ONE DESIGN NEWS
Volume 1 Issue 2 January/February 1995
A Bimonthly publication for builders, pilots, and
enthusiasts of the ONE DESIGN series
I must start issue # two of the ONE DESIGN NEWS by thanking all of you who have subscribed to the newsletter, as of February over 170 people have returned the form. Many of you had comments and observations, ranging everywhere from technical advice to “how about a swimsuit issue.” Some of the more repeated comments include, a plans revision section, a tips section, include lots of info and pictures of builders projects, and the number one request, to publish a list of builder’s names, address, and phone numbers. This last request presents a problem. I should have provided a spot on the subscription form asking if you mind your address and number published. I realize that is can be great benefit to builders or even prospective builders to contact others in their area, to exchange information, compare projects, and share material, however, I hesitate to publish names without prior permission. I think that a compromise would be to wait until the next issue to include a subscriber list, and if you do not want your name in the list please let me know beforehand. I will not include names of plans holders who have not subscribes, merely because they have not seen this notice. I hope this works.
I have encountered another problem that I did not anticipate, I have had a hard time deciding where to cut this issue off. I have received some great information, and photos from builders. Please do not take this to mean that I am not encouraging future submissions. I could easily have produced a fifteen page newsletter, and I hope to have this much information for each issue. To my knowledge there are at least fifty serious builders, which means that by fall of this year we should see some aircraft flying. There is some great work being done on ONE DESIGN projects, and this is just the beginning.
IAC ONE DESIGN NEWSLETTER
Dan Rihn has written his last issue of his original newsletter dated vol 2, # 6. Dan produced this newsletter to keep builders and others up to date with plans progress, and the ONE DESIGN category. However as it is now redundant, Dan gets a well deserved break. This original newsletter certainly served its purpose, and really helped keep the interest level high. Dan will continue to be a regular contributor to the ONE DESIGN NEWS.
PLANS UPDATE
Part three of the drawings are due to be released shortly, this will be the final set of drawings. There may be additions, error correction, or clarification of existing information, but all of these will be included in future issues of this newsletter.
ONE DESIGN RULES
The ONE DESIGN rules were published in the December issue of Sport Aerobatics. The rules have been an ongoing subject of discussion and for some, dispute. I would really like to see the concept work, and I imagine many others also would. When the original concept was introduced in Sport Aerobatics it generated an amazing amount of mail. I must admit that there has been a fairly even split in the comments received to date, but here is also a large group of people building what they feel is a magnificent aircraft, with little consideration to the concept. There will certainly be enough ONE DESIGN aircraft to hold a competition within two years, however, will they all be red, white, and blue? Time will tell.
ONE DESIGN WING – A construction overview, Part II
We left off in issue one with a complete wing skeleton, glued together, but without stringers, or fittings.
We decided very early in the project that with 128 individual stringer cutouts we had better devise a way to do them quickly and accurately, if you intend to approach them with a coping saw and a straightedge you had better book a couple of days off. We built a small jog for a router to ride in. You will need a sharp ½” end cut router bit, we have tried both straight flute and spiral flute, and although the spiral flute cuts marginally better with less breakout, they are very expensive. I would think that you might be better off purchasing two straight flute end cut bits, and if the first shows any sign of getting dull, switch to the other, remember 128 slots! We used an 8” by 9’ strip of ¼” plywood as the base of our jig. We added ¾” square runners along each side. This enables the router base to follow along the runner, and as it is circular there is no particular alignment necessary. We then determined where each rib was located along the length of the jig, and made about a 3” notch along the jig with the router, we then clamp the jig along each respective stringer line using the tip rib and the base rib stringer notches as a guide, and then by running the router down the jog along the runner you get an exact stringer line. We have found that it is better to make two passes long each line, once at 3/8ths, and another at the finish depth of 5/8ths, this minimizes the tearout at each gusset. Along the nose ribs we leave the stringers slightly proud ,and finish sand with a long board to maintain the correct contour.
Installing the fittings is pretty straightforward, we use all machined components for the aileron hinges and drive fittings. Make sure you install plywood crush plates between the fittings and the spars. The bellcrank errors are covered in this issue elsewhere. It is very important to maintain alignment between the three aileron hinges because misalignment can cause bindig, and because over a 6 foot aileron incorrect alignment will be very noticeable. I would recommend that you align and drill the rear spar for the hinges on a drill press before you assemble the wing.
We have also added tie down fittings in the wing, these are attached to the main spar at station #84. The fittings are a simple machined strap with a 3/8ths female thread mounted flush with the bottom skin, we have removable 3/8ths male thread eye fittings. I imagine there will be lots of variations on this idea, (I have already seen four different types). We have mounted the pitot system at both the location shown on the plans, and in one wing we mounted the pitot block on the outside of the tip rib, this means that if it ever gets bumped, and they do, we still have access to the block and the fitting. We mount the static source on the fuselage. Make sure that you varnish under all fittings, and use large 970 washers up against wood, or even better a 4130 crush plate, and anchor nuts. Next issue, sanding, skinning, and ailerons.
A SPAR CLAMPED AND GLUED IN THE JIG
THE STRINGERS IN PLACE
WING CONSTRUCTION – ANOTHER PERSPECTIVE
My name is Christopher Gardner. The new editor of this newsletter, Peter Groves, has asked that I write an article discussing a second viewpoint on wing construction techniques. Some of you may recognize my name from my participation in the prototype One Design program; in addition, I have over nine years experience as an A& P involved in the maintenance and manufacture of aircraft ranging from homebuilts to transport category jets.
Because the very nature of this aircraft deals with construction from raw materials and blueprints only, I feel it is incumbent upon any potential builder to familiarize him/herself with basic woodworking practices available in books from a number of sources, two of which are the FAA’s AC 43-13 and the EAA’s Wood/EAA Aircraft Building Techniques. With this in mind, this article will concentrate on details of One Design wing construction only.
One question all builders are faced with at the beginning of any project concerns the type and quantity of equipment needed to accomplish the job. The following is a brief list of equipment I consider essential to construction of this wing:
1) 18 ft long x 4 ft wide flat table top
2) 8 point water level system (about 30 ft of ½ inch clear vinyl Tubing and some “T” fittings
3) Clamps. You cannot have too many clamps. 2 x 4 Block and Allthread Clamps (more about this in spar section); C-Clamps (at least 11 each of 4” capacity); Spring clamps (10 or 12 each of 1 in and 2 in capacity)
4) 10 ft angle iron straight edge or equivalent
5) 24-in x 16-in carpenters square
6) 12-in combination square
7) Chalk line
8) 7-1/4 in Circular saw
9) Hand jig saw
10) Electric or pneumatic hand drill and drill bits
11) 3 in x 6 ft minimum sanding block (straight and absolutely flat)
12) Fine wire staple gun and ½ in x .033 chisel point wire staples
13) 10 in hand place
14) Dust mask/respirator
While not essential, the following make the task significantly easier:
1) 6 in motorized jointer
2) Table mounted combination of disk and belt sander
3) Air compressor (if pneumatic tools used)
We start with fabrication of the main spar, which utilizes douglas fir. The stock we found was already mill cut to ¾ in x 4, 6, and 8 in. dimensions, with a radiused edge on the boards. This requires squaring the edge of the boards on a jointer to remover the radius. Next we cut each of the boards to the proper length and dry assemble the spar so that the grain slope on each lamination is opposite the successive lamination, and each butt joint is staggered on successive lamination. We then cut the spar stack so that each of the lamination layers has the same overall width of 9.75 in. Before disassembly, we match mark the boards in sequence to facilitate reassembly and mark the profile for the scallop cutout at the ends of the boards. After disassembly, we cut out the scallop profiles with a hand-held jog saw and sand the edges smooth. Although our spar assembly jig is straight-forwards and inexpensive to make, it is constructed of item #1 in the essential equipment list, the 18-foot x 4-foot table. This table is the foundation of all the wing construction, and as such, it must be reasonably flat and dimensionally stable. As can be seen in the accompanying photos, ours are constructed from ¾-inch x 4-foot x 8-foot plywood, 1-inch x 6-inch x 8-foot side boards, a few 2-inch x 4-inch x 4-foot brace boards on bottom, and several pre-fab steel table legs with adjustable screw feet installed at their base for leveling. We leveled ours with a builder’s transit, but any method including simple line levels, etc will do. One top of this table, we install our spar jig which is fabricated from 1-inch x 6-foot boards and plywood end gussets. They are simple “L” shaped platforms with triangle gussets on the ends for rigidity. We place a platform at each end of the table 17.5 inches apart. Placing household door shim stock under each platform, we level the end platforms and screw them to the table top. We then string two lines of fluorescent fishing line taughtly between these platforms on each outside top edge. We finish the jig by placing eight additional platforms equally spaced between the ends and shim to flush with the bottom of the strings and secure each platforms to the table with screws. This provides an elevated true surface with clearance for the clamps used during spar assembly.
In regards to these clamps, ours are made from 2 x 4’ yellow pine boards with 5/8 inch allthread secured through holds in the outer ends of the boards. We tack welded a nut to one end of the allthread, with the other nut free spinning. As can be seen in the photo, these clamps are positioned so that we can provide clamp pressure for both the laminations and the butt joints simultaneously. A word of caution, this incorporates two steps into one, and with a finite amount of epoxy working life and large surface areas to cover, speed is of the essence. A minimum of two people are required during this stage. Also, don’t forget to apply a layer of wax paper or equivalent between the clamps and spar surfaces to avoid the obvious.
At this point, we have a rectangular spar blank ready for tapering and beveling. This is accomplished by first marking a centerline on the spar forward face with a chalkline. Next we transfer the measurements for the spar’s height at the root rib and tip rib locations using our centerline for reference, and mark these heights on the spar. This gives us the taper profile of the spar. We use a circular saw and a long straightedge to rip cut both the spar taper and bevel simultaneously. We position and clamp our 10-foot angle iron straight edge an exact distance from the profile marks to allow for the width of our circular saw base plate which will be following the straight edge. We adjust the saw base plate to the proper 4.5 degree bevel angle, and make the cut. This procedure is performed four times, for each of the two top and two bottom surfaces of the spar. This completes the fabrication of the main spar.
We manufacture our ribs with production templates used to router out multiple pieces; however, the same things can be accomplished with a jig saw and patience. Pre-assembly of the ribs is limited to gluing the capstrips, center vertical stiffeners, and center gussets in place on both main and nose ribs. The forward and rear verticals and gussets are not installed at this time; however, we use a table-mounted 8-inch disk sander with an adjustable platen to sand the angles into the nose rib forward edge and main rib trailing edge surfaces prior to rib installation. Incidentally, we use production truss rib style fixtures for building the ribs, but again these could all be built free hand with some extra effort and care. At this point, I want to mention a real time saver for which I feel the cost is justifiable. Instead of using wire nails for assembling various rib parts, etc., during construction, we purchased a pneumatic fine wire staple gun manufactured by ITW Paslode for approximately $180.00. This tool speeds construction considerably (important when working with epoxy) and greatly reduces the effort expended. Sometimes tools just have to be viewed as investments, and no, I don’t own any ITW stock.