TECHNICAL FEATURE

WORKING IN ALUMINUM Making A Fairing BY BUDD DAVISSON

The alloy used for this fairing is .040" 3003 H-14 which is the same stuff your heating contractor uses. It is harder and it work hardens, but this fairing doesn't require a huge amount of stretching so it is the best choice. This would be especially true if we were making a wing root fairing which was likely to be stepped on. 3003 H-14, however, must be annealed prior to working. This is done by marking the surface with a felt tip pen, then heating the entire piece uniformly with a rosebud tip until the marks fade. Then it is quickly quenched in cold water.

There aren't a whole lot of homebuilts, antiques or even ultralights that couldn't benefit from a nice fairing at the wing root. Or where the interplane strut on a biplane hits the wing. We'd all like long, sweeping, one piece fairings, but each of those fairings includes that dreaded combination of words . . . compound curve. When any kind of a fairing contacts the wing and any other surface, there is automatically a compound curve because the surface of the wing curves one direction and whatever surface is next to it is either straight or curved in

another direction. One of the most common ways that problem is attacked is by making the fairings out of several smaller straight pieces which are joined together to form a series of straight lines which ratchet, rather than sweep, over the surface. For those who are driven to achieve smooth, unbroken lines, the approach for the last 30 or 40 years has been to do it in glass. This is not at all a bad approach but it involves several steps including forming a female mold right on the airplane by gluing blocks in place. Then the blocks are painstak-

ingly sanded to shape. The glass is applied. And applied. And then applied again (at least). Then all of t h a t is sanded smooth and filled. The final fairing is nice looking, but is usually thicker than we would like and weighs several pounds. A l u m i n u m has none of the problems of glass in that it is light, thin and eliminates a huge amount of labor. If aluminum has a problem it is that it scares most people half to death, but, as we mentioned in an early piece on forming aluminum, that is a problem easily overcome. By purchasing a few mallets and hammers, making a shot bag, and running down to your local heating company for some aluminum, you're set to start banging on the stuff. The nicest thing about a l u m i n u m is that the progress is so fast you can make a part, screw it up, junk it and keep making new ones until you're satisfied. In so doing, you'll climb the learning curve much, much faster than with any other material. Jim Younkin at Historic Aviation in Springdale, AR agreed to make one of the more common types of fairings for us. In this case it is where the "I" strut hits the bottom wing on a biplane, but the exact same procedures work for any type of similar fairing including a wing root fairing.

In the case of the "I" strut fairing, a left and right piece would have to be made to go around the strut and then joined at the front. In going through the photos it is important to understand the basic rules which apply to all aluminum forming and we'll repeat these every time we talk about the material: SPORT AVIATION 63

The initial bent but unstretched blank is on the

left, next to a sort-of mold. Jim made this to use

in seeing how he's doing, not to do any serious forming. This saves putting the piece against the airplane continually. This isn't necessary unless a

bunch of the same part is to be made.

Jim's first move is to roughly form the "U" shape needed. He starts it with his fingers, then moves to the piece of pipe and leans on it. If necessary he uses a large mallet to further persuade the aluminum to take the necessary curve.

The edge of the fairing which contacts the wing has to be made longer which is another way of saying it has to be stretched. By pounding the edge into the shot bag with a round nosed hammer or ball peen the material is stretched locally and is then smoothed with a plastic mallet over a nearly flat surface.

64 JANUARY 1996

An alternative way to stretch the edge is by using one of the inexpensive stretchers which are readily available. They do a smoother job and make it easier to see how much curve is being introduced but they are definitely not a necessity.

(Below left) The hammer-stretched edge needs to be smoothed and here Jim uses a small, homemade, bench-wheel to get rid of the wrinkles caused by the crude, hammerstretching operation. Simply hammering the edge smooth with first a mallet and then a flat faced steel hammer would do the same thing but not nearly as quickly. A wheel like this can be made if a lot of fairings are needed, but the amount of time spent making the wheel would probably be more than is required to make all the fairings without it.

Designed To Perform, And Out-Perform.

Lam-air— a company with a ten-year tradition of proven engineering and solid customer support— brings you the spectacular new tancair Super US. With its increased horsepower, the Super ES otters a 225-mph cruise speed,

spectacular climb rates, and tremendous load-hauling capacity, all with the beauty of a simple, fixed-gear, spacious four-seat aircraft. Plus, you'll still have that very gentle, solid, slow-speed handling that has made the Umcair ES so relaxing to fly.

Lancair is represented by Netco Aviation Inc. 2244 Airport Way, Redmoml, Oregon l)"5o Tel (503) 923-22-B Pax (503) 923-2255 For more information on the Super liS and the entire. Lancair family of aircraft yon may order our information packet for $ 15, or video for $20, or both for only $30. For information, use SPORT AVIATION'S Reader Service Card

SPORT AVIATION 65

The most serious stretching is where the fairing curves around the front of the strut, or in the case of a wing fairing, where it curves over the wing. That stretching is done by hammering the front down over the shot bag. Don't get the use of the bag for stretching confused with using it for forming. Here the hammer blows force the metal down into the slightly pliable surface of the bag causing it to stretch everywhere it is hit. This causes excess material to magically appear and the compound curve to form. If the initial blank wasn't trimmed right, it is during this part of the operation that the excess must be continually trimmed off so no

more metal than is necessary is being worked.

As the freshly-stretched material comes out of the

shot bag it is really rough so a plastic mallet is used

to get rid of the most seri-

ous wrinkles and rough

hammer it to shape. During this part of the operation, the part will have to be continually either tested against the airplane or the form to see if enough stretching was done and whether it was all in the right place. Don't wait until the final smoothing operations to see how it fits. Keep checking it constantly so you'll know early in the process whether you stretched it too much or the entire part has gone awry and it's time to start over again. 66 JANUARY I 996

Once the general shape and fit

of the piece is getting really close, it's time to start smoothing it out. Here again, the midget English wheel can be used, but a light metal hammer will do the same thing. The material moves easily with this hammer and the intent is to smooth, not stretch, so the hammer movement is a gentle tap, tap, tap all over the surface. No major forming is being done at this point. The fairing is being constantly moved around on the metal dolly which is approximately the shape wanted. The dolly is almost never the exact shape needed so an area which is close to the right

shape is chosen and the aluminum is moved around constantly as it is being tapped in an effort to get it smooth and

shaped correctly. When 3003 alloy is being tapped against a steel surface by a steel hammer it work hardens quite quickly, so

if it needs additional stretching, it may have to be annealed again. Tapping the edges steel to steel is also a good way to build additional hardness into an area where the screws will go through.

sptsooei

as

The Elements For Success In Homebuilding Cozy Mark I V . . . complete plans &. materials packages available. Call us tor information.

Control cables, push-pull tubes, 's, pulleys, turnbuckles

^ Customized instrument panels, engine

Windshield products

3^^^^— l^^^^r

rocl enc

Fuel systems lines, tanks, quick drains, shut-oftValves^

Propellers, bolts, spinners, hub plates,

monitoring

instruments, avionics

'locks, reinforcing plates

You'll find everything you need for homebuilts, restoration projects and modern certified aircraft amonp the 12,000 items listed in the Aircraft Spruce Catalog. Over 1,000,000 ports in stock, each one at an unbeatable price!

Fiberglass cloth, tapes, fillers, rubber gloves, foam

Strobes, beacons, - nav lights, panel lights, wiring, circuit breakers

•—^Wheels, brakes, axles, hubcaps, wheelpants, brake lines

Aircraft Spruce Sweepstakes. Win A QlaStar Aircraft Kit. Call for Details. Call now for your Aircraft Spruce Catalog or Fax or mail in

the coupon. 456-page catalog... $5 ($20 overseas airmail). Name-

Phone

Address

201 W. Truslow Ave. • P.O. Box 424 • Fullerton, CA 92632 (714) 870-7551 • FAX: (714) 871-7289

Q Check; rjMC; Q Visa

For information, use SPORT AVIATION'S Reader Service Card

SPORT AVIATION 67

1. The two most common alloys are 3003 H-14 and 1100, with 3003 being the hardest. 2. Always use the hardest aluminum practical for the application which is consistent with the amount of stretching to be done.

3. Try to visualize where the

stretching has to be done ahead of time. 4. Make the blank as small as possible and continually trim away excess as the forming takes place. 5. When doing stretching, forget finesse and j u s t hammer away. Your intent is to stretch, not form.

This is the final shape at the front as it came out from under the hammers. Because the material is so thick, the final finish will be by sanding which will eliminate all the hammer marks and imperfections.

6. If the part is getting too twisted or warped to easily straighten, junk it and start over. It takes more time to straighten it than to make a new one.

Besides, that's part of learning. 7. Look at the piece carefully and see if it doesn't make sense to make it in several pieces and weld it together to keep the stretching to a minimum. 8. Make friends with an aluminum welder, if you aren't going to do it yourself. Sooner or later you'll need the skill. +

The final piece has a curve stretched into both edges to fit the strut and the wing and the front is highly stretched to fit around the strut. It would be welded to a matching, left handed piece at the centerline of the strut or it could be flush riveted to a joiner strip and the rivets sanded smooth. This piece took about 15 minutes to complete! Pretty neat!

All Epoxies Are Not Created Equal! ITM&W Industries introduces AEROPOXY, the first epoxy laminating resin to combine modern non-toxic hardener technology with superior high temperature cured strength. Easy to use, AEROI'OXY is specially formulated for engine cowlings, wing spars, landing gear legs, and other very high performance applications.

Quality Materials For High Performance Composite Parts

Manufacturer! by ITM&W Industries, Inc. Santa Fc Springs, CA 90670

Call 8OO-421-1518 For information, use SPORT AVIATION'S Reader Service Card

68 JANUARY 1996

bomeca runs so cool that the heat

shield is really unnecessary. "You can run the engine, shut it down and a minute later you can put your hand on the side of it. There just isn't any heat build-up in the engine compartment." There is no carbon fiber in the prototype, but to reduce weight, it will be

used in the next one to build the spars and probably the leading edges. The prototype airframe was a typical homebuilder's wet layup job, but prepreg material will be used in the future. The empty weight of the prototype is 2,200 pounds, but Bo hopes to reduce that to about 1,700 pounds with the use of carbon fiber and prepreg materials. The prototype's landing gear consists

of mains off a Piper Lance and a nose gear built by Airight in Wichita. A decision is still pending on whether to continue using the Lance main gears or have Airight build the entire landing gear. The fuel capacity of the prototype YT-33, minus tip tanks, is 75 gallons. The main tank is in the fuselage ahead of the engine, and fuel from the tip tanks, when installed, will be brought into the main tank by means of transfer pumps actuated by a float switch in the tank. It's a completely automatic system, requiring no effort by the pilot. When the float switch turns them on, the transfer pumps will run for three minutes, at which time a built-in timer will cut them off. Fuel gages and a low fuel warning light in the cockpit allow the pilot to monitor the system. The next and all future YT-33s will have a 100 gallon main fuselage tank and two 50 gallon wing tanks. The Turbomeca burns about 60 gallons per hour, so the YT-33 w i l l have an endurance approaching three hours, with VFR reserve. Bo had a bit of an aesthetic problem in scaling down the tip tanks. The real T-33 has very large tip tanks, and when he reduced its dimensions by 2/3, the resulting YT-33 tip tanks were grotesquely large on an airplane with only a 26 ft. span and fuselage length. To make them look right, the YT-33 tips were further reduced to 60% scale . . . and yet they're still 108 in. long! It's just as well, however, because the airplane has absolutely no baggage space in the fuselage. The tip tanks will carry fuel in their center portions, with both the front and aft ends available for baggage storage. The YT-33's canopy is currently a one-piece, swing-over, quarter-inch Plexiglas™ bubble, but a fixed windshield is being considered for future versions of the airplane. Bo readily concedes that the prototype's cockpit needs more room inside. He plans to add 10 inches to the cockpit length in order to accommodate lightweight ejection seats that are available in Europe and to provide a

little more leg room and space for an instrument panel for the back seat. He is also t h i n k i n g about building the crew compartment, as he calls it, in one or two pieces that will simply plug into the fuselage during construction. All the controls on the YT-33 are balanced 100% or more. The ailerons use rather large torque tubes for actuation, SPORT AVIATION 73

III!"

and the elevators are actuated by a pushpull tube that extends back under the engine. From that point, two Teleflex cables, in tension only, run back to the elevators. The rudder is controlled by Teleflex cables that extend all the way back from the pedals. Simple flaps are used on the prototype, but Fowlers are being considered for future versions. 747 captain John Watt of Vancouver, BC was the test pilot for the YT-33 and has logged most of the 60 hours

fpm rate of climb. Cruise at 22,000 ft. is expected to be 320 mph, with a redline of 500 mph. Stall is expected to be about 75 mph, and the approach speed with 15 degrees of flap will be 85 mph. Bo Case grew up on a farm in central Missouri. After high school he worked for a phone company for a time and began sky diving in 1971. He jumped for most of the 1970s at tractor pulls, fairs, horse shows and such and says he had made 133 jumps before he

Carl Penner of Park City, UT has also flown the airplane. The performance figures they have come up with include a cruise of 260 mph and an over-the-fence landing speed of 90 mph. This is with an empty weight of 2,200 pounds and a gross of 3,300 pounds. The projected performance of future versions with carbon spars and prepreg airframe materials, with an empty weight of 1,700 pounds, include a ground roll of 2,000 ft., a lift-off speed of 80 mph and a 1,700

joined the Air Force in 1980 and was a crew chief on an F-111 for three years. He spent an additional year working as a machinist, which, he says, was the most valuable experience he had in the service. For a good bit of his four year tour of duty, Bo was based at the

the prototype has been flown to date.

74 JANUARY 1996

ever rode an airplane to the ground. He

Mountain Home AFB in Idaho. While there he began teaching sky diving at the city of Mountain Home's civilian airport and ended up operating the fixed base operation there. He learned to fly in 1982 in a Cessna 140 and later

owned a Varga and a 1 72 which he

used in his FBO operation, along with

a couple of other leasebacks. In the spring of 1985, shortly after his discharge from the Air Force, Bo went to work for Dan Denny in his then new Kitfox operation. He helped build production tooling initially, but was later involved in sales. He left Kitfox after a couple of years to start work on the YT-33. Bo and his wife, who is a CPA,

currently live in McMinnville, OR . . . which is famous today as the home of the Spruce Goose. The plan is to develop a more refined version of the YT-33 and offer it as a k i t . . . which is expected to take about a year. The company that has been formed to develop and market the airplane is called Stargate and the address is 1301 N. Highway 99 West, Suite 227, McMinnville, OR 97128. For the time being, Bo would prefer that those seeking additional information communicate by FAX. Stargate's FAX number is 503/434-9109. +