Saturday, June 26, 2010

Finishing the chinny-chin-chin

With just two more pages to go in Section 22, today was the final stretch for the lower front fuselage, or what I have taken to calling "the chin."

 It started out easily enough with the installation of the mount that will hold the fuel flow transducer. That little gadget will measure the amount of gas running through the line and pass that measurement along to the Dynon display. It was simply a matter of installing a pair of nutplates (although I had to counter-sink some holes in the mount despite there being no mention of doing so in the manual) onto the mount, clecoing the mount to the inside belly skin, final drilling the #30 holes for the rivets, and riveting it in.

This is the transducer set in place just to see what it will look like.

At long last, the chin was finally ready to be riveted to the rest of the fuselage. I wanted to have it positioned so that I could get clecos in to hold it in place, so I flipped the rest of the fuselage over. Not only was that somewhat tricky to do alone, it also turned out to be a mistake. No matter how I wriggled and jiggled the chin, I could not get it to mesh with the front of the fuselage.

If turning the big Chunk O' Fuselage over alone was a pain (it was!), turning it back over again would be even worse because I'd have to be very careful to align it with the sawhorses so as to avoid having them place untoward torque on the protruding clecos, thus running the risk of bending the skin. I had to ask co-pilot Egg for assistance. With her help I was able to get it turned over and see what the problem was.

It seems that parts of the chin skin that has to overlap the fuselage skin have notches to allow the flanges to mesh, while other parts do not. The only way I could get the non-notched parts to mesh was to force the fuse skin to slide under the flange of the chin. All of the pushing and prodding had scratched up the skins a little bit, and as this is the bottom of the plane and thus likely to be exposed to relatively wet and dirty conditions now and then, I cleaned up the skins and applied a coat of primer to each.

Here's what it looks like in the area where there's no notch:

Here's an area with a notch:

With the chin finally tentatively held into place with a few clecos, Egg helped me get it flipped back over again for riveting. That accomplished, I release her from servitude.

While I had been having problems getting the chin to fit on the rest of the fuselage, I checked with some other RV-12 blogs to see what the problem was. To no avail, as it turns out, as no one else seems to have had a problem with it. I did see one of those helpful suggestions that I run across now and then that suggested installing a couple of parts from Section 23 before getting too far along with the riveting of the chin. Just as I started the riveting of the chin to the fuselage, I realized that I hadn't installed those parts yet. Doing so now would require either calling Egg back downstairs to help flip the fuselage over again or crawling around on the floor to do the riveting. 

I chose the floor.

With that done, it was just a lot of routine riveting. I thought about hauling the whole thing up to the hangar so I could use the air riveter, but I'd only have to being it right back when done. I just did them all with the manual puller.

The reason I would have had to bring the whole back to the shop rather than just leave it out in the hangar is that I'm going to skip ahead to Section 28. Section 23, which would normally come next, is where the side skins get attached. If I do that now, Section 28, which is the installation of the fuel lines, will be much harder because I'll have to lean down into the fuselage to reach all of the places in the bottom of the fuselage where fuel fittings and lines are to be installed. Better to just do all of that while the access to the areas that stuff has to be installed is much easier, I figure. And better to do it in the temperature controlled basement than in the hot, muggy hangar.

I've got all of the fuel system parts, fittings, and materials laid out and ready to go.

I still have to get those pesky system blocks screwed into place, though, Living in a house full of women, I haven't got anybody that can hold the wrench tight enough or turn the screwdriver while I hold the wrench. My only options at this point are to call for external help or adopt a little boy and wait fifteen years until he's old enough to help.

Tough choice, that.

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