ZNLine Factory Enigma Build by Mark Novack

Here we have our 1.5mm carbon/ply cross-mounted hold down, and a plate of Formica mounting tabs. Instead of using the little Formica squares, we will use 4mm light ply squares that will give us nice spacing for the mounting tabs.

Here JP is using a lipped drilling guide to put the holes at the right distance from the edge to meet the hole in the mounting tab. We have placed these holes about 2" in front of the landing gear cutout.

Give the square a little rounding, fit it, mark it, and drill the hole into it.

A little glue, and use the screw to keep the holes perfectly aligned. We use a 3mm screw and the hole in the square is drilled to 2.9mm, so the screw grips and holds it very well.

OK, the basic idea is a single cross brace with a screw in the center in the rear of the pan, two screws into tabs just forwards of the landing gear cutouts, and one screw on the front. This keeps the pan impeccably aligned and very secure. For the cross brace, we want it to fit very flat so we use an angle grinder to flatten out the extra material where the brace shall sit.

This is where the brace shall go

Center the brace in the position selected on the fuse and drill the hole. This position will allow a ball driver to slip past the pipe and engage the screw. It will also stiffen the rear of the pan and keep it perfectly aligned.

Even what can't be seen is carbon laminated. When our customers order all of the options, they get all of the options. A blind nut goes into the end it gets glued under the hole for the cross brace screw.

I had trouble getting a good focus, but here the cross brace is screwed down, the belly pan is tape into place with perfect alignment and the cross brace is glued to the belly pan with 24 hour epoxy and micro balloon. If you look at the lip of the belly pan, you will notice a black piece. This is felt tape which is used as anti-vibration/scuffing material and applied after the airplane is painted. It must be applied now to achieve the perfect spacing. The belly pans are cut to allow for a thin material for seating nicely against the fuselage. We use the felt tape for wing seating and anywhere that the belly pan contacts the fuselage.

We have mounted the rear in place and prepared the front of the pan with the ply screw bosses and taped everything into perfect alignment. Here, a serious JP displays his work. This will dry until tomorrow, and then we will mount the tabs to the fuselage and securely mount the forward part of the pan. All mounting hardware is in place and screwed down while the glue dries with the belly pan perfectly aligned. When all is dry and the tape is removed, the belly pan will remain perfectly aligned. Again, tomorrow we will finish the forward mounts. I have been instructed to bring in my DZ too. Hmm, I think firewalls are coming soon. The wings have the last piece of ply drying on the TE tonight and require no further pieces added. Just finalizing any shaping of LE and tips if needed, and then sanding and filling and sanding and filling and sanding and, you get the idea I'm sure.

The glue has dried and the brace is securely mounted in the rear. So, we untape the pan, remove the rear screw, and now we will install the forward hold down tabs. First , the tab must sit against the ply screw boss, so the belly pan lip is ground down to allow for clearance.

Remount the belly pan and use a short straight edge to mark the exact location of the screw line onto the fuselage. Be accurate. The tabs look very nice when vertical.

This photo show the next few steps all at once. Tape across the area so that you can mark on the fuselage. The distance from the fuse side to the slot is the thickness of the ply square and belly pan thickness. We use a drill to make three holes across the slot and then a needle file to open them nice and square. Allow a little play here; the epoxy/micro balloon will fill everything nicely. Slide the tab up from the inside for a good test fit.

OK, several steps at once here because it is so easy. Roughen and clean the area around the slot on the inside of the fuse. Use a piece of clear sticky tape over the slot. Slice a slot in the tape just big enough for the tab to go through. The tape should fit tightly around the tab as this will keep the epoxy flush with the fuselage surface giving an incredibly clean appearance. Slide in the tabs and keep them in place with a piece of tape on the inside of the fuse. Mount the belly pan, screwing down the rear and the two front tabs. The rear will be perfectly aligned from the cross brace. Now, carefully align the front of the pan and tape it securely into place. Tape it SECURELY into place. Flip the fuselage so it is sitting upright. Mix up a batch of epoxy with micro balloon. Make this mixture a little bit thick. It should not run or spread. Using a long spatula (balsa stick or other suitable object for placing the glue), and cover the T portion of the tab with glue. Remember the tape on the other side; the glue will go only that far and lock this tab into place. Here is the tab with it's glue in place.

If satisfied with everything, then take a night and take the Mrs's shopping. Do not disturb this until it is dry. Here is sits drying.

The tape comes off, the screw come out, remove the tape from around the tabs, and this is how they look.

Symetrical, straight, professional. This is not difficult at all. And, it does not take much time. All of the work, front and rear, took only a little more than one hour, not including glue drying time.

Here is what the result of this method. Perfectly fitting belly pan, and when the rear screw is engaged, the two forward screws turn in with absolutely no wiggling or jiggling. The holes have absolute perfect alignment and will stay that way for the life of the airplane.

First, the side screw holes will be inset so the the head is flush (that is why the 4mm light ply instead of a thinner wood). Then, after the nose ring mount is installed, one more screw goes into the front to lock the front into place. Again, this is only one way of many to do this job. The magic boxes from MK with guide pins in the rear and one screw up front, and various other clip or sliding pin or spring tension methods are also very good. If you prefer another method, then by all means use it. Me, I do not mind these four screws and it is probably the easiest (and least expensive at about 25cents for the screws) method there is to get professional alignment. The motor should be next.

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