May 7, 2010

Fuel Pump and Cover - New Approach - 5.5 Hrs.

After taking some time to really think this over and check with some of my resources, I made what I believe to be a wise decision. Sometimes when you're upset or troubled about something, you need to just walk away for a while before you do something stupid. I think I've learned this by now. And, I have to say, I have some REALLY good friends. I posted some pictures of my bowed cover and a description of my problem on the online forums, and my friends came to my rescue to help me think straight and see my way to a simple, elegant solution to this problem. And, most important, saved me from drilling out my floor ribs, which I can't believe I was actually contemplating. Note to self, and word to the wise: Never, I mean NEVER, seriously consider altering or doing something to structural components of the airplane if they have been built correctly and there's any way to find an alternative solution. The floor ribs are structural components. The cover is just cosmetic. So the choice of which part to re-make becomes a no-brainer. Re-make or alter the cover to make it fit better. And there's no point getting upset that Vans didn't tell me in the plans that the distance between the floor ribs is important. What's done is done and it's time to just fix it and move on. So basically, I decided to cut the flanges off the F-782C cover, make some new ones out of lightweight angle stock, and rivet them on. I'm also ditching the 3/4 x 3/4 angle crossbeams in favor of a stiffener plate under the fuel pump bracket. Those crossbeams are 1/8" thick and I think it's overkill to have material that thick. Besides, I will need to run brake lines and electrical lines under this cover and those angles were in the way. I would have had to cut them or trim them anyway. It will all become clear below and in the next few days as I finish up this task.

First, I drove over to Vans this afternoon. I needed a piece of angle material for this project. I'm using .032 x 3/4 x 3/4. Vans sells a 4' length of it for $5.85. Can't beat that for a cheap fix! The part number is: AA3-032x3/4x3/4. Perfect! This material has a radiused curve and is lightweight, very closely matching the material used for the 782C cover, so by the time I cut the flanges off and replace them with this material, I don't think I'm adding any measurable weight at all. I'll be able to use the existing holes that have already been drilled in the floor ribs, so I don't have to risk weakening them any further by drilling unnecessary extra holes.

While I was at Vans, I picked up another little goodie off their shelf in the little sideroom store. I got my fire extinguisher! Vans has discontinued selling these because they can't ship them anymore (I believe it's because of the Halon under pressure, hazmet rules and such). So, their existing stock is being sold and when they're gone, they're gone.

I only saw two of these on the shelf, and I grabbed one of them. I don't know if they have any more in the back storeroom, so if you need one and you're in the area, you better hurry and get the last one!

After I got home and got to work, I measured and then cut the new angle stock into the two new pieces I need. Once I had them deburred, I put them in place in the fuselage and drilled them to the floor ribs through the existing holes.

Also seen above, is the stiffener plate I'll be using in place of the angle crossbeams. I had this piece of .040 stock in the trim bundle that came with the empennage kit.

Next, I cut the flanges off the 782C cover with my band saw. Boy, this thing is flimsy without the flanges. That's why I'm going to use angle stock that runs the entire length of the cover, rather than just a few short pieces. I don't want it vibrating and rattling in the cabin. I filed and deburred the edges nice and clean.

I laid out the rivets and nutplates for the stiffener plate and drilled it to the cover, and also drilled out the larger holes where the nuts and bolt ends will protrude from the fuel pump bracket. Then, since my cover is already painted, I put down masking tape to draw the rivet lines and lay out all the rivet holes for the angles. Then I drilled them slightly undersized using a #41 drill bit.

With the stiffener clecoed in place under the cover, I carefully installed the cover in the fuselage laying on top of the new angle pieces already in place. Then I match-drilled the cover to #40 to the new angles. Cleco as you go. Then I pulled it all out, vacuumed up all the drill shavings, and took it apart for deburring. After deburring, it's now ready for dimpling and priming, but I had to call it a night. I'll be out of town all weekend, but it REALLY feels good to see this cover lying flat as it should, without being under stress.

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Contact me: swayze "at" europa.com (replace "at" with the @ sign... no spaces... you know the deal)