From The EAA Designee File Information Submitted by Participants in the EAA Designee Program RESORCINOL GLUE SCALE

(Measure U parts resin to 1 part catalyst by weight)

license numbers on your fuselage sides can be a real time-consuming job. However, using a guide as shown be-

low, it is no problem. Make the guide the dimensions you desire out of a stiff material such as aluminum or cardboard.

X-2i inches

Using this guide as a template, the outlines of all numbers and letters can be quickly traced directly on the surface. This guide also aids in keeping the numbers uniform. Mask off and spray paint, using three coats. Before applying the first coat of paint, rub down the edges of the masking tape and apply a thin coat of clear dope

along the edges. This will help prevent the color dope from bleeding under the tape."

NOTE:

End suspension points

HOW TO USE..

and pivot point must be on straight line.

1. 2.

Hard Aluminum

Wire or Nails e to Wedge shape

Place cup and scoop in position. Balance by means of sliding weight.

3.

Pour desired amount of resin into cup.

4.

Add catalyst to

scoop until balance is restored. 5. Pour catalyst into resin*

DETAIL 'A*

TEACUP USED AS MEASURING SCALE TO MIX RESIN AND CATALYST FOR GLUE One of the most accurate methods of measuring correct proportions of resin and catalyst for resorcinol glues is by weight. My hat is off to Bob MacDonald of the Greater Boston EAA Chapter for this excellent measuring scale. It works fine and is amazingly accurate. An old teacup is ideal for the glue pot, and easy to mix and wash after use. (Contributed by Jack Denison, EAA Designee 115.)

TIP TO MAKE NUMBER PAINTING ON HOMEBUILTS AN EASIER JOB Prolific in his help to builders, Jack Denison, EAA Designee 115 of Stoneham, Mass., has this hint for those painting the numbers on their machines: "Laying out the

BEVELING OF SPARS SIMPLIFIED BY USE OF HAND PLANE Jack Denison, EAA Designee 115 of Stoneham, Mass., is one of our most frequent contributors to this SPORT AVIATION feature, and we are all grateful to him for his efforts. In recent correspondence, Jack stated, "Usually wooden wing spars are beveled on at least one edge. Either the spar must be made ta fit the ribs or the ribs msde to fit the spar. Most homebuilders seem to build the ribs first and therefore the spar must bs beveled to fit the slot ni the ribs. This should be a good fit. Spar blanks

Spar-

-Plywood or other stiff material.

Work Bench

the slot in the ribs. This should be a good fit. Spar blanks bevel the edges. This beveling can be done quite easily with a hand plane. Using one of your ribs, plane down one end of the spar to fit this rib. Now make a gauge as shown and using this gauge start planing to the other end of the spar. Check often with the gauge. The beauty of this gauge is that it allows you to check the spar while it still clamped to the side of your workbench. "One more thing. Your tools must be very sharp to

obtain the best possible job with the least trouble."

24 H

RELIEVING STRESSES IN WELDED STRUCTURES Luther Sunderland, EAA Designee 60 of Apalachin, N.Y., brought out a problem area which has occurred in a few aircraft. Lu states, "To quote Bob Deyelle, our FAA inspector, 'One of our biggest problems is to get builders to stress relieve their structures after welding.' During the welding of a cluster there is necessarily an uneven cooling which takes place. Since with cooling there is considerable contraction, tremendous stresses are locked up in the structure. Not only are these stresses locked (Continued on next page) SPORT AVIATION

13

DESIGNEE FILE . . . (Continued from page 13)

up in the immediate vicinity of the weld, but also in the surrounding structure if a complex structure is involved. "For instance, when welding a structure which might be compared to a wheel with spokes, as each spoke is welded and cooled, the contraction sets up tremendous stresses. But even very simple weld joints can cause problems. John Thorp told me he has seen a person make a long weld simply joining two 4130 steel plates and when the welder got to the end of the weld, the plates cracked completely apart due to locked up stresses. This illustrates how vicious this problem can be if rapid uneven cooling takes place. "There are a number of ways to solve the problem. Here are a few: 1. Keep the design simple. Avoid highly complex clusters and redundant members. 2. When welding a wheel-like structure (such as the clusters at a fuselage station), start welding at the center and work outward. Never weld the outer clusters and then finish in the center. 3. When finished welding at one station, stress-relieve every weld at that station. Stress-relieve a weld by evenly heating the whole cluster with a slightly car-

borizing flame just to a "cherry red." Then continue to bathe joint in flame and cool slowly. 4. When a weld is first completed, don't whip flame away fast. Keep weld enveloped in flame while it cools slowly. 5. Inspect all welds with a magnifying glass for minute cracks. Piper magnafluxes all critical parts such as engine mounts and landing gear. Our chapter members were scared stiff when we saw the large number of parts which must be reworked after inspection. There were usually many cracks on a single part. Many builders say they wouldn't ride in a homebuilt that didn't have gear and mount magnafluxed. Jim Wickam, a Boeing engineer who built the four-place all-metal "Bluebird", didn't zinc chromate his gear and mount for several years after construction. He coated them with a clear protective material which allowed inspection of all welds for cracks. A good idea for any airplane. 6. Use the right kind of welding rod with 4130 tubing. The FAA recommends Number 7 mild steel rod. "Don't be afraid to stress-relieve a joint because of the possibility of weakening. If it was hot enough to be welded, it already was heated to a higher temperature than is needed for stress-relieving." ®

DURAND XD-85 . . . (Continued from page 12}

climb. The pilot, also, was unable to determine the attitude of the airplane visually without reference to the airspeed indicator, probably because of the unusually wide visibility afforded. It should be noted, too, that the elevator control stops had not yet been installed. In summary, the testing program indicated that the XD-85 had superior ground handling characteristics even under adverse wind conditions; and, the take-off and landing characteristics, without flaps, confirmed predicted values. The airplane demonstrated strong inherent longitudinal stability and gentle stall behavior. No flutter was observed in the tail boom, which was considered as possibly critical before flight testing. What eventually happened to the Durand XD-85? The handwriting was already on the wall when the major airframe manufacturers were cutting back and shelving new designs, and in some instances losing the battle for their economic lives. The project's future was already questionable when the airplane was damaged during the flight tests. The damage was very slight, and the ship was placed in the hangar for repairs. While awaiting these repairs, a painting crew refinishing the interior of the hangar accidentally let a section of scaffolding fall on the wing of the XD-85, inflicting major damage. With fewer than 20 flights on it, the airframe was stripped of the engine, instruments, wheels and other major items, and abandoned. It was decided definitely that production would not be profitable in the foreseeable future. Therefore, the actual performance figures were never fully determined, nor was the craft's spin behavior. The effect of reducing the remaining wing strut turbulence 14

OCTOBER 1967

The Durand XD-85, two-place with 85 hp engine, was another of a long string of hopeful new designs following World War II that were just not meant to be. Piper had also developed a similar but somewhat larger airplane

which was also abandoned.

through better streamlining of the fairings was never fully learned; neither was the effectiveness of the trim and control stop arrangement, nor the performance with the semi-automatic flaps in operation. Although the builders were disappointed that the airplane did not reach production, there was sufficient satisfaction in its creation, and exhilaration in making the initial flights to compensate in large measure. Following the termination of the project, Durand returned to teaching at the University of Omaha and, by 1950, had completely drifted away from flying. Interest and his license were both recently renewed and, along with association with Eastern Nebraska Chapter 80, of which he is president, his interest in aircraft design. Since then, he has designed a small, two-place, negative stagger biplane known as the Durand "Mark V", the prototype of which is being built as a group project by members of Chapter 80. ®