tailwheels

Unintended Adventures

A student’s approach to avionics

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On October 22, 2016

In S-20

Pretty excited at the moment. I think I’m actually going to get this engine monitor project off the ground and it will look nice as well.

If you recall my last posting I kind of talked about that I was going to limit myself to simple displays powered by an Arduino because I was having trouble finding a way to create a GUI on the Raspberry Pi. I resigned myself to pixely LCD displays and figured I would start looking for one to buy until a magical moment when I was searching Google for a display and with a combination of search terms I ended up on a search page on SourceForge. SourceForge is a website that can serve as a repository for software projects and sharing those projects.

Wouldn’t you know that I stumbled upon a really cool project that mimicked exactly what I wanted to do and it even used some tools that I had looked at before I gave up. The picture below shows the display that was created. If your into software I encourage you to check it out. You can find it at (https://sourceforge.net/projects/enginemon/). It looks to be a great jumping off point for my project and I think we’ll end up with something very cool.

So after discovering the code I set off getting my Raspberry Pi setup to run it. It wasn’t too hard and there were much fewer headaches then the path I had started down a few weeks ago. I got it running and then decided to try interfacing the Pi and the Arduino. That took a little time, but I used a quick tutorial I found online and I got it working. The video below shows me turning on an LED on the Arduino using a program running on the Raspberry Pi. The method of communicating back and forth is what I’ll use to transmit values received from sensors by the Arduino to the Raspberry Pi.

The current thought is to house the Arduino itself as a standalone sensor box and then the RPi will be housed with or near the display and use some wires to connect to the Arduino. That way I won’t have too massive of a box hanging off the back of the panel.

I also found a 6.5″ screen that is being used by some glider pilots running an open source glider computer. They seem to have good luck with reading it in direct sunlight and they see more sunlight more often than a normal plane. The nice thing too is that the display is relatively inexpensive, so if it doesn’t work as well or I find a brighter one it should be a trivial process to change out the displays.

(3 h)

Riveting

By

On October 13, 2016

In S-20

Little late, but wanted to get a short note written to just stay on top of the log.

Last weekend was devoted to getting the fabric on the right wing riveted down. I thought it would be fairly quick, but as usual it was not. Nothing hard for this part, but just a lot of repetition. The plastic strips all laid down nicely and seemed to go better than when I was using the strips on the horizontal stabilizer.

Maria helped out with the riveting and we got it done pretty quick. It was a quick work day, but now we’re all set to start adding exit rings, patches, and tapes.

On an aside, I have started on a side project to attempt some simple avionics. I really like the systems produced by Dynon and Garmin, but I’m haven’t been able to fully commit myself to one for this airplane. The information that I really am interested in is engine data and specifically temperatures. My idea is to use a popular micro controller (Arduino) to interface with the thermocouples and then display this data on a small screen. The end goal would be then to use the power of 3D printing to make a case for the system and be able to mount it in the panel.

I’ve looked into also using a small Linux computer (Raspberry Pi) in order to get access to nicer displays and graphics, but my lack of GUI programming has limited that area. I have a Raspberry Pi, so I may try to figure something out, but the Arduino is a relatively simple platform with a lot of community support for sensor applications.

If anyone reads this and has questions or has done this sort of thing shoot me an email. Should be a fun project and lower my desire for a full-blown glass cockpit. I’m going to add this stuff to the avionics page on the blog and try and track some progress there.

(5 h)

Covering the wings

By

On September 19, 2016

In S-20

My original plan was to start covering my wings in early August after Oshkosh and some other traveling. What that means is that I started covering the wings this past weekend.

Everything was pretty straight forward and it seemed easier to do than the fuselage. There was a lot less trimming around things.

The one thing I messed up and didn’t like was the top fabric. I tackled this alone which probably led to the problem. I had laid out the fabric in what looked like a nice, straight, and somewhat tight layout. I went ahead and attached the fabric to the trailing edge spar and then began on the leading edge. The problem showed itself when I got closer to the wing tip. I had a decent bunch of fabric on that end and I wasn’t sure what to do with it. I tried some creative cuts, but I probably did more harm than good. In the end after I shrunk everything, there is one spot that I don’t like and it is on the aft side of the wing and maybe a foot inboard of the tip bow. It’s just a big wrinkle that I don’t find pleasing, so I’m planning on making a small patch to put over it and tidy it up before laying the tapes down.

Other than that one misstep, I think it went pretty good. Between going away during the week for school and some weekend activities for the next two weekends, it will sit untouched till the second weekend of October. Next on the agenda is to get all the riveting done on the fabric before laying out patches and tapes.

(11 h)

Plane’s new clothes

By

On September 19, 2016

In S-20

I never posted this draft of a post from a month ago, so here it is.

Finally it appears that the painting on the fuselage is mostly completely save for some touching up. We’ve learned a lot and it looks pretty awesome.

The colors are Insignia White, Battleship Gray, and Firethorn Red from Stewart Systems. The scheme came from RANS.

Few things from spraying EkoPoly Premium we found. The biggest one is make sure the booth is dry. It seems humidity played a large part in some of our more frustrating sessions. So make sure the air is dry in the line and in the booth. The nasty picture of a light coat of red below was what we ended up with in the beginning of putting the red on. A combination of drying the booth out more and increasing the tip pressure on the gun seemed to do the trick.

Next time I think I’ll try removing the tapes prior to the paint drying. Maybe that will allow me clean up the lines and make them better.

Either way, I’m a happy guy.

(10 h)

Sanding (Painting)

By

On August 12, 2016

In S-20

Took a while for an update, but Oshkosh and visiting family made for a pretty hectic end to July and beginning of August.

As of this writing, the fuselage has it’s white top coat complete. Now it’s time for masking and sanding in preparation for the second half that will be red. Not much else to report besides that.

The painting has been a learning curve, but it’s starting to come together. The biggest hurdle is the time between spraying products. Usually means waiting a day and when you’re just painting one part, it seems like eternity.

I haven’t tracked my hours very closely in this section of work, but I’ll make a guess about what it seems like it has been.

Hope to have pictures of the plane with red on it by the end of next week. Till then, here are some of the white. We did get orange peel in the finish, but I’m satisfied with how it turned out and I have a feeling it will fly just fine.

(30 h)

It’s getting serious

By

On July 21, 2016

In S-20

Last update prior to Oshkosh.

Fuselage is ready for a light sanding followed by the topcoat colors after I get back from my summer tour in a week and a half or so.


I’m also finishing up my wing rack build today and tomorrow so I can transport/store the wings more compactly.


See you at OSH!

(6 h)

Sanding

By

On July 19, 2016

In S-20

The painting process is in full swing at the moment. Between life obligations and other flying obligations, it takes forever to get anything done, but it is getting done.

Currently we have a horizontal stabilizer and fuselage that has all the coats of EkoFill on it and is ready for EkoPrime. Took a decent amount of trial and error to get everything working right and we did a good bit of sanding to get some runs out.

Brushing the EkoFill on the fuselage took a good 4 hours give or take 30 minutes.

The EkoPrime should be on this week and then we can start shooting color (EkoPoly) the next day. I’m not sure when this will happen. I’d like to say this week too, but we’re closing in on Oshkosh and I’ve got other things to take care of before the end of the week.

In somewhat unrelated news, I’m building a wing rack so I can transport my two wings and store them easier.

(20 h)

It is done! (part of it)

By

On July 5, 2016

In S-20

The day has finally arrived where the fuselage is completely covered in fabric and ready for paint. I thought for sure it wouldn’t take 3 weeks since my last update, but summer seems to extend all timelines.

The objective is to move the fuselage this afternoon to get ready for paint and then hopefully start painting in the next week or so. We shall see how that timeline works out.

I was trying to think of some helpful covering hints or tips for the fuselage and can;t find anything groundbreaking except for the patches that go on the rear of the door frame. RANS instructs you to place patches and then tapes, but this is one area where I think they want you to put the patches on after you place the tapes. I did not and I don’t think it’s a huge problem, but I think it would look cleaner.

The areas in question are where other tapes start/end. A patch over the top of these tapes would finish those junctions off very nicely and then you would place the tape that goes around the door frame over that patch.

The other was a recommendation from another S-20 builder to use some bias tape for the vertical stabilizer transition area. That worked out great and I would recommend it.

I’m going to finish a horizontal stabilizer, aileron, and maybe cover the doors to get a few pieces to get my painting skills adjusted.

(16 h)

It’s neverending

By

On June 15, 2016

In S-20

Still slugging my way though the fuselage covering. All the work has been more sporadic than I would have liked.

The current state of the fuselage is that all the patches are on and I’m maybe halfway through the tapes.

Nothing too remarkable to report for this, so if there are any questions or suggestions, bring them up.

On another note, I received my first batch of painting supplies from Stewart Systems. I’m going to try and attempt a RANS scheme that was on the first SLSA. I;m going to replace the orange with Stewart’s Firethorn Red.

I’m also still learning the best way to put on patches and tapes with the glue. My technique has improved a lot and I think I may be able to go back with some diluted glue and soak it into the spots that aren’t a consistent color. 

(12 h)

So that’s what it looks like

By

On May 28, 2016

In S-20

Covering the fuselage has been going pretty well. It’s time consuming, but it’s nothing crazy.

I’ve been working on and off throughout the past week to try and keep making steady progress. As of tonight, all the sides of the fuselage are now attached. The right side needs to have the initial shrink done and then all sides can be shrunk to 350 degrees.

I’ve learned a few things through covering the fuselage and using Stewart Systems. I’ve had a few cases where the fabric would come un tacked when I would brush glue down through the top of the fabric in an area that I had previously tacked down with the iron per Stewart Systems procedure. I think the issue is that my iron wasn’t hot enough or I didn’t have enough glue underneath the fabric for it it really adhere. This didn’t cause big problems, but I did have to pull the fabric and then tack it down again after the glue had dried. If anyone is confused, shoot me a message/email and I can go through it in more detail.

The next part that took some learning and I still don’t feel great about doing is the transition from the top center former and the vertical stabilizer. So the procedure I used seemed to work ok. To preface this, I followed the same sequence as in the RANS manual. I attached the fabric to the bottom longeron completely and then started tacking the fabric into place around the cabin and working my way towards the baggage compartment. I then attached the fabric around the vertical stabilizer. This let me get everything in place and then trim all the excess fabric off with some degree of certainty that I had enough everywhere. Then I started working on tacking down the fabric onto the top center former working towards the transition. What I found was that I did need to slit the fabric around the radius area, but I didn’t have to cut all the way to the tube to get the transition to lay down. It still took a lot of work and I’m not completely happy with the amount of wrinkles I have, but I think it will look better after the final shrink. Overall, it worked out pretty well and I ended up with good coverage over the vertical stabilizer tube in that area.

The other interesting part it the baggage compartment. I also followed RANS here as well. I got all the fabric for the side in question fully glues down and all the wrinkles out of the bonded area. I then applied some glue the inside of the baggage window area so the fabric wouldn’t fray when I cut. Of course enough fabric must be left to wrap to the inside of the baggage window frame and glued down. This worked out pretty well and the fabric played down on the window frame quite nicely during the initial shrink.

I have some decent wrinkles, but I’m planning on them being taking care of during the shrink. I didn’t shrink at 250 degrees on the left side because I was concerned with pulling the top center former out of alignment. Now that both sides are on I can at least shrink each side equally. That’s the plan at least.

I’ve got lots of pictures, but it’s late and I don’t have them readily available to upload. I’ve been making lots of time lapse videos as well so I’ll be posting those as well. If you have questions about pictures, let me know. They all make sense to me because of the order and I did it myself, but that doesn’t really help others sometimes.

(15.5 h)

 

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