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Tuesday, September 3, 2013

Edge EXP__Tweaking The Night Set Up

After a reasonably successful pitch black night test, I wanted to make a few changes to the way I mounted the light bars of my Aurora Genesis light system. If you have seen the video you'll remember how well the SFGs were lit up, which just showed how much light they were blocking from getting on to the airplane.

Also, the wires came out the end of the wing, where I taped them down on the SFG to keep them from flapping. This made my OCD go totally ape and I wanted to find neater way.

When I first inquired about the system, I spoke to Alex at Aurora RC and he suggested notching out the tips of the stab and mounting the rear light bars there. It did not occur to me at the time that I could do the same thing with the lights on the wing, but when brainstorming how to mount the wing lights in a neater way, I remembered this.

I really hated to cut out the notches on the wings of a brand new plane, but they are not so bad. I had to be careful to do a neat job, and also to get the notches the right depth. The idea is for them to bottom out in the notch and for the outsides of the bars to be flush with the outside of the wing tip

Once the wing was notched, I pushed the light bar into the notch and bolted the SFG down over top to hold it into place. This is a very elegant solution to mounting the lights. There are no wires hanging out, and no aero knots and light bars sticking out in the breeze.  Because of where I notched out the wing for the light bar, the wires go straight into the wing and from the outside you can't see a single wire. It's just very, very clean.

This arrangement resulted in some really important improvements beyond cleaning up the aesthetics and getting more light on the plane, though I feel much, much better now that I have a clean installation.

Now with the light bars tucked almost up against the inside of the SFG, they will create much less turbulence and upset the plane's aerodynamics much less.  Also the wires now go straight into the wing instead of on the outside of the SFG. When you remove the aero knots on top of all of this, the airflow around the SFGs has been cleaned up enormously. There was a lot od stuff out there messing up the airflow, but now it's righteously tightened up.

Because I no longer have to worry about the SFG blocking the light, I can go back to the lighter and larger original size EXP style SFG. The plane flew fine with the smaller SFGs, but I still missed having the KE lift and yaw authority afforded by the full size versions.

I save weight by losing the aero knot mounting points and the heavier plywood SFGs. Losing weight is always really good.

Because I mounted the lights further forward, along with losing the aero knots, and that moved a lot of weight that was previously behind the CG to right about on top of the CG.  Right now I've got my battery all the way forward in the radio compartment and the plane flies dead neutral. I generally like them a little forward of that and I think this will get it dialed in dead on.

Lastly, you'll notice on most planes when you hit an SFG on the ground it grinds  the bottom of the SFG near the rear. The way I had the lights mounted before, that's right where they were, and they were very vulnerable in that position. Now they are well past mid cord forward, and hopefully a little safer from ground strikes.

You can see how much better the light now hits the plane. We're going to try really hard to get some footage Thursday night, but it all depends on getting one of my camera guys to come out.

You know, this improves and corrects so many things that I feel a bit silly I ever did such a sloppy job the first time. I'm actually a little bit embarrassed by it, but that's what happens when you do LIVE reports. Sometimes people see your warts.

I knew from the beginning this was going to be a learning process and I would probably screw it up. With this in mind I was very careful not to do anything that I couldn't simply unbolt so I could change it. I notched the wings as a last resort, but again, it's not so bad.

If I ever want to convert the plane back to day use, I can cut a small piece of red 3M High Performance Vinyl out and slap it over the notches. The stuff goes down and sticks so well, and the seams are so close to invisible that I can live with it.

Just for reference, here is the mess that I made for myself before. Every so often my aileron trim would change, so I either had a poor centering servo or the wires were moving around and disrupting the airflow. The wingtip creates the most turbulence of the entire airframe, so you don't want any loose stuff out there.  I checked the servos over and over and they are fine, so getting everything out of the airflow seemed to be the next logical step.

You can also see how far behind the CG the light bar and it's mounting pieces are.

That, and it just looks like crap. When I was building the plane in my mind it did not look this messy, but once I paid the money to get the SFGs custom laser cut and ran all over town looking for aero knots, I was going to at least try the damm things!

I was also getting some wing rock, which I have never, ever, ever seen on an EXP, especially not on an Edge EXP. Since I have never ever seen that kind of thing on one of these planes before, the only possible cause simply has to be all the junk hanging off the wing tip, so cleaning all of that up was essential.

Another nice touch is that by going back to the original, full-size EXP style SFGs, I can run my cool new Sphere Of Doc Austin decals.

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