A Record of important things…

Switch Labels

Finishing up the Instrument pod is coming right up. I have been toying with ways to label the switches and decided to try employing my CNC router. This current trial involved taking sheets of polystyrene, which can be found on Amazon for about $0.40/sheet.
Paint the white sheets with a couple of heavy-ish coats of satin black, then route the labels with a very fine point engraving bit. It took a couple of tries to get the right bit and the correct depth, but I am quite satisfied with the results.

Since I have the detailed CAD for the panels I can easily come up with shapes that surround the entire switch area and are held in place by the switches. These are just test pieces, but I think I will go with this approach.

Cabin Interior painting


I had, at one point, considered lining the cabin interior with a fabric, but quickly dismissed it as weighty and labor intensive for limited gain in looks. To keep it simple and light, I lightly sanded it to remove the high-stranding fiberglass artifacts, then primed with the epoxy grey. I did not bother to fill the weave, or anything like that.


I wanted a finish that was light colored, but not reflective. The ideal solution was a stone finish spray paint. This is very similar to "spatter paint" that used to be popular as trunk paint for automobiles. I used Rustoleum "Simply Stone" granite finish. To me it looks nothing like granite, but for this application it looks pretty good.


The best part is that it really masks the open weave of the rough interior of the fiberglass. I highly recommend this stuff as simple and easy for this application.

Cabin Exterior Painting

And thus begins the sad story of my cabin painting…

I have primed a bunch of stuff with only one real problem (see my SP priming entry), then I painted my fins and seat pan. The fins came out super-nice as did the seat pan. I was feeling like there were a bunch of pansies out there on the web, saying that painting was so hard and such an art form. If you read some folks descriptions it sounds like some god-like skills are needed. All of my things came out well enough that I was thinking there was not much to it. How wrong I was.

To make it easy for myself I had chosen a single-stage 2-part polyurethane paint for the cabin. The color is plain white, just to avoid any of the shading issues I read so much about.

When I painted the fins I was impressed with how nicely the urethane paint "flowed-out", and leveled itself, creating a glass smooth surface. So I jumped in to the cabin exterior using the skills and techniques I thought were developed at this point. The surfaces were primed, wet-sanded, masked and cleaned well. No problems. I used the same gun that I used for the fins.

The first coat went on fairly light. It was mid-morning and the temps were in the 70's and the humidity was relatively low outside. There wasn't as much "flow-out" on the first coat as I would have liked, but it was a light first coat. I expected the second coat to flow out better.

Between coats there must have been something in the gun that I had missed during the previous cleaning that broke off and clogged one of the output holes on the nozzle. No problem, I had another of the exact same gun in the shop. I would just swap the paint, set the new gun exactly as I had the first and carry on. This was my mistake. I made a couple of test swipes on my practice piece that is always outside when I am painting. It was a little grainy, but basically OK - or so I thought. I figured it would flow out in a minute or two.

Coupled with that was the fact that is was later in the day, the sun was now out brightly, and the humidity was even lower than before. After I laid down the next coat (on both cabin half exteriors) I noticed that it was not flowing out as I had experienced in the past. OK. Not good. I increased the flow a tad to try to increase the quantity So it would flow better and "fill-in" the grain. What I learned later was that I should have lowered the pressure as what I was experiencing was dry-spray, not a flow problem. Too much air was effectively drying the paint on the way out of the gun causing a graininess. Nuts. Even though my second gun looked exactly the same and was the same model, the second gun was a newer gun and was very different internally (I learned later).

Decision time; Stop or continue? In that few seconds I decided to lay down as much paint as I had and sand it smooth later. It was either that, or stop, let it dry, sand it all off, reprime, and re-paint. Other factors at work were the fact that this was probably one of the last days I was going to get with a good temperature and warm enough outdoors to paint.

So there I was - I had two cabin halves with the surface texture of table salt. It really looked bad. Time to start sanding. I hoped that I had laid down enough paint so that I would not thin it too much.


The next two weeks of evenings were spent with a spray bottle of water, sandpaper and dual-action orbital polisher. Start with 500 grit (yes 500 grit for real), wet sand, then work to 800, 1000, 1200, 1500, and then 2000. Follow that with a multiple passes of the polisher with an aggressive cutting compound. Wipe it all off, look at it with a bright light and repeat, starting with the coarse grit on up. Repeat. Repeat. Repeat.

I learned an awful lot about how paint behaves. First or all, it is very possible to work with paint. If it was just some light orange peel, I am confident that I could have smoothed it out nicely, with labor, of course, but not too bad. The problem with my situation was depth. If you think of the surface in profile as a jagged series of little sawtooth mountains, it is easy to sand off the "peaks". However, once you have created "plateaus", you have a much larger surface area, the ever growing plateaus, to sand to work in to the "valleys". Initial progress is fast and noticeable, then it slows way down.


Coupled with that is that once you get close to the bottom of the valleys, the paint is getting very, very thin. There are couple of spots that thinned through. I am pretty sure that someday I will repaint the cabin, but I am not looking forward to it.


After all that, I got it to the 10-foot stage, From 10 feet away it looks OK. Closer and you start to notice the problems. I thinned it too much in 4 places. The lip around the door was impossible to smooth. I am at the point where I could spend 3 or 4 times longer than I have and it might improve, but it will never be perfect. I have decided to call the effort, continue on, and if it really bothers me down the line I will repaint the bird when it is down some winter. This is a learning experience. My next helicopter will be perfect.

Final Pan and Pod Painting

This has been an incredibly busy summer. Unfortunately little of it has had to do with helicopter building; trips to Asia, Europe, India and Mexico for work, and buying a house in Virginia have consumed all of my time and energy.

When I have had time to allocate to the helicopter, I wanted to get some of the cabin pieces completed so that over the coming winter things could be mounted permanently.

I started the final painting with the seat pan. The finish selected is satin "Rat Rod Black". This is a flat black with a little bit of texture. The intention is that there be no unwanted reflections on the canopy.

After my priming problems I was a little wary, but the Rat Rod Black went on beautifully. I have found that textured paints are forgiving and relatively easy to apply.

I a quite satisfied with the results on the pan. The pod and panels were painted with the same stuff and they also came out nicely and as expected.


Doesn't that look nice? Very satisfying. The pod was a little more challenging because of the curves and undercuts, but it too came out well. Overall, I am very satisfied with these pieces.

CNC Mill

Buoyed by the positive results from Attempting to CNC route some parts for the tail rotor scissors, I decided a more substantial machine was needed to allow for more serious metal cutting. I purchased a Grizzly G0704 for conversion to CNC. This is a fairly popular model for conversion and there is much information on the web detailing how others have converted this machine.


I did not want to spend a lifetime converting the machine, nor did I want to spend more than about $3500. This machine is substantial enough to cut up to maybe 1/2" aluminum. Parts and plans are readily available. I procured all the bits and pieces, and budgeted 3 weekends for the conversion. It took about three times that long as there is a lot of fiddling to get things dialed in perfectly.

The conversion deserves its own page, which can be found here: CNC_MILL.

CNC Routed Parts

After much diddling and fiddling I am finally able to achieve a good deal of accuracy from my CNC router. While great for engraving and shaping wood, it is challenged for metal.

Fundamentally it lacks the stiffness for super-high accuracy or extremely clean cuts. It is belt driven and belts stretch. If you grab the carriage and wiggle it, you can move it back and forth maybe 10-15 mils. I have braced the metal frame, but fundamentally it is limited by that design compromise.


Still, for some sorts of things it is fine. I have just cut a new set of tail rotor control scissors. They are cut just as accurately as the hand cut ones I did earlier. The two pieces are nearly an exact match. The holes are drilled on the drill press as routing those holes would be insufficient accuracy. The routed slots for the steel bushings ARE at least as accurate as the hand cut ones.


I am satisfied with the results. Perhaps I will later try a new TR walking beam for pedal attach, The pieces I can fabricate are certainly straight, and light.


Old and new compared.

Rotor Tach

A lot of builders have added expanded scale tachometers for the rotor. The gauge supplied by Eagle has a very narrow active range. In flight, reading the range while flying would be tough. The acceptable range is 610 to 620 which is just a couple of needle widths.


I built this little display item. It is based on a 2" display from eBay and an Arduino processor. There will need to be some conditioning to amplify the incoming signal and to make sure the analog tach is not affected. On the bench I use an audio tone generator to mimic the signal form the sensor.


If the rotor is in the range of 610 to 620 the RPM is displayed in green.



When in the range of 605 to 610 the RPM is yellow with a downward pointing arrow and a tone. Between 620 and 625 the RPM is also yellow with a higher pitched tone. Above 625 the reading is red with a red up arrow and a higher pulsing tone. Similarly below 605 it is also red with a red down arrow and a pulsing low pitch tone.

This is designed to be easy and very quick to read with an attention getting audio tone mixing in to the headset feed. I plan on mounting it on the top of the pod as it is critical to interpret this quickly during autorotations. In the final incarnation this will be packaged well and be brighter. The display shown here is a tired old one I have beaten and abused and use for development where I may actually damage it.