ZNLine Factory Enigma Build by Mark Novack

There are several good ways to do this job. This way is nice because the blade cuts a perfect 3mm slice. It also leaves the faces perpendicular to the wing surface. The 3mm slice is great because it will allow capping the aileron and the wing cut with 1mm balsa and leave 1mm clearance, which after covering will be about a .5mm gap, perfect for smooth airflow with neutral aileron and beautiful to look at. This table saw has all of the stops and squaring devices to set-up and run a series of wings through rather quickly. PLEASE, if you ever try this method, BE CAREFUL. Table saws are one of the woodworking industry's number one finger takers. Always be mindful of the blade. In this operation the blade is set at maximum height and angled to cut the proper angle. Here it is ready to be turned on and make the cut.

The wing is passed right over the blade. It cuts 80% of the way through. The final cut with be made on the scroll saw.

Having sanded a few airplanes, the first thing I noticed when I started sanding the sheeting from ZN (my first prep job was on Mr. T. Yamada's Synergy) was that contest weight sheeting requires special care. First off, any seams and rough work is knocked down with worn 80 grit. Yes, 80. A soft hand will not scrape into the balsa. IMPORTANT: During final sanding, some compressed air course really helps. The paper must be lifted often and and hard particles blown out to keep from scratching the surface. The ears will tell immediately if there is debris in the paper. Once all of the shapes are there, 240 is used to remove any remaining bumps. A wood block keeps from sanding dips around any hard spots. Then 400, first with the grain, and then I do the little circles. I use foam as my block because it conforms to the curve of the surface and rounds any spots flattened in the earlier processes.
After the 400 is finished, I fill all imperfections. Sand off the filler, recheck, refill other imperfections, sand off, then I start with the 1000 grit. 1000 grit sands contest grade balsa in about the same way that 400 grit sands heavier grade, albeit leaving the surface with a 1000 grit finish. When the surface is as smooth as possible, I blow it with compressed air (GENTLY, it is possible to blow right through 1.5mm balsa with compressed air). This clears out the grain and shows any nicks that remain. Nicks that look pressed get a licked finger, nick that look a little torn get a spot of filler. (filler is NHP balsa filler; my friend and real professional builder Nathan [he does Christophe's prototypes and advises me when I need help] from ZNLine France used dope and talc).  As far as boundaries (LE and wing tips where they join the sheeting), if they show a line, then they get a little filler. Normally, it is only the tips because the grains are 90 degrees and that will be highlighted under the covering after a month. I also fill the deeper grain pathways. The finished product, when held at various angles to the lights, should have an even grained surface with no manmade nicks, no pits or ripples. I would love to know if there are easier methods that can achieve the same results. I know of no method other than the elbow grease method of sand, clean, look, fill and continue on until the surface looks as perfect as possible. There are so many blocking techniques and most work as well as the other because the hand learns the feel of the tool and the same result can be achieved. Maybe a separate thread on F3A airplane finishing techniques could be started? Like I wrote earlier, contest weight balsa needs different techniques than harder grades of balsa, so this is special in a way to F3A. Is all of this work overkill? After the first few flights the wing normally has nicks just from insects or grass or a clumsy hand with dried CA on the fingers. I have heard some highly experienced people give theories on smooth versus rough finishes and that rougher finishes fly better. I have also seen CPLR's personal paper finished wings that look great at 20 feet but up close are obviously optimized for winning in the air, not on the static display. I guess it's like this; we will give the customer the best and lightest finish that we can do using our methods (balsa sheeted, Oracover finished). If the desire for a rougher finish is there, we can supply unsheeted cores with a basic kit for the person who wants to do it all, as there are so many good techniques. OK, that was long winded. I hope that this answered some questions. I continue to learn and we continue to experiment with new methods, continually striving to find better ways to make better airplanes.  Well, it has been a few days. There are several painstakingly sanded stabs and rudder sets. We have commenced designing four new airplanes and conception of another. Last years show damage has been repaired, we visited Sinsheim show and have strategized kit fabrication for the next year. Now it is time to build.
The last step performed was clipping away the aileron. We used the table saw to make the 3mm slice at the root end, and then the scroll saw to finish any cutting still needed. The lumps where smoothed on the belt sander and I commenced facing the ailerons and wing TEs. With the ailerons cut off, first the marks for the TE facing inlay were made. This is of such great importance that if it is not done, I can assure you that the wing will fail. 
 

Here are the markings for the inlayed root end of the TE face.

The wing is carried to the band saw and the parallel cuts are made.

I use a hobby knife and sever the end and slice down to cleanly cut the foam. The scab drops right out.

Again, wood glue. The ailerons are already capped and drying. It takes about an hour to glue all nicely. During the gluing of the aileron, one is provided a chance to remove any warp that occured in the aileron by gluing it onto the cap nice and straight.

We inlay this 4cm into the root. There is no reason why it cannot be inlayed 6 or even 8cm, but 4cm relieves the stress riser that always occures in the corner. This is so important with wing as light weight as these are. Do not skip this step when sheeting with contest balsa.
Tomorrow, I shall sand down the faces and cap the root of the aileron and the opposing face on the wing. I will use 1mm ply for that operation, then the TE of the aileron and wing will be capped with the same 1/64" ply used on the TE of the stab and rudder. Then it is hinging, beveling, final sanding, and we will finish up the fuselage.

Here is what the aileron looks like sitting flush on the wing after the faces have been sanded flush with the surface. The razor plane followed by 80grit and 240 makes this failry quick and easy. It is ready to start hinging.

Just like the elevator and the rudder. The surface is taped to the wing for marking the hinge locations. The ailerons will each get 6 hinges, spaced on these ailerons 18mm from root and tip with 97.6mm between each hinge. Please refer to the stab hinging process for the formula we use to determine the spacing. It is just easier to calculate mathematically than to use the TLAR system.

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