough that you can slip the gear legsinto their tubular sockets.

Because the gear leg sockets havealready been jigged and welded to-gether as part of the engine mount, thegear configuration in the RV designshas been automatically and preciselyestablished. All that remains for you todo 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 angleiron (about 88" long) be clamped ortaped to each axle. This will automati-cally align both axles with the zero de-

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

grees toe-in recommended by the de-signer.

Next, be sure each gear leg is fullyinserted with its upper end flush in theengine mount socket. Then, carefullydetermine the best location for the bolthole and punch mark it.

Check one more time that the fuse-lage is level and that the axles arealigned.

Drill the initial pilot hole with a 1/8"cobalt drill bit. Be sure to use a goodlubricant to keep the drill bit and thework cool. Begin drilling with a variablespeed electric drill using a slow rpm andsufficient pressure to keep the drill bitcutting. DO NOT ALLOW THE DRILLBIT TO SPIN WITHOUT CUTTINGMETAL, otherwise you will harden themetal even more and further drilling willbecome almost impossible.

This hand drilling is a slow tiresomeprocess because you must keep addingthe cutting oil to the bit and hole ...

and, at the same time, give constantattention to holding the drill steady.

In time the drill will work through theouter tubular socket and begin an evenslower penetration of the gear leg. Keepdrilling until you have drilled into thegear leg just enough to definitely estab-lish the hole location. Then quit and re-move the gear leg from the aircraft.

Move it over to the drill press and de-vise a way to jig it level . . . somehow.This may require the use of a clamp ortwo and some kind of support at theaxle end . . . if you don't have some-body to help you.

Adjust the drill press table as neces-sary to get the drill bit positioned in thepartially started hole. Rotate the gearleg so that the drill bit is aligned with thecenter of the leg.

Then, tighten the drill vise to im-mobilize the gear leg.

That hole can be drilled through theleg quickly and accurately in the drill

Attempting to drill the hardened steel landing gear legs installed on the airplane witha hand held drill is a very slow and difficult way to do it. It is better to do the heavydrilling with the gear jigged in your drill press. Note how the spare drill bit (A) is usedas a sight gage to align the gear for the second drilling.30 MARCH 1990

press. But don't rush it. Keep the drillspeed slow and, that's right, use plentyof cutting oil.

Next, remove the gear leg from thedrill press and reinstall it in the aircraft.Realign it carefully with the angle ironcross bar (wiggling an awl in the drilledhole helps).

Then, using that same 1/8" drill bit,run it into the hole you just drilled whilethe gear was in the drill press, and drillthrough the back wall of the gear soc-ket. Now you have an aligned gear legand a pilot hole all the way through theassembly.

The next objective is to enlarge thatinitial 1 /8" pilot hole.

Chuck a 3/16" bit in your electric handdrill and begin enlarging the hole by drill-ing through the outer socket and, onceagain, slightly into the gear leg.

Remove the gear leg for the secondtime and jig it in the drill press so youcan complete drilling through that hardleg with the larger bit. Be sure whenyou clamp the gear leg in the drill pressthis time that the 1/8" pilot hole is verti-cally aligned.

You can verify the hole's alignmentby slipping a spare 1/8" bit in the holeand sighting it against the 3/16" bit al-ready chucked in the drill press. One ofthe photos shows how this was done.

After the 3/16" bit is run through thegear leg, it's back to the airplane whereyou once again align the axle. Insertthat larger 3/16" drill bit and again drillthrough the back wall.

You will notice that enlarging a drilledhole is easier than attempting to drill anoriginal starter hole. The final bolt holesize is 5/16" for the RV-6.

This drilling method in hardened steelis far quicker, more accurate, and saferthan trying to do all drilling with a handheld drill with the gear installed.

Keep this in mind. Only a single boltthrough the upper gear leg secures it inplace and establishes the wheel align-ment. An oversized or wallowed outhole can spell trouble.

COPING WITH A STAINLESSSTEEL FIREWALL

Preparing the firewall installation willrequire the drilling of as many as 16holes (see Figure 2). If you don't al-ready know it, drilling that many holesin a stainless steel firewall is not easy.

Drilling a small hole is not so bad.Simply make a punch mark with an au-tomatic punch, and then you can drillthrough that point with a small (No. 30or 40) drill bit without difficulty. But theproblem develops when you attempt toenlarge your pilot holes enough to ac-cept grommets.

That stainless steel material is veryhard and very difficult to drill into. And

AIR/OIL SEPARATOR

OPENING FOR WIRING IVOLTAGE REGULATOROVER-VOLTAGE REG.

ON. PRESSURE SENDER

MANIFOLD PRESSURE(ANBJ3-3D ELBOW)

CAIIN VENTILATION (PASS I

LANDING GEARSOCKET ORCNTATK3N

BRAKE LINE OPENING(RUS)

NOTE-ALL FIREWALL OPENINGS FOR WIRINGAND ENGINE CONTROLS TO BE SEALEDWITH PROTECTIVE METAL SHIELDS.

VACUUM PRESSURE REGULATOR

-i FUEL PRESSURE SENDER

BRAKE FLUID RESERVOIR

3"——1 CABIN VENTILATION (PILOT)

ENGINE MOUNT BOLTS (6)

CABIN HEAT VALVE(CESSNA IV))

BRAKE LINE OPENING(LHS)

' • • - , IV4~ ,k^—t— * ——-- - -t—t--,—-EXH,- .. ' - '- '

IAUST OUTLET POSITIONING

FIGURE 2.

RV-6 FIREWALL LAYOUT (TONY'S)

yet it is also very ductile. So ductile thatthe back side of a drilled hole willdevelop sharp jagged edges as the drillbreaks through. Deburring the holewithout messing up its symmetry canalso be difficult.

The best holes in stainless steel arethose made with a Whitney punch orsome other metal punching set up.

Unfortunatley, the Whitney punchcan be used only for punching out holesnear the edges of the material.

A hand held nibbler tool will also doan excellent job of cutting out very largeholes in the thin steel. Holes like thoseneeded to install 2" ducting, for exam-ple.

I have not dared to use my expensiveUnibit to enlarge any drilled hole in thestainless steel firewall. Instead, I en-large the small initial hole with a largerbit. However, it is almost impossible toget a nice round hole everytime. Be-sides, the backside of the poorlyshaped hole is usually somewhat jag-ged as well. The remedy seems to beto drill a slightly undersized hole, roundit out and deburr it up with a smooth-cutrattail file. Yes, you can file the stainlesswith a good file, but it isn't easy.

I've had pretty good results enlargingholes in stainless with a tapered rotaryfile. However, it tends to stretch-form

the metal around the edges of the hole.All these hole enlarging "techniques"

for stainless steel have one thing incommon. They generate a lot of vibra-tion. So much so I was appalled to seethat the needle in my vacuum gauge

had dropped off and was lying in thebottom of the case. The gauge, ofcourse, was ruined because it was asealed type that cannot be opened.

Based on that experience, I havelearned to remove the instrument panel,

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

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Shown here is one landing gear socket and the lower part of the firewall. Notice howcritical the placement of the gascolator (A) and the battery and starter solenoids (Band 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 spaceddrill holes outlining the area to be cut out. As shown here, a cold chisel can be usedto cut away the metal between the drilled holes. A smooth file is used to finish the job.

or at least the instruments already in-stalled, BEFORE I attempt to enlargedrilled holes in the firewall, or do anyadditional riveting.

CUTTING THAT LARGE RADIOSTACK OPENING

If you choose to mount your radio(s)in the instrument panel, you will have tofind some way to cut out that largeopening.

The radio trays are 6-1/4" wide so Imake my opening slightly wider (6-5/16", actually). How much total space toallow vertically is another matter. Forexample, my radio tray is 2-5/8" high,the loran tray 2" high, and the transpon-32 MARCH 1990

der tray measures about 1-5/8". Theopening I cut for my 3 avionic units hap-pens to measure 6-5/16" x 6-5/16".

Actually, you should already haveyour avionics selected before you cutthe opening to accommodate the sets.

As for cutting out the hole, you don'thave many options. For example, you

Right - Most builders consider the de-signer-recommended narrow center con-sole depicted in the plans to be ugly. Con-sequently, builders are going with a 3" to4" wide console as is evident here. Leginterference with controls? Apparently itdepends on where your knees will bepositioned.

can't get at that inside area with yourbandsaw. Nor can you cut the thick(.060" to .080") aluminum material withaviation tin snips . . . or for that matterwith a hand held nibbler.

The old reliable method is a bit slow,but it always works. This is illustrated inone of the photos. You merely drill a lotof closely spaced holes along themarked cut-out lines to develop a perfo-rated pattern. These individual holescan then be connected using a coldchisel and a hammer. Do this chiselwork while the panel is clamped in avise, or positioned over the edge of asolid steel surface.

Don't try to save a little work by dril-ling the holes too close to the markedlines. You might drill into the line andmess up what could have been a per-fect job. Anyway, the relatively softaluminum panel files easily and trim-ming the opening down to the markedlines won't take much time.

MY RV-6 ASSEMBLY NOTES

One note reminds me to be sure theaileron push-pull tubes are in the wingsbefore attaching the wings to the fuse-lage. You can't get them in afterwards.

I also noted that I installed and riggedthe wings, tail and control surfaces be-fore I installed the landing gear and theengine. This made the structure lighterand easier to hoist and level for the in-itial assembly.

After the rigging was completed, thewings and tail were removed for the lasttime.

However, before beginning the disas-sembling, I obtained two coffee canswith plastic lids. One I labeled "WingHardware", and the other, 'TailHardware".

As I removed each bolt, washer,spacer, nut, etc. used in that installa-tion, I placed it in the appropriate can.

When the job was finished, the lidswere taped on the cans and set asidein a large cardboard box. This carbonis intended to accommodate most ev-

erything that will be needed at the air-port for the final assembly of theairplane.

ITLL BE FINISHED SOON,IF NOT LATER

Visitors keep saying, "Wow, you're al-most finished, aren't you?" Almostfinished?

I can understand why they think thatbecause I have already fitted and riggedthe wings, tail surfaces, control sur-faces, installed the engine and have theairplane standing on the gear.

In addition, I had just received andinstalled a beautiful set of Alan Tolle'scross-over exhausts custom made formy RV-6, acquired all the radios I intendto install (a King KX175B 720 channelnav/com, an Apollo Super Bandit 618loran, a King KT78 transponder and ablind encoder), ordered a Warnke cus-tom built prop and have jammed mypanel full of instruments. Does all thatmake me almost finished?

Not when I realize that I still don'thave the seat belts and shoulder har-nesses, upholstery or paint supplies.Besides, I haven't even ordered a bat-tery yet.

SPEAKING OF ORDERING

There is another thing we buildersmust do at this stage of construction -order our aircraft registration numberfrom the FAA in Oklahoma City. For apaltry $10 you can request a "specialNumber". Here's what I asked for andwhy.

My first choice was N7TX. The sec-ond, N69TX. The third, N187TX, andmy fourth choice, any two numbers end-ing in TX.

Why those particular numbers? Well,this is my 7th powered aircraft project,I'm 69 years old, my EAA Chapter is187 and you probably guessed that Ilive in Texas. Besides, I've learned tosay "Tango X-ray" over the radio realgood.

You'll have to admit that I did all Icould to make it easy for the FAA to finda number for me. Apparently that didn'thelp them much because all they havebeen able to do so far was to cash mycheck. More than a month has passedand I am still waiting.

However, they are not holding me upbecause I still have a "few" other thingsto accomplish . . . simple tasks such ascutting and fitting the Plexiglas canopy,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 whenthat can be undertaken. It is a poor timeof the year to be painting an airplane in

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

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

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

If you wish to contact the author of thiscolumn for additional information, pleasewrite to Tony Bingelis, 8509 Greenflint Ln.,Austin, TX 78759.

BOOKS BY TONY

The following books by Tony Bingelis areavailable from the EAA Aviation Foundation,EAA Aviation Center, Oshkosh, Wl 54903-3086, 1-800/843-3612, in Wl 1-800/236-4800. Major credit cards accepted.

- Sportplane Builder (Aircraft Construc-tion Methods, 320 pages) - $17.95.

- Firewall Forward (Engine InstallationMethods, 304 pages) - S19.95.

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

Add $2.40 postage and handling for eachpublication ordered . . . or order all three for$52.97 plus $6.95 postage and handling.Wisconsin residents add 5% sales tax.

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