AC Spark Plug's . . . "Tip Of The Month Contest nother month has rolled around again and another award has been made for the best tip received, this one from Henry E. Winslow, EAA 595 of Inglewood, Calif. Here in Hank's own words is a tip on making metal trim tabs: One of the most fascinating things about building one's own plane is the variety of materials available to use in its construction. Too often, however, the builder seems unwilling to change the choice of materials to suit the unit. Because of this a great many homebuilts have ugly looking rectangles of tubing covered with fabric for their trim tabs, when a neat, lightweight one could be constructed of aluminum. (Refer to Fig. 1). The trim tab described in this article is easy to construct and will give a professional look to your homebuilt. See the example on Fig 2. The only tools needed are ordinary hand tools with the exception of a sheet metal brake. The skin could be hand formed, however the time involved in making a form and a clamp to hold it is much too great when less than five minutes at the brake will finish the bending operation. The three micarta ribs are made up first, then the brackets are made and attached with a couple of 6-32 countersunk headed screws and stop nuts. One of the outboard ribs is notched for the tab horn so the countersunk holes will be in the horn on that side. Bend up the skin over a 3/32 in. radius bar to about 70 deg. on the first bend, then you will be able to get a 70 deg. angle on the second bend. Clamp the trailing edges together and put the skin back in the brake with about Vz in. of the leading edge protruding from the radius bar. Now clamp down LIGHTLY until the skin forms the proper contour.

A

Fig. 2

Slip in the center rib and drill the rivet holes through the assembly. Select the proper length rivets and rivet in the rib. This can be done with a ball-pein hammer but care must be taken not to crush the micarta as it is quite brittle. Now fit the end ribs by cutting slots in the leading edge of the aluminum tab for the two brackets to extend through and drill and rivet as with the

center rib. Now drill and rivet the trailing edge and the tab is complete. It is a good idea to spray zinc chromate on the inside of the skin before riveting it up. I used brazier head rivets on the tab as the skin is too thin to countersink and dimpling requires much more work especially as the trailing edge cannot be dimpled anyway. It is good design practice to have the horn arms tilt forward so that the center line of the bolt holes passes through the center of the bracket bolt hole. If the trailing edge on your control is not straight the proper contour can be followed by varying the length of the micarta ribs to suit and trimming the trailing edge to the proper curve. The question may be raised as to the forming of a streamlined leading edge. It should be easy to form but I am not sure that the gradually curved nose will be stiff enough to resist the flexing and warping it will

encounter in service. However, as the FORMERS 3-EEQ'O. HINGE. BBtCT MKT'L.OfeO /BOTH ENDS') I ——————————— - '

TAB HO KM

. ,OG>O 24- S>T2>/Kl_

——— 6-32. COONTgg FLAT -ft LOCK WASHES?

FIG. 1

tab is very simple to construct, the reader might try building one up and see if that configuration still has the necessary stiffness. Again the use of formed metal ribs instead of micarta might be tried. The problem of riveting the skin to the ribs near the trailing edge will tax one's patience, however, and unless the builder has had quite a bit of sheet metal experience I suggest that he stick to the simpler tab described in this article. continued on bottom of page 26 SPORT AVIATION

25

EAA Design Competition By Harry Zeisloft would you like a big slice of the $5,000 prize H owmoney which will be awarded at the EAA Fly-In in

Rockford next summer?

The EAA Design Competition is an opportunity for you to have just that, as well as an opportunity to help out your brother aviation enthusiasts and at the same time to gain recognition for an important personal contribution. The EAA Design Competition was initiated to help develop a simple, safe and reliable sport plane for the amateur builder. In the last several years many articles have appeared in SPORT AVIATION attempting to clarify this objective of the competition. It may seem repetitious to some of you who have been aware of the design competition from its inception to hear, again, that the big idea is to develop a plane that is simple to build, fun to fly, is demonstrated to be a safe airplane, and can be towed home and put in the family garage. Any EAA member is eligible to compete. However, in view of the extremely short time remaining, those of you who will be able to fly your entries to Rockford next summer are undoubtedly well along the way to completion. In fact, if your first flight has not already taken place very early in 1962, you will be under a severe handicap to accumulate your 50 hours of flight and to accomplish the refinements in performance and handling that are the mark of a thoroughly completed amateur built project. If you plan on entering, please contact EAA Headquarters immediately, get your registration form back as soon as possible, and give the judges the advantage of a preliminary review of your entry and data so that they can be more thoroughly acquainted with your entry when they see it at Rockford. When the competition was initiated, special emphasis was made on the point that developing a new aircraft was a complex job in itself without considering,

AC SPARK PLUG . . . continued from page 25

Thanks, Hank, for a good tip and for your neatly typed and illustrated entry. Each month an award certificate is granted to the winning entry selected by EAA. These certificates are for either a set of AC Spark Plug aircraft plugs or for an AC Spark Plug Tachourmeter, at the winner's option. All you need do to enter is write up your tip and send it to EAA at Hales Corners, Wis. Be sure to mark it as an entry for the "AC Spark Plug Tip of the Month" contest. If you have sketches or drawings it would help ease the work load here at Headquarters if they were neatly done with good contrast, so that they're ready for printing in SPORT AVIATION with no further work. But, whether you have a draftsman friend or not, the important thing is to get your ideas in and share them with other amateur builders. Good luck. • 25

DECEMBER

1961

also, the development of an experimental aircraft engine. We also felt that many people would want to build an airplane like the winning entry and, therefore, the power plant should be readily available and completely reliable. This led to the rule calling for a certificated aircraft engine. In the several years since the contest was initiated, the Lycoming 0-290-G engine became available in great numbers at modest prices. A decision has therefore been made and approved by the EAA Board of Directors that 0-290-G engines converted to a configuration comparable to a corresponding ATC'd aircraft engine would be considered to meet the requirements for the use of a certificated engine in the design competition. We would welcome your comments on this matter. One of the factors which was not discussed in much detail in previous articles is the matter of flight testing your aircraft. If you are an amateur builder of limited flight experience, make use of the help of others having the qualifications which would minimize "pilot-error" risk in the initial test hop of your pride and joy. It seems unnecessary to point out the need for a calm and objective approach to the initial flight test and to the insistence that every factor be as right as possible, the wind, the weather, the terrain, condition of the runway, traffic, condition of the aircraft, qualification of the pilot, physical condition of the pilot—don't get railroaded into making your first test hop on a scheduled basis. One more suggestion—check in the June, 1961 issue of SPORT AVIATION for a rundown of the rules, and review in the October, 1960 issue the portion of the annual business meeting wherein it was designated the prize money distribution. If you have suggestions, comments or assistance to offer, now is the time. Just drop a letter to EAA Design Competition, EAA Headquarters, Hales Corners, Wis. A

OPPORTUNITY KNOCKS!! Looks like aeronautical engineers who specialize in light aircraft design and construction are hard to find.

We recently received word of an exceptional opportunity for EAAers who have the necessary qualifications and experience. The Piper Development Center at Vero Beach. Fla., occasionally has openings for qualified engineers and designers whose main interest or experience is in light commercial aircraft. Inquiries should be sent either to Fred Weick, Director, or Karl Bergey, Assistant Chief Engineer. A Don't trust every last detail in your plans. Most plans turn out to contain at least minor errors of commission or omission. If things don't jibe, look for such mistakes before tearing apart the work you have done. It is better to write to the designer and clear up a vague point

rather than to have it haunt you while flying.