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Jul 20, 2019, 09:17 PM
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2019 Xplorer X3 Build - Wing Prep

In this post I'll be discussing getting the wing prepped for servo installation.

The Wing - Prep

I start working on the wing first. I like to get this out of the way first. The wing is the most complex part of the build. Spending time getting everything right here will ensure that your model launches true, holds trim and flies right, and lasts for many years. The key to achieving this is having good tight, zero-slop control surfaces along with correctly aligned push-rods. The following steps will help you prep the wing for the servo install.

I use lots of blue painters tape to write mark spots on the wing as well as to protect the surface. You may find that your tape doesn't stick well. This is because there may still be some mold release on the surface. As a general first step I wipe down the wing surface with isopropl alcohol. This also gives you a good opportunity to caress and love your model .

The next step you take is to stabilize the control surfaces. Most likely when you got the model out of the box NAN had the edges taped so that the ailerons and flaps wouldn't move around during shipment. It's best to go ahead and reinforce this a bit. I put about 15 cm (6") of tape on either side of top of the wing along the skin so that the tape overlaps the aileron or flap and the wing. Make sure to do the control surface is in a "neutral" flight position, like cruise. It isn't important to be exact you just want the aileron or flap to be in a position where it is easy to lay a ruler across it. Also, don't put the tape over where the control horn screws in or where the pushrod will exit the wing.

Once the flight surface is stabilized the next step is to put tape around the servo bays. This serves a couple purposes. It keeps the area right around the servo bay protected from glue and tools and it also gives you a spot to make registration marks and write down various measurements. I can't stress how important it is to draw out these measurements directly on the tape. Some people are good at mocking out on a napkin or piece of paper dimensions, measurements, etc, but I find it infinitely better to have those marks and notes directly where I'll be working. When taping here on the inboard, outboard, and leading edge sides of the bay put two widths of tape out from the bay. The tape I use is 24mm (~1") in width. On the trailing edge side put one piece of tape about 20 cm (8") in length centered over the hinge line and then work up to the bay.

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At this point there is one last bit of very important taping that must be done. Read the following twice and look at the pictures! Take a piece of tape and cut one end so that it has a clean, straight edge that is square. Start from the top of the control surface along the end where the wiper meets the skin of the control surface and go around the trailing edge and back up to the servo bay. At the start you want to make sure that the small end of the tape is right along the edge of the skin and that the tape is centered left to right over the hole where the control horn will go.

The goal here is to be able to mark down perpendicular lines so that it is explicit how the pushrod will be traveling and how to best align the servos so that the movement of the servo arm is directly in line with the control horn on the control surface. Once this piece of tape is wrapped around from the top of the skin to the servo bay it is time to get a felt tipped pin or a Sharpie marker and make some reference lines. Start by taking a ruler and laying it along the hinge line. Draw a line the shows the hinge line on top of the tape. It isn't necessary to be 100% over the hinge line parallel is fine.

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Now for the important line. This line will trace the path of the pushrod to the control horn. The goal is to have this line, and thus the pushrod, to be perpendicular to the hinge line. Start on the top of the wing. Place the pen so that it is in the middle of the hole where the control horn goes. Take the ruler and align it so that it you will be drawing a line perpendicular to the hinge AND NOT THE TRAILING EDGE. A t-square would be extremely helpful here. When you draw the line you want to make sure the marker drags over the trailing edge so that you're able to see where the line terminates on the trailing edge from the bottom of the wing.

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On the other side of the wing take a ruler (or the t-square) and line up one edge where the line on the top terminated on the trailing edge. Make the ruler line up perpendicular to the hinge line, I use one of the registration marks on it, and draw a line from the trailing edge to the servo bay.

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This is done for each servo bay on the wing. A good double check is to measure from the edge of the servo bay to the line. Make sure that both flaps have the same offset as well as the ailerons. When this is completed you'll have the confidence that as you start installing the servos in the wing each one will be positioned correctly. This is the start of building a great wing!

One last thing! Before going any further get that spray car wax out. Spray down the entire outer part of the wing. Work the wax into the wing. Why would you do this? Because doing this makes any CA or glue that gets dripped on the surface less likely to remain there permanently. This may not seem like something that is important, but if you drop that bit of CA while doing some task and you're unable to get it off you'll be pretty bummed.
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