Pounding More Dimples

Yesterday, after a long day of winterizing the house, sprinkler system, and trailer, I managed to gather up enough time to pound out the remaining dimples in the top inboard wing skin for the left wing - minus the area where the scarf joint goes.

I am also reading ahead in the plans a bit to figure out the details of the fuel tank construction. Last night I ended up on the section that states: "If you are installing the capactive fuel tank sender instead of the float senders, it is best to install those now." So I pulled out a bag of parts that had been sitting on my shelf for a very long time, and pulled out the assembly plans and familiarized myself with the various electrical and metal construction components of this assembly.

SO far it all makes pretty good sense, and the assembly seems pretty straight forward. The part that I don't get has to do with how these things actually work. I understand the concept of capacitance in electronics, storing up current to a certain level, but I don't really understand how it works in the fuel tank as the fuel level increases and decreases, other than the fact that the capacitance changes as the fuel level changes. I also don't quite understand how this system can give you an accurate reading of the actual level of fuel in the tank, if the installed plates that are not located on the ribs at each end of the fuel tank. Instead, they are actually installed on each inboard rib just next to each end rib, and then electric wiring is installed and attached to each plate, and then ultimately to a BNC connector on the inboard rib.

The rest of the system involves a capacitance converter, the other half of the BNC connector, and the wires that run from the converter back to the fuel quantity indicator circuit or gauges. All that gets done during the final stages of the fuselage assembly when you are installing your avionics. Anyway, it was fun studying this assembly, and I am still glad I did NOT go with the float senders, but time will tell, since I read a lot of posts from other builders that say that you still have issues with getting accurate readings from either method.

With the inboard top wing skin dimpled, I need to finish dimpling the inboard main wing ribs, and countersinking the holes in the wing spar flanges, followed by priming those holes. I am fairly convinced that I may also need to go back and deepen the countersinks in all the holes just a bit more so that the dimples will insert properly during riveting, but I need to do some more tests on that before I commit to doing it in the wing spar.

I would have done some of that tonight, but we got snow this morning, and the temps are a bit chilly, my tree in my back yard is dropping very large branches that are breaking off without warning, and we lost power for almost 10 hours (not due to my tree issue thank god, but somebody elses), so I am taking a break tonight.

After all that is done both the inner and outer top skins go back on the spar, with enough clecoes removed around the area where the scarf joint will be applied, so I can bend back the skins just enough to take my cheepo HF die grinder air tool and the sanding and abrasive disk set that I bought, and start removing the material in the corner of each skin per the plans. The only way I can figure to do this properly, without having to put on and take off the wing skins multiple times, is to do it while the fuel tank assembly is secured to the wing spar so that the skins will butt up to each other and you can check the fit, and remove a little more material from one skin or the other as necessary, while everything is still on the spar. I don't want to have to spend hours putting skins on and taking them off until I get the fit just right - I don't want to waste that much time. I may, however, decide to put the attachment in my battery powered drill instead of the air tool, just to prevent myself from taking too much metal off, which would be very bad.

I also called Cleaveland Tools today to ask about their 12 inch long extended back rivet set. I think Mike Rettig may already have one of those so I will hit him up for that this week. I plan on using the beefy flat set that I bought a long time ago and back rivet the skin rivets against that, since many builders report getting better looking rivets on the top skins by using that method, instead of the rivet gun and bucking bar.

So that's a rap for tonight. More exciting stuff tomorrow - same bat time, same bat channel....

KPR, or dimples............