ZNLine Factory Enigma Build by Mark Novack

These are the horn mounting plate we will be using. Normally they come without the milled recess, but as all of these airplanes will use ZNLine aluminum horns, we use a file that cuts a 1mm depth into the plate that captures the horn nicely. I shall post a few pictures of the 3meter routing table at work on a small job.

This table cuts everything from these little parts, to fuselage sides for the 300XL Extra, and even wing parts for Mudry Aviation for their full size CAP aircraft.

These are some very nice horns. Specially made to use the MK ball bearing connectors. These screw into the plate with a 5mm wood screw. If that sounds like it's not enough, we have never had one pull out or heard of one pulling out. The plates are aircraft ply.

It is actually two 5mm wood screws that hold it to the plate. The plate itself will contact balsa all around for a very strong attachment to the control surface.

The number one way to do this job it with the router. It is depth locked at 3mm. The outline of the plate is drawn onto the control surface and the piece is routed out. The corners are then finished by hand and fresh #11 blade.

A little work with the knife on the corners and the plate goes in.

The same method, routed out to depth. The hard point gets a little rounding to fit nicely into it's recess. At the point on the stab where the hard point sits is a balsa block. The stab tube is glued into a balsa block under the sheeting. It does not sit directly in Styrofoam.

OK, if it seems like I skipped something, I will show all in close-ups tomorrow. All of the hard points are mounted with 24 hour epoxy and a generous helping of micro balloons. I fairly well load the recess with the mixture and let any extra ooze out and wipe it away. I also push the mixture into the foam a bit...I want this to be a very hard mounting. I then clamp it in place with balsa blocks covered with release tape. The epoxy/micro balloon mixture will push the plate flush with the sheeting and the whole thing should require little filling with balsa filler. Here you can see the clamping on the hard points (mounting plates) also seen here is the trailing edge. The balsa stick you see is NOT the trailing edge, the trailing edge is a .4mm ply strip (1/64th ply). This creates a very ding resistant, durable trailing edge that adds a negligible amount of weight. The balsa strip is necessary to distribute even pressure along the thin strip of ply for a good glue joint. It is also glued on with epoxy. The very thin TE could warp with a water based glue, and CA is a little messy. When all is dry, I shall get close-ups pf all of these mountings. Still left to do on these surfaces is filling any dings and imperfections, final sanding, and then store them in their saddles until they go to the coverer.

Last photo for tonight. A long day to prepare three empennage sets. Ailerons are next. 

OK, here are some close-ups of the almost finished empennage. A bit of NHP filler and final sanding, and we will take a drive to the coverer. The first couple of photos show the 1/64th ply trailing edge. By the way, I put all of the trailing edge material for one airplane on the gram scale to see the actual weight and I could not get it to register. 4 grams for the whole airplane including the epoxy is my estimate, it may be a little less.

This it the top tip of the rudder. It is very durable now. Not at all difficult to apply the TE, I can't see why use a balsa TE anymore. Just cut the cores to a taper and cap the back with the ply.

The plate is almost perfectly flush with the sheeting. I will sand off the epoxy shine and poke a little NHP filler where it is still needed.

The ZN horns come in pairs of a left and right handed horn. They are very pretty, about 3 grams for a pair, and just too easy to mount. This whole mounting set-up is really strong now. The plate will come out only by pulling the entire control surface apart.

Here are a couple of shots that I wanted to include but it was too late the other day.
This shows all plates and recesses for the empennage.

Here is an elevator. Before the router went to work, I positioned the plate and scored the outline with a knife. Then marked it clearly with a pen so that it was easy to see during the routing process. This creates clean edges and the router gives an even depth.

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