Monday, July 30, 2012

Eighty Percent Done, Eighty Percent to Go!

Experienced builders will warn anyone willing to listen that there will come a time in your build when you take a step back and view your creation as something more akin to an actual airplane than a collection of formed aluminium parts cluttering up your shop. It is at this point, they warn you, that you will estimate that you're about eighty percent done. You aren't. If you're really lucky, you might be about half done. It's a lot like having a house built: you stop by the build site one day and there it is, all framed and sided and roofed - it's almost done! Yeah, no. Not by a long shot.

But me? I think I really am about eighty percent done. Other than a couple of more weeks of small jobs, the only thing left is the avionics. Which, by the way, have arrived at Schmetterling HQ.

An interesting thing, these kits. The more they cost, the smaller the package they're delivered in. There, sitting on my kitchen shelf, is the cost equivalent of a brand new Mazda 2 or a Honda Fit or, as I call them, Viking engines in training.

The centerpiece of the suite is the glorious Dynon Skyview. It looks pretty lame sitting there in its box, but just wait until the first time it lights up! It's a thing of beauty. 747 captains would be jealous of its capabilities.

This is the Van's command center. All of the miles of wire meet inside there. For what purpose, I do not know. Some form of electronic alchemy is my best guess.

Ah, switches! Switches and fuses! Touchy-feely things! I couldn't resist turning each and every switch on and off, over and over.

Garmin provides the walkie-talkie, or maybe flyie-talkie is more apropos.

I did the inventory in the morning - nothing was missing. Then it was out to the hangar to continue the work on the cooling duct. It was time to do the final fitting of the fiberglass rectangle that provides the interface between the aft end of the cooling duct and the front of the radiator. Trimming and fitting this particular piece has been something of a pain for some reason. It just didn't want to fit onto the cooling duct well. I finally got it to fit, after hours of judicious and, admittedly, injudicious trimming. At the end of the day, it was required to end up sitting 1/4" from the front of the radiator. To achieve this gap, I cut some 1/4" blocks from some scrap wood and taped them to the radiator face.

By the time I had applied a healthy dose of trimming (the injudicious kind), the duct interface was kind of "floaty" on the cooling duct. It wouldn't reliably stay in the correct position when the cooling duct/cowl were removed from the plane, which of course would need to be done in order to glue the whole assembly together.

To alleviate this, Van's has us drill some holes in the top and side of the interface to allow some clecoes to hold the parts together. Easily accomplished on the top.

Not so easy on the side. The inner side (towards the engine) was impossible to drill. There was no room at all to get a drill down in there. There is quite a bit of engine in the way, after all. After a struggle, I was able to get one cleco on the outer side. Oh, how proud I was to get that cleco in there, even if the hole ended up too big for a silver cleco.

Well, that was all for naught. There is no interface skin in that game. I spent all of that effort putting in a cleco to nowhere.  There's nothing but open air on the other side - there is no cooling duct on that side.

I traced around the flanges of the duct so I would know where to smear epoxy.

I gathered up my fiberglassing supplies. Van's suggests putting the resin/flox mixture that will be used to bond the parts together into a plastic food bag and cutting off a corner of the bag so it can be used like one of those frosting bags that pastry chefs use. I was uncomfortable with that idea, having found it to be a particularly fast way to make a horrible mess when I was instructed to do the same when building my kayak. Instead, I decided to use some syringes. The other problem with using the food bag is that the epoxy gets very hot when it starts to cure, and given the eighty-five degree ambient, that was going to happen very quickly.

Normally I mix by resin in paper cups, but they weren't large enough for the amount that I would need. I decided to use a plastic cup, even though I knew that this method too was going to require very quick work to avoid the worst of the heating problem.

There are no pictures of the actual glassing. Not only was there no time to stop and take pictures, but there was also my concern over getting epoxy on my new camera. It was a rather frantic operation and it was truly a blessing to have Pete on hand to get things for me and to help me get the cowls back on the plane before the epoxy set up into a wrong position.

Oh, and about that plastic cup? It got pretty hot!


Julien said...

Thanks for the write-up, always a pleasure to read. What on Earth is the "spar pins" knob for? Preventing ignition if the spar pins are not in? And in which situation would you want to override?

DaveG said...

Yes, exactly so. When they're in place, the wing pins close a magnetic reed switch to prove to the electronics that they are in place and ready to keep the wings attached. If the pins aren't in (or, more accurately, if the pins aren't detected by the magnetic switches) it will lock out the ignition. In a case like this, the red light will be illuminated.

As to the override, well, there's no polite way to say it: the magnetic switches are a ridiculously complex way to do this. Not only were they a miserable chore to get installed and working, I suspect that there will be no shortage of occasions in which they fail to work, no matter how the wing pins are positioned. Without and override option, one could easily find himself stranded miles from home with no way to start the engine. It would be at this point that one would use the 'Press to Override' function, hopefully after taking a good look to make sure that the pins are actually in.

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