INTRODUCTION by Luther D. Sunderland The T-18 Newsletter began in the fall of 1964 as a result of several letters and a visit with Dick Cavin, 10529 Somerton Drive, Dallas, Texas 75229. Dick had essentially "kicked off" the T-18 Mutual Aid Society with his fine article in the September 1963 Sport Aviation magazine entitled "Reflections From Rockford" in which he told about building the T-18 fuselage in just 3 1/2 days at the EAA Fly-In at Rockford, Illinois. But we felt that there was a real need for a "house organ" to circulate to the T-18 builders. Sport Aviation was fine for reaching the general EAA membership, but the time lag was too great, and there was not the editorial freedom found in an informal newsletter. So, Dick and I agreed to publish a newsletter for the exclusive use of T-18 builders with the editing and publishing being done alternately in New York and Texas. This continued for the first five issues. Then family illness and work demands made it impossible for Dick to continue, so I published all subsequent issues up through number 44 in 1976. All articles in these Newsletters were written by me unless otherwise noted after the title. Then in December 1979, Dick retired from Braniff Airlines and resumed as editor, publishing t~le next 23 issues (by October 1986). This volume contains a reprinted version of the first 44 issues of the T-18 Newsletters, which have been edited to omit material that is no longer applicable. Also, comments have been added occasionally with the notation (1986 Note:) to provide guidance to builders where we have since learned additional information that would shed further light on the particular subject under discussion. Perhaps the reader is not familiar with the T-18 aircraft and you have obtained this book as a general reference to learn about fabrication of a riveted all-aluminum airframe. For anyone in this category who is not familiar with the design concept of the T-18/S-18, a brief historical sketch is included here. In the early 1960s, the Experimental Aircraft Association sponsored a design contest intended to stimulate designers to develop aircraft that would be easy for the person with average home workshop skills to build, one that was safe for the low-time private pilot to fly, and one that could be converted for transport on the highway and kept in the family I I garage. The several finalists that were able to meet all contest requirements, including completion of flight tests for a prototype, were not notably good designs and are long forgotten, for all practical purposes. However, a design that was not completed in time for contest judging has proven to be the undisputed winner, for it dominated the display area at Oshkosh for years and is still a very popular homebuilt. It has captured a number of records for homebuilts, including the coveted first (and so far only) homebuilt to fly around the world and to the North Pole. This aircraft, of course, is the T-18, and its designer is the well-known aeronautical engineer, John Thorp. The T-18 was his 18th design. Some of his other designs were the Fletcher agricultural plane, the Thorp Sky Scooter, Piper Cherokee 135, Lockheed P-2V Neptune, and Wing Derringer. When John Thorp established priorities on design criteria for the T-18, he placed construction simplicity higher than ease of conversion to highway configuration. The wing was constructed in four panels, each four feet wide, so standard width aluminum sheets could be wrapped from trailing edge to trailing edge with no spanwise drag-producing joints. The 20' 10" wing could be detached in one piece when seven detented pins were removed. The main drawback was that it was a three-man operation that took about 20 minutes. In 1974, at John Thorp's suggestion, I undertook the design of a wing that would be much easier to convert to highway configuration. Also, I widened the cabin by two inches to improve passenger comfort. For eleven years, I sold modification plans using the designation T-18CW for convertible wing with wide body. Then in 1985, after John Thorp took the T-18 plans off the market, I produced a complete set of new drawings for the entire aircraft. Since such extensive changes had been made to the original T-18 design, the model designation was changed to S-18. These construction drawings, along with complete detailed building instructions, are marketed by Sunderland Aircraft, 5 Griffin Drive, Apalachin, NY 13732. The following sections, consisting mainly of reprints of articles from the first 44 issues of the T-18 Newsletter, not only give a detailed history of one of the most important homebuilt designs, but they also present much valuable information about how to build every part of an all-metal aircraft. How-to-do-it articles describe making fiberglas molds and parts, bubble canopies, plush upholstery, hand formed ribs, no-fixture aircraft structures, etc. Also, advice is given on how to do weight-and-balance measurement and how to flight test an aircraft. This is a veritable gold mine of information that is of value to anyone building any type of aircraft. III The first twelve newsletters contained much material that has been outdated, so these have been condensed into a single section. The remaining newsletters have been placed in 32 separate sections. IV EXCERPTS FROM T-18 NEWSLETTERS *1-12 Luther D. Sunderland RIVETS: by Dick Cavin. Apparently some of the newcomers are a little confused about the use of Hi-Shear rivets and Pop rivets. Basically Hi-Shears are high shear strength steel rivets, with an aluminum retaining collar, that are used instead of AN bolts. They are lighter and in some other respects superior. They can be installed very easily, using only a hammer and a simple installation tool. It is perfectly acceptable to replace a number 10 (3/16-inch) Hi Shear rivet with a 3/16-inch AN bolt of the proper length, a washer, and elastic stop nut if you have difficulty obtaining Hi-Shears. Almost all aluminum rivets in the T-IB structure are liB inch in diameter. With matched-hole tooling techniques, when the rivet holes are made around the edges of skins, frames, and ribs, they are punched with a hand punch that was originally invented by the Whitney Tool Company of Rockford, Illinois. The Whitney punch set (the #5 Jr.) is obtainable from the Whitney Tool Company or from industrial supply stores. (Other brand names are available in 19B6 which are very similar, do the job, and cost less.) You should order extra #30 punches with and without the little "nib." Or you can easily make extra punches from drill rod on a lathe by copying the shape of the bought punch. You cannot put a liB-inch rivet in a liB-inch hole. It takes a #30 hole. If you dimple the skin around a liB-inch hole, the hole will enlarge enough so that a liB-inch rivet ~111 go in. Also, it is accepted practice to dimple the lighter gauge skin and countersink the thicker material (040). If you plan to flush rivet, you might want to get a set of dimple dies for the Whitney punch. They are needed for dimpling ribs and frames, but they do not do an acceptable job in external skins. (Make a hand dimpling tool for skin dimpling as described in a subsequent newsletter.) USING TEMPLATES: by Dick Cavin. The T-IB is constructed without the use of jigs or fixtures through a process developed by John Thorp called matched-hole tooling. Once a hole pattern is laid out in a particular part, it is transferred to the mating part with a transfer template made of scrap aluminum. Here are some tips on the transferring (marking and drilling or punching) of holes by the use of templates. The first thing the builder of a metal aircraft, using matched-hole-tooling techniques, needs to learn is how to properly transfer hole patterns with templates. Holes are transferred from templates with a hand duplicator punch. A hand duplicator punch is either the liB-inch nibbed male page 1 punch from a Whitney punch, or a similarly-shaped slightly longer tool that you can make yourself. It takes a little practice and skill, believe it or not, to properly use the liS-inch duplicator punch. Hold it between the thumb and middle finger and sort of wiggle it in the hole. Do not try to push it straight down into the hole, for this will not work. Tap the punch with a hammer, not too hard. Be sure the punch is in the hole before tapping so as to avoid damage to the template. Absolutely do not drill through the template. Always use the punch that has a little center nib to transfer the hole centers. (Make sure that the nib is perfectly centered on the end of the punch. I bought a punch with a nib that was off center, so I had to true it up on the lathe.) Remove the template before you actually drill holes. Take care to keep your drill at 90 degrees to the sheet and, in the case of fuselage sides, drill both sides and transfer strip at one time. To transfer the hole pattern from the skins to the bulkheads the important thing is to VERY accurately locate a starting point. We cannot transfer hole patterns at points where bulkheads are joggled, as this would cause mismatch. I chose the first rivet hole above WL 42 as my "anchor" hole. On my form blocks, I drilled a tiny hole at this point. I tapped a wire brad lightly through this hole, making a tiny mark on frames. On a penciled rivet hole center line, I punched the rivet hole. Next, a rivet dowel was used and skin transfer strip and frame were pinned and clamped together. The hole pattern was then transferred with nibbed punch. Sounds complicated, but it really is not. Transfer strips should be labeled as to "up" or "out," etc., and extreme Care should be used so that transfer strips are always turned the same way. THINK. Leave the 523-1 bottom skin extend forward to cover the main spar cutout to aid in aligning the 523-2 floor. Important! After alignment, drilling and clecoing, cut it out. To use rivet as a dowel through worksheet, put head on bottom, and secure on top with tiny C clamp or piece of masking tape. DRILLING: Great care must be taken to prevent drift during drilling. It helps to first drill a 3/32 hole and then enlarge to liS. Also, if two centerlines (a vertical, a horizontal) are first drawn through the center punch mark, they can be observed during drilling. Keep drill vertical. Practice on some scrap aluminum. SIDE SKIN SPLICE: If you decide not to purchase a long piece of rolled aluminum for the fuselage side skins, make a splice just aft of STA 179.2 (T-1S), using a 0.032 strip 2.5 inches wide as a doubler. Four vertical rows of AN426 AD4 rivets are used. Rivet centers should be 0.25 inches from sheet edges. Rivet spacing is about one inch. Do not continue the doubler under the angle at WL 42. It is much better, however, to purchase a roll of skin material from Airparts Incorporated in Kansas City and make the skins in one piece. page 2 Actually, in 1986 there is no need to use a splice in the side skins, for it is just as economical to purchase coiled aluminum in thicknesses up to 0.032 inches. Two side skins can be made from a 20-foot long piece four feet wide with the two 14-foot long skins overlapped. FORM BLOCKS: by Dick Cavin. Have had a considerable number of you ask "From what material do I make form blocks?" I used a select grade of maple for all my small parts (ribs, etc.). I used 3/4-inch fir plywood for the fuselage bulkheads. I have heard of Beneflex (tooling masonite) being recommended, but know it is hard to find and very expensive. Some builders used wood chip composition board for fuselage frame forms. If you expect to make more than one airplane from the form blocks, glue a layer of 1/8-inch tempered masonite to the top surface. Actually, most any wood material will do for form blocks if it will not splinter badly. It is important to make all form blocks in duplicate, as you must always make a block-metal-block sandwich and clamp it together tightly while forming. Metal will creep from forming stress if not held tightly. The backup block need not be a complete duplicate but can be made from pieces of scrap wood 3/4 inches x 1 1/2 inches. Use two index pins or 1/4-inch bolts in each side of the form block. Put pins completely through the "sandwich" to both align parts and restrain them. Put them near a corner so the index holes can be punched rather than drilled in the metal part. TOOLS: by Dick Cavin. I highly recommend another tool, the Mead Bandsander, which looks like a small band saw. It deburrs, sands, shapes, profiles, etc. It uses l-inch x 42- inch belts that can be torn to 1/2 or 1/4 widths for small areas. It is used in every aircraft factory and is tremendous for sanding the edges of aluminum parts. Here is something else that will save you many hours of tedious labor. You can write Mead Specialties, Chicago, IL. If you want to saw aluminum plate, Sears has a blade (both six inches and nine inches) that does a beautiful job. It is their Kremedge Non-Ferrous cutting blade. Carbide-tipped circular saw blades are available in 1986 very inexpensively. They will last almost indefinitely. If you have a band saw, get a skip-toothed blade for best results, although you can use ordinary wood cutting blades if you use a wax or grease stick to lubricate them and keep the teeth from clogging. MAKING FITTINGS: by Dick Cavin. You can make your own fittings of aluminum plate quite easily. Saw them oversize and sand or file down to a scribe line. An ordinary disk sander works fine. I used a rubber-backed five-inch one in areas that I could not get to with the sander, followed by sanding with the little Mead bandsander. If you turn the rotary files very fast, they will chatter. Take very light page 3 cuts, too. Final sanding is by hand using wet-or-dry sandpaper in progressively finer grades. Make all scratches parallel to the part edge, not perpendicular. Sprinkle a little Bon ami on the sandpaper. This (or toothpaste) makes a fine light abrasive. If you want to get fancy and do real first class work, buff your fittings with a cloth buffing wheel, using emery buffing compound, working down to tripoli or jeweler's rouge for a true mirror finish that rivals chrome plate in brilliance. Before you get carried away, however, remember that all aluminum fittings must be sprayed with zinc chromate primer to prevent corrosion, so your nicely polished parts will not be visible for very long. Actually you should always finish aluminum edge to as fine a finish as possible, so as to eliminate starting places for cracks. This gets very important on thin sheet parts (ribs, etc.) that do more flexing. Finish the edge of sheet parts to the extent that there are no visible scratches or nicks perpendicular to the sheet edge. This also applies to deburring holes. Always deburr holes before dimpling, as the forming stress of dimpling may possibly crack light skin. If this happens, you will have to drill it out and use an oversize rivet. FORMING RIBS FOR THE T-18: by Dr. B. John Shinn. Introduction: I had always looked at formed metal ribs, bulkheads, etc. with a sort of envious awe. I dreamed of building my own all-metal plane, but thought that the cost of special tooling would be too high. Having things like ribs hydropress formed would also be too expensive. But, then came the series,of Sport Aviation articles on the T-1B. John Thorp made it sound like an ordinary guy could make acceptable ribs himself with only a mallet, a bucking bar, and some wood form blocks. Besides that, he mentioned an alloy, 6061-T4, which could be formed without annealing. To me, all aircraft sheet aluminum had been 2024-T3, which required considerable care even in bending straight line corners, let alone compound curves. My interest mounted to the point that I was mentally stretch-forming ribs, so I decided I would just have to build the T-1B. Although the article in Sport Aviation ("Building the T-1B" Part 3, July 14, 1962) was well written, I feel that a look at my rib forming experiences might be helpful to those who are also now ·'tin benders. '1 Form Blocks: After reading Part 3 in Thorp's articles, checking prices on form block material (maple, birch, birch plywood, tempered masonite, etc.) I decided on birch. It has a fine-grained surface for non-bumpy layout, and does not split out under heavy pounding. Besides that, it COmes in widths (6 inches to 9 inches) which are more manageable than page 4 large sheets of plywood. Thickness should be 3/4 inch to allow forming a good flange out to 5/8 inch. (1986 Note: Today 1986 builders might find solid birch hard to locate and very expensive, but most lumber yards have good quality 3/4- inch birch plywood that is used for making cabinet doors. This stands up quite well when used for rib form blocks. Also, it is quite difficult to find 6061-T4 aluminum sheet. Most suppliers have only T6, which can be used for ribs, but it is much more difficult to stretch form. Phil Tucker who bought Ken Knowles' Sport Aircraft Inc., 104 E. Avenue, K-4 Unit G, Lancaster, CA 93535 has T4 sheet, however.) The complete airfoil template was laid out on 0.040-inch aluminum and 0.025 inch (the thickness of the rib material) was trimmed off the complete perimeter of the template. The airfoil coordinates given in the plans have the exact dimension of the main spar height. So, when a form block is made for a specific thickness rib (0.025, 0.032 or 0.040), then the appropriate thickness must be removed from the original airfoil contour to allow for the thickness of the rib material. Several 1/4-inch indexing holes were punched to align nose and center rib sections. The location of these locating holes is important for they must be reachable with the Whitney punch when there is a 7/8-inch wide flange on the rib blank. Put two of these holes along the lower side of the nose rib portion of the template so there is adequate distance from the bend line for the spar flange on the shortest rib. This airfoil template was laid on top of two 3/4-inch birch boards and the indexing holes were drilled through the boards simultaneously. A couple of 1/4-inch metal dowel pins held the template on one board for the layout marking. A sharp knife was used to trace around the template. Then a pencil, sharpened to a fine wedge shape, was traced lightly through the knife groove. This made an accurate layout line which was easy to saw along. The template was "flopped" over, doweled, and traced by knife and pencil on the other piece of birch for the "opposite hand" rib. For the sawing process it was discovered that the band saw was the most practical. By carefully staying about 1/32 of an inch from the pencil line, with this cut I avoided excessive sanding time later. The rough-cut form blocks were then sanded to the center of the knife groove outline. A sanding disc mounted in a table saw works well for this. The disc was tilted so that it undercut the form block to compensate for the spring back of the rib after forming. About four degrees was used for "straight" sections while a six-degree tilt was used for the more highly curved nose of the rib. (It is important to note that it is much easier to make this spring-back allowance with the initial sanding than it is to first sand to the line page 5 perpendicularly and then try to add the angled undercut without over-shooting the mark.) The edges of the form blocks were rounded to give the proper bend radius of 3/32 inch. It was found that a small Stanley Surform file made quick work of this with only a minor amount of sandpapering to smooth it out. Rib Blanks: For quick layout of the rib blanks, a 0.040 metal rib blank template was made for the nose ribs and another was made for the center section ribs. (For the rest of this article, we will concentrate on the nose rib fabrication since it is the more difficult.) The airfoil template was laid on a piece of scrap aluminum and traced around for the nose rib section. A pair of dividers set for 7/8 inch was used. By trimming this metal to the outer mark, a 7/8-inch flange was left all around this nose rib blank. This blank was again placed under the airfoil section and the indexing (locating) holes punched through. The cutout at the front of the nose rib was made in this nose rib blank template per the 201 drawing. It is strongly recommended that the cutout in the actual ribs be made only after the rib has been formed. If it is made before forming, it is almost impossible to prevent sharp double-back creases at the front edges of the nose rib. So, leave the rib blank at least 1/2 inch longer than the form block at the leading edge. When the excess is trimmed off after forming, it will remove most of the folded-back part of the flange. Holes were also punched through this template for the corner relief (as indicated on the prints) for the 201-1, -3, and -4 nose ribs. The -1 and -2 were close enough alike to use the same relief holes. Cutting Out Blanks: The 3' x 12' sheet of 6061-T4 was unrolled on a rug in the family room (to prevent scratches) and a few quick trial and error layouts with the rib blank templates produced the most economical layout. A "grease pencil" was used for this since it has enough contrast to be visible and is easily wiped off when desired. Since the ribs were to be trimmed after forming and generous flanges were allowed it was not necessary to make precision layout marks- just a quick trace around the rib blank with the grease pencil was all. Again, do not mark the nose cutout. For cutting up the sheet, I found that the 6061-T4 sheet was cut up with least waste and least scratching by using a regular pair of straight sheet metal shears. The two sides of the sheared piece were spread apart (by one hand and one foot) so the shears did not bind. This resulted in a slight curvature of the new blank but it was insignificant when compared to the stretching it was soon to undergo. The blanks were then placed under the rib-blank template, the locating holes were punched, and the nose cutout was scribed page 6