More Front Spar Work   February 26th, 2006

After preparing the reinforcement angles, the spar channel itself has to be bent as well. The spar is also used in the RV8, so it needs to be trimmed for the RV7. The trimming consists of removing a small amount of flange on each side of the channel.

To avoid creating stress points, I first drilled a #30 hole where the flange would be removed. I then enlarged the hole with a unibit so that the edge of the hole coincides with the location where the flange is to be cut off.

I then used sheet metal shears to cut off the flange. Rather than remove all the material in one cut, I removed a little at a time. This is a trick I learned when I first met with my EAA tech advisor. Instead of having the flange deform as I cut it, the small piece deforms, and the ‘good’ side of the material remains nice and straight.

Finally, I used this little tip (see below) on the dremel tool to smooth out the edge a bit. I’ve found this tip very useful for quickly removing small amounts of material.

Finally, I used a Scotch-Brite wheel to polish the edges so no sharp points remain.

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Now for the Front Spar..   February 25th, 2006

The front spar is the other main component in the horizontal stabilizer. The main differences between the front and rear spar is that the rear spar is angled ‘back’ at 6 degrees, and it uses short aluminum reinforcement angles instead of the long reinforcement bars.

The aluminum angles came from the factory as shown on the first picture below; they were pre-cut and pre-drilled. So, I just clecoed them to the spar and match drilled all of the holes in the center section, except for the four called out in the plans. I marked these with ‘NO’ just so I wouldn’t drill them out by accident.

Once the angles are match-drilled, they ends have to be tapered. I marked them up using the dimensions given in the drawing as shown below. I still don’t have a bandsaw or other cutting tool, so I first tried using a coarse wheel on the grinder. It turned out OK, but it was hard to get a straight tapered edge.

I ended up using a vixen file. I thought I’d be there all night filing away, but this file is an aggressive bugger! It only took me about 5 minutes per side, and I was able to get a nice smooth edge to about 1mm from my drawn line. I then used the Scotch-Brite wheel to grind it down to final size.

Once the two reinforcement angles have been tapered, the tapered ends have to be bent back 6 degrees. The bend is made along the line shown in the picture above. The manual says to secure the angle and whack it with a hammer. I figured the best way to do this would be to sandwich the tapered end between two blocks of wood and just push until I reached the desired angle. The only caveat is to make sure the angle is perpendicular to the wood, so the bend occurs along my line. To check the bend, I made a cardboard template using a protractor to draw the 6 degree angle.

After the angles have been bent, we just need to countersink the center two holes, since these two will have flush-head rivets.

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Match Drilling the Rear Spar   February 24th, 2006

Now that the spar is nice and smooth, it’s time to match-drill it to the skins. This is pretty simple. Make sure the holes in the skin and the spar match up, and cleco everything together. Next, drill the holes to size #40. The holes are already drilled, just not to the right size. Once every other hole is final-drilled, move the clecos to those holes, and drill out the rest.

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Deburr Deburr Deburr…   February 23rd, 2006

Deburring basically means polishing the aluminum surfaces to the point where there aren’t any sharp corners, scratches, etc. This reduces the probability of having the piece crack under stress. At this point I’m starting to understand that deburring is going to take a large chunk of the total building time.

Here’s a picture of my favorite way of deburring. I found the mini-die grinder at Lowe’s, and put in the small Scotch-Brite wheel. It does a perfect job every time! A lot smoother than using Emery Cloth. I will probably still use Emery Cloth on the skins and other thin material, though.

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What’s this blue stuff??   February 23rd, 2006

Most of the aluminum parts come with a blue plastic covering. Van’s recommends removing it as soon as possible. I figured it wouldn’t hurt to leave it on until I finish each piece, as it will help protect the aluminum pieces from getting scratched as I move them around.

I still needed to remove enough material to deburr, drill holes, etc. I used the old soldering iron trick. I used my Scotch-brite wheel to polish the tip of the iron into a nice blunt point, and ran it along a metal straight-edge to ‘score’ the plastic. I then used the same straight-edge as a guide to tear the unwanted plastic off.

Note that the iron is never actually going all the way through the plastic. It it just making it thin enough to where it’s easy to rip. This ensures the aluminum doesn’t get scratched if the iron isn’t perfectly smooth.

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Mr. Cheapass Strikes Again!   February 20th, 2006

Ok, so this isn’t plane-construction related, but I’ve gotta write it down for posterity.

Remember those nice tables I built? Well, I have a circular saw, but not a miter saw, and I figured I’d need to get one if I was to make straight cuts on all those 2×4’s.

I found a used 10″ saw on for $50, and snapped it up.

After finishing my workbenches, it was obvious the saw took up way too much space. So, I just listed it back on craigslist for $60! I figured there’s gotta be someone out there who’d buy it.

Well sure enough, I got a call the next day…Short story is I had a very happy customer who got a very nice power tool, and I got paid $10 for using a miter saw!

A guy at work said something like “Next time you need to use a miter saw you’d wish you hadn’t sold it” …Well, next time I need a saw I’ll just buy another one on craigslist!

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Enough of this cheap table!   February 20th, 2006

If you’ve been looking at the pictures on other postings, you’ll notice I’m using an eight-foot folding table as my work surface. I’m sick of it. It’s too low to the ground, to rickety, etc.

So, it’s time to build some real workbenches!

I downloaded the plans for the EAA 1000 standard worktable, and decided to make me a couple of them.

I ended up spending about $160, and got two ‘standard’ 2ftx5ft tables. I had enough material left over to do another two smaller tables (I did have to make a trip to HD for a few more 2X4’s).

Here’s a picture of the tables with the horizontal stabilizer skins sitting on them.

The plans for the tables call out ‘wood screws’. I bought the Zinc screws they sell at Home Depot in boxes of 50, and found out they are CRAP. Some of them are OK, but perhaps 20% of them had their head turn to mush when I screwed them in with my cordless drill. At first I thought I was maybe using too much force, or the wrong size screwdriver bit, but after trying on two or three different size bits, I got about the same results. The other 80% had no problems at all. Perhaps a woodworker out there can enlighten me?

Anyway, I think if I ever need to do this again, I’d buy the black ‘drywall’ screws. A lot cheaper, and I’ve never had a problem with screwing them in. Sure, the threads are a lot coarser, but the tables have so many screws it’s not going to matter.

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Drilling the Rear Spar   February 20th, 2006

Once the reinforcement bars have been rounded off and are nice and shiny, it’s time to match-drill them to the rear spar.

I laid the pieces on the table and drilled the outer two holes through the pieces and into the table. This allowed me to cleco everything down before drilling all the other holes. I also put in the brackets that go in the spar, so everything is match drilled in place.

This picture shows how I keep track of what part goes where after I take things apart for cleaning or deburring. I just draw lines at different angles through the different parts. When the parts are put back together correctly, the lines match. Now I gotta figure out how I’m going to keep those lines when I clean things up for priming!

It may be worth mentioning that when I first placed the reinforcement bars inside the rear spar, it was hard to get the holes to match without having a small gap between the bar and the spar. I went back to the grinder and radiused the bottom edge of the bar just a little bit more, and everything fit perfectly.

Since I had the hinge bracket in place, I match-drilled it as well.

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Ok, so I finally started working on the kit!

The first order or business is to polish/deburr the two reinforcement bars for the rear spar. The manual talks about polishing them to the equivalent of #400 grit sandpaper. I wanted to use the Scotch-Brite wheel in my grinder, but wasn’t sure what grit equivalent it is. So, I actually went to the hardware store and got some #400 sandpaper! After trying it out on a scrap piece of aluminum I quickly determined the Scotch-Brite wheel is definitely finer than this.

The idea here is to remove all the grooves, dents, etc., and end up with a nice shiny surface. Here is a shot of the two reinforcement bars after polishing one of them.

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I guess I need a shop now!   February 6th, 2006

I knew this day was going to come sooner or later. I would have a kit to put together, and nowhere to do it. My initial plan was to use an 8ft folding table, at least for the first few months, and then try to figure out what worked and what didn’t.

This also had the advantage of being able to clean things up, fold the table up, and lean it against the wall, leaving enough room to pull both cars in the garage.

Here’s a couple of pictures of the shop. Nothin’ fancy, as you can see..

You will note this funny looking pink stuff on the garage door. This is one of the best 60 bucks I’ve ever spent.You see, the difference between a bare-sheet-metal garage door, and an insulated one, is several hundred dollars (I recall it was over $600 at Home Depot). But, for about $60 of this pink stuff, and an afternoon of measuring and cutting, I get incredible insulation!

It can be 30 degrees outside but the garage is still comfortable enough to be in a short-sleeved shirt. Now, we don’t get many 30-degree days out here, but we do get MANY 90 and 100-degree days once the Texas summer rolls around! I’m hoping that’s where this stuff will really pay off! I will probably bring a fan out, or perhaps crack the house door open and let some of the Air-Conditioned air in the garage.

Eitherway, it will at least be bearable…

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