Thanks goes once again to Mike Rettig for this lovely work of art, written on my dust-filled horizontal stabilizer, that I have not hung back up on the wall since my build party a couple (few) months ago. I stil have some touch up priming and a couple other things to do before I hang it back up again. Sadly, it does not take very long for just about anything in my garage to accumulate a rather thick coat of dust. I am ashamed to have let it get this bad.
Since my last post I have suffering from a bit of analysis paralysis regarding how many additional holes I need to drill in my wing ribs to install the necessary conduit to run all of my electrical wires through the wings. In order to figure this out, I also needed to come to terms with some avionics decisions that would also determine what kind of electrical wires and antenna wires I would need to run.
One of the key decisions you have to make in this day and age is to determine if your airplane will fly using mainly GPS navigational assistance, or if you intend to continue to take advantage of the VOR,Localizer, and glide slope information that is still in use and available to both VFR and IFR pilots alike. My decision? Since I am a pilot that is rated to conduct flight in both VFR and IFR environments, I plan on being able to exercise either one when the opportunity suits me. I threfore plan on installing a GPS unit that is qualified for both enroute and approach IFR (WAAS capable), and, as an independent back up system, I plan to to continue to use, or have the capability to use the existing ground-based VOR navigation system.
In order to do this, you have to install the avionics equipment for each system, and run the electrical wiring and the antenna wiring for both.
Up to now, my experience with VOR antennas has always involved what is known as a cat's whisker antenna. This is basically a rather thick wire antenna that is shaped like two sides of a triangle with the base missing. The pointed end of the antenna is usually mounted on the top of the vertical stabilizer, with the "whiskers" spreading outward towards the rear of the airplane. THe traditional IFR installation for this system was to install two separate VOR receivers, both of which would be tied to the same antenna. I don't see too many experimental aircraft using this installation method, nor do I see many cat's whiskers antennas.
I have since learned of a different option that was introduced by an antenna whiz by the name of Bob Archer. He has invented some Nav and Com antennas for a variety of different airplanes that can be installed inside a Wing tip, thus reducing drag and allowing faster cruise speeds. I have seen many pics of this antenna and I have access to several builders who have used this same installation. This weekend I attended the annual EAA Chapter 301 picnic, complements of Rudy Kniese and Ted Lemen. While there I met Lyn (Will get last name and add later) who is building an RV-7A. He invited me to look at this Wings so that I could see how he had routed his wires nd so I could see the Archer antenna installation in his WIng tip. It was fantastic to see another build again. I learned so much more than just about wire runs while I was there.
I learned about the distinction between fuel injected engines with vertical induction vs. horizontal induction. Horzontal requires an inlet mod that most make out of fiberglass. This eliminates the need for the scoop on the bottom of the engine cowl, which still has to be used if you use vertical induction. I also learned about the routing of the fuel vent lines, placement of the engine cooling baffles, and directing airflow to various components within the engine compartment.
Anyway, back to antennas. One of the other things I had read somewhere was that the antenna needs to be run separately from the wires for nav and strobe lights, landing lights, autopilot servos, etc. It is also supposed to be at least 1 foot away from all other wires to prevent RF interference from distorting or disrupting the signal. Lyn showed me that he as able to run the main wiring bundle for the lights and such up toward the front of the main ribs, and the VOR antenna cable can run through some conduit that is attached by a hangar through the rear lighteining hle of each rib. Lyn had a very spiffy looking zip tie clamp that was riveted to the outside of the rear lightening hole with two rivets. THe conduit is then attached by a zip tie assembly. Very neat setup. I also found some other hangars today at HD that I had read about from several others. the 3/4 inch hangar should work just fine. THis puts the conduit right through the center of the rear lightening hole, so you don't even have to drill another 3/4 inch hole in your wing rib, which is also a plus. The antenna cable will also be at least 16 inches away from any other wiring through the wing, so this will work nicely.
The antenna cable being used these days is RG400 - really expensive stuff I guess, but my life and the lives of my passengers is worth it. My plan is to run the Nav antenna out to the right Wing tip, another comm antenna out to the Left Wingtip, and then most all remaining antennas except for the GPS antennas will go on the belly of the airplane.
TO close for the night, I spent two hours finishing up the straightening of the remaining fuel tank ribs, and I sorted all the main ribs and stacked them together so that the correct rib sequence is set for each wing. I then numbered each rib so I know which one goes where. I still have deburring that needs to be done to certain areas of each rib, but the hard part is over. Actually the next hard part will be all the scuffing and cleaning of the ribs, but first I get to match drill the holes to the spar - have to get the sapr down off the shelf to do that. Yippee, I am building an airplane again!
Stacks of ribs waiting to be attached to the wing spar.
No comments:
Post a Comment