RV-10 Airplane Build Update

First off, (this is Becky speaking) here it is a beautiful February day, the airport is buzzing with aircraft activity ... and we can not join in the fun. Our Cessna is still in annual, in our hangar, just sitting there teasing us!
I have not been in the air for two months. A pilot is kind of like a drug addict, you have to get the high from mastering and commanding the skies and returning to the earth safely at least once a week. Our neighbor was kind enough to help calm the withdrawls by taking me up in his Glastar and allowing me to pilot it for a good amount of time on Sat. Jack Lenhardt was also kind enough to fly me to Independence for lunch on Mon., in his light sport plane. He has a Garmin 496, GPS with satelite so we listened to his music on the way to lunch (the kind you hear in elevators). On the way home he allowed me to pick the music, so I introduced '70's rock to him (he is around 70 years of age, or so). We landed at Lenhardt's with him singing "... sexy lady ...". Maybe I should have started with '50's rock! Thanks John and Jack for the flights!

Getting Caught Up
It's been way too long since I've (this is Bruce speaking) posted any RV-10 progress, so I'm gonna go way back! Almost 3 years ago (May '05), Rob Hickman (yes, the famous Rob Hickman of www.advanced-flight-systems.com) and I were emailing back and forth and realized we were both picking up our wing kits in mid June '05. It was agreed that we would get together and design our electronic fuel-level system since Van's didn't offer one for our planes. Strange - they offer a "capacitive" kit for the other models (except the RV-3), but not the biggest and beastliest kit of them all! The advantage of a capacitive system versus a mechanical fuel float is accuracy (maybe) and no moving parts to come undone. Well, to be a good neighbor, I jumped ahead in the plans to the fuel tank section and spent days, weekends and months getting the tanks to the point that I was ready for Rob's call. Every few months I'd email to see where he was at, meanwhile going back to the beginning and starting on the wings where everyone else does. Being a business owner of an avionics company, he was against the wall with projects that had to be completed or he was going to get buried by his competitors. Alas, the RV-10 project gathered dust (rumor has it that his wife REALLY wants the RV-10 so the whole family can travel together. Makes perfect sense to us) as he worked to get his new products up and running. After a full year of construction, I was at the point in the manual where it was time to get the tanks done. I emailed Rob. His response blew me away; he had decided to go with mechanical floats! Aghh!! He had a good reason: Another RV-10 builder had passed away and Rob had purchased his project which was closer to completion, so there was no reason to rebuild what the other guy had already done. Ok. Now I'm on my own. A quick email to my EAA Tech Counselor (Experimental Aircraft Association), Dan Benua and I was back in the saddle! Dan had also done capacitive senders,
(http://www.flickr.com/photos/9030616@N02/sets/72157603781952661/),
so with his words of wisdom, to the design board I went. Van's support people told me that I needed 70 square inches of aluminum (per 2 plates) per tank to pull it off. With a little math, and way too much aluminum, I had designed a plate that I thought might work. Dan pointed out that a capacitive sending unit looks to see how much fluid is between it and what it's attached to. Being that the plates were attached to ribs, there were holes, lumps and bumps that would make the distance between the plate and the rib vary as the fuel level dropped. Not accurate. So, I decided to build a second plate (with all that extra purchased aluminum) that attached directly to the rib, giving it a smooth surface. This assured that as the fuel level dropped, the rate of fuel exhaustion would be constant on the gauges and not seem to go fast at one point and slow at another.





Here's a shot of the inside of the tank showing the installed rib with the wired capacitive plate. Note the white wire. Believe it or not, this was the source of the last little tiny leak I found when testing the completed tanks. Air was able to travel the inside of the wire and get out of the tank through the center post of the electrical BNC connector I had mounted to the outside of the tank!


After assembling the tank with FlameMaster (http://www.flamemaster.com/sealants.html), I plugged all the holes and added a little air pressure. Using warm water and a little dishwashing soap, I brushed the solution around joints and every rivet to see if it had truly sealed or not. NOT! Found some beautiful bubbles that needed to go away.


When all was said and done, I inflated the tanks just enough to fill a couple balloons. The balloons held their shape long enough to convince me that the tanks had sealed. I could find no more leaks on either assembly. Wahoo!


The next step involved mounting the tanks to the main spar of the wing. Using screws dipped in a non-hardening fuel-proof product (Fuel Lube), it went together beautifully.



Now, in February '08, we're working on the bottom skins. I'll drill, dimple and prime them, but not rivet them to the wing assembly 'til I'm certain that we have no good reason to get back into the wings. The aforementioned "Rob" has an Angle of Attack product that needs to go in, and, the wing servo for our auto-pilot (http://www.trutrakflightsystems.com/) also needs to be mounted before closure.


Months ago, I had built a wing cradle. What a space-saver! It holds both wings, protects them, and allows us the freedom to move them around the hangar with ease.